Hach 16900 User manual

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16900-08

Digital Titrator

Model 16900

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SPECIFICATIONS.................................................................................................................... 7

OPERATION..........................................................................................................................9

GENERAL DESCRIPTION ................................................................................................... 11

1.1 Introduction ....................................................................................................................... 11

1.1.1 Following a Procedure for the First Time................................................................ 12

1.2 Step-By-Step ..................................................................................................................... 13

1.3 Helpful Hints..................................................................................................................... 18

1.3.1 To Reuse a Partially Emptied Cartridge .................................................................. 18

1.3.2 To Calculate Titrant Volume Used........................................................................... 18

1.3.3 To Fill Your Own Titration Cartridges..................................................................... 18

1.3.4 Verifying Technique................................................................................................. 19

1.4 Adapting a Buret Titration to the Digital Titrator ............................................................. 22

1.5 Using PermaChem

1.6 Safety................................................................................................................................. 24

TITRATION PROCEDURES ..........................................................................................27

Powder Pillows................................................................................ 23

ACID-BASE

Acid Determination................................................................................................................. 29

Base Determination................................................................................................................. 31

ACIDITY

Methyl Orange Method ........................................................................................................... 35

Phenolphthalein (Total) Method.............................................................................................. 37

ALKALINITY

Phenolphthalein and Total Method ......................................................................................... 41

AMMONIA, HIGH RANGE (Ammonium Hydroxide)

Ammonia Titration Procedure................................................................................................. 49

CARBON DIOXIDE

Using Sodium Hydroxide........................................................................................................ 55

CHELANT, FREE

Using Magnesium Chloride .................................................................................................... 59

CHELANT, TOTAL

Using Bismuth Nitrate............................................................................................................. 63

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TABLE OF CONTENTS, continued

CHLORIDE

Mercuric Nitrate Method ........................................................................................................ 67

Silver Nitrate Method ............................................................................................................. 68

CHLORINE, FREE AND TOTAL

DPD-FEAS Method................................................................................................................ 75

CHLORINE, TOTAL Iodometric Method (1 to 400 mg/L as Cl Iodometric Method (20 to 70,000 mg/L as Cl

CHLORINE, FREE

Amperometric Forward Titration............................................................................................ 87

CHLORINE, TOTAL

Amperometric Back Titration................................................................................................. 93

CHLORINE, TOTAL

Amperometric Forward Titration.......................................................................................... 105

CHROMATE

Using Sodium Thiosulfate .................................................................................................... 113

Using Sodium Thiosulfate) ................................. 79

Using Sodium Thiosulfate) .......................... 82

HARDNESS DECISION TREE........................................................................................... 119

HARDNESS, CALCIUM

Using EDTA.......................................................................................................................... 121

HARDNESS, TOTAL

Using EDTA.......................................................................................................................... 127

HARDNESS, TOTAL, SEQUENTIAL

Sequential Titration Procedure (Limited Sample)................................................................ 135

HYPOCHLORITE (Bleach)

Iodometric Method ............................................................................................................... 143

IRON

Using the TitraVer

Titration Cartridge ............................................................................... 147

NITRITE

Using Ceric Standard Solution ............................................................................................. 151

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TABLE OF CONTENTS, continued

OXYGEN, DISSOLVED

Azide Modification of Winkler Method................................................................................ 155

Using a 300-mL BOD Bottle ................................................................................................ 155

Using a 60-mL BOD Bottle .................................................................................................. 157

SALINITY

Using Mercuric Nitrate.......................................................................................................... 161

SULFITE

Using Iodate-Iodide............................................................................................................... 163

TURBIDITY STANDARDS

Preparing Turbidity-Free Water ............................................................................................ 167

VOLATILE ACIDS

Using Sodium Hydroxide...................................................................................................... 173

APPENDIX A

ACCURACY CHECK AND STANDARD ADDITIONS.................................................... 177

GENERAL INFORMATION .........................................................................................189

REPLACEMENT PARTS AND ACCESSORIES ................................................................ 191

HOW TO ORDER................................................................................................................. 193

REPAIR SERVICE................................................................................................................ 194

WARRANTY ........................................................................................................................ 195

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SPECIFICATIONS

Digital Titrator

Delivery: 800 digits/mL or 0.00125 mL/digit

Accuracy*: ± 1% for readings over 100 digits. (Uncertainty of readings is 1 digit. Most samples require more than 100 digits.)

Weight: 132 g (4.7 oz.)

Cartridges for the Digital Titrator

Volume: 13 mL

Number of tests: Most reagents are formulated to provide 100 typical titrations; the number may vary depending on sample concentration.

Weight (full): 56.75 g (2 oz.)

* Overall method accuracy includes, in addition to the Digital Titrator, other sources of error controlled by the analyst. The other sources of error include: sampling, sample volume, dilution (if required), end point detection, reagent quality, and interferences.

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OPERATION

DANGER

Handling chemical samples, standards, and reagents can be dangerous. Review the necessary Material Safety Data Sheets and become familiar with all safety procedures before handling any chemicals.

DANGER

La manipulation des échantillons chimiques, étalons et réactifs peut être dangereuse. Lire les Fiches de Données de Sécurité des Produits (FDSP) et se familiariser avec toutes les procédures de sécurité avant de manipuler tous les produits chimiques.

PELIGRO

La manipulación de muestras químicas, estándares y reactivos puede ser peligrosa. Revise las fichas de seguridad de materiales y familiarícese con los procedimientos de seguridad antes de manipular productos químicos.

GEFAHR

Das Arbeiten mit chemischen Proben, Standards und Reagenzien ist mit Gefahren verbunden. Es wird dem Benutzer dieser Produkte empfohlen, sich vor der Arbeit mit sicheren Verfahrensweisen und dem richtigen Gebrauch der Chemikalien vertraut zu machen und alle entsprechenden Materialsicherheitsdatenblätter aufmerksam zu lesen.

PERIGO

A manipulação de amostras, padrões e reagentes químicos pode ser perigosa. Reveja a folha dos dados de segurança do material e familiarize-se com todos os procedimentos de segurança antes de manipular quaisquer produtos químicos.

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GENERAL DESCRIPTION

1.1 Introduction

Hach’s Digital Titrator is a new concept in titrimetric analysis. It is a precision dispensing device fitted with compact cartridges that contain concentrated titrants. Accurate titrations are made without the bulk and fragility of conventional burets.

A main drive screw in the Digital Titrator controls a plunger which forces the concentrated titrant from a titration cartridge in a carefully regulated flow. The titrator body is constructed of precision-molded, heavy-duty, chemical- and impact-resistant acetal plastic. Accuracy is rated at ± 1% or better for a titration of more than 100 digits. For titrations less than 100, accuracy is ± 1 digit.

Titration solutions (titrants) are packaged in disposable polypropylene or Kynar neoprene seals and polyethylene resealable closures to cover the cartridge tips. Each cartridge contains approximately 13 mL of titrating solution, enough for 50–100 average titrations. Titrant solutions are typically controlled to ± 0.5% concentration with normality and tolerances listed on the label. Titrant concentrations are designed for titrations of 10 to 40 turns (100 to 400 digits) of the delivery knob. For the most commonly used concentration ranges, the digits appearing in the counter window correspond to the sample concentration.

containers with Teflon-covered

Figure 1 Hach Digital Titrator

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GENERAL DESCRIPTION, continued

Both portable and fixed-position titrations are possible with the Digital Titrator. The instrument has a grip for hand-held operation or it can be clamped to a TitraStir for stationary setups. See Figure 1.

Each Digital Titrator comes with five delivery tubes and a methods manual, which covers the most commonly tested parameters and the corresponding titrant cartridges. Right-angle (ninety-degree) delivery tubes for stationary setups are available as an optional accessory.

1.1.1 Following a Procedure for the First Time

Each method is divided into five sections: Procedure, Accuracy Check, Interferences, Summary of Method, and Reagents and Apparatus. For more information about how to select a procedure or for answers to chemical questions, see Hach’s Water Analysis Handbook (literature 8376). For more information about chlorine measurement, also see the technical booklet titled, Current Technology of Chlorine Analysis for Water and Wastewater (literature 7019).

The Procedure details how to perform the method step-by-step. To select the appropriate sample volume and titration cartridge based on expected sample concentration, use the tables provided in each procedure. If the expected sample concentration is not known, start with one of the smaller sample volumes and determine its approximate concentration. Retest with the appropriate sample size.

Stir Plate or laboratory stand

The ranges in the table overlap to offer more flexibility. In most procedures, the number of digits used for each concentration range will be 100 to 400 digits.

To determine the actual concentration of the sample, use the correct digit multiplier for the sample volume and titration cartridge used.

Throughout the procedure, the notes will provide additional information.

The Accuracy Check provides a way to verify the results and determine if interferences are present. It also provides a method for checking the performance of reagents, the Digital Titrator and the operator’s technique. Further information is provided in Appendix A, Accuracy Check and Standard Additions.

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GENERAL DESCRIPTION, continued

The Interferences section identifies common interferences causing inaccurate results and describes how to eliminate their effects. The interference levels are based on the sample volume that has 1.0 as the digit multiplier. Higher interference levels may be tolerated if a smaller sample is used.

The Summary of Method section discusses the chemical reaction taking place and information that applies to the entire procedure.

The Reagents and Apparatus list concludes the procedure. All the items required to perform the test are listed first and are available from Hach. The items listed in the notes or interferences sections are included in the optional listings.

1.2 Step-By-Step

1. Select a sample volume and titration cartridge corresponding

to the expected sample concentration from the table given in each procedure.

If the expected sample concentration is not known, start with one of the smaller sample volumes and determine its approximate concentration. Retest with the appropriate sample size.

2. Slide the cartridge into the titrator receptacle and lock in

position with a slight turn. See Figure 2.

Figure 2 Sliding the Cartridge into Place

3. Remove the polyethylene cap and insert a clean delivery tube

into the end of the cartridge until it is tight. See Figure 3. Use a straight tube with a hook at the end for hand-held titrations; use a 90° tube with a hook at the end for stationary setups.

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GENERAL DESCRIPTION, continued

Do not insert tube past cartridge extension; see illustration below. In some instances, it might be necessary to remove a small burr on the leading edge of the tube before insertion.

Figure 3 Inserting the Delivery Tube

4. For stationary titrations, use a TitraStir Stir Plate or a clamp

holder and clamp to attach the titrator to a laboratory stand. See Figure 4 and Figure 5.

The TitraStir Stir Plate holds the Digital Titrator during the titration and also stirs the sample at a constant speed, leaving the analyst free to detect the end point. When a TitraStir Stir Plate is used, substitute or add the following Optional Apparatus.

APPARATUS

Quantity Required

Description Per Test Unit Cat. No.

Delivery Tubes, 90° with hook for TitraStir® Stir Plate........... 1 ............. 5/pkg .......... 41578-00

Flask, Erlenmeyer, 125 mL....................................................... 1 ............... each .............. 505-43

Flask, Erlenmeyer, 250 mL....................................................... 1 ............... each .............. 505-46

Stir Bar, 28.6 x 7.9 mm............................................................. 1 ...............each.......... 20953-52

TitraStir TitraStir

Stir Plate, 115 Vac....................................................1 ............... each .......... 19400-00

Stir Plate, 230 Vac....................................................1 ............... each .......... 19400-10

5. To start titrant flowing and flush the delivery tube, hold the

tip of the cartridge up. Advance the plunger release button to engage the piston with the cartridge (push the button in and toward the cartridge). Do not expel solution when pushing the piston toward the cartridge. Turn the delivery knob until air is expelled and several drops of solution flow from the tip. As you turn the knob a drive screw pushes a piston against the cartridge seal and forces liquid out through the delivery tube. Then use the counter reset knob to turn the digital counter back to zero and wipe the tip. The tip can be rinsed with deionized water rather than wiped, if desired.

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GENERAL DESCRIPTION, continued

Figure 4 Using the TitraStir® Stir Plate

Figure 5 Using a Laboratory Stand

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GENERAL DESCRIPTION, continued

Figure 6 Titrating the Sample

6. Use the smallest appropriate graduated cylinder or pipet to

measure the sample volume from the given table. Transfer the sample into a 125-mL or 250-mL Erlenmeyer flask. Dilute to the appropriate total volume with deionized water if necessary.

Note: Sample volume measurements and dilutions (if required) must be

made accurately. However, final total volume of titrated solution is not critical.

7. Add the necessary reagents to the sample and swirl to mix.

8. Immerse the delivery tube tip in the solution and swirl the

flask while titrating. Titrate by turning the delivery knob. Keep turning the knob and swirling the sample until the end point is reached. Record the number of digits that appear in the digital counter window. See Figure 6.

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GENERAL DESCRIPTION, continued

Note: The number of digits required will usually range from 100 to 400.

In nearly all of the procedures if the digits required is less than 100 or more than 400, an alternate sample volume or titrant cartridge should be used.

Note: Inaccurate results will occur if the delivery tube tip is held out of

the solution rather than under the solution surface.

9. Calculate the concentration of your sample by using the

following formula:

Digits Required Digit Multiplier× Sample Concentration=

Where:

Digits Required = the number that appeared in the digital counter window in Step 8.

Digit Multiplier = the number from the table given in the procedure. It takes into account the sample dilution and titrant strength.

10. After completing testing for the day, press the plunger release

button and manually retract the plunger into the body of the titrator. Remove the cartridge. Remove the delivery tube and reseal the cartridge with the polyethylene cap. See Figure 7.

Figure 7 Retracting the Plunger

11. Discard or clean the delivery tube immediately after use. To

clean, force water, then air, into the tube opening with a syringe or wash bottle.

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GENERAL DESCRIPTION, continued

1.3 Helpful Hints

1.3.1 To Reuse a Partially Emptied Cartridge

1. With the plunger fully retracted, attach cartridge to

the titrator.

2. Press the plunger release; then manually push the plunger

against the cartridge seal.

3. Attach a delivery tube. Hold the tip of the cartridge up. Eject

air and a few drops of titrant, zero the counter, and wipe the tip.

4. Titrate as usual.

1.3.2 To Calculate Titrant Volume Used

Normalities of many Hach titration cartridge solutions have been designed so that the number of digits used in a titration corresponds to the sample concentration in mg/L. To determine the volume used in mL, divide the Digital Titrator reading by 800.

1.3.3 To Fill Your Own Titration Cartridges

Cartridges may be cleaned and refilled, or new empty cartridges, Cat. No. 14495-01, can be purchased from Hach Company. See Figure 8. When preparing to refill old cartridges, push the cartridge seal out of the cartridge with air pressure applied through the tip. Cap the tip, fill with solution and reinsert the cartridge seal using care to avoid wrinkling the Teflon sheath. Filling also can be accomplished at the tip with a syringe.

Figure 8 Digital Titrator Cartridges

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GENERAL DESCRIPTION, continued

1.3.4 Verifying Technique

Whenever procedures are changed or new equipment is used, it is helpful to run a sample of known concentration. This technique will confirm the operator is following the procedure correctly and the new equipment is working properly. One objective important to Hach Company is making our tests self-verifying. This means Hach makes the tools available so the operator can check their own work for accurate results without relying on an outside lab or chemist.

For most of the tests in this manual, Table 1 on page 20 lists each procedure, the suggested standard, the volume of standard needed, the titration cartridge used, and the number of expected digits when the test is performed correctly. The suggested standards are Voluette possible because of their superior accuracy and stability.

