• question_answer Why common salt is added to precipitate out soap from the solution during its manufacture?

Soap is sodium salt of higher fatty acids (RCOONa). On adding common salt, $N{{a}^{+}}$ ion concentration increases. Hence, the equilibrium $RCOONa(s)\rightleftharpoons \,RCO{{O}^{-}}+N{{a}^{+}}$ shifts in the backward direction, i.e., soap precipitates out.