ISO 685:1975
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Analysis of soaps -- Determination of total alkali content and total fatty matter content

This standard was last reviewed* in 2010.

*ISO standards are reviewed every five years.


The method consists in decomposition of the soap by a known volume of standard volumetric mineral acid solution, extraction and separation of the liberated fatty matter with light petroleum and determination of a total alkali content by titration of the excess of acid contained in the aqueous phase with a standard volumetric sodium hydroxide solution. After evaporation of the light petroleum from the extract, dissolution of the residue in ethanol and neutralization of the fatty acids with a standard volumetric potassium hydroxide solution. Evaporation of the ethanol and weighing of the soap formed to determine the total fatty matter content.


  • Document published on: 1975-10-01
    Edition: 1 (Monolingual) ICS: 71.100.40
    Status: Published Stage: 90.20 (2015-07-15)
    TC/SC: ISO/TC 91 Number of Pages: 3
  • Revises: ISO/R 455:1965

  • No corrigenda or amendments available

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