JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS similarly to that obtained from another source, in the case of the alkylola- mides he often buys a mixed preparation, which is efficient or otherwise according to its mode of preparation and the skill or lack of it possessed by the manufacturer. Fatty acid alkylolamides can be broadly subdivided into two main classes: (a) freely water-soluble derivatives (b) relatively insoluble waxy materials. The compounds falling within classification (a) are chiefly used as deter- gents (or in some cases foaming agents), as wetting and emulsifying agents, :and as dyeing assistants. Some special examples are used in conjunction with detergents of the alkyl sulphate and alkyl-aryl-sulphonate types, :generally in liquid preparations, to augment the foaming powers of the latter. Compounds falling within class (b) are mainly used as emulsifying agents and emulsion stabilisers, and some particular compounds as additives to various commercially useful detergents to enhance the lathering power and soil removal efficiency of the latter. Recently, certain compounds of this class have been used as dye solvents in cosmetic manufacture. No individual compound will, of course, be ideally suited for all these purposes, and it is a feature of these materials that the product may be "tailor made" for any particular purpose. The critical factor determining in which class a compound would fall is the balance between the hydrophilic "head" (the alkylolamine residue) and the hydrophobic "tail" (the fatty acid chain) of the molecule. In the case of the water-soluble class the "head" generally derives its hydrophilic character in one of three ways. Firstly, the compound may be derived from a simple mono-alkylolamine, but the hydroxyl group of this may be sulphated to give a sulphuric acid ester linkage. Secondly, the fatty acid alkylolamide may be derived from an alkylolamine of greater com- plexity containing more than one hydroxyl group. Thirdly, the fatty acid alkylolamide may be derived from a simple or complex alkylolamine and subsequently condensed with ethylene oxide to increase its water solubility. The sulphated compounds are, of course, anionic detergents. They will in general possess a structure which may be indicated as: R.CO.NH.CH•.CH•... O.SO•Na where R.CO is a fatty acid radical. When R.CO is derived from fatty acids, profusely lathering types of detergents are obtained, which, when correctly manufactured, not only equal lauryl sulphates in most respects, but are superior to them in some, being at the same time far more economically priced. Products based on longer fatty acid chains yield excellent heavy duty detergents with almost unsurpassed lime-soap dispersing properties, but of less profuse lather. Concentrated preparations may be obtained in powder, liquid, or paste form, depending on the particular compound and 170

FATTY ACID ALKYLOLAMIDES the extent to which water or other inert diluents such as inorganic electrolytes are present. The products are mainly used as detergents, and are principally of interest to cosmetic chemists for the formulation of shampoos or bubble bath preparations and the like. Some sulphated compounds do, however, find applications as emulsifying agents and may be used effectively, in conjunction with unsulphated fatty acid alkylolamides of the water-insoluble class, in much the same way as, in the past, sulphated 'cetyl alcohol has been used in conjunction with the insoluble waxy unsulphated cetyl alcohol. When considering the sulphated alkylolamides, we come face to face with the problem of impurities. Most commercial preparations are impure to the extent that they contain significant amounts of unsulphated alkylolamide. Whereas in, for example, a sulphated lauryl alcohol preparation the presence of unsulphated fatty alcohol may not always be desirable, in the case of fatty acid alkylolamides, however, it is true to say that some percentages of unsulphated material usually improve the efficiency of the preparation. Materials offered commercially are frequently not more than 85 per cent sulphated. Unfortunately, there is another potential impurity deriving from the reactivity of the alkylolamines which is quite undesirable, and in the early days considerable difficulties were experienced, on this account, in producing really satisfactory products. The undesirable impurity may arise in one of two ways. The impurity may be present in the wax before sulphation, due to condensation having taken place the wrong way round, giving the ester: R.CO.O.CH•.CH•.NH2 or it may be produced during the sulphation by a cyclisation mechanism thus: O--CH• /- R. CO.NH.CH•.CH•.OSO•Na --• R.C. q- H.SO•Na % N--CH• H•O ----• R.CO.O.CH2.CH•.NHo. These undesirable by-products have to be avoided by employing special methods for the preparation of the fundamental acyl-alkylolamides and by developing special sulphation techniques. Sulphated fatty acid alkylola- mides are manufactured in the U.S.A., France, Holland, Great Britain and elsewhere. Well-known foreign brands include the: Eriopons, Enerpons, Sodapons, Somepons, Amitex T B, Alframine, Sulframine, Emcol, etc. In Great Britain the CO•I)A•OL range of detergents is based on similar deriva- tives. A voluminous patent literature, of which only a few examples are quoted here, attests to the growing importance of this class (U.S. Pat. 171