ISO 731-5:1977

Formic acid for industrial use — Methods of test — Part 5: Visual limit test for inorganic sulphates

The principle consists in a comparison of the turbidity, obtained by the addition of barium chloride to a solution prepared from a test portion in the presence of hydrochloric acid, with that similarly obtained from a standard sulphate solution. The method is a applicable to products having inorganic sulphates contents, expressed as sulphate (SO42-), in the range 0,001 to 0,1 % (m/m).