To use titration standards follow these steps:

1. Select the procedure of interest and order the appropriate

standard. Use the given catalog numbers.

2. Measure the volume of standard to be used as the sample in

the procedure using a TenSette

or PourRite™ Ampules whenever

Pipet or Class A pipet.

3. Perform the procedure as written, adding deionized water

as necessary.

4. After titrating, the required number of digits should

approximately equal the expected digits.

Call Hach Technical and Customer Service (1-800-227-4224) for additional help.

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GENERAL DESCRIPTION, continued

Table 1 Titration Standards

Procedure

(Parameter)

Acid-Base:

Standard Description

(Cat. No.)

0.500 N H

(2121-26) 1.0

2SO4

Volum e o f

Standard

Acid

Base 0.500 N Na

2CO3

(14278-10)

Acidity 0.500 N H2SO4 (2121-26) 0.1

Alkalinity 0.500 N Na

Calcium*:

mg/L CaCO

10,000 mg/L CaCO

G.d.h. 10,000 mg/L CaCO

(14278-10) 0.1

2CO3

(2187-10)

Carbon

10,000 mg/L CO

(14275-10) 0.2

Dioxide

Chloride 12,500 mg/L Cl (14250-10) 0.1

(mL)

5.0

1.0

5.0

1.0

0.1

1.0

0.2

1.0

2.0

0.1

1.0

Titration Cartridge

(Cat. No.)

1.600 N NaOH (14379-01)

8.00 N NaOH (14381-01)

1.600 N H2SO4 (14389-01)

8.00 N H2SO4 (14391-01)

0.1600 N NaOH (14377-01)

1.600 N NaOH (14379-01)

0.1600 N H2SO4 (14388-01)

1.600 N H2SO4 (14389-01)

0.0800 M EDTA (14364-01)

0.800 M EDTA (14399-01)

0.1428 M EDTA (14960-01)

0.714 M EDTA (14959-01)

0.3636 N NaOH (14378-01)

3.636 N NaOH (14380-01)

0.2256 N Hg(NO

3)2

(14393-01)

0.2256 N AgNO

(14396-01)

1.128 N AgNO

(14397-01)

2.256 N Hg(NO

(921-01)

Expected

Digits

250 250

250

250 250

100 100

112 112

100

125 125 250 125

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GENERAL DESCRIPTION, continued

Table 1 Titration Standards (Continued)

Procedure

(Parameter)

Standard Description

(Cat. No.)

Chlorine ~50 mg/L Cl2

(14268-20)

(see certificate)

~25 mg/L Cl

(26300-20)

Chromate 1000 mg/L Cr

(2231 mg/L CrO

(14664-42)

Hardness:

mg/L CaCO

10,000 mg/L CaCO3 (2187-10)

G.d.h. 10,000 mg/L CaCO

Iron 50 mg/L Fe

(14254-10)

1000 mg/L Fe

(2271-42)

Oxygen,

Dissolved****

Sulfite 5000 mg/L SO

10 mg/L as DO

(401-1 1)

Volum e o f

Standard

(mL)

2.0

Titration Cartridge

(Cat. No.)

0.02256 N Na

(24091-01)

0.5

0.00564 N FEAS (22923-01)

1.0 0.2068 N Na2S2O3

)

0.1

(22676-01)

0.0800 M EDTA (14364-01)

0.1

0.0800 M CDTA (14402-01)

1.0

0.800 M EDTA (14399-01)

1.0

0.800 M CDTA (14403-01)

(2187-10) 0.2

0.1428 M EDTA (14960-01)

1.0

0.714 M EDTA (14959-01)

10.0

0.0716 M TitraV er (20817-01)

10.0

0.716 M TitraVer (20818-01)

100

0.2000 N Na (22675-01)

200

2.00 N Na

2S2O3

(14401-01)

(22674-10) 1.0 0.3998 N KIO

(14961-01)

2S2O3

–

Expected

Digits

varies**

varies***

223

100 100 100 100

112 112

200 100

500 100

250

* One to two drops of Magnesium Standard Solution (10 g/L as CaCO

) must be added to get a sharp

end point. These added drops will not change the results. ** The expected digits equal the volume of standard times the concentration on the certificate (e.g., 2 mL x 50 mg/L = 100 digits). *** The expected digits equals the volume of standard times the concentration on the certificate times the constant, 4. (Example: 0.5 mL x 50 mg/L x 4 = 100 digits) **** Add one Sulfamic Acid Powder Pillow to the volume of standard and follow Steps 10 to 12 in the Dissolved Oxygen Procedure. It is not necessary to add the first two reagents.

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GENERAL DESCRIPTION, continued

1.4 Adapting a Buret Titration to the Digital Titrator

Adapt any standard titration procedure using a buret to the Digital Titrator by using the following procedure.

1. Determine the approximate number of digits required. The

Digital Titrator dispenses 1 mL per 800 digits on the counter. Using the following equation, determine the digits required for your buret method.

Digits Required

NtmLt800××

-------------------------------------- -= N

Where:

Nt = Normality of buret titrant mLt = milliliters of buret titrant required for an average titration

= Normality of Digital Titrator cartridge

2. If the number of digits required is within the range of 70 to

350, you can use the procedure as written, substituting the Digital Titrator directly for the buret. Or, if the number of digits is outside of this range, make the following modifications:

a. If the number of digits required is more than 350, reduce

the sample size to save titrant.

b. If the number of digits required is less than 70, increase

the sample size to increase precision.

c. If the sample size is altered, adjust the amount of

buffering or indicating reagents by the same proportion.

3. When using the Digital Titrator for your buret method, note

the number of digits required for a sample titration. To convert the digits required to the equivalent number of milliliters if the buret method was used, calculate:

Equivalent Buret Milliliters Digits Required

----------------------

×=

800 x N

If the sample size was changed, adjust the equivalent buret milliliters accordingly. If the sample size was increased, reduce the equivalent buret milliliters; if the sample size was reduced increase the equivalent buret milliliters. Multiply the equivalent

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GENERAL DESCRIPTION, continued

buret milliliters by any normally used factors to calculate concentration in oz/gal, g/L, etc.

Example: Adapt a buret procedure, which normally requires about 20 mL of a 0.4 N titrant, to the Digital Titrator. Try an 8.0 N titration cartridge. The first equation above gives:

Digits Required

0.4 20× 800×

------------------------------------- 80 0 di g its==

Because this would use excessive titrant, reduce the sample size to one fourth its normal size to reduce the digits required to 200, well within the recommended range.

Upon completion of the titration using the smaller sample size, calculate the equivalent buret milliliters by the second equation above. If 205 were the digits required:

Equivalent Buret Milliliters

Multiply the 5.13 mL by 4 to account for the reduction in sample size to give the true equivalent buret milliliters of 20.5 mL. If the buret method called for multiplying the number of milliliters of titrant by a factor to calculate the concentration of a sample component, then multiply 20.5 by that factor.

1.5 Using PermaChem® Powder Pillows

1. Tap the PermaChem on a hard surface to collect the

powdered reagent in the bottom.

8.0

205 8.0×

------------------------ 5. 1 3 mL== 800 0.4×

2. Tear across on the dotted pillow line marked “TEAR”

holding the pillow away from your face.

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GENERAL DESCRIPTION, continued

3. Using two hands, Push both sides toward each other until

thumbs and forefingers form a diamond. Make sure to Crease the foil pack, so that it forms a spout.

4. Pour the pillow contents into the sample. The polyfilm lining

is specially formulated to deliver all the powder necessary for accurate results (no tapping on the vessel edge is necessary).

1.6 Safety

Safety is the responsibility of each individual when performing analysis procedures, and the analyst must develop and maintain good safety habits. Because many of the procedures in this methods handbook use potentially hazardous chemicals and apparatus, it is important that the analyst practice good laboratory techniques to minimize accidents. The following paragraphs present several techniques applicable to water analysis in the laboratory and in the field. They are not all inclusive, of course, nor do they apply only to the procedures provided in this handbook. They are general in nature but emphasize practices that are often key factors in personal injury incidents.

• Read labels carefully. Never remove the label from a reagent

container. When preparing a reagent or standard solution, be sure to label the container clearly and date it.

• A Material Safety Data Sheet (MSDS) comes with each

reagent. This sheet contains helpful information on first aid,

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GENERAL DESCRIPTION, continued

spill and disposal procedures, and precautionary measures and should be read before using the product.

• Warning labels also appear on some of the apparatus used

with the test procedures.

• Wear protective clothing when handling chemicals that cause

irritation or burns. Eye protection in particular is important to guard against spattering and splashes from accidental spills when caustic materials are being used.

• Use tongs or finger cots when transferring apparatus that

is hot.

• Use mechanical pipetters: Mouth pipetting could result in

accidentally ingesting dangerous chemicals. Make a habit of using mechanical pipet fillers for all pipetting. This will avoid mistakes that could cause serious injury.

• Use special care with dangerous chemicals and apparatus.

• Follow the test procedure steps carefully and observe all

precautionary measures. It is good practice to read the entire procedure carefully before beginning the procedure. Use safety equipment, such as pipet fillers, protective clothing, and ventilating hoods, appropriate for the test being conducted. Wipe up all spills promptly. Do not smoke or eat in an area where toxic or irritating chemicals are used. Use reagents and apparatus only as they were meant to be used and use them only as directed in the test procedure. Do not use damaged labware and malfunctioning equipment.

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TITRATION PROCEDURES

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ACID-BASE (10 to 4000 mg/L as meq/L)

Acid Determination

Method 8200

1. Select the sample

volume corresponding to the expected acid concentration in milliequivalents (meq)/L or normality (N) from Table 1.

Note: See Sampling and Storage following these steps.

5. Add the contents of

one Phenolphthalein Indicator Powder Pillow and swirl to mix. The solution should be colorless.

Note: Four drops of Phenolphthalein Indicator Solution may be substituted for the Phenolphthalein Indicator Powder Pillow.

2. Insert a clean

delivery tube into the appropriate Sodium Hydroxide Titration Cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step, for

assembly instructions.

6. Place the delivery

tube tip into the solution and swirl the flask while titrating with sodium hydroxide until a light pink color forms and persists for 30 seconds. Record the number of digits required.

3. Flush the delivery

tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

7. Calculate:

Digits Required x Digits Multiplier = Milliequivalents per Liter of Acid

Note: To determine the normality of the sample, divide the milliequivalents per liter obtained by 1000.

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 1 . Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

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ACID-BASE, continued

Tabl e 1

Range meq/L Range N

Sample

Volume (mL)

Titration

Cartridge

1-4 0.001-0.004 100 1.6 N NaOH

1.6 N H

4-10 0.004-0.01 50 1.6 N NaOH

1.6 N H

10-40 0.01-0.04 100 8 N NaOH

8 N H 8 N HCl

20-80 0.02-0.08 50 8 N NaOH

8 N H 8 N HCl

50-200 0.05-0.2 20 8 N NaOH

8 N H 8 N HCl

100-400 0.1-0.4 10 8 N NaOH

8 N H 8 N HCl

200-800 0.2-0.8 5 8 N NaOH

8 N H 8 N HCl

500-2000 0.5-2 2 8 N NaOH

8 N H 8 N HCl

1000-4000 1-4 1 8 N NaOH

8 N H 8 N HCl

2SO4

Catalog Number

14379-01 14389-01

14381-01 14391-01 14390-01

Digit

Multiplier

0.02

0.04

0.1

0.2

0.5

1.0

2.0

5.0

10.0

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ACID-BASE, continued

Base Determination

1. Select the sample

volume corresponding to the expected base concentration in milliequivalents/L or normality from Ta b l e 1.

5. Add the contents of

one Phenolphthalein Indicator Powder Pillow and swirl to mix. The solution should be a pink color.

Note: Four drops of Phenolphthalein Indicator Solution may be substituted for the Phenolphthalein Indicator Powder Pillow.

2. Insert a clean

delivery tube into the appropriate Hydrochloric Acid or Sulfuric Acid Titration Cartridge. Attach the cartridge to the titrator body. See General

Description Section, Step-by-Step, for

assembly instructions, if necessary.

6. Titrate with 8.00 N

hydrochloric acid or sulfuric acid until the solution is colorless. Record the number of digits required.

3. Flush the delivery

tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TitraStir Stir Plate. See General Description, Step 3 in Step-by-Step.

7. Calculate:

Digits Required x Digit Multiplier = Milliequivalents per Liter of Base

Note: To determine the normality of the sample, divide the milliequivalents per liter obtained by 1000.

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 1 . Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

Page 32

ACID-BASE, continued

Sampling and Storage

Accuracy Check

Interferences

Collect samples in clean plastic or glass bottles. Fill completely and cap tightly. Minimize agitation or prolonged exposure to air. Sample may be stored at least 24 hours by cooling to 4 °C (39 °F) or below if they cannot be analyzed immediately. Warm to room temperature before analyzing.

Using a clean Class A 20.00 mL pipet, transfer 20.00 mL 0.100 N NaOH Standard Solution (for base determination) or 20.00 mL

0.100 N Sulfuric Acid Standard Solution (for acid determination) to a clean 250-mL Erlenmeyer flask. Dilute to about 100 mL with deionized water.

Follow the procedure for base determination using 8.00 N HCl or H NaOH Titration Cartridge. About 200 digits of titrant should be required.

Highly colored or turbid samples may mask the color change at the end point. Use a pH meter for these samples.

Titration Cartridge or for acid determination using 8.00 N

2SO4

Summary of Method

A measured amount of sample is treated with a colorimetric indicator and then titrated with a strong acid or base. The amount of titrant used is directly proportional to the milliequivalents of acid or base in the sample. These titrations also can be performed using a pH meter instead of a colorimetric indicator. In this case, titrate to pH 7 or to the pH required.

REQUIRED REAGENTS

(varies with sample characteristics)

Description Cat. No.

Acid Determination Reagent Set (about 100 tests)

1-10 meq/L includes: (1) 942-99, (1) 14379-01 .......................................................24459-00

10-4,000 meq/L includes: (1) 942-99, (1) 14381-01 ................................................24460-00

Page 33

ACID-BASE, continued

REQUIRED REAGENTS, continued

Description Unit Cat. No.

