FINAL REPORT
FINAL REPORT
FINAL REPORT
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2Ag + +CrO 2- 4 →Ag 2 CrO 4 (s)<br />
Materials<br />
0.005M AgNO 3 standard solution<br />
5% potassium chromate solution<br />
Burette<br />
100ml conical flasks<br />
Experimental procedure<br />
Pipette 20ml of water extract into a 100ml conical flask and add the 1ml indicator of<br />
potassium chromate solution and titrate as a solution of AgNO 3 to precipitate silver chromate<br />
which has a distinctive reddish-brown color.<br />
8. Determination of content sulphate ion<br />
Methodology<br />
An excess of barium chloride (BaCl 2 ) is added to the sample. The barium ion reacts with the<br />
sulfate to precipitate barium sulfate crystals of uniform size:<br />
Ba 2+ + SO 2- 4 →BaSO 4(S)<br />
The colloidal suspension is measured using a spectrophotometer and the sulfate concentration<br />
determined by comparison with standards. Suspended particles present in large amounts will<br />
interfere and these can be removed by filtration. Highly colored samples may give erroneous<br />
results.<br />
Materials<br />
Spectrophotometer and absorption cell<br />
Barium chloride, crystalline<br />
Sodium chloride-hydrochloric acid reagent<br />
Glycerol-ethanol solution<br />
Standard sulfate solution, 100mg/l<br />
Experimental procedure<br />
Measure 10ml of sample into a 25ml flack and add 2ml of the NaCl-HCl solution and 2ml of<br />
the glycerol-alcohol solution. Add approximately 0.03g barium chloride. Stir for 2 min<br />
exactly after adding the barium chloride. Immediately pour some solution into an absorption<br />
cell and measure the absorbance at 420nm after exactly 3 min. Prepare series of calibration<br />
standards by pipetting aliquots of the standard sulfate solution corresponding to between 0.5<br />
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