Determination of soaps in fatty products

Soaps are strongly basic in glacial acetic acid solution, and may be titrated with hydrogen bromide in the same solvent. Zarins et al. [25] determined soaps in various types of fatty products by this method. 

Dissolve a 2 g sample in 15 ml glacial acetic acid and 5 ml benzene. 

Titrate with 0.1 M hydrogen bromide in glacial acetic acid, using crystal violet as indicator. The colour change is from violet to blue-green. 

Both the titration flask and the burette must be protected from atmospheric moisture with drying tubes. The titrant enters the flask via a Luer tip and a PTFE tube passing through a neoprene stopper. During the titration the solution is stirred with a magnetic stirrer. 

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