Hydrochloric Acid Titration Cartridge, 8.00 N..............................................each .......14390-01

Phenolphthalein Indicator Powder Pillows ..............................................100/pkg ...........942-99

Sodium Hydroxide Titration Cartridge, 1.600 N ...........................................each .......14379-01

Sodium Hydroxide Titration Cartridge, 8.00 N .............................................each .......14381-01

Sulfuric Acid Titration Cartridge, 1.600 N ....................................................each .......14389-01

Sulfuric Acid Titration Cartridge, 8.00 N ......................................................each .......14391-01

Water, deionized...............................................................................................4 L ...........272-56

REQUIRED APPARATUS

Digital Titrator................................................................................................each .......16900-01

Flask, Erlenmeyer, 250-mL............................................................................each .......... 505-46

Select one or more based on sample concentration:

Cylinder, graduated, 5-mL .............................................................................each ...........508-37

Cylinder, graduated, 10-mL ...........................................................................each ...........508-38

Cylinder, graduated, 25-mL ...........................................................................each ...........508-40

Cylinder, graduated, 50-mL ...........................................................................each ...........508-41

Cylinder, graduated, 100-mL .........................................................................each ...........508-42

OPTIONAL REAGENTS

Phenolphthalein Indicator Solution, 5 g/L ............................................. 100 mL*...........162-32

Sodium Hydroxide Standard Solution, 0.100 N..................................... 1000 mL...........191-53

Sulfuric Acid Standard Solution, 0.100 N.............................................1000 mL

...........202-53

OPTIONAL APPARATUS

Bottle, wash, poly, 500-mL ............................................................................each ...........620-11

Clamp, 2-prong, extension, 38-mm................................................................each .......21145-00

Clamp Holder .................................................................................................each ...........326-00

Demineralizer Assembly, 473-mL .................................................................each .......21846-00

Delivery Tubes, with 180° hook...................................................................5/pkg .......17205-00

Delivery Tubes, 90° with hook for TitraStir

Pipet, volumetric, Class A, 1-mL...................................................................each .......14515-35

Pipet, volumetric, Class A, 2-mL...................................................................each .......14515-36

Pipet, volumetric, Class A, 5-mL...................................................................each .......14515-37

Pipet, volumetric, Class A, 10-mL.................................................................each .......14515-38

Pipet, volumetric, Class A, 20-mL.................................................................each .......14515-20

Pipet, volumetric, Class A, 50-mL.................................................................each .......14515-41

Pipet, volumetric, Class A, 100-mL...............................................................each .......14515-42

Support Ring Stand ........................................................................................each ...........563-00

TitraStir TitraStir

* Contact Hach for larger sizes.

Stir Plate, 115 Vac .........................................................................each .......19400-00

Stir Plate, 230 Vac .........................................................................each .......19400-10

Stir Plate ..............................5/pkg .......41578-00

Page 34

Page 35

Methods 8201 and 8202

ACIDITY (10 to 4000 mg/L as CaCO

)

Methyl Orange and Phenolphthalein (Total) Methods

Methyl Orange Method Method 8201

1. Select a sample

volume and a Sodium Hydroxide (NaOH) Titration Cartridge corresponding to the expected acidity concentration as mg/L calcium carbonate (CaCO

Note: See Sampling and Storage following these steps.

) from Table 1.

(mg/L as CaCO3)

500-2000

1000-4000

Range

10-40

40-160 100-400 200-800

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step for

assembly instructions, if necessary.

Sample Volum e

(mL)

100

50 20 10

3. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Tabl e 1

Titration Cartridge (N NaOH)

0.1600

1.600

Stir Plate. See

Catalog Number

14377-01 14377-01 14379-01 14379-01 14379-01 14379-01

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 1. Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

Note: Minimize agitation because dissolved gases in the sample such as carbon dioxide, hydrogen sulfide and ammonia may be lost and cause inaccurate results.

Digit

Multiplier

0.1

0.4

1.0

2.0

5.0

10.0

Page 36

ACIDITY, continued

5. Add the contents of

one Bromphenol Blue Indicator Powder Pillow and swirl to mix.

Note: Six drops of Bromphenol Blue Indicator Solution may be substituted in this step.

6. Place the delivery

tube tip into the solution and swirl the flask while titrating with sodium hydroxide from yellow to blue-violet (pH 3.7). Record the number of digits required.

Note: A solution of one pH

3.7 Buffer Powder Pillow and one Bromphenol Blue Indicator Powder Pillow in 50 mL of deionized water is recommended as a comparison for determining the proper end point color.

7. Calculate:

Digits Required x Digit Multiplier = mg/L as CaCO3 Methyl Orange Acidity

Page 37

ACIDITY, continued

Phenolphthalein (Total) Method Method 8202

1. Measure a second

portion of the sample selected from step 1 on page 35 into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

2. Add the contents of

one Phenolphthalein Indicator Powder Pillow and swirl to mix.

Note: Four drops of Phenolphthalein Indicator Solution may be substituted for the Phenolphthalein Indicator Powder Pillow.

Sampling and Storage

3. Titrate with sodium

hydroxide from colorless to a light pink color that persists for 30 seconds. Record the number of digits required.

Note: A solution of one pH

8.3 Buffer Powder Pillow and one Phenolphthalein Powder Pillow in 50 mL of deionized water is recommended as a comparison for determining the proper end point color.

4. Calculate:

Digits Required x Digit Multiplier = mg/L as CaCO Phenolphthalein Acidity

Collect samples in clean plastic or glass bottles. Fill completely and cap tightly. Minimize agitation or prolonged exposure to air. Samples may be stored at least 24 hours by cooling to 4 °C (39 °F) or below if they cannot be analyzed immediately. Warm to room temperature before analyzing.

Accuracy Check

Standard Additions Method

This accuracy check should be performed when interferences are suspected or to verify analytical technique.

1. Snap the neck off an Acidity Voluette

Ampule Standard,

0.500 N.

Page 38

ACIDITY, continued

Interferences

2. Use a TenSette® Pipet to add 0.1 mL of standard to the sample titrated in step 6 for methyl orange acidity or step 3 for phenolphthalein acidity. Resume titration back to the same end point. Note the number of digits required.

3. Repeat using two more additions of 0.1 mL. Titrate to the end point after each addition.

4. Each 0.1 mL addition of standard should require 25 additional digits of 1.600 N titrant or 250 digits of 0.1600 N titrant. If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

• Highly colored or turbid samples may mask the color change

at the end point. Use a pH meter for these samples.

• Chlorine may interfere with the indicators. Add one drop of

0.1 N Sodium Thiosulfate to eliminate this effect.

Summary of Method

• To determine the phenolphthalein acidity of samples

containing hydrolyzable metals such as iron, manganese or aluminum, use the following procedure:

a. Adjust the sample in step 1 for phenolphthalein acidity to

pH 4.0 or less (if necessary) by using the Digital Titrator with an acid titration cartridge of identical normality to the Sodium Hydroxide Titration Cartridge used. Record the number of digits of acid added to lower the pH.

b. Add five drops of 30% Hydrogen Peroxide Solution and

boil the solution for 2-5 minutes.

c. Cool to room temperature. Titrate following the

Phenolphthalein Procedure steps 2 and 3. Subtract the number of digits of acid added to lower the pH from the number of digits required in step 3 of the Phenolphthalein Procedure. Continue with step 4.

Bromphenol blue (pH 3.7) or phenolphthalein (pH 8.3) indicator is used to titrate the sample with sodium hydroxide to a

Page 39

ACIDITY, continued

colorimetric end point. Bromphenol blue gives a better end point than methyl orange indicator. Titration to pH 3.7 determines strong mineral acidity (also referred to as methyl orange acidity), whereas the pH 8.3 phenolphthalein end point includes weaker acid species as well, and represents the total acidity. The results are expressed in mg/L as calcium carbonate (CaCO specified pH.

REQUIRED REAGENTS

(varies with sample characteristics)

Description Unit Cat. No.

Acidity Reagent Set (about 100 tests) ..........................................................................22728-00

Includes: (1) 942-99, (1) 14377-01, (1) 14379-01, (1) 14550-99

Bromphenol Blue Powder Pillows ...........................................................100/pkg .......14550-99

Phenolphthalein Powder Pillows ..............................................................100/pkg ...........942-99

Sodium Hydroxide Titration Cartridge, 0.1600 N .........................................each .......14377-01

Sodium Hydroxide Titration Cartridge, 1.600 ..............................................each .......14379-01

Water, deionized...............................................................................................4 L...........272-56

) at a

REQUIRED APPARATUS

Digital Titrator................................................................................................each .......16900-01

Flask, Erlenmeyer, 250-mL............................................................................each ...........505-46

Select one or more based on sample concentration:

Cylinder, graduated, 10-mL ...........................................................................each ...........508-38

Cylinder, graduated 25-mL ............................................................................each ...........508-40

Cylinder, graduated 50-mL ............................................................................each ...........508-41

Cylinder, graduated, 100-mL .........................................................................each ...........508-42

OPTIONAL REAGENTS

Acidity Standard Solution, Voluette® Ampules,

0.500 N H

Bromphenol Blue Indicator Solution ............................................. 100 mL MDB .......14552-32

Buffer Powder Pillows, pH 3.7...................................................................25/pkg .......14551-68

Buffer Powder Pillows, pH 8.3...................................................................25/pkg ...........898-68

Hydrogen Peroxide Solution, 30%................................................. 200 mL MDB ...........144-45

Phenolphthalein Indicator Solution, 5 g/L ................................... 100 mL MDB* ...........162-32

Sodium Thiosulfate Standard Solution, 0.1 N.............................. 100 mL MDB* ...........323-32

* Contact Hach for larger sizes.

, 10 mL...........................................................................16/pkg .......14330-10

2SO4

Page 40

ACIDITY, continued

OPTIONAL APPARATUS

Description Unit Cat. No.

Bottle, wash, poly, 500-mL............................................................................ each........... 620-11

Clamp, 2-prong extension, 38-mm ............................................................... each....... 21145-00

Clamp Holder................................................................................................. each........... 326-00

Demineralizer Assembly, 473-mL................................................................. each....... 21846-00

Delivery Tubes, with 180° hook .................................................................. 5/pkg....... 17205-00

Delivery Tubes, 90° with hook for TitraStir

Hot Plate, 3½-inch circular, 115 V ................................................................ each....... 12067-01

Hot Plate, variable control, 4-inch circular, 230 V ........................................ each....... 12067-02

Pipet, TenSette Pipet Tips for 19700-01 TenSette

, 0.1 to 1.0 mL ..................................................................... each.......19700-01

Pipet................................................... 50/pkg....... 21856-96

Pipet, volumetric, Class A, 10-mL ................................................................each....... 14515-38

Pipet, volumetric, Class A, 20-mL ................................................................each....... 14515-20

Pipet, volumetric, Class A, 25-mL ................................................................each....... 14515-40

Pipet, volumetric, Class A, 50-mL ................................................................each....... 14515-41

Pipet, volumetric, Class A, 100-mL ..............................................................each....... 14515-42

Pipet Filler, safety bulb.................................................................................. each.......14651-00

sens

ion™1 Basic Portable pH Meter with electrode ...................................each....... 51700-10

Support Ring Stand........................................................................................ each...........563-00

TitraStir TitraStir Vo l u e t t e

Stir Plate, 115 Vac......................................................................... each....... 19400-00

Stir Plate, 230 Vac......................................................................... each....... 19400-10

Ampule Breaker Kit ...................................................................... each.........21968-0

Stir Plate.............................. 5/pkg.......41578-00

Page 41

ALKALINITY (10 to 4000 mg/L as CaCO

Phenolphthalein and Total Method

Method 8203

)

1. Select the sample

volume and Sulfuric Acid (H Cartridge corresponding to the expected alkalinity concentration as mg/L calcium carbonate (CaCO Table 1.

Note: See Sampling and Storage following these steps.

) Titration

2SO4

) from

Range

(mg/L as CaCO

10-40

40-160 100-400 200-800

500-2000

1000-4000

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step for

assembly instructions, if necessary.

Sample

)

Volum e (mL)

100

50 20 10

3. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Tabl e 1

Titration

Cartridge

0.1600

1.600

2SO4

)

Stir Plate. See

Catalog Number

14388-01 14388-01 14389-01 14389-01 14389-01 14389-01

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 1 . Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

Digit

Multiplier

0.1

0.4

1.0

2.0

5.0

10.0

Page 42

ALKALINITY, continued

5. Add the contents of

one Phenolphthalein Indicator Powder Pillow and swirl to mix.

Note: A solution of one pH

8.3 Buffer Powder Pillow and one Phenolphthalein Powder Pillow in 50 mL of deionized water is recommended as a comparison for determining the proper end point color.

Note: Four drops of Phenolphthalein Indicator Solution may be substituted for the Phenolphthalein Indicator Powder Pillow.

6. If the solution turns

pink, titrate to a colorless end point. Place the delivery tube tip into the solution and swirl the flask while titrating with sulfuric acid. Record the number of digits required.

Note: If the solution is colorless before titrating with sulfuric acid, the Phenolphthalein (P) Alkalinity is zero; proceed with step 8.

7. Calculate:

Digits Required x Digit Multiplier = mg/L CaCO3 P Alkalinity

8. Add the contents of

one Bromcresol GreenMethyl Red Indicator Powder Pillow to the flask and swirl to mix.

Note: Four drops of Methyl Purple Indicator Solution may be substituted for the Bromcresol Green-Methyl Red Indicator Powder Pillow. Titrate from green to a gray end point (pH

5.1).

Note: Four drops of Bromcresol Green-Methyl Red Indicator Solution may be substituted for the Bromcresol Green-Methyl Red Indicator Powder Pillow.

Page 43

ALKALINITY, continued

9. Continue the

titration with sulfuric acid to a light greenish blue-gray (pH 5.1), a light violet-gray (pH

4.8), or a light pink (pH

4.5) color, as required by the sample composition; see Table 2. Record the number of digits required.

Note: A solution of one Bromcresol Green-Methyl Red Powder Pillow and one pillow of the appropriate pH buffer in 50 mL of deionized water is recommended as a comparison for judging the proper end point color. If the pH 3.7 end point is used, use a Bromphenol Blue Powder Pillow instead of a Bromcresol Green-Methyl Red and titrate to a green end point.

10. Calculate:

Total Digits Required x Digit Multiplier = mg/L as CaCO3 Total (T or M) Alkalinity

Note: Carbonate, bicarbonate and hydroxide concentrations may be expressed individually using the relationships shown in Table 3.

Note: meq/L Alkalinity = mg/L as CaCO

÷ 50.

Tabl e 2

Sample Composition

Alkalinity about 30 mg/L Alkalinity about 150 mg/L Alkalinity about 500 mg/L Silicates or Phosphates present Industrial waste or complex system

End

Point

pH 4.9 pH 4.6 pH 4.3 pH 4.5 pH 4.5

Page 44

ALKALINITY, continued

Sampling and Storage

Collect samples in clean plastic or glass bottles. Fill completely and cap tightly. Avoid excessive agitation or prolonged exposure to air. Samples should be analyzed as soon as possible after collection but can be stored at least 24 hours by cooling to 4 °C (39 °F) or below. Warm to room temperature before analyzing.

Alkalinity Relationship Table

Total alkalinity primarily includes hydroxide, carbonate and bicarbonate alkalinities. The concentration of these alkalinities in a sample may be determined when the phenolphthalein and total alkalinities are known (see Table 3).

Table 3 Alkalinity Relationship

Row Result of Titration

Phenolphthalein

Alkalinity = 0

Phenolphthalein

Alkalinity equal to T otal

Alkalinity

Phenolphthalein

Alkalinity less than one

half of Total

Alkalinity

Phenolphthalein

Alkalinity equal to one

half of Total Alkalinity

Phenolphthalein

Alkalinity greater than

one half of Total

Alkalinity

Hydroxide

Alkalinity

is equal to:

00Total

Total Alkalinity 0 0

0 2 times the

0 Total Alkalinity 0

2 times the

Phenolphthalein

minus Total

Alkalinity

Carbonate Alkalinity

is equal to:

Phenolphthalein

Alkalinity

2 times the

difference between

Total and

Phenolphthalein

Alkalinity

Bicarbonate

Alkalinity

is equal to:

Alkalinity

Total Alkalinity minus

two times

Phenolphthalein

Alkalinity

To use the table follow these steps:

a. Does the phenolphthalein alkalinity equal zero? If yes,

use Row 1.

b. Does the phenolphthalein alkalinity equal total

alkalinity? If yes, use Row 2.

