2006-12-15 22:58:12 · 1 answers · asked by el nams 1 in Science & Mathematics ➔ Chemistry
These are usually measured from samples in the final product and not from the mother liquid of the batch of soap made. With fresh ingredients, no carbonate is usually found. The free alkali is used to estimate possible skin irritation.
A small, measured amount of soap is totally dissolved in warm water and then allowed to cool to room temperature. The free alkali plus carbonate is usually determined by volumetric titration with a known acid solution.
The carbonate is not an added ingredient, but is usually present in small amounts from the reaction of the alkali with Carbon dioxide in the air. The carbonate can also be removed using Barium nitrate and the resulting solution is filtered and then used to determine the free alkali.
Free alkali plus carbonate can also be determined by dissolving the soap in ethanol and titration with HCl in ethanol. The free alkali can also be determined by removal of the soap and carbonate using Barium chloride and then titration.
An analysis of the free Sodium and Potassium ions in the solution will be a good check as to the accuracy of the method.
2006-12-17 02:13:04 · answer #1 · answered by Richard 7 · 58⤊ 0⤋