Soap is an anionic surfactant used for washing and cleaning, producing a surface-active anion in water. Soaps are alkaline salts of higher fatty acids that are water-soluble. Potassium salts are called soft soaps, while sodium salts are called hard soaps. For cosmetic purposes, only hard soaps are used, which may contain moisturizing agents, fragrances, or stabilizers. Soaps have an alkaline pH in water, typically above 9.