Page 45

ALKALINITY, continued

For example:

A sample has 170 mg/L as CaCO 250 mg/L as CaCO hydroxide, carbonate and bicarbonate alkalinities?

The phenolphthalein alkalinity does not equal 0 (it is 170 mg/L), see step a.

The phenolphthalein alkalinity does not equal total alkalinity (170 mg/L vs. 250 mg/L), see step b.

c. Multiply the phenolphthalein alkalinity by 2.

d. Select Row 3, 4, or 5 based on comparing the result of

step c with the total alkalinity.

e. Perform the required calculations in the appropriate row,

if any.

f. Check your results. The sum of the three alkalinity types

will equal the total alkalinity.

phenolphthalein alkalinity and

total alkalinity. What is the concentration of

The phenolphthalein alkalinity multiplied by 2 = 340 mg/L, see step c.

Because 340 mg/L is greater than 250 mg/L, select Row 5, see step d.

The hydroxide alkalinity is equal to: (see step e).

340 – 250 = 90 mg/L hydroxide alkalinity

The carbonate alkalinity is equal to:

250 – 170 = 80 80 x 2 = 160 mg/L carbonate alkalinity

The bicarbonate alkalinity equals 0 mg/L.

Check: (see step f).

90 mg/L hydroxide alkalinity + 160 mg/L carbonate alkalinity + 0 mg/L bicarbonate alkalinity = 250 mg/L

The above answer is correct; the sum of each type equals the total alkalinity.

Page 46

ALKALINITY, continued

Accuracy Check

Standard Additions Method

This accuracy check should be performed when interferences are suspected or to verify analytical technique.

1. Snap the neck off an Alkalinity Standard Solution Voluette

2. Use a TenSette

3. Repeat, using two more additions of 0.1 mL. Titrate to the

4. Each 0.1 mL addition of standard should require 25

Ampule, 0.500 N.

Pipet to add 0.1 mL of standard to the sample titrated in Steps 6 or 9. Resume titration back to the same end point. Record the number of digits needed.

end point after each addition.

additional digits of 1.600 N titrant or 250 digits of 0.1600 N titrant. If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Interferences

Summary of Method

• Highly colored or turbid samples may mask the color change

at the end point. Use a pH meter for these samples.

• Chlorine may interfere with the indicators. Add one drop of

0.1 N Sodium Thiosulfate to eliminate this interference.

The sample is titrated with sulfuric acid to a colorimetric end point corresponding to a specific pH. Phenolphthalein alkalinity is determined by titration to a pH of 8.3, as evidenced by the color change of phenolphthalein indicator, and indicates the total hydroxide and one half the carbonate present. M (methyl orange) or T (total) alkalinity is determined by titration to a pH between

3.7 and 5.1, and includes all carbonate, bicarbonate and hydroxide.

Page 47

ALKALINITY, continued

REQUIRED REAGENTS

(varies with sample characteristics)

Description Unit Cat. No

Alkalinity Reagent Set (about 100 tests) ......................................................................22719-00

Includes: (1) 942-99, (1) 943-99, (1) 14388-01, (1) 14389-01

Bromcresol Green-Methyl Red Powder Pillows......................................100/pkg ...........943-99

Phenolphthalein Powder Pillows ..............................................................100/pkg ...........942-99

Sulfuric Acid Titration Cartridge, 1.600 N ....................................................each .......14389-01

Sulfuric Acid Titration Cartridge, 0.1600 N ..................................................each .......14388-01

Water, deionized...............................................................................................4 L ...........272-56

REQUIRED APPARATUS

Digital Titrator................................................................................................each .......16900-01

Flask, Erlenmeyer, 250-mL............................................................................each ...........505-46

Select one or more based on sample concentration:

Cylinder, graduated, 10-mL ...........................................................................each ...........508-38

Cylinder, graduated, 25-mL ...........................................................................each ...........508-40

Cylinder, graduated, 50-mL ...........................................................................each ...........508-41

Cylinder, graduated, 100-mL .........................................................................each ...........508-42

OPTIONAL REAGENTS

Alkalinity Standard Solution Voluette® Ampules,

0.500 N Na

Bromcresol Green-Methyl Red Indicator Solution ........................ 100 mL MDB.......23292-32

Bromphenol Blue Indicator Solution ............................................. 100 mL MDB .......14552-32

Bromphenol Blue Powder Pillows ...........................................................100/pkg .......14550-99

Buffer Powder Pillows, pH 3.7...................................................................25/pkg .......14551-68

Buffer Powder Pillows, pH 4.5...................................................................25/pkg ...........895-68

Buffer Powder Pillows, pH 4.8...................................................................25/pkg ...........896-68

Buffer Powder Pillows, pH 5.1...................................................................25/pkg ...........897-68

Buffer Powder Pillows, pH 8.3...................................................................25/pkg ...........898-68

Methyl Purple Indicator Solution................................................... 100 mL MDB .......21934-32

Phenolphthalein Indicator Solution, 5 g/L ................................... 100 mL MDB* ...........162-32

Sodium Thiosulfate Standard Solution, 0.1 N................................ 100 mL MDB...........323-32

* Contact Hach for larger sizes.

, 10-mL ........................................................................16/pkg .......14278-10

2CO3

Page 48

ALKALINITY, continued

OPTIONAL APPARATUS

Description Unit Cat. No

Bottle, wash, poly, 500-mL............................................................................ each........... 620-11

Clamp, 2-prong extension, 38-mm ................................................................ each....... 21145-00

Clamp Holder................................................................................................. each........... 326-00

Demineralizer Assembly, 473-mL................................................................. each....... 21846-00

Delivery Tubes, with 180° hook .................................................................. 5/pkg....... 17205-00

Delivery Tubes, 90° with hook for TitraStir

Pipet, TenSette Pipet Tips for 19700-01 TenSette

0.1 to 1.0 mL ...................................................................... each.......19700-01

Pipet................................................... 50/pkg....... 21856-96

Pipet, volumetric, Class A, 10-mL ................................................................each....... 14515-38

Pipet, volumetric, Class A, 20-mL ................................................................each....... 14515-20

Pipet, volumetric, Class A, 25-mL ................................................................each....... 14515-40

Pipet, volumetric, Class A, 50-mL ................................................................each....... 14515-41

Pipet, volumetric, Class A, 100-mL ..............................................................each....... 14515-42

Pipet Filler, safety bulb.................................................................................. each.......14651-00

sens

ion™1 Basic Portable pH Meter with electrode ...................................each....... 51700-10

Support Ring Stand........................................................................................ each...........563-00

TitraStir TitraStir Vo l u e t t e

Stir Plate, 115 Vac......................................................................... each....... 19400-00

Stir Plate, 230 Vac......................................................................... each....... 19400-10

Ampule Breaker Kit ...................................................................... each.......21968-00

Stir Plate.............................. 5/pkg.......41578-00

Page 49

Method 10222

AMMONIA, HIGH RANGE (Ammonium Hydroxide)

5 to 35% (50 to 350 g/L) as NH3 or 5 to 60% (50 to 600 g/L) as NH4OH Acid Titration Method For use with Digital Titrator Test Kit, Model NI-HRDT (Cat. No. 29304-00)

Scope and Application: For determining high levels of aqua ammonia (ammonium hydroxide) in solutions used for chloramination of drinking water, for determining aqua ammonia feed pump rates or applications requiring the determination of high concentrations (g/L) of aqua ammonia.

CAUTION: Handling chemical samples, standards, and reagents can be dangerous. Review the Material Safety Data Sheets before handling chemicals. Wear eye protection and protective gloves when sampling.

Measuring Hints and General Test Information

• Wash all labware between tests. Contamination may alter test results. Rinse with clean

water (preferably deionized water).

• Hach recommends that reagent accuracy and analyst technique be checked using a

standard solution. Use the Ammonium Hydroxide solution listed on page 53 and follow the procedure in the Accuracy Check section on page 52.

Ammonia Titration Procedure

To ensure accurate results, read carefully before proceeding.

1. Insert a clean

delivery tube into the

8.00 N Sulfuric Acid Titration Cartridge. Attach the cartridge to the titrator body.

Note: See section 1.2 on page 13 for assembly instructions.

2. Flush the delivery

tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TitraStir section 1.2, step 4 on page 14.

Stir Plate. See

3. Fill a clean 125-mL

Erlenmeyer flask to about the 75-mL mark with deionized water.

Select sample

volume

4. Select a sample

volume for the expected concentration range from Table 1–Table 4 on page 51.

Note: See Sampling and Storage following these steps.

Page 50

AMMONIA, HIGH RANGE (Ammonium Hydroxide), continued

5. Attach a clean tip to

the pipettor and collect 100-µL (0.100 mL) of the aqua ammonia sample.

Note: Alternatively, use a TenSette 19700-01) with a clean tip.

Note: Review the instructions supplied with the 100-µL pipettor before using. Depress the plunger to the first stop and release to fill with sample.

Pipet (Cat. No.

6. Dispense the sample

below the liquid level in the flask. Dispense another 100 µL of sample into the flask (200 µL sample size). For other sample sizes, repeat until the required sample volume from step 4 has been added.

Note: Review the instructions supplied with the 100-µL pipettor before using. Depress the plunger to the first stop to fill; depress the plunger completely to dispense.

Find Digit

Multiplier

7. Add 1 mL (one full

dropper) of Wide Range pH Indicator Solution to the flask.

8. Swirl to mix. The

solution will turn purple.

9. Place the delivery

tube tip into the solution. Swirl the flask while titrating with the sulfuric acid titrant until the solution color changes from purple to orangered. Record the number of digits used.

10. Find the digit

multiplier from Ta b l e 1– Table 4 on page 51.

11. Calculate:

Digits Used x Digits Multiplier = concentration.

Note: See example on page 51.

Page 51

AMMONIA, HIGH RANGE (Ammonium Hydroxide), continued

Example

A bulk solution of aqua ammonia was delivered to a facility and was expected to have a concentration of 19 percent (19% NH portion of the sample was titrated to confirm the concentration.

The sample volume from Table 1 was found to be 0.2 mL (200 µL). The acid titration procedure was followed and 218 digits were used to reach the endpoint. The digit multiplier from Table 1 was found to be 0.085. The concentration of ammonia was found to be 18.5 percent:

% NH3218 digits 0.085×= % NH

18.5%=

Tables for Sample Volume and Digit Multiplier

Find the expected sample concentration from one of the tables for ammonia (% or g/L) or ammonium hydroxide (% or g/L) and then find the corresponding sample volume and Digit Multiplier:

Table 1 Ammonia (Percent)

). A

Expected % NH

5–15

10–35

Expected g/L NH

50–150

100–350

Expected % NH

5–15 10–30 25–60

Expected g/L NH

50–150 100–300 250–600

Table 3 Ammonium Hydroxide (Percent)

OH Sample Volume (mL) Digit Multiplier

Table 4 Ammonium Hydroxide (g/L)

OH Sample Volume (mL) Digit Multiplier

Sample Volume (mL) Digit Multiplier

0.5

0.2

Table 2 Ammonia (g/L)

Sample Volume (mL) Digit Multiplier

0.5

0.2

0.5

0.2

0.5

0.2

0.034

0.085

0.34

0.85

0.035

0.070

0.175

0.35

0.70

1.75

Page 52

AMMONIA, HIGH RANGE (Ammonium Hydroxide), continued

Sampling and Storage

Collect samples in clean glass bottles and cap tightly. Store in a cool place. Analyze as soon as possible.

Interferences

Other strong bases such as sodium hydroxide and potassium hydroxide will cause a positive interference in the test. Other alkaline substances, such as carbonates, will also react with the strong acid titrant. The amounts of these compounds should be insignificant in aqua ammonia solutions, however, and will not affect test results. High levels of alkalinity in the dilution water will cause high results. Be sure to use deionized water in step 3.

Accuracy Check

1. Fill an Erlenmeyer flask with approximately 75 mL of

deionized water.

2. Use a Class A 1.0-mL pipet to transfer 1.0 mL of a

10% ammonium hydroxide solution to the flask.

Precision

3. Add 1 mL (one full dropper) of Wide Range pH Indicator

Solution to the flask. The solution will turn a purple color.

4. Titrate the sample using the Digital Titrator to the red-orange

endpoint with 8.00 N sulfuric acid. The titration should use 270–300 digits of 8.00 N sulfuric acid to reach the endpoint.

Note: If the number of digits used to reach the endpoint does not fall

within the 270–300 digit range, make sure that the dilution water does not contain excess alkalinity and that the 1.0 mL of ammonium hydroxide is measured accurately. Ammonium hydroxide solutions that are left open to the atmosphere will lose ammonia over time and will give low results. Store the solutions in tightly-capped bottles.

In a single laboratory using an ammonium hydroxide solution of

9.71%, a single operator obtained a standard deviation of ± 0.1% as NH

OH.

Page 53

AMMONIA, HIGH RANGE (Ammonium Hydroxide), continued

Summary of Method

Ammonia exists in water as ammonium hydroxide. The hydroxide ions are titrated with sulfuric acid to a colorimetric end point corresponding to a pH value between 4.4 and 6.2. The hydroxide concentration is directly proportional to the volume of acid titrant used.

REQUIRED REAGENTS

Description Cat. No.

HR Aqua Ammonia Reagent Set (about 100 tests).......................................................29305-00

Includes: (1) 14391-01, (1) 23293-32

Sulfuric Acid Titration Cartridge, 8.00 N................................................each .......14391-01

Wide Range pH Indicator Solution.................................................... 100 mL.......23293-32

Water, deionized...............................................................................................4 L ...........272-56

REQUIRED APPARATUS

Digital Titrator Assembly...............................................................................each .......16900-01

Delivery Tubes, J hook .................................................................................5/pkg .......17205-00

Flask, Erlenmeyer, 125-mL............................................................................each .......... 505-43

Pipettor, 100 µL..............................................................................................each .......22753-00

Pipettor Tips, for 22753-00 ........................................................................10/pkg .......22754-10

OPTIONAL REAGENTS AND APPARATUS

Ammonium Hydroxide Solution, 10%..................................................... 500 mL.......14736-49

Bottle, sampling, square glass 118 mL ........................................................3/pkg .......21631-03

Bottle, wash, poly, 500-mL ............................................................................each ...........620-11

Demineralizer Bottle, 473-mL .......................................................................each .......21846-00

Delivery Tubes, 90° with hook for TitraStir

Gloves, chemical resistant, size 9–9½*...........................................................pair .......24101-04

Goggles, safety ...............................................................................................each .......25507-00

Hypochlorite, HR (Bleach) Digital Titrator Kit .............................................each .......26871-00

Notebook, field...............................................................................................each .......20918-00

Pipet, TenSette, 0.1–1.0 mL ...........................................................................each .......19700-01

Pipet, volumetric, Class A, 1.0 mL ................................................................each .......14515-35

Pipet Bulb.......................................................................................................each .......14651-00

Pipet Tips, for TenSette Pipet 19700-01 ....................................................50/pkg .......21856-96

Tech Board with built-in calculator................................................................each .......27473-00

TitraStir TitraStir

Stir Plate, 115 VAC .......................................................................each .......19400-00

Stir Plate, 230 VAC .......................................................................each .......19400-10

Pipettor Tips, for 22753-00 ....................................................................1000/pkg .......22754-00

* Other sizes available.

