Determination of Acetates

Determination of Acetates

Julian and Smart state that cyanide solutions undergoing decomposition form not only formates but acetates. Clennell states that he has never found acetates present in a working cyanide solution unless lead acetate was being used, but on the assumption that acetates may perhaps be formed in certain circumstances he suggests the following equation.

4KCN + 5H2O = CH3CO2K + 2KCNO + KOH + 2NH3

Method of assaying and determining acetates

To 50 cc of the solution to be tested add neutral solution of silver sulphate in slight excess. Agitate, settle, and filter, wash with cold water. The acetates will be in the filtrate. Evaporate the filtrate to a small bulk, transfer to a boiling flask, and distill in the presence of sulphuric acid, collecting the distillate in 50 cc of decinormal NaOH. Continue distillation until about 10 cc remains in the flask, say for one hour. Titrate the residual NaOH in distillate with N/10 acid.

1 cc N/10 alkali consumed = 0.0059 gm. CH3CO2

This method assumes that the filtrate from precipitation with Ag2SO4 contains no volatile acid except acetic. The presence of acetic acid in the distillate may be confirmed by making slightly acid with HCl, adding ferric chloride and boiling. A deep red color should be produced on addition of FeCl3 giving a light red flocculent precipitate on boiling.