FINAL REPORT

Materials.
0.1M NaOH
Eriochrome black T
Buffer solution (dissolve 7.0g NH 4 Cl in 57.0ml of concentrated ammonia solution and dilute
to 1.0L)
Standard disodium ethylenediamnietetraacetate dehydrate
Experimental procedure
Determination of content Ca + Mg: Pipette 20.0ml of the water extract into a 250ml conical
flask and add 10ml of buffer solution and 5 drops of indicator solution. Carry out one rough
titration to get an idea of the location of the end point. The color change is the same as in the
standardization experiment. Repeat the titration using another 20ml aliquot of the water
sample but this time add ¾ of the expected titrant before adding the buffer and indicator. If
sufficient sample is available, repeat the titration several times and take the average.
Determination of content Ca. Adjust the pH of 20ml water extract to between 12 and 12.25
using 1M NaOH. Do not add buffer. Add 0.2g of indicator to the solution and titrate as before
until the color changes from wine red to blue. Repeat the titration several times on different
20ml aliquots of sample and take the average. Calculate the calcium hardness in the water
sample as mg CaCO 3 L -1 using the same expression as for total hardness.
10.Determination of heavy metals
Heavy metals are extracted into acid solution and analyzed by AAS.
Nitric Acid –Hydrochloric Acid Digestion
Methodology
Heavy metals are digested by solution of hot mixture of nitric end hydrochloric acid.
Me 2 O x +2õH + ⇢2Me x+ +xH 2 O
Materials.
Hydrochloric acid, concentrated
Nitric acid, concentrated
Hydrochloric acid, 1N
Hot plate with magnetic stirrer
Filter paper
Experimental Procedure.
Weigh 0.5g of soil sample. Add 5ml nitric acid and 10ml hydrochloric acid. Boil until end of
liquid phase. Repeat last two steps. Then solute the sample by 100ml hydrochloric acid, 1N.
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