Stir Plate ..............................5/pkg .......41578-00

Page 54

Page 55

CARBON DIOXIDE (10 to 1000 mg/L as CO

Using Sodium Hydroxide

1. Select a sample size

and a Sodium Hydroxide (NaOH) Titration Cartridge corresponding to the expected carbon dioxide (CO concentration; see Ta bl e 1.

Note: See Sampling and Storage following these steps.

)

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step for

assembly instructions if necessary.

3. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

Method 8205

)

4. Collect a water

sample directly into the titration flask by filling to the appropriate mark.

Note: Minimize agitation because carbon dioxide may be lost.

Note: For most accurate results, check the calibration of the Erlenmeyer flask by measuring the proper volume in a graduated cylinder. Mark the proper volume on the flask with a permanent marker.

Range

(mg/L as CO2)

10-50

20-100

100-400

200-1000

Sample

Volum e (mL)

200 100 200 100

Tabl e 1

Titration Cartridge (N NaOH)

0.3636

3.636

Catalog Number

14378-01 14378-01 14380-01 14380-01

Digit

Multiplier

0.1

0.2

1.0

2.0

Page 56

CARBON DIOXIDE, continued

5. Add the contents of

one Phenolphthalein Indicator Powder Pillow and mix.

Note: Four drops of Phenolphthalein Indicator Solution may be substituted for the Phenolphthalein Indicator Powder Pillow.

Note: If a pink color forms, no carbon dioxide is present.

6. Place the delivery

tube tip into the solution and swirl the flask gently while titrating with sodium hydroxide from colorless to a light pink color that persists for 30 seconds. Record the number of digits required.

Sampling and Storage

7. Calculate:

Total Digits Required x Digit Multiplier = mg/L as CO2

Collect samples in clean plastic or glass bottles. Fill completely and cap tightly. Avoid excessive agitation or prolonged exposure to air. Analyze samples as soon as possible after collection. If immediate analysis is not possible, the samples may be stored for at least 24 hours by cooling to 4 °C (39 °F) or below. Before analysis, warm the samples to room temperature.

Accuracy Check

Standard Additions Method

This accuracy check should be performed when interferences are suspected or to verify analytical technique.

1. Snap the neck off a Carbon Dioxide Standard Solution

Voluette

Ampule, 10,000 mg/L CO2.

Page 57

CARBON DIOXIDE, continued

2. Use a TenSette® Pipet to add 0.1 mL of standard to the

sample titrated in step 6. If using 0.3636 N titrant, use 1.0 mL of standard. Resume titration back to the same end point. Record the number of digits required.

3. Repeat, using additions of 0.2 mL and 0.3 mL (2.0 and 3.0).

Titrate to the same end point after each addition.

4. Each addition of standard should require 50 additional digits

of titrant. If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Interferences

• Other acid components in the sample will be titrated and

interfere directly in this determination.

• Sodium hydroxide standard solutions tend to lose strength

slowly with age and should be checked periodically by titrating a known standard. Check the solution frequently (monthly) by titrating 50 mL of Potassium Acid Phthalate Standard Solution, 100 mg/L CO Indicator Solution. The titration should require 5.00 mL of titrant. If the volume required for this titration is greater than

5.25 mL, discard the sodium hydroxide and replace it with a fresh supply.

, using Phenolphthalein

Summary of Method

Acidity due to carbon dioxide in a sample is titrated with sodium hydroxide to a phenolphthalein end point. Strong acids are assumed to be absent or of insignificant concentration. Request Hach’s Water Analysis Handbook, Publication 8376, to obtain additional information on carbon dioxide determinations.

Page 58

CARBON DIOXIDE, continued

REQUIRED REAGENTS

(varies with sample characteristics)

Description Unit Cat. No.

Carbon Dioxide Reagent Set (about 100 tests) ............................................................22727-00

Includes: (1) 942-99, (1) 14378-01, (1) 14380-01

Phenolphthalein Powder Pillows ............................................................. 100/pkg...........942-99

Sodium Hydroxide Titration Cartridge, 0.3636 N......................................... each....... 14378-01

Sodium Hydroxide Titration Cartridge, 3.636 N........................................... each....... 14380-01

Water, deionized...............................................................................................4 L........... 272-56

REQUIRED APPARATUS

Digital Titrator ............................................................................................... each.......16900-01

Select one or more based on sample concentration:

Flask, Erlenmeyer, 250 mL............................................................................ each........... 505-46

Flask, Erlenmeyer, 125 mL............................................................................ each........... 505-43

OPTIONAL REAGENTS

Carbon Dioxide Standard Solution Voluette® Ampules,

10,000 mg/L as CO

Phenolphthalein Indicator Solution, 5 g/L....................................100 mL MDB*.......... 162-32

Potassium Acid Phthalate Standard Solution, 100 mg/L as CO Potassium Acid Phthalate Standard Solution, 400 mg/L as CO

, 10 mL .................................................................. 16/pkg.......14275-10

.............100 mL.......... 2261-42

.............500 mL......... 1885-49

OPTIONAL APPARATUS

Clamp, 2-prong extension, 38 mm ................................................................ each.......21145-00

Clamp Holder................................................................................................. each........... 326-00

Delivery Tubes, with 180° hook .................................................................. 5/pkg....... 17205-00

Delivery Tubes, 90° with hook for TitraStir Pipet, TenSette Pipet Tips for 19700-01 TenSette

, 0.1 to 1.0 mL ..................................................................... each.......19700-01

Pipet................................................... 50/pkg....... 21856-96

Pipet Filler, safety bulb .................................................................................. each ....... 14651-00

sens

ion™1 Basic Portable pH Meter with electrode ...................................each....... 51700-10

Support Ring Stand........................................................................................ each...........563-00

TitraStir TitraStir Vo l u e t t e

* Contact Hach for larger sizes.

Stir Plate, 115 Vac......................................................................... each....... 19400-00

Stir Plate, 230 Vac......................................................................... each....... 19400-10

Ampule Breaker Kit ...................................................................... each.......21968-00

Stir Plate.............................. 5/pkg.......41578-00

Page 59

CHELANT, FREE (0 to 20.0 mg/L as CaCO

Using Magnesium Chloride

Method 8352

)

1. Insert a clean

delivery tube into the Magnesium Chloride Titration Cartridge. Attach the cartridge to the titrator body. See

General Description, Step-By-Step, for

assembly instructions.

2. Hold the Digital

Titrator with the cartridge tip pointing up. Turn the delivery knob until a few drops of titrant are expelled. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

3. Use a graduated

cylinder to measure the 100 mL of sample into a 125-mL Erlenmeyer flask.

Note: Filter sample if necessary. If sample is boiler water or highly alkaline, refer to Interferences following these steps.

4. Using the 1-mL

calibrated dropper, add 2 mL of Hardness 1 Buffer Solution to the flask and swirl to mix.

Page 60

CHELANT, FREE, continued

5. Add the contents of

one ManVer Hardness Indicator Powder Pillow to the flask and swirl to mix. If the solution turns blue, free chelant is present. Proceed to step 6. If the solution turns red, a deficiency of chelant exists.

Note: Four drops of ManVer Hardness Indicator Solution or a 0.1 g scoop of ManVer 2 Hardness Indicator Powder may be substituted in this step.

Accuracy Check

6. Place the delivery

tube tip into the solution. While swirling the flask, titrate until a red-violet color appears. Record the number of digits required.

7. Calculate:

Digits Required x 0.10

= mg/L Free Chelant

(as CaCO3)

Note: The results may be expressed as mg/L tetrasodium EDTA (digits required x 0.38 = mg/L as Na

EDTA).

Standard Additions Method

This accuracy check should be performed when interferences are suspected or to verify analytical technique.

1. Use a TenSette

Pipet to add 0.4 mL of 0.035 N EDTA Standard Solution to the solution titrated in step 6. Resume titration back to the same end point. Record the number of digits required.

2. Each 0.4 mL addition of standard should require 70

additional digits of 0.0800 M titrant. If this increase does not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Page 61

CHELANT, FREE, continued

Interferences

• If chelant residual in boiler water is being analyzed, adjust

the pH before adding the Hardness 1 Buffer Solution as follows:

a. To another 100-mL sample, add 2 drops of

Phenolphthalein Indicator Solution.

b. Counting the drops, add 5.25 N Sulfuric Acid Standard

Solution one drop at a time until the solution changes from pink to colorless. Discard this sample.

c. To the actual 100-mL sample, add the same number of

drops of 5.25 N Sulfuric Acid Standard Solution before adding the buffer in step 4.

• Orthophosphate causes a slow end point. Polyphosphate must

be absent for accurate results.

• All apparatus must be scrupulously clean and rinsed

frequently with acid and deionized water to remove any hardness present on the plastic or glass.

Summary of Method

• Run reagent blanks occasionally, using deionized or distilled

water in place of the sample. Subtract the value of the blank from the sample value before recording the final answer.

Chelant residual is determined by titration with a standard solution of magnesium chloride at pH 10. The end point is determined by a color change from blue to red-violet.

Page 62

CHELANT, FREE, continued

REQUIRED REAGENTS

Description Unit Cat. No.

Hardness 1 Buffer Solution......................................................... 100 mL MDB..............424-32

ManVer

Magnesium Chloride Titration Cartridge, 0.0800 M..................................each..........20625-01

REQUIRED APPARATUS

Cylinder, graduated, 100-mL......................................................................each .............. 508-42

Digital Titrator ............................................................................................ each .......... 16900-01

Flask, Erlenmeyer, 125 mL.........................................................................each.............. 505-43

OPTIONAL REAGENTS

EDTA Standard Solution, 0.035 N ............................................. 100 mL MDB .......... 23499-32

ManVer ManVer

Phenolphthalein Indicator Solution, 5 g/L................................. 100 mL MDB

Sulfuric Acid Standard Solution, 5.25 N .................................... 100 mL MDB............2449-32

Water, deionized............................................................................................4 L.............. 272-56

OPTIONAL APPARATUS

Clamp, 2-prong extension, 38 mm..............................................................each..........21145-00

Clamp Holder..............................................................................................each.............. 326-00

Clippers (shears), 7.25 inch ........................................................................each.......... 23694-00

Delivery Tubes, with 180° hook ...............................................................5/pkg.......... 17205-00

Delivery Tubes, 90° with hook for TitraStir

Filter Paper, folded, 12.5 cm................................................................. 100/pkg ............ 1894-57

Flask, Erlenmeyer, 250 mL.........................................................................each.............. 505-46

Funnel, analytical, poly, 65 mm..................................................................each............ 1083-67

Pipet, TenSette Pipet Tips for 19700-01 TenSette

Spoon, measuring, 0.5 gram .......................................................................each.............. 907-00

Support Ring Stand.....................................................................................each .............. 563-00

TitraStir TitraStir

2 Hardness Indicator Powder Pillows...................................100/pkg.............. 851-99

2 Hardness Indicator Powder....................................................113 g.............. 280-14

2 Hardness Indicator Solution ...................................100 mL MDB*..............425-32

............. 162-32

Stir Plate........................... 5/pkg .......... 41578-00

, 0.1 to 1.0 mL ..................................................................each .......... 19700-01

Pipet................................................50/pkg.......... 21856-96

Stir Plate, 115 Vac......................................................................each .......... 19400-00

Stir Plate, 230 Vac......................................................................each .......... 19400-10

* Contact Hach for larger sizes.

Page 63

CHELANT, TOTAL (0 to 40.0 mg/L as Na

Using Bismuth Nitrate

EDTA)

Method 8350

1. Insert a clean

delivery tube into the Bismuth Nitrate Titration Cartridge. Attach the cartridge to the titrator body. See General

Description, Step-ByStep, for assembly

instructions.

2. Hold the Digital

Titrator with the cartridge tip pointing up. Turn the delivery knob until a few drops of titrant are expelled. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

3. Use a graduated

cylinder to measure the 50 mL of clear sample into a 125-mL Erlenmeyer flask.

Note: Filtration is required for turbid samples.

4. Add the contents of

one Ascorbic Acid Powder Pillow to the flask and swirl to mix.

Page 64

CHELANT, TOTAL, continued

5. Add the contents of

one Methylthymol Blue Powder Pillow to the flask and swirl to mix.

Interferences

6. If the solution in the

flask is yellow, add one drop of 5.25 N Sulfuric Acid Standard Solution.

If the solution is blue, add 5.25 N Sulfuric Acid Standard Solution dropwise until the solution changes to yellow. Add one additional drop.

7. Place the delivery

tube tip into the solution. While swirling the flask, titrate with the Bismuth Nitrate until the color changes from yellow to blue-green. Record the number of digits required.

Note: Titrate slowly as the end point is approached.

Note: For best results, determine a reagent blank. Use 50 mL of deionized water in step 3. Subtract the number of digits required for the reagent blank from the number of digits required for titrating the sample.

8. Calculate the final

concentration:

Digits Required x 0.188 = Total Chelant (as mg/L Na4EDTA)

Interference from ferric iron (Fe3+) is minimized by adding ascorbic acid. The end point should by approached slowly in samples containing ferric iron because the iron decreases the sharpness of the color change.

Summary of Method

Total chelant is determined by titrating an acid sample with bismuth nitrate the presence of methylthymol blue indicator. The end point is signaled by a color change from yellow to blue-green.

Page 65

CHELANT, TOTAL, continued

REQUIRED REAGENTS

Description Unit Cat. No.

Ascorbic Acid Powder Pillows..............................................................100/pkg ..........14577-99

Bismuth Nitrate Titration Cartridge, 0.0200 M.......................................... each ..........24345-01

Methylthymol Blue Indicator Powder Pillows ........................................50/pkg ..........22847-99

Sulfuric Acid Standard Solution, 5.25 N.....................................100 mL MDB ............2449-32

REQUIRED APPARATUS

Cylinder, graduated, poly, 100 mL............................................................. each ............1081-42

Delivery Tubes, 90° with hook for TitraStir

Digital Titrator............................................................................................ each ..........16900-01

Flask, Erlenmeyer, 125 mL ........................................................................ each ..............505-43

Stir Bar, analytical, Teflon-coated, 50 mm................................................. each ..........20953-55

TitraStir TitraStir

Stir Plate, 115 Vac ..................................................................... each ..........19400-00

Stir Plate, 230 Vac ..................................................................... each ..........19400-10

OPTIONAL REAGENTS

Water, deionized........................................................................................... 4 L ..............272-56

OPTIONAL APPARATUS

Clamp, 2-prong extension, 38 mm ............................................................ each ..........21145-00

Clamp Holder ............................................................................................. each ..............326-00

Clippers (shears), 7.25 inch........................................................................ each ..........23694-00

Delivery Tubes, with 180° hook................................................................5/pkg ..........17205-00

Filter paper, folded, 12.5 cm .................................................................100/pkg ............1894-57

Flask, Erlenmeyer, 250 mL ........................................................................ each ..............505-46

Funnel, analytical, poly, 65 mm ................................................................. each ............1083-67

Stir Plate ...........................5/pkg ..........41578-00

Page 66

Page 67

CHLORIDE

Mercuric Nitrate and Silver Nitrate Methods

Mercuric Nitrate Method (10 to 8000 mg/L as Cl

Methods 8206 and 8207

–

) Method 8206

1. Select the sample

volume and Mercuric Nitrate Titration Cartridge corresponding to the expected chloride concentration from Table 1.

