Question

How to determine total anhydrous soap in hand liquid soap?

Answer 1

Anhydrous soaps are a hydrated, water and fatty acids free form of soaps that are used for a wide variety of applications. Anhydrous soaps can be obtained by certain chemical processes.

Complete step-by-step answer: To determine the total anhydrous soap in liquid hand wash, the sample of liquid hand wash is treated through various steps as follows:
- The liquid soap sample is dissolved in hot ethanol around $60{}^\circ C$.
- Add excess of sulfuric acid while heating at the same temperature.
This will separate the fatty acids from the liquid soap as a distinct layer.
-Now transfer and separate the mixture in the separating funnel by removing the acid layer.
- Add some ether to take out the acid layer from the funnel.
- Wash this obtained solution of acid and ether with water until a neutral solution is obtained and transfer this into a flask.
- Add ethyl alcohol to this and then set up titration with sodium hydroxide.
- Now evaporate out the ethanol and ether using a steam bath.
- Then dry this at $105{}^\circ C$ until a solid of constant weight is obtained.
From this process you can calculate the amount of anhydrous soap present in the sample. Measure the amount of anhydrous soap obtained from the sample taken.
Hence, anhydrous soap is determined.

Note: While doing this practically, take the amount of sample carefully otherwise the calculations may differ. The anhydrous soap extracted is useful and free from microbes and contamination.