[via4ngel]

Hi There!

So I make calcium soap, i want to check the free alkali / free acid of the soap.
I have checked with method from AOCS using titration with ethanol as the solvent. But i got problem, because calcium soap can not dissolve in ethanol. therefore, i'm not sure whether my analysis is true or not. Is there any other method to check the free alkali/free acid for Calcium Soap?

[Borek]

For soluble free alkali/free acids it should be enough to just shake the soap with water and titrate the solution, inert solids won't react, acids/alkali will. Not sure why they use ethanol.

[via4ngel]

thank you for the reply.

Well, i think if you use water, the soap itself will break apart due to the presence of water. That breakdown will provide OH- ions. We don't want to measure OH- ions that come from soap, only free OH- ions in the soap. That is why they use etanol, i guess.