Range

(mg/L as Cl-)

10-40

40-160 100-400 200-800

500-2000 1000-4000 2000-8000

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description Section, Step-by-Step,

for assembly instructions if necessary.

Tabl e 1

Sample

Volum e

(mL)

100

50 20 10

(N Hg(NO

3. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, step 3 in Step-by-Step.

Titration

Cartridge

0.2256

2.256

Stir Plate. See

Number

)

3)2

14393-01 14393-01

Catalog

921-01 921-01 921-01 921-01 921-01

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 1 . Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

Note: See following these steps.

Digit

Multiplier

0.1

0.4

1.0

2.0

5.0

10.0

20.00

Page 68

CHLORIDE, continued

5. Add the contents of

one Diphenylcarbazone Powder Pillow and swirl to mix.

Note: Results will still be accurate if a small amount of the powder does not dissolve.

6. Place the delivery

tube tip into the solution and swirl the flask while titrating with mercuric nitrate from a yellow to light pink color. Record the number of digits required.

7. Calculate:

Digits Required x Digit Multiplier = mg/L Chloride

Note: Results may be expressed as mg/L sodium chloride by multiplying the mg/L chloride by 1.65.

Note: meq/L Chloride =

mg/L Cl

÷ 35.45.

Silver Nitrate Method (10 to 10000 mg/L as Cl–) Method 8207

1. Select the sample

volume and Silver Nitrate Titration Cartridge corresponding to the expected chloride concentration from Table 2.

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description Section, Step-by-Step,

for assembly instructions if necessary.

3. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

4. Use a graduated

cylinder or pipet to measure the sample volume from Table 2 . Transfer the sample into a clean 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water, if necessary.

Note: See following these steps.

Page 69

CHLORIDE, continued

Tabl e 2

Range

(mg/L as Cl-)

10-40

25-100

100-400

250-1000 1000-4000

2500-10000

5. Add the contents of

one Chloride 2 Indicator Powder Pillow and swirl to mix.

Note: Results will still be accurate if a small amount of the powder does not dissolve.

Sample

Volum e

(mL)

100

40 50 20

5 2

(N AgNO

6. Place the delivery

tube tip into the solution and swirl the flask while titrating with silver nitrate from a yellow to red-brown color. Record the number of digits required.

Titration

Cartridge

)

0.2256

1.128

7. Calculate:

Digits Required x Digit Multiplier = mg/L Chloride

Note: Results may be expressed as mg/L sodium chloride by multiplying the mg/L chloride by 1.65.

Catalog Number

14396-01 14396-01 14397-01 14397-01 14397-01 14397-01

Digit

Multiplier

0.1

0.25

1.0

2.5

10.0

25.0

Sampling and Storage

Note: meq/L Chloride =

mg/L Cl

÷ 35.45.

Collect at least 100 to 200 mL of sample in a clean glass or polyethylene container. Samples may be stored up to 7 days before analysis.

Page 70

CHLORIDE, continued

Accuracy Check

Standard Additions Method

This accuracy check should be performed when interferences are suspected or to verify analytical technique.

1. Snap the neck off a Chloride Standard Solution Voluette

–

Ampule, 12,500 mg/L Cl

2. Use a TenSette

sample after titration in step 6. Resume titration back to the same end point. Record the number of digits required.

3. Repeat, using additions of 0.2 and 0.3 mL. Titrate to the end

point after each addition.

4. Each 0.1 mL addition of standard should require 12.5

additional digits of 2.256 N titrant, 25 digits of 1.128 N titrant, or 125 digits of 0.2256 N titrant. If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Pipet to add 0.1 mL of standard to the

Interferences Using the Mercuric Nitrate Method

• Chromate, ferric iron, and sulfite in excess of 10 mg/L

interfere with this method.

• Eliminate sulfite interference by adding three drops of

hydrogen peroxide, 30%, in step 4.

• Remove sulfide interference by adding the contents of one

Sulfide Inhibitor Reagent Powder Pillow to about 125 mL of sample, mixing for one minute, and filtering through a folded filter paper.

• Iodide and bromide interfere directly and titrate as chloride.

• Neutralize strongly alkaline or acid samples to a pH of 2 to 7

with 5.25 N Sulfuric Acid Standard Solution or 5.0 N Sodium Hydroxide Standard Solution. Determine the amount of acid or base necessary in a separate sample because pH electrodes will introduce chloride into the sample.

Page 71

CHLORIDE, continued

Interferences Using the Silver Nitrate Method

• Iron in excess of 10 mg/L masks the end point.

• Orthophosphate in excess of 25 mg/L will precipitate

the silver.

• Sulfite in excess of 10 mg/L interferes. Eliminate sulfite

interference by adding three drops of 30% hydrogen peroxide in step 4.

• Remove sulfide interference by adding the contents of one

Sulfide Inhibitor Reagent Powder Pillow to about 125 mL of sample, mixing for one minute, and filtering through a folded filter paper.

• Cyanide, iodide, and bromide interfere directly and titrate

as chloride.

• Neutralize strongly alkaline or acid samples to a pH of 2 to 7

Summary of the Mercuric Nitrate Method

When using Mercuric Nitrate Standard Solution, the sample is titrated under acid conditions in the presence of diphenylcarbazone indicator. Upon addition of a slight excess of mercuric ion, a pink-purple complex is formed with the indicator, signaling the end point.

Summary of the Silver Nitrate Method

The sample is titrated with Silver Nitrate Standard Solution in the presence of potassium chromate (from the Chloride 2 Indicator Powder). The silver nitrate reacts with the chloride present to produce insoluble white silver chloride. After all the chloride has been precipitated, the silver ions react with the excess chromate present to form a red-brown silver chromate precipitate, marking the end point of the titration.

Request Hach’s Water Analysis Handbook, Publication 8376, to obtain additional information on chloride determinations.

Page 72

CHLORIDE, continued

REQUIRED REAGENTS FOR THE MERCURIC NITRATE METHOD

Description Unit Cat. No.

Mercuric Nitrate Chloride Reagent Set (about 100 tests) ............................................ 22726-00

Includes: (2) 836-46, (1) 921-01, (1) 14393-01

Diphenylcarbazone Reagent Powder Pillows .......................................... 100/pkg...........836-99

Mercuric Nitrate Titration Cartridge, 0.2256 N............................................. each....... 14393-01

Mercuric Nitrate Titration Cartridge, 2.256 N............................................... each........... 921-01

Water, deionized...............................................................................................4 L........... 272-56

REQUIRED REAGENTS FOR THE SILVER NITRATE METHOD

Silver Nitrate Chloride Reagent Set (about 50 tests).................................................... 22880-00

Includes: (2) 1057-66, (1) 14396-01, (1) 14397-01

Chloride 2 Indicator Powder Pillows......................................................... 50/pkg......... 1057-66

Silver Nitrate Titration Cartridge, 0.2256 N .................................................. each....... 14396-01

Silver Nitrate Titration Cartridge, 1.128 N.................................................... each....... 14397-01

Water, deionized...............................................................................................4 L........... 272-56

REQUIRED APPARATUS FOR THE MERCURIC NITRATE METHOD AND SILVER NITRATE METHOD

Clippers, for opening pillows......................................................................... each...........968-00

Digital Titrator ............................................................................................... each.......16900-01

Flask, Erlenmeyer, 250-mL ...........................................................................each........... 505-46

Select one or more based on sample concentration:

Cylinder, graduated, 10-mL........................................................................... each...........508-38

Cylinder, graduated, 25-mL........................................................................... each...........508-40

Cylinder, graduated, 50-mL........................................................................... each...........508-41

Cylinder, graduated, 100-mL......................................................................... each...........508-42

OPTIONAL REAGENTS

Chloride Standard Solution, 1000 mg/L Cl-.............................................500 mL...........183-49

Chloride Standard Solution Voluette

12,500 mg/L Cl

, 10-mL......................................................................... 16/pkg....... 14250-10

Hydrogen Peroxide, 30%, ACS ................................................................200 mL...........144-45

Sodium Hydroxide Standard Solution, 5.0 N .................................100 mL MDB......... 2450-32

Sulfide Inhibitor Powder Pillows ............................................................. 100/pkg.........2418-99

Sulfuric Acid Standard Solution, 5.25 N ........................................100 mL MDB.........2449-32

Ampules,

Page 73

CHLORIDE, continued

OPTIONAL APPARATUS

Description Unit Cat. No.

Bottle, wash, poly, 500-mL ............................................................................each ...........620-11

Clamp, 2-prong extension, 38-mm ................................................................each .......21145-00

Clamp Holder .................................................................................................each ...........326-00

Demineralizer Assembly, 473-mL .................................................................each .......21846-00

Delivery Tubes, with 180° hook...................................................................5/pkg .......17205-00

Delivery Tubes, 90°

Filter Paper, folded, 12.5 cm ....................................................................100/pkg .........1894-57

Funnel, poly, 65-mm ......................................................................................each.........1083-67

Pipet, TenSette Pipet Tips for 19700-01 TenSette

Pipet, volumetric, Class A, 2-mL...................................................................each .......14515-36

Pipet, volumetric, Class A, 5-mL...................................................................each .......14515-37

Pipet, volumetric, Class A, 10-mL.................................................................each .......14515-38

Pipet, volumetric, Class A, 20-mL.................................................................each .......14515-20

Pipet, volumetric, Class A, 25-mL.................................................................each .......14515-40

Pipet, volumetric, Class A, 50-mL.................................................................each .......14515-41

Pipet, volumetric, Class A, 100-mL...............................................................each .......14515-42

Pipet Filler, safety bulb...................................................................................each .......14651-00

sens

ion™1 Basic Portable pH Meter with electrode....................................each .......51700-10

Support Ring Stand ........................................................................................each ...........563-00

TitraStir TitraStir Voluette

Stir Plate, 115 Vac .........................................................................each .......19400-00

Stir Plate, 230 Vac .........................................................................each .......19400-10

Ampule Breaker Kit.......................................................................each .......21968-00

with hook for TitraStir® Stir Plate...............................5/pkg .......41578-00

, 0.1 to 1.0 mL......................................................................each .......19700-01

Pipet ...................................................50/pkg .......21856-96

Page 74

Page 75

CHLORINE, FREE AND TOTAL (0 to 3.00 mg/L as Cl

DPD-FEAS Method

Method 8210

)

1. Insert a clean

delivery tube into a

0.00564 N Ferrous Ethylenediammonium Sulfate (FEAS) Titration Cartridge. Attach the cartridge to the titrator body. See General

Description, Step-byStep, for assembly

instructions, if necessary.

5. Place the delivery

tube tip into the solution and swirl the flask while immediately titrating with FEAS to a colorless end point. Record the number of digits required.

Note: Complete the titration rapidly.

2. Turn the delivery

knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TitraStir General Description, Step 3 in Step-by-Step.

Stir Plate. See

6. Calculate:

Digits Required x 0.01 = mg/L Free Chlorine

3. Pipet 25.0 mL of

sample into a 50-mL Erlenmeyer flask.

7. If total residual chlo-

rine is desired, return to step 3 and substitute a DPD Total Chlorine Powder Pillow in step 4. Wait three minutes before titrating. Continue with step 5. The results will be expressed as mg/L total chlorine.

mg/L Total Chlorine mg/L Free Chlorine = mg/L Combined Chlorine

4. Add the contents of a

DPD Free Chlorine Powder Pillow to the sample and swirl to mix.

Note: Accuracy is unaffected if a small portion is undissolved.

Note: See Sampling and Storage following these steps.

Page 76

CHLORINE, FREE AND TOTAL, continued

Sampling and Storage

Chlorine in water is easily lost. Therefore, start chlorine determinations immediately after sampling, avoiding excessive light and agitation. Do not store samples.

Accuracy Check

Standard Additions Method

This accuracy check should be performed when the analyst suspects interferences or to verify analytical technique.

1. Snap the neck off a Chlorine Standard Solution

PourRite™ Ampule.

2. Use a TenSette

standard, respectively, to three 25-mL samples. Mix each well.

3. Analyze each sample as described in the procedure.

4. Each 0.1-mL addition of standard should require

approximately 20 digits. Check the certificate enclosed with the PourRite Ampules to obtain the exact concentration. To determine the exact number of digits required for each

0.2-mL addition, multiply the exact concentration times the volume of the addition in mL times four. (Example: 50 mg/L x 0.1 mL x 4 = 20 digits.) If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Pipet to add 0.10 mL, 0.20 and 0.30 mL of

Interferences

Higher room temperatures tend to lead to higher free chlorine residual due to reaction of chloramines. Higher room temperatures also result in increased color fading. If the sample contains more than 250 mg/L alkalinity or 150 mg/L acidity as CaCO may instantly fade. To overcome this interference, adjust the pH of a separate 25-mL sample to a 6 to 7 pH by adding 1 N Sulfuric Acid Standard Solution or 1 N Sodium Hydroxide Standard Solution in small increments and using a pH meter. Record the amount of acid or base required. Add this amount of acid or base to the sample to be tested and proceed with step 4.

, the sample may not develop the full amount of color or it

Page 77

CHLORINE, FREE AND TOTAL, continued

Bromine, iodine, ozone, and oxidized forms of manganese and chromium will also react and read as chlorine. To compensate for the effects of manganese, Mn drops of Potassium Iodide, 30 g/L to 25 mL of sample. Mix and wait one minute. Add three drops of Sodium Arsenite, 5 g/L and mix. Analyze this solution as described above. (If chromium is present, allow exactly the same reaction period in step 7 with the DPD for both analyses.) Subtract the result from the original analysis to correct for the interference.

Summary of Method

The DPD-FEAS method provides a titrimetric procedure for determining free available chlorine and for estimating free and combined chlorine fractions present together. The magenta species, resulting from the oxidation of DPD by chlorine, is destroyed quantitatively by titration with ferrous ethylenediammonium sulfate and the volume of titrant required to reach a colorless end point is proportional to the chlorine concentration. Total residual chlorine may also be determined by this test.

, or chromium, Cr6+, add three

Page 78

CHLORINE, FREE AND TOTAL, continued

REQUIRED REAGENTS

Description Unit Cat. No.

Free and Total Chlorine Reagent Set (about 100 tests) ................................................24453-00

Includes: (1) 14064-99, (1) 14070-99, (1) 22923-01

DPD Free Chlorine Powder Pillows, 25 mL.........................................100/pkg..........14070-99

DPD Total Chlorine Powder Pillows, 25 mL........................................100/pkg.......... 14064-99

Ferrous Ethylenediammonium Sulfate Titration Cartridge, 0.00564 N .....each .......... 22923-01

REQUIRED APPARATUS

Digital Titrator ............................................................................................ each .......... 16900-01

Flask, Erlenmeyer, 50-mL ..........................................................................each..............505-41

Pipet, volumetric, Class A, 25-mL .............................................................each .......... 14515-40

Pipet Filler, safety bulb...............................................................................each .......... 14651-00

OPTIONAL REAGENTS

Chlorine Standard Solution, PourRite™ Ampules,

50-75 mg/L Cl

Potassium Iodide Solution .......................................................... 100 mL MDB..............343-32

Sulfuric Acid Standard Solution, 1.000 N .................................. 100 mL MDB............1270-32

Sodium Hydroxide Standard Solution, 1.000 N ......................... 100 mL MDB............1045-32

Sodium Arsenite Solution........................................................... 100 mL MDB............1047-32

, 2-mL.........................................................................20/pkg.......... 14268-20

OPTIONAL APPARATUS

Clamp, 2-prong, extension.......................................................................... each .......... 21145-00

Clamp Holder..............................................................................................each.............. 326-00

Delivery Tubes, with 180° hook ...............................................................5/pkg.......... 17205-00

Delivery Tubes, 90° with hook for TitraStir Pipet, TenSette Pipet Tips for 19700-01 TenSette

, 0.1 to 1.0 mL ..................................................................each .......... 19700-01

Pipet................................................50/pkg.......... 21856-96

PourRite™ Ampule Breaker.......................................................................each .......... 24846-00

Support Ring Stand.....................................................................................each .............. 563-00

TitraStir TitraStir

Stir Plate, 115 Vac......................................................................each .......... 19400-00

Stir Plate, 230 Vac......................................................................each .......... 19400-10

Stir Plate........................... 5/pkg .......... 41578-00

Page 79

CHLORINE, TOTAL

Method 8209

Iodometric Method (1 to 400 mg/L as Cl

1. Select the sample

volume and Sodium Thiosulfate Titration Cartridge corresponding to the expected chlorine concentration from Table 1.

