Question

What is the purpose of 4% calcium chloride solution, and trisodium phosphate on preparation of soap experiement.

Organic Chemistry Experiment.

Answer 1

CaCl₂ (calcium chloride) is a salt with high affinity for water, and gets easily hydrated. Salts have the opposite effect that the soap has, because it can increase water surface tension, and therefore, adding CaCl₂ to soap solution will decrease the foam level. This behavior is very useful in chemistry, when it is required to perform "extractions" involving water/ organic solvent. Salt water is added so that the foam is not formed and the compound of interest can be extracted easily.

Na₃PO₄ (TSP) is highly soluble in water producing an alkaline solution, so it makes calcium ions precipitate. Its a common water softener.