Kern AES-A01N User guide

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KERN & Sohn GmbH

Ziegelei 1

E-Mail: info@kern-sohn.com

Tel: +49-[0]7433- 9933-0

Internet: www.kern-sohn.com

Operating instructions Density Determination Set

KERN AES-A01N

Version 1.0

09/2012

D-72336 Balingen

Fax: +49-[0]7433-9933-149

AES-A01N-BA-e-1210

KERN AES_N/AEJ_N

KERN AES-A01N

Contents:

1 INTRODUCTION ............................................................................................................................ 3

1.1 SCOPE OF DELIVERY ................................................................................................................. 3

1.2 DIMENSION [MM] ....................................................................................................................... 4

2 PRINCIPLE OF DENSITY DETERMINATION ............................................................................... 5

2.1 INFLUENCING MAGNITUDES AND ERROR SOURCES ...................................................................... 6

3 INSTALLING THE DENSITY DETERMINATION SET .................................................................. 7

Version 1.0 09/2012

Operating instructions Density Determination Set Analytical Balances

4 DENSITY DETERMINATION OF SOLIDS ..................................................................................... 9

4.1 ACTIVATE "DENSITY DETERMINATION SOLID MATTER" MODE ...................................................... 10

4.2 CALCULATE DENSITY .............................................................................................................. 12

4.3 DENSITY DETERMINATION OF SOLID MATER IAL WITH A DENSITY OF LESS THAN 1 G/CM3 ............... 14

5 DETERMINING DENSITY OF LIQUIDS ...................................................................................... 15

5.1 CALL UP "DENSITY DETERMINATION FLUID" ............................................................................... 16

5.2 CALCULATE DENSITY .............................................................................................................. 18

6 PRECONDITIONS FOR PRECISE MEASUREMENTS ............................................................... 20

6.1 CALCULATION OF RESULTS ..................................................................................................... 20

6.2 INFLUENCE FACTORS FOR MEASUREMENT ERRORS ................................................................. 20

6.2.1 Air bubbles ....................................................................................................................... 20

6.2.2 Solid matter sample ......................................................................................................... 20

6.2.3 Liquids .............................................................................................................................. 21

6.2.4 Surface ............................................................................................................................. 21

6.3 GENERAL INFORMATION .......................................................................................................... 21

6.3.1 Density / Relative Density ................................................................................................ 21

6.3.2 Drift of Balance Display ................................................................................................... 21

7 DENSITY TABLE FOR FLUIDS ................................................................................................... 22

8 USER INSTRUCTIONS ................................................................................................................ 23

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1 Introduction

• In order to guarantee a safe and trouble-free operation, please read carefully the operating instructions.

• These operating instructions only describe the operation of the

1.1 S cope of delivery

 Check packaging and density determination set immediately when unp ack ing for

possible visible damage.

 Make sure that all parts are completely present.

density determinati on set . For further information on how to operate your balance please refer to the operating instructions supplied with each balance.

No. Description

1 Hook for sinker 9 Wire 2 Frame

10 Additional frame (tray for sample

dishes/sinkers)

3 Wire 11 Lower filter bowl of immersion basket

4 Beaker 400 ml 12

Immersion basket for floati ng soli d matter (density < 1 g/cm³)

5 Glass sinker Thermometer not illustrated 6 Additional weights (See chap. 4 and 5) Thermometer bracket not illustrated

7 Platform for glass beaker Tweezers not illustrated

Upper sample dish of the

immersion basket

Operating instructions

AES-A01N-BA-e-1210 3

1.2 Dim ension [mm]

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ρ =

A-B

ρ =

m V

2 Principle of Density Determination

Three physical magnitudes are the volume and the mass of bodies as well as the density of matter. In density mass and volume are related.

Density [ ρ ] is the relation of mass [ m ] to volume [ V ].

SI-unit of density is kilogram divided by cubic meter (kg/m³). 1 kg/m³ equals the density of a homogenous body that, for a mass of 1 kg, has the volume of 1 m³. Additional frequently applied units include:

The application of this density determination set in combination with the KERN AES_N/AEJ_N balances provides fast and safe determination of solids and fluids. Our set uses the "Principle of Archimedes" to determine density:

BUOYANCY IS A FORCE. IT AFFECTS A BODY THAT IS IMMERSED INTO A FLUID. THE BUOYANCY OF THE BODY EQUALS THE WEIGHT FORCE OF THE DISPLACED FLUID. THE FORCE OF BUOYANCY ACTS VERTICALLY UPWARDS.