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step, for

assembly instructions, if necessary.

Using Sodium Thiosulfate)

3. Flush the delivery

tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the

TitraStir General Description, Step 3 in Step-by-Step.

Tabl e 1

Stir Plate. See

4. Use a clean

graduated cylinder to take a water sample. Pour sample into a clean 125- or 250-mL Erlenmeyer flask. Dilute to about the 100-mL mark with deionized water.

Note: See Sampling and Storage following these steps.

Range

(mg/L Cl

1-4 2-8

5-20 10-40 20-80

50-200

100-400

)

Sample

Volume (mL)

100

50 20 10

5 2 1

Titration

Cartridge

(N Na

2S2O3

0.02256

)

Catalog Number

24091-01 24091-01 24091-01 24091-01 24091-01 24091-01 24091-01

Digit

Multiplier

0.01

0.02

0.05

0.10

0.20

0.50

1.00

Page 80

CHLORINE, TOTAL, continued

5. Add 2 Droppers

(2 mL) Acetate Buffer Solution, pH 4 and swirl to mix.

9. Continue the

titration until the solution changes from dark blue to colorless. Record the number of digits required.

6. Clip open the end of

one Potassium Iodide Powder Pillow. Add the contents to the flask. Swirl to mix.

10. Calculate:

Digits Required x Digit Multiplier = mg/L Total Chlorine (Cl2)

Note: These procedures can be used to check iodine and bromine concentrations if chlorine is not present. Multiply the test result (in mg/L chlorine) by 3.58 or 2.25, respectively, to accurately express the iodine or bromine content of your sample.

7. Place the delivery

tube tip into the solution and swirl the flask while titrating with sodium thiosulfate until the solution is a pale yellow.

8. Add one dropper of

starch indicator solution and swirl to mix. A dark blue color will develop.

Page 81

CHLORINE, TOTAL, continued

Sampling and Storage

Collect at least 200 mL of sample in a clean glass or polyethylene container. Analyze on site or as soon as possible after collection.

Accuracy Check

Standard Additions Method

Perform this accuracy check when you suspect interferences or to verify analytical technique.

1. Snap the neck off a Chlorine Standard Solution

PourRite™ Ampule.

2. Use a TenSette

standard to three aliquots of sample of the same volume as used in the procedure.

3. Analyze each sample as described in the procedure.

4. Each 0.2-mL addition of standard should require

approximately 10 digits of the titration cartridge solution. Check the certificate enclosed with the PourRite Ampules to obtain the exact concentration. To determine the exact number of digits required for each 0.2-mL addition, multiply the exact concentration times the volume of the addition in mL. (Example: 50 mg/L x 0.2 mL = 10 digits.) If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Pipet to add 0.2 mL, 0.4 mL, and 0.6 mL of

Page 82

CHLORINE, TOTAL, continued

Iodometric Method (20 to 70,000 mg/L as Cl2 Using Sodium Thiosulfate)

1. Select the sample

volume and Sodium Thiosulfate Titration Cartridge corresponding to the expected chlorine concentration from Table 2.

Range

(mg/L Cl2)

20-80

50-200

100-400 250-1000 500-2000

2000-9000 (0.2-0.9%)

5000-18,000

(0.5-1.8%)

10,000-35,000

(1.0-3.5%)

20,000-70,000

(2.0-7.0%)

2. Insert a clean

delivery tube into the titration cartridge. Attach the cartridge to the titrator body. See

General Description, Step-by-Step, for

assembly instructions, if necessary.

Sample

Volum e (mL)

25 10

5 2 1 4

2 1

0.5

3. Flush the delivery

tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: For added convenience use the TirtaStir apparatus. See General Description, Step 3 of Step-by-Step.

Tabl e 2

Titration

Cartridge

(N Na

2S2O3

0.113

2.00

stirring

)

Catalog Number

22673-01 22673-01 22673-01 22673-01 22673-01 14401-01

14401-01 14401-01 14401-01

4. Use a pipet or

graduated cylinder to measure the sample volume from Table 2 . Transfer the sample into a 125-mL Erlenmeyer flask and dilute to about the 50-mL mark with deionized water.

Digit

Multiplier

0.2

0.5 1

2.5 5

22.2

44.3

88.7 177

Page 83

CHLORINE, TOTAL, continued

5. Add the contents of

one Dissolved Oxygen 3 Powder Pillow.

Note: Normally the addition of the powder pillow will lower the pH to 4 or less. If the sample size is large and highly alkaline, verify the solution pH is 4 or less with a pH meter or pH paper before proceeding.

6. If you are using the

2.00 N titration cartridge, add the contents of one Potassium Iodide Powder Pillow (Cat. No. 20599-96) to the flask and swirl to mix.

If you are using the

0.113 N titration cartridge, add the contents of one Potassium Iodide Powder Pillow (Cat. No. 1077-99) to the flask and swirl to mix.

7. Place the delivery

tube tip into the solution and swirl the flask while titrating with sodium thiosulfate until the solution is a pale yellow.

8. Add one dropperful

of starch indicator solution and swirl to mix. A dark blue color will develop.

9. Continue the

titration until the solution changes from dark blue to colorless. Record the number of digits required.

10. Calculate:

Digits Required x Digits Multiplier = mg/L Total Chlorine (Cl2)

To convert the above results to the equivalent percent chlorine (Cl divide by 10,000.

Page 84

CHLORINE, TOTAL, continued

Accuracy Check

Standard Additions Method This accuracy check is applicable only for the 0.113 N titration cartridge. Perform it when interferences are suspected or to

verify analytical technique.

1. Snap the neck off a Chlorine Standard Solution

PourRite Ampule.

2. Use a TenSette Pipet (or glass pipet) to add 1.0 mL, 2.0 mL,

and 3.0 mL of standard to three samples of the same volume as used in the procedure.

3. Analyze each sample as described in the procedure.

4. Each 1.0-mL addition of standard should require

approximately 10 digits of the 0.113 N titration cartridge. Check the certificate enclosed with the PourRite Ampules to obtain the exact concentration. To determine the exact number of digits required for each 1.0-mL addition, multiply the exact concentration times the volume of the addition in mL. Divide this by five. For example: (50 mg/L x 1.0 mL) ÷ 5 = 10 digits. If these uniform increases do not occur, refer to Appendix A, Accuracy Check and Standard Additions.

Summary of Method

Total chlorine concentration equals the concentration of the free and the combined forms of chlorine. Free chlorine reacts readily with ammonia to form combined chlorine such as monochloramines. When potassium iodide is added to a sample containing chlorine at a pH less than 8, free iodine is liberated in direct proportion to the amount of total chlorine present. The iodine is then titrated with sodium thiosulfate.

Page 85

CHLORINE, TOTAL, continued

REQUIRED REAGENTS (For Using the 0.02256 N Titration Cartridge)

Description Unit Cat. No.

Acetate Buffer Solution, pH 4........................................................ 100 mL MDB .......14909-32

Potassium Iodide Powder Pillows............................................................100/pkg .........1077-99

Starch Indicator Solution.............................................................. 100 mL MDB* ...........349-32

Sodium Thiosulfate Titration Cartridge, 0.02256 N ......................................each .......24091-01

REQUIRED REAGENTS (For Using the 0.113 N Titration Cartridge)

Chlorine Reagent Set, 20-2,000 mg/L (about 100 tests)...............................................22725-00

Includes: (1) 349-32, (1) 987-99, (1) 1077-99, (1) 22673-01

Dissolved Oxygen 3 Powder Pillows .......................................................100/pkg ...........987-99

Potassium Iodide Powder Pillows............................................................100/pkg .........1077-99

Sodium Thiosulfate Titration Cartridge, 0.113 N ..........................................each .......22673-01

Starch Indicator Solution.............................................................. 100 mL MDB* ...........349-32

Water, deionized...............................................................................................4 L...........272-56

REQUIRED REAGENTS (For Using the 2.00 N Titration Cartridge)

Chlorine Reagent Set, 2,000-70,000 mg/L (about 100 tests) .......................................24448-00

Includes: (1) 349-32, (1) 987-99, (2) 14401-01, (2) 20599-96

Dissolved Oxygen 3 Powder Pillows .......................................................100/pkg ...........987-99

Potassium Iodide Powder Pillows..............................................................50/pkg .......20599-96

Sodium Thiosulfate Titration Cartridge, 2.00 N ............................................each .......14401-01

Starch Indicator Solution.............................................................. 100 mL MDB* ...........349-32

Water, deionized...............................................................................................4 L...........272-56

REQUIRED APPARATUS

Clippers, for opening pillows .........................................................................each ...........968-00

Digital Titrator................................................................................................each .......16900-01

Flask, Erlenmeyer, 125 mL ............................................................................each ...........505-43

Pipet Filler, 3-valve ........................................................................................each .......12189-00

Select one or more based on sample concentration:

Pipet, serological, 1 mL..................................................................................each ...........532-35

Pipet, volumetric, Class A, 1 mL ...................................................................each .......14515-35

Pipet, volumetric, Class A, 2 mL ...................................................................each .......14515-36

Pipet, volumetric, Class A, 4 mL ...................................................................each .......14515-04

Pipet, volumetric, Class A, 5 .........................................................................each .......14515-37

Pipet, volumetric, Class A, 10 mL .................................................................each .......14515-38

Pipet, volumetric, Class A, 25 mL .................................................................each .......14515-40

* Contact Hach for larger sizes.

Page 86

CHLORINE, TOTAL, continued

OPTIONAL REAGENTS

Description Unit Cat. No.

Chlorine Standard Solution, PourRite™ Ampules,

50-75 mg/L as Cl

OPTIONAL APPARATUS

Clamp, 2-prong, extension, 38 mm................................................................ each.......21145-00

Clamp Holder................................................................................................. each........... 326-00

Cylinder, graduated, 5 mL ............................................................................. each........... 508-37

Cylinder, graduated, 10 mL ........................................................................... each...........508-38

Cylinder, graduated, 25 mL ........................................................................... each...........508-40

Delivery Tubes, with 180° hook .................................................................. 5/pkg....... 17205-00

Delivery Tubes, 90° with hook for TitraStir Pipet, TenSette Pipet Tips for 19700-01 TenSette

pH Paper, 1-11 pH ............................................................................... 5 rolls/pkg........... 391-33

PourRite™ Ampule Breaker.......................................................................... each....... 24846-00

sens

ion™1 Basic Portable pH Meter with electrode ...................................each....... 51700-10

Support Ring Stand........................................................................................ each...........563-00

TitraStir TitraStir

Stir Plate, 115 Vac......................................................................... each....... 19400-00

Stir Plate, 230 Vac......................................................................... each....... 19400-10

, 2 mL........................................................................ 20/pkg....... 14268-20

Stir Plate.............................. 5/pkg.......41578-00

, 0.1 to 1.0 mL ..................................................................... each.......19700-01

Pipet................................................... 50/pkg....... 21856-96

Page 87

CHLORINE, FREE (0 to 1000 µg/L as Cl

Amperometric Forward Titration

USEPA Accepted for Reporting*

Method 10024

)

1. Assemble the

Amperometric Digital Titrator System according to the instructions in the

Amperometric Titrator Instruction Manual.

2. Install the 0.00564 N

Phenylarsine Oxide (PAO) cartridge. Flush the Digital Titrator delivery tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: When a new probe is placed in service or when the probe has not been used recently, prepare it according to the Probe Stabilization instructions in the Amperometric Titrator Instruction Manual.

3. With minimum

agitation, measure 200 mL of sample with a clean graduated cylinder. Transfer the sample to a clean 250-mL beaker containing the 50-mm stirring bar supplied with the system.

Note: An improper stirring bar size can result in volatilization of chlorine, instability of readings and loss of sensitivity.

4. Add 1 mL of

pH 7 Phosphate Buffer Solution.

Note: If the sample pH is between 6.5 and 7.5 it is not necessary to add the buffer.

* Procedure is equivalent to Standard Methods for the Examination of Water and Wastewater (18th ed.) 4500 Cl D for drinking water.

Page 88

CHLORINE, FREE, continued

5. Place the beaker on

the TitraStir and immerse the tips of the probe and delivery tube in the solution. The probe's platinum wires must be submerged. Turn on the stirring motor.

Stir Plate

6. Note the LED

reading on the Amperometric Titrator. Unlock the BIAS control and adjust the BIAS control knob until a reading between 0.50-

0.60 is obtained. Lock the BIAS control.

Note: The bias adjustment controls the slope of the titration curve. The actual instrument reading is not important; but rather the change in the readings as the titration proceeds. The adjustment need not be precise.

7. Using the Digital

Titrator delivery knob, dispense the PAO titrant Solution in 5-10 digit increments while noting the LED reading.

Note: If the chlorine content of the sample is high, add titrant at a faster rate; only the end point of the titration and the volume of titrant used at the end point are of concern. For example, if the chlorine content is approximately 500 µg/L, up to 300 digits of 0.00564 N PAO could be added at once. As the end point is approached, dispense in small increments.

Note: If excess reductant such as sulfite, bisulfite or sulfur dioxide is present in the sample, the LED readings will not decrease and may even increase. This indicates that no free chlorine is present in the sample

8. As the end point of

the titration is approached, record the LED readings along with the corresponding digits displayed on the Digital Titrator counter. Near the titration end point, add 2 to 5 digits of titrant; wait a few seconds for a stable reading and record.

Page 89

CHLORINE, FREE, continued

Meter Reading

End Point

Digits

9. Continue the

titration, recording at least three points on the downward sloping curve and at least three points after the end point has been reached. The latter points will have little change in the LED readings.

Figure 1 Sample Plot

10. Using linear graph

paper, plot the recorded readings from the Amperometric Titrator on the vertical axis and the corresponding Digital Titrator digits on the horizontal axis. Draw the two best intersecting lines through the points; see Figure 1. Determine the number of digits at the intersection of the lines; this is the end point.

11. Calculate the µg/L

free chlorine:

Digits at End Point x 1.25 = µg/L free chlorine as Cl

Meter Reading

End Point

Digits

Page 90

CHLORINE, FREE, continued

Accuracy Check

Standard Additions Method*

1. Snap the top off a Chlorine Standard Solution PourRite™

Ampule. Note the certificate value of the standard in mg/L.

