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1 Overview
Precipitation titration is a titration analysis method based on precipitation reaction
The method of titration analysis by the reaction of the formation of insoluble silver salt precipitation is called the silver measurement method
2.
Moire is potassium chromate (K 2 of CrO .
(1) The principle of titration
According to the principle of stepwise precipitation, since the solubility of AgCl is lower than that of Ag 2 CrO 4 , AgCl precipitates first during the titration process
(2) Measurement steps
1) Take a certain amount of water sample and add a little K 2 CrO 4 , titrate with AgNO 3 , titrate until brick red appears, and record the volume V 1 of AgNO 3 consumed .
2) Take the same volume of water sample blank (without CI - ), add a little CaC03 .
3) Prepare a standard solution with reference NaCl to calibrate the concentration of the AgNO 3 solution
(3) Matters needing attention
1) A small amount of CaCO 3 is added to the blank water sample without CI - as a foil to make the two at the end point from white precipitation → brick red precipitation to reduce the color difference of the end point, so that the end point is more consistent .
2) The influence of pH value on CI - determination
3) Shake vigorously during titration
(4) Calculation
In the formula, CAgNO 3 —— the concentration of AgNO 3 standard solution, mol/L;
V water -the volume of the water sample, ml;
V 0 ——Volume of AgNO 3 standard solution consumed by distilled water , ml;
V 1 ——The volume of AgNO 3 standard solution consumed by the water sample , ml;
35.