Tensides (or Surfactants) and Heavy Metal Soaps

Metal carboxylates-higher carboxylates of alkali (Soaps) and other metals (metallic soaps)-are used in many areas of daily life and industry. While the basic colloidal and other physicochemical properties of these derivatives have already been extensively studied, there has recently been a revival of interest in the various modes of bonding exhibited by metal carboxylates. Many metal carboxylates have been known from ancient times. The oldest organic derivatives of metals are the alkali metal carboxylates, commonly known as soaps. These soaps are soluble in water, with which they readily produce foam, commonly used for washing or cleansing purposes. Carboxylates of metal other than alkali metals (with the exception of lithium) are generally insoluble in water and are called Metallic soaps. The first use of such soaps in the form of lead linoleates appears to have been made quite early in paints for mummification. Metallic soaps are, therefore, simple carboxylates of alkaline earths or other polyvalent metals with the general formula, M(O₂CR)n, where 'M' is a metal in oxidation state 'n' and 'R' is an organic radical containing at least 6-7-carbon atoms. The term metallic soaps is restricted by some of the salts of fatty acids (i.e. those in which R is an aliphatic radical) although in the broad sense the term also includes salts of certain cyclic acids.