Thus, density is calculated according to the formulae below:

To determine the density of solid matter

Our balances enable weighing of solids in air [ A ] as well as water [ B ]. If the density of the buoyancy medium is known [ ρo ] the density of the solid [ ρ ] is calculated as

follows:

ρ = Density of sample A = Weight of the sample in air B = Weight of the sample in the aid liquid

= Density of the aid liquid

AES-A01N-BA-e-1210 5

ρ =

A-B

ρ =

G V

Determining density of liquids

The density of a fluid is determined with the help of a sinker providing a known volume ([ V ] see embossin g) . The sinker is weighed in air [ A ] as well as in the test fluid [ B ].

According to the Archimedes’ Principle a body immersed in a fluid experiences a force of buoyancy. [ G ]. This force equals the weight force of the fluid displaced by the volume of the body. The volume [ V ] of the immersed body equals the volume of the displaced fluid.

G = buoyancy of sinker Buoyancy of sinker =

Weight of the sinker in air [ A ] - weight sinker in test liquid [ B ] From this follows:

ρ = Density of test liquid A = Weight of sinker in air B = Weight of the sinkers in test liquid V = volume of sinker

2.1 Influencing magnitudes and error sources

 Air pressure  Temperature  Volume deviation of the sinker  Surface tension of the liquid  Air bubbles  Immersion depth of the sample dish or of the sinker  Porosity of the solid

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• Switch off balance and separate it from the power supply.

3 Installing the density determination set

• If necessary, carry out necessary adjustment before installation of the density

 Remove the following parts from the weighing scale

set.

• Correct adjustment is no longer possible after the density kit has been installed.

• For reasons of adjustment, take away the density set and place the standard weighing plate.

(1) Standard weighing platform (2) Support for weighing plate (3) Screening ring

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 Installing the density determination set

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Additional weight

4 Density determination of solids

For the determination of the density of solids, the solid is first weighed in air and then in the aid liquid, whose density is known. From the weight difference results the buoyancy from where the software calculates the density. As aid liquid, usually distilled water or ethanol is used, see density table chapter 7.

Prepare balance as described in chapter 3 "Installation of density determination set".

 Place the platform for glass containers in a way that it does not touch the

weighing plate.

 Place beaker in the centre of the platform Make sure that it has no contact

with the frame.

 Hang the immersion basket on the rack. Make sure that it is centred in the

recess.

 Pour the liquid into the glass beaker. Filling height should be approx. ¾ of the

capacity. Immerse thermometer

 Bring liquid and instruments to the right temperature until you achieve a

constant temperature. Observe the warm-up time of the balance.

 Close the glass doors. Connect balance to power supply, the balance will

carry out a self-test. The balances of the AEJ series also carry out an adjustment with the internal adjustment weight. Wait until the gram display appears.

 Add additional weights if error message “Er 1 Hi“ appears, or if the display

does not react.

AES-A01N-BA-e-1210 9

4.1 Activate "density determination solid matter" mode

The first function “F1 basic“ appears.

Press repeatedly, until “F6 d_Co“ is displayed

Acknowledge with ; "Liquid" followed by the currently set auxiliary fluid will be displayed.

 Press or until the required auxiliary liquid is displayed.

Display Auxiliary fluid H20 Distilled water C2H5OH Ethyl alcohol (ethanol) Another Auxiliary liquid of your choice

 Acknowledge selection by .

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Either

When selecting distilled water or ethanol read the temperature on the thermometer and use to increase and to decrease t he nu meri c

value.

Confirm your entry by pressing ; density determination of the solid will be starting at this point. (See chap. 4.2).

When selecting "Another" enter density of auxiliary fluid of your choice.

The currently set density of the auxiliary liquid is displayed. The active digit is flashing.

To change by applying or select the digit to be changed an d increase the numeric val ue by or decrease it by applying .

Confirm your entry by pressing ; from here the density determination of the solid will be starting at this point. (See chap. 4.2).

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4.2 Calculate density

1. As soon as LOAD A followed by zero has been displayed, put the solid in the upper sample bowl. The weight of the „sample in air“ is displayed.

2. Wait for stability display ( ), then press . The weight of the sample in air is saved.

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3. As soon as LOAD L followed by zero has been displayed remove the sample from the upper sample bowl and put it in the lower filter bowl. Use the tweezers supplied and do your best to ensure that no air bubbles are stuck to the solid. The weight of the sample in the auxiliary liquid will be displayed.

4. Wait for stability display ( ), then press . The weighing scale calculates the density of the solid and displays it in [g/cm3].

 If you have an optional printer connected you can print the result by .

2.3456 g/cm3

 Remove the sample. To carry out further measuring, press , and then start

with step 1.