2. Split a fresh sample into two 200-mL portions.

3. Using a TenSette

standard to one portion and swirl to mix. This is the spiked sample.

4. Analyze both the sample and spiked sample and record the

chlorine concentration of each.

5. Calculate the theoretical concentration of the spiked sample:

Theoretical concentration

Where:

Cu = measured concentration of sample, in mg/L (µg/L divided by 1000) Vu = volume of sample in mL C

= concentration of chlorine standard (mg/L, certificate value)

Vs = volume of standard added in mL

Pipet, add from 0.1 to 0.5 mL of the

(CuVu)CsVs×()+×

----------------------------------------------------------= VuVs+

6. Calculate the percent spiked recovery:

% Spike Recovery

---------------------------------------------------------------------------------------------------------------------- Theoretical concentration calculated, in mg/L

Spiked sample result, in mg/L

100×=

Example:

Sample result (Cu) = 120 µg/L or 0.120 mg/L Spiked sample result = 185 µg/L or 0.185 mg/L Volume Sample (Vu) = 200 mL Volume Standard (V Chlorine Standard (Cs) = 68.1 mg/L

Theoretical concentration

% Spike recovery

) = 0.2 mL

0.185 mg/L

----------------------------- -

0.188 mg/L

(0.120 200) (68.1 0.2)×+×

----------------------------------------------------------------------- - 0.188 mg/L==

200 0.2+

100 = 98%×=

Ideally, the percent recovery should be 100%. Generally, results from 80-120% recovery are considered acceptable.

* The standard additions technique is not applicable for samples containing excess reducing agents such as sulfur dioxide, sulfite, or bisulfite.

Page 91

CHLORINE, FREE, continued

Precision

In a single laboratory, using a standard solution of 338 µg/L chlorine, a single operator obtained a standard deviation of ± 5.2 µg/L chlorine.

Detection Limit

With good operator technique, the estimated detectable concentration is approximately 15 µg/L chlorine using

0.00564 N PAO.

Sampling and Storage

Chlorine is rapidly lost from water. Avoid exposure to sunlight or other strong light. Avoid excessive agitation. Analyze samples immediately.

Interferences

• Silver ions poison the electrode.

• Copper ions interfere.

Summary of Method

• Interferences are sometimes found in highly turbid water and

those containing surface active agents.

• Oxidized manganese and other oxidizing reagents give

positive interferences.

• Some uncertainty in the end point may be observed with

samples containing high organic content.

• Samples containing excess reducing agents, such as sulfur

dioxide, sulfite, and bisulfite do not contain free chlorine and can not be titrated under the conditions of the test.

• Highly buffered samples or extreme sample pH may exceed

the buffering capacity of the buffer reagent. If necessary, add additional buffer and check pH of sample prior to titration.

In the amperometric forward titration procedure for free chlorine, a small electrical current is applied across two identical platinum electrodes. No current can flow between the electrodes unless a

Page 92

CHLORINE, FREE, continued

substance that can be oxidized at the anode and a substance that can be reduced at the cathode are both present. In the case of the free chlorine titration with phenylarsine oxide (PAO), chlorine is reduced at the cathode to chloride due to the addition of PAO and PAO is oxidized from the +3 oxidation state to the +5 oxidation state at the anode. Prior to the end point of the titration, both free chlorine and chloride are present in solution; allowing current to flow, even with a very small applied potential. At the end point, no free chlorine remains and the solution cannot conduct even if excess PAO titrant is added. The end point is defined when no change in current occurs, signaling all free chlorine has been reacted.

REQUIRED REAGENTS

Description Unit Cat. No.

Phenylarsine Oxide Solution, 0.00564 N Digital Titrator Cartridge ............. each.........1999-01

Phosphate Buffer Solution, pH 7 ....................................................100 mL MDB.......21553-32

REQUIRED APPARATUS

Amperometric Titrator Assembly.................................................................. each....... 19299-00

Digital Titrator ............................................................................................... each.......16900-01

Beaker, low-form, 250 mL............................................................................. each........... 500-46

Cylinder, graduated, 250 mL ......................................................................... each........... 508-46

Delivery Tubes, 90° with hook .................................................................... 5/pkg....... 41578-00

Probe Assembly, Amperometric Titrator....................................................... each.......19390-00

Stir Bar, octagonal, Teflon-coated, 50.8 x 7.9 mm ........................................ each....... 20953-55

TitraStir TitraStir

Stir Plate, 115 Vac......................................................................... each....... 19400-00

Stir Plate, 230 Vac......................................................................... each....... 19400-10

OPTIONAL REAGENTS

Chlorine Standard Solution PourRite™ Ampules,

50-75 mg/L Cl

, 2 mL ............................................................................ 20/pkg.......14268-20

Water, deionized...............................................................................................4 L........... 272-56

OPTIONAL APPARATUS

Pipet, TenSette® 0.1 to 1.0 mL ...................................................................... each.......19700-01

Pipet Tips for 19700-01 TenSette

PourRite™ Ampule Breaker.......................................................................... each....... 24846-00

Standard Methods for the Examination of Water

and Wastewater, 19th edition...................................................................... each....... 22708-00

Pipet................................................... 50/pkg....... 21856-96

Page 93

CHLORINE, TOTAL (6 to 1000 µg/L as Cl

Amperometric Back Titration

USEPA Accepted for Reporting*

Phase 1: Adjusting the Electrode Response Slope

Method 10025

) For wastewater

1. Assemble the

Amperometric Digital Titrator System according to the instructions in the

Amperometric Titrator Instruction Manual.

2. Install the Standard

Iodine Titrant Cartridge,

0.028 N. Flush the Digital Titrator delivery tube by turning the delivery knob to eject a few drops of titrant. Reset the counter to zero and wipe the tip.

Note: When a new probe is used or the probe has not been used recently, prepare it according to the Probe Stabilization instructions in the Amperometric Titrator Instruction Manual.

3. Using a graduated

cylinder, measure 200 mL of deionized water into a clean 250-mL beaker. Place the 50-mm stirring bar supplied with the system into the beaker.

Note: An improper size stirring bar can result in volatilization of iodine, instability of readings and loss of sensitivity.

4. Add 1 mL of pH 4

Acetate Buffer and the contents of one Potassium Iodide Pillow.

* Procedure is equivalent to USEPA method 330.2 and Standard Methods for the Examination of Water and Wastewater (17th ed.) 4500-Cl C for wastewater.

Page 94

CHLORINE, TOTAL, continued

5. Place the beaker on

the TitraStir and immerse the tips of the probe and delivery tube in the solution. The probe's platinum wires must be submerged. Turn on the stirring motor.

Stir Plate

6. Using the Digital

Titrator delivery knob, add 50 digits of Standard Iodine Titrant Solution.

Phase 2: Standardization of the Iodine Titrant

1. Set-up the

Amperometric Digital Titrator System as in

Phase 1: Adjusting the Electrode Response Slope if it has not

already been done. Reset the Digital Titrator counter to zero and wipe the tip.

2. Using a graduated

cylinder, measure 200 mL of deionized water into a clean 250-mL beaker. Place the 50-mm stirring bar supplied with the system into the beaker.

Note: An improper size of stirring bar can result in volatilization of iodine, instability of readings and loss of sensitivity.

7. Note the LED

reading on the Amperometric Titrator. Unlock the BIAS control and adjust the BIAS control knob until a stable reading between

0.50-0.60 is obtained. Lock the BIAS control.

3. Using a Class A

pipet, transfer 1.00 mL of 0.00564 N Sodium Thiosulfate Solution to the beaker. Swirl to mix.

Note: Alternatively, use

0.00564 N Phenylarsine Oxide (PAO), Cat. No. 1999, instead of thiosulfate.

8. Remove the probe

arm from the beaker and rinse the platinum wires with deionized water. Adjustment of the electrode response slope is complete.

4. Add 1 mL of pH 4

Acetate Buffer Solution and the contents of one Potassium Iodide Powder Pillow.

Page 95

CHLORINE, TOTAL, continued

5. Place the beaker on

the TitraStir Stir Plate and immerse the tips of the probe and delivery tube in the solution. The probe's platinum wires must be submerged. Turn on the stirring motor.

6. Note the LED

reading on the Amperometric Titrator. It should read 0.00 ± 0.05. DO NOT adjust the BIAS control.

7. Using the Digital

Titrator delivery knob, dispense 100 digits of Standard Iodine Titrant Solution and note the LED reading.

8. Continue dispensing

titrant in 5-10 digit increments while noting the LED reading. Record at least 3 points (null current values and Digital Titrator reading), before the end point is reached. After the end point of the titration (nominal 160 digits), record the increasing LED readings along with the corresponding digits displayed on the Digital Titrator counter. Add 5-10 digits of titrant; wait a few seconds for a stable reading and record it. Stop adding titrant when the LED readings exceed 0.60.

Note: LED readings above 0.60 will be excessively noisy.

Page 96

CHLORINE, TOTAL, continued

Meter Reading

End Point

Digits

9. Using linear graph

paper, plot the recorded readings from the Amperometric Titrator on the vertical axis and the corresponding Digital Titrator digits on the horizontal axis. Draw the two best intersecting lines through the points plotted. See Figure 1. Determine the number of digits at the intersection of the lines. This is the standard end point.

Figure 1 Back Amperometric

itration Graph

10. Record the

standard end point digits value. This value will be used in calculation of the sample chlorine concentration.

Note: The iodine titrant concentration is approximately 0.0282 N, which relates to 160 digits needed to titrate 1.00 mL of 0.00564 N Thiosulfate. If the calculated end point is greater than 160 digits, this indicates the Standard Iodine Titrant is weaker than when packaged. Discard the Standard Iodine Titrant cartridge if the calculated standardization end point is greater than 200 digits.

11. Locate the

appropriate multiplier based on the standard end point in Table 1 on page 99. The multiplier is used in Phase 3:

Titration of Sample for Total Residual Chlorine.

Interpolation between values in the table is not necessary.

Page 97

CHLORINE, TOTAL, continued

Phase 3: Titration of Sample for Total Residual Chlorine

1. Set-up the

Amperometric Digital Titrator System as in

Phase 1: Adjusting the Electrode Response Slope if it has not

already been done. Reset the Digital Titrator counter to zero and wipe the tip.

2. Place a clean 50-mm

stirring bar supplied with the system into a clean 250-mL beaker. Using a Class A pipet, transfer 1.00 mL of

0.00564 N Sodium Thiosulfate Solution to the a beaker. Add 1 mL of pH 4 Acetate Buffer Solution to the beaker.

Note: An improper size stirring bar can result in volatilization of chlorine, instability of readings and loss of sensitivity. Alternatively, use 0.00564 N Phenylarsine Oxide (PAO), Cat. No. 1999, instead of thiosulfate.

3. With minimum

agitation, measure 200 mL sample with a clean graduated cylinder and transfer the sample to the beaker. Swirl to mix the reagents with sample.

Note: Steps 2-3 can be performed at the sampling site thereby "fixing" the sample for later analysis. Pipet 1.00 mL of 0.00564 N Sodium Thiosulfate and add 1.0 mL of Acetate Buffer into a clean, dry glass sampling bottle (e.g. BOD bottle). At the sample site, measure 200 mL of sample with a graduated cylinder and transfer to the sampling bottle. Swirl to mix. Before analysis, quantitatively transfer the entire contents of the sampling bottle to the 250-mL beaker. Minimize delay between sampling and analysis (1 hour maximum) to prevent decomposition of thiosulfate in the sample.

4. Place the beaker on

the TitraStir Stir Plate and immerse the tips of the probe and delivery tube in the solution. The probe's platinum wires must be submerged. Turn on the stirring motor.

Page 98

CHLORINE, TOTAL, continued

5. Add the contents of

one pillow of Potassium Iodide Reagent to the beaker and allow the powder to dissolve.

6. Note the LED

reading on the Amperometric Titrator. It should read 0.00 ± 0.05. DO NOT adjust the BIAS control.

7. Using the Digital

Titrator delivery knob, dispense the Standard Iodine Titrant Solution in 5-10 digit increments while noting the LED reading. Record at least 3 points (null current values and Digital Titrator reading), before end point is reached.

8. After the end point

of the titration is reached, record the increasing LED readings along with the corresponding digits displayed on the Digital Titrator counter. Add 5-10 digits of titrant; wait a few seconds for a stable reading and record. Stop the titrant addition when the LED readings exceed 0.60.

Note: LED readings above 0.60 will be excessively noisy. With samples containing excess de-chlorinating agents, such as sulfur dioxide, sulfite or bisulfite, the titration end point (number of digits) will be greater than the number of digits obtained during the standardization. It is not necessary to continue the titrant addition if the number of digits used in the sample titration exceeds that calculated for the standardization end point. This indicates that no free or combined chlorine is present in the sample.

Page 99

CHLORINE, TOTAL, continued

9. Using linear graph

paper, plot the recorded readings from the Amperometric Titrator on the vertical axis and the corresponding Digital Titrator digits on the horizontal axis. Draw the two best intersecting lines through the points plotted. See Figure 1 on page 96. Determine the number of digits at the intersection of the lines. This is the sample end point.

10. Calculate the µg/L

total chlorine:

[Digits (Standard End Point) - Digits (Sample End Point)] x Multiplier = µg/L Cl (Multiplier is from Phase 2.)

Example: Standard EP = 160 digits Multiplier = 6.25 Sample EP = 150 digits

µg/L total chlorine = [160 - 150] x 6.25 = 10 x 6.25 = 63 (round up)

Note: To preserve the strength of the iodine titrant solution, always remove the delivery tube from the Digital Titrator cartridge and replace the cap when not in use. Protect the iodine titrant solution from direct sunlight.

Table 1

Digits

(standard end point)

160 6.25 165 6.06 170 5.88 175 5.71 180 5.56 185 5.40 190 5.26 195 5.13 200 5.00

Multiplier

Page 100

CHLORINE, TOTAL, continued

Sampling and Storage

Chlorine is rapidly lost from water. Avoid exposure to sunlight or other strong light. Avoid excessive agitation. Analyze samples immediately or fix the sample by pre-addition of standard thiosulfate and buffer as indicated in Phase 3: Titration of Sample for Total Residual Chlorine. The fixing procedure should be used for brief transportation delays—not for storage of samples.

Accuracy Check

Standard Additions Method*

Snap the top off a Chlorine Standard Solution PourRite™ Ampule. Note the certificate value of the standard in mg/L.

1. Split a fresh sample into two 200-mL portions.

2. Using a TenSette

standard to one portion and swirl to mix. This is the spiked sample.

3. Analyze each sample as described above and record the

chlorine concentrations.

Pipet, add from 0.1 to 0.5 mL of the

4. Calculate the theoretical concentration of the spiked sample:

Theoretical concentration

CuVu×()CsVs×()+

---------------------------------------------------------- -= VuVs+

Where:

Cu = measured concentration of sample, in mg/L (µg/L divided by 1000) Vu = volume of sample in mL

= concentration of chlorine standard (mg/L, certificate value)

Vs = volume of standard added in mL

5. Calculate the percent spiked recovery:

% Spike recovery

* Standard additions is not applicable for samples containing excess reducing agents such as sulfur dioxide, sulfite, or bisulfite.

---------------------------------------------------------------------------------------------------------------------- Theoretical concentration calculated, in mg/L

Spiked sample result, in mg/L

100

100×=