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Abstract
A new adoption of the methylene blue test has been applied to the analysis of gelatin for its thiosulphate content. Sulphide is produced by borohydride reduction of thiosulphate in alkaline solution. In the presence of p-dimelhylaminooniline and ferric ion in acid solution, the sulphide forms methylene blue. The method is simple. specific. and sensitive. An undesirable side reaction which consumes about one-third of the sulphide in formation of a red by-product is eliminated by iodide ion.
Notes
Paper presented at a symposium on “Photographic Gelatin” organized by the Science Committee or lhe Royal Photographic Society On 19-22 September 1967 in ambridge.