Determination of soap and free fatty amine

Three approaches are possible, which are briefly described here. Free fatty amine in sulphosuccinamates cannot be determined by potentiomet-ric titration because the carboxylate group is also titrated. 

For extraction of fatty acid, acidify with 1 M hydrochloric acid. For extraction of fatty amine, make alkaline with 1 M sodium hydroxide. 

Extract with three 50 ml portions of petroleum ether. Wash the combined extracts with 50 ml 50% aqueous ethanol, evaporate to dryness, cool and weigh. 

Titrate two 25 ml portions with 0.004 M benzethonium chloride, one portion using acid mixed indicator and the other using bromophenol blue in alkaline solution. 

The titration in acid solution measures acyl taurates or methyltaurates. The titration in alkaline solution measures the same actives plus soap. 

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