LaMotte AB-COD User Manual

CHEM I CAL OX Y GEN DE MAND

MODEL AB-COD · CODE 7637

QUANTITY CONTENTS CODE

10 g *Mercuric Sulfate Powder *7581-D
230 mL *Potassium Dichromate, 0.25N *7582-K
3 x 230 mL *COD Reagent #3 *7583-K
30 mL *Ferroin Indicator *7584-G
2 x 230 mL *Ferrous Ammonium Sulfate, 0.05N *7585-K
30 mL *Sulfuric Acid, 25% *7588-G
60 mL Potassium Biphthalate Solution 7589-H
2 x 250 mL Deionized Water 5115PS-K
1 Flask, Flat Bottom, 50 mL, glass 0887
1 Condenser, 20 cm, glass 0888
2 Clamps, utility, metal 0396
1 Vial Glass Beads 0889
2 Flasks, Erlenmeyer, 125 mL, glass 0431
1 Graduated Cylinder, 50 mL, glass 0418
2 Graduated Cylinders, 10 mL, glass 0416
1 Spoon, 0.1 g, plastic 0699
1 Latex Tubing, 6 feet 0891-6
1 Automatic Buret 0427
1 Pipet, plain, plastic 0352
1 Pipet Assembly, 20 mm 0341
1 Water Sample Bottle 0688

*WARNING: Reagents marked with an * are considered hazardous substances.
To view or print a Material Safety Data Sheet (MSDS) for these reagents see
MSDS CD or our web site. To obtain a printed copy, contact us by e-mail, phone
or fax.

To order a complete set of refill reagents, order as R-7637. To order individual
reagents or test kit components, use the specified code number.

SAM PLING AND STOR AGE

Samples are taken with clean water sampling bottles which are free of
organic matter. The COD determination should be made almost
immediately after the sample is taken. If, for some reason, the COD
analysis cannot be made immediately, the sample is made acidic (pH 2 ­pH 3) by adding a few drops of 25% Sulfuric Acid (7588) and stored at
4-8oC. For longer storage periods, deep-freezing is recommended. Samples
containing detritus or settleable solids should be homogenized by a blender
to obtain a representative sample. All dilutions should be made with
deionized water and should be measured accurately in volumetric flasks.

AP PA RA TUS

A hot plate is necessary to provide adequate boiling of the reagents in the
reflux mixture. A metal stand is required to hold both the distilling flask
and the reflux condenser. All the other material required to make a COD
analysis is supplied with the LaMotte Chemical Oxygen Demand Outfit.

STAN DARD IZA TION

*Ferrous Ammonium Sulfate, 0.05N (7585) must be restandardized before
a series of analysis is started, due to its unstable nature. To determine the
normality of *Ferrous Ammonium Sulfate, 0.05N (7585), dilute 5 mL of
*Potassium Dichromate, 0.25N (7582) to 50 mL with Deionized Water
(5115). Add 15 mL *COD Reagent #3 (7583) and allow to cool. Titrate
with *Ferrous Ammonium Sulfate, 0.05N (7585) using 3-5 drops of Ferroin
Indicator (7584) and substitute the values in the following equation:

Normality of Reagent #5 =

mL Potassium Dichromate, 0.25N

mL Ferrous Ammonium Sulfate, 0.05N

x .25

PRO CE DURE

A blank consisting of 10 mL of distilled water must be run with all the
reagents. The blank is refluxed and analyzed in the same manner as
outlined above.

1. Fill graduated cylinder (0416) to 10 mL line with sample water.
Transfer to 50 mL flat bottom flask (0887).

2. Use the 0.1 g spoon (0699) to add 0.2 g *Mercuric Sulfate Powder
(7851). Mix.

3. Use a second graduated cylinder (0416) to add 5 mL of *Potassium
Dichromate, 0.25N (7582). Mix.

4. Fill graduated cylinder (0418) to 15 mL line with *COD Reagent #3
(7583). Add small portions at a time to the distillation flask, mixing
well with each addition.

CAUTION: *COD Reagent #3 (7583) is Sulfuric Acid. Read
Material Safety Data Sheets (MSDS).