Determination of Total Alkali Content in Soaps

The ISO 684 standard covers a test method for the determination of the total free alkali content of commercial soaps.

The soap sample cannot be tested under the following conditions under the standard test procedure:
- If it contains additives (alkali silicates, etc.) that can be decomposed with sulfuric acid,
- The method is also not applicable to colored soaps if the color interferes with the phenolphthalein endpoint.

Sum of free caustic alkali and free carbonate alkali content; defined as total free alkali. Determination of Total Alkali Amount within the scope of ISO 684 standard is carried out with the following principle.

- Dissolving soap in an ethanolic solution,
- Neutralization of free alkali with known excess sulfuric acid solution
- Back titration of excess acid with ethanolic potassium hydroxide solution.

It should not differ more than 0.05% between the Determination of Total Alkali Content and two different results expressed as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

- ISO 684: Analysis of soaps — Determination of total free alkali
- BS 1715-2.1: Analysis of Soaps. Quantitative Test Methods. Method For Determination of Total Alkali Content and Total Fatty Matter Content
- BS 1715-2.2: Total free alkali content

You can contact Nanolab Cosmetic Analysis Laboratory for the Determination of Total Alkali Amount.