 Press to return to menu, then use to return to weighing mode.

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4.3 Density determination of solid material with a density of less than 1 g/cm

At solid material with density less than 1 g/cm3 , a density determination with two different methods is pos si bl e.

Method 1:

As aid liquid is used a liquid with less density than that of the solid material, e.g. ethanol approx. 0.8 g/cm3.

This method should be applied when the density of the solid is just slightly different from that of the distilled water.

Using ethanol is not recommended, when the solid material is being attacked.

When working with ethanol, you must observe the applicable safety regulations.

Method 2:

Here the sample is not placed upon, but under the lower sample dish. For this purpose, use the immersion basket for floating solid matter [See chap. 1.1, no. 12].

 Activate "density determination solid matter" and enter the parameters for the

auxiliary fluid, see chap. 4.1.

 Density measurement see chapter 4.2, in step 3 place the sample under the

sifting bowl. If the buoyancy of the sample is so much that the immersion basket is lifted, place a dummy weight on it and tare it away when weighing in air.

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5 Determining density of liquids

A glass sinker of a known volume is used for a density determination of liquids (See embossing on suspension hook). The glass sinker is weighed first in air and then in the liquid whose density is to be determined. From the weight difference results the buoyancy from where the software calculates the density.

Prepare balance as described in chapter 3 "Installation of density determination set".

 Install holder for the thermometer on beaker rim.  Suspend thermometer  Pour test liquid into glass beaker. Filling height should be approx. ¾ of the

capacity.

 Heat test liquid until temperature is constant.  Prepare glass sinker

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Additional weight

 Add additional weights if error message “Er 1 Hi“ appears, or if the display does

not react.

5.1 Ca ll up "density determination fluid"

The first function “F1 basic“ appears.

Press repeatedly until “F7 d_Li“ appears.

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Acknowledge with .

 Enter the glass sinker’s volume when “vol“ appears (See embossing on

suspension hook). Enter as many decimal places as required by the weighing scale. The volume of the most recently used glass sinker will be displayed.

 To change, select by pressing or the digit you wish to change (the

active digit will be flashing) and press to increase or to decrease the numeric value.

 Confirm entry by pressing and the volume of the glass sinker will be saved.

Density determination will be star ting at this point (See chap. 5.2).

AES-A01N-BA-e-1210 17

5.2 Calculate density

1. As soon as LOAD A followed by zero appears, attach the glass sinker. The weight of the sinker in air will be displayed.

2. Wait for stability display ( ), then press . The sinker’s weight in air will be saved.

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3. As soon as LOAD L followed by zero appears put the glass beaker containing the test liquid on the platform. Immerse glass sinker completely in the fluid, trying to avoid bubble formation. The test liquid should cover the glass sinker to a level of about 10 – 15 mm.

5. Wait for stability display ( ), then press . The weighing scale calculates the liquid’s density and will show the result in [g/cm3].

 If you have an optional printer connected you can print the result by pressing

2.3456 g/cm3

 Remove the sample. To carry out further measuring, press , and then start

with step 1.

 Press to return to menu, then use to return to weighing mode.

AES-A01N-BA-e-1210 19

ρ =

A-B

6 Preconditions for Precise Measurements

There are numerous error possibilities during density determination. Accurate knowledge and caution are required to achieve precise results when applying this density set in combination with the balance.

6.1 Ca lculation of Results

The balance displays results for density determination by giving four decimal places. However, this does not mean that the results are accurate down to the last decimal place as this would be the case for a calculated value. Therefore all weighing results used for calculations have to be examined closely. Example for density de ter mi n ati on o f soli ds : To ensure high-grade results, numerators as well as common denominators of the formula below must show the desired accuracy. If either of them is instable or flawed, the result, too, will be instable or flawed.

ρ = Density of sample A = Weight of the sample in air B = Weight of the sample in the aid liquid

= Density of the aid liquid

6.2 Influence Factors for Measurement Errors

6.2.1 Air bubbles

A small bubble with a diameter of 1 mm results in a raise of 0.5 mg, while those with 2 mm Ø already produce a raise of 4 mg. Therefore, make sure that no air bubbles adhere on the solid object or sinker that is immersed in the liquid. An oily surface causes air bubbles when immersing in the liquid, so

 Remove grease from solvent resistant solid matter sam pl e  clean all parts that are immersed regularly and don't touch them with bare

fingers

Don't lay solid samples (particularly flat objects) outside of the liquid on the sample bowl, because this results in air bubbles by the joint immersion.

