Soaps are made from animal fats or vegetable oils. They contain glyceryl esters of long chain fatty acids. When the glycerides are heated with a solution of sodium hydroxide they become soap and glycerol. We have already learnt this reaction under the preparation of glycerol by saponification. Common salt is added to the reaction mixture to decrease the solubility of soap and it helps to precipitate out from the aqueous solution. Soap is then mixed with desired colours, perfumes and chemicals of medicinal importance.$\mathrm{vegetable} \mathrm{oil} \mathrm{or} \mathrm{Animal} \mathrm{fat} + \mathrm{Sodium} \mathrm{hydroxide}\underset{∆}{\overset{\mathrm{Saponification}}{\to }}\mathrm{Glycerol} + \mathrm{Sodium} \mathrm{salt} \mathrm{of} \mathrm{fatty} \mathrm{acid} \left(\mathrm{Soap}\right)$