Colorimetric determination of aliphatic acids.

A colorimetric method for the determination of carboxylic acids based on the dicyclohexylcarbodiimide-coupled reaction of 2-nitrophenylhydrazine and carboxylic acids is described. The product of the reaction is extracted into aqueous sodium hydroxide to produce a blue color. This method is suitable for the analysis of aliphatic acids, but aromatic acids do not react under these conditions.