6.2.2 Solid matter sample

A sample possessing too great a volume that is immersed in fluid will result in an increase in fluid level inside the glass pitcher. As a result, part of the suspension bracket of the sample dish will also be immersed causing buoyancy to increase. As a consequence the weight of the specimen in the fluid will drop. Samples that change the volume or assimilate fluid are unsuitable for measurement.

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6.2.3 Liquids

Solids are generally not sensitive to temperature changes, so that the corresponding density changes are not rel ev ant . However, since you work with an aid liquid by the density determination of solids, according to the "Archimedean Principle", its temperature is taken into account. The temperature change effects liquids greater and causes changes in the density in order of 0.1 to 1 ‰ per °C. Hereby, the third digit after the decimal point is affected.

6.2.4 Surface

The suspension bracket of the sample dish penetrates the surface of the fluid. This state undergoes continuous change. If the sample or the sinker is relatively small, the surface tension will impair repeatability. Adding a small amount of tenside (detergent) makes surface tension negligible and increases reproducibility.

6.3 G eneral information

6.3.1 Density / Relative Density

Relative density follows from the weight of a specimen divided by the weight of water (at 4° Celsius) of the same volume. For this reason relative density does not have a unit. Density equals mass divided by volume. The application of the relative density instead of the density of a fluid in a formula produces an incorrect result. In the case of fluids only their density is physically meaningful.

6.3.2 Drift of Balance Display

The drifting of a balance does not influence the final result of the density determination altho ugh the shown weight of weighing in air is affected. Accurate values are merely required if the density of fluids is determined by means of a sinker. When changing the ambient temperature or location, an adjustment of the balance is necessary. For this purpose, remove the density set and carry out adjustment using the standard weighing pan.

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Temperatur

Density ρ [g/cm

]

Water

Ethyl alcohol

Methyl alcohol

0.9997

0.7978

0.8009

0.9996

0.7969

0.8000

0.9995

0.7961

0.7991

0.9994

0.7953

0.7982

0.9993

0.7944

0.7972

0.9991

0.7935

0.7963

0.9990

0.7927

0.7954

0.9988

0.7918

0.7945

0.9986

0.7909

0.7935

0.9984

0.7901

0.7926

0.9982

0.7893

0.7917

0.9980

0.7884

0.7907

0.9978

0.7876

0.7898

0.9976

0.7867

0.7880

0.9973

0.7859

0.7870

0.9971

0.7851

0.7870

0.9968

0.7842

0.7861

0.9965

0.7833

0.7852

0.9963

0.7824

0.7842

0.9960

0.7816

0.7833

0.9957

0.7808

0.7824

0.9954

0.7800

0.7814

0.9951

0.7791

0.7805

0.9947

0.7783

0.7896

0.9944

0.7774

0.7886

0.9941

0.7766

0.7877

7 Density Table for Fluids

e [°C]

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8 User Instructions

• T o form a reproducible mean value several density measurement are necessary

• Remove fat from solvent-resistant sample / /glass sinker /beaker.

• Regularly clean sample dishes/g l ass sinker /beaker, do not touch immerse d par t

with your hands

• Dry sample/glass sinker/pincers after each measurement.

• Adjust sample size to sample dish (ideal sample size > 5 g).

• Only use distilled water.

• When immersing for the fi r st time, lightly shake sample dishes and sinker, in order

to Dissolve air bubbles.

• Always ensure that, when re-immersing into the liquid no additional bubbles

adhere; it is better to use pincers to place the sample.

• Remove firmly adherent air bubbles with a fine brush or a similar tool.

• T o avoid adherent air bubbles smoothen samples with rough surface.

• T ake care that no water drips onto the upper sample dish when weighing with the

help of tweezers.

• In order to reduce the surface tension of water and the friction of the liquid on the

wire, add three drops of a common detergent (washing-up liquid) to the measuring liquid (density modification of dist. water occurring due to the addition of tensides can be ignored).

• Oval samples can be held more easily with pincers when you cut grooves into

them.

• T he density of porous solids may only be determined approximately. Buoyancy

errors occur when not all the air is eliminated from the pores during immersion in the measuring fluid.

• T o avoid great vibrations of the balance, place sample carefully.

• Avoid static charge, e. g. dry glass sinker with cotton cloth only.

• If the density of your solid only deviates slightly from that of distilled water,

ethanol may be used as measuring flui d. However, check beforehand whether the sample is solvent-proof. In addition you must observe the applicable safety regulations when working with ethanol.

• Handle glass sinker with care

(no warranty claims in case of damage).

• T o avoid corrosion, don't leave the density set immersed in liquid for a long time.

AES-A01N-BA-e-1210 23