Titration with benzethonium chloride and hydrolysis

These materials can be titrated with benzethonium chloride, either by ISO 2271 or potentiometrically. 

The sulphate group is easily hydrolysed, but prolonged boiling with strong acid is necessary to hydrolyse the amide group. The products of 

However, direct titration of the liberated acidity is not really practicable, because of the high level of acid reagent. Also, the liberated hydrogen ion is neutralised by protonation of the alkanolamine, and titration to bromocresol green or methyl orange (ASTM method D 1570, ref. 6) would not measure it. On the other hand, titration to phenolphthalein (with alkali in alcoholic solution) would titrate not only that proton but the liberated fatty acid as well. It is therefore necessary to extract the fatty acid and to determine fatty acid and alkanolamine separately. 

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