Soaps are sodium or potassium salts of long-chain carboxylic acids. Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids.
Soaps do not form lather in hard water because hard water contains calcium and magnesium salts. Soap molecules react with calcium and magnesium salts to form an insoluble precipitate called SCUM.
Two problems which arise because of the use of detergents are:
(i) Detergents are non-biodegradable; hence, detergents accumulate in the environment and cause problems.
(ii) Certain phosphate additives are added to detergents which form a thick green scum over the river water and harm the animal life in the river.
