The main effective component of soap is sodium fatty acid, which is weakly alkaline when it meets water. Only by using more hydroxyl groups in the alkaline solution can the oil stain be removed, and the hydrogen ions in the acidic solution cannot react with the oil stain.

Soap is also called high-grade fatty acid soap, and its scientific name is carboxylate. Carboxylates are generally saponified by oil and alkali under heating conditions. This is an anionic surfactant. Because the grease and alkali used are different, laundry soap with different properties can be made.