Soap and Detergents
SOAPS
Ordinary soaps are derived from fats and oils by saponification with sodium hy-droxide. Saponification is a special case of hydrolysis in which an alkaline agent is present to neutralize the fatty acids as they are formed. Beef fat and cottonseed oil are used to pro-duce low-grade, heavy-duty soaps. Coconut and other oils are used in the produc-tion of toilet soaps.
All sodium and potassium soaps are soluble in water. If the water is hard, the calcium, magnesium, and any other ions causing hardness precipitate the soap in the form of metallic soaps. Soap must be added to precipitate all the ions causing hardness before it can act as a surfactant, usually indicated by the onset of frothing upon agitation The synthetic surfactants are of three major types: anionic, nonionic, and cationic.
Cationic Detergents
The cationic detergents are salts of quaternary ammonium hydroxide. In quaternary ammonium hydroxide, the hydrogens of the ammonium ion have all been replaced with alkyl groups. The surface-active properties are contained in the cation.
The cationic detergents are noted for their disinfecting (bactericidal) properties. They are used as sanitizing agents for dishwashing where hot water is unavailable or undesirable.
The alkyl-benzene sulfonates de-rived from propene were highly resistant to biodegradation, and their persistence resulted in excessive foaming in rivers and groundwaters in the 1950s. This presented some of the first evidence of the potential harmful environmental consequences of synthetic organic chemicals. For this reason, the detergent manufacturing industry changed to the production of LAS surfactants. LAS is readily degradable under aerobic conditions, and its use has helped relieve the most serious problems of detergent foaming. However, unlike common soap, it is resistant