FATTY ACID ALKYLOLAMIDES are not such that they would normally have been welcomed for inclusion into lipstick compositions, and they have exhibited disadvantages, being in some cases slowly volatile and in others hygroscopic. Certain fatty acid alkylo- lamides are good solvents for the dyes and have a consistency such that they are easily incorporated into lipstick compositions. They are non-volatile and non-hygroscopic. Further, they would not be expected to be toxic since it would be expected that in the body they would yield on hydrolysis fatty acid and alkylolamine, the latter being oxidised to an amino acid. Practical animal-feeding tests have shown that selected acyl-alkylolamides of a high degree of purity are quite free from any apparent toxicity. The solubility of the dyes seems to be dependent upon the presence of the amide linkage, since compounds chemically closely related but devoid of this linkage do not show the solvent power to anything like the same extent. The measured solvent power, however, does vary not only with the alkylolamine residue in the molecule, but also with the fatty acid chain. Patent applica- tion has been made both here and in the U.S. in respect of the use of fatty acid alkylolamides in lipsticks for this purpose, and specially prepared alkylolamides are available in the LOI•AMINE range. A further use of the compounds in our classification (b), which are sub- stantially water insoluble and show a reasonable oil solubility, is as pigment- dispersing agents in oily media. Here again, the interest is mainly to the lipstick chemist who is faced with the problem of grinding insoluble lake colours in an oily medium to produce a uniform dispersion. It is well known that to produce a good dispersion, not only is first-class milling equipment necessary, but also the oil or mixture of oils used must be a good grinding medium. Mineral oil, which by virtue of its freedom from smell and rancidity is ideal for many cosmetic purposes, is not a good grinding medium. The incorporation, however, of significant amounts of fatty acid alkylolamides into the oil can remedy this defect. It has been shown experimentally that it is possible to prepare two lipsticks, one containing only half the amount of the same lake colour as the other, yet each as effective in use from a colour standpoint. The difference in manufacture is that in one case the lake was ground in mineral oil alone and in the other in mineral oil containing oleic mono-ethanolamide. Fatty acid alkylolamides of both classifications (a) and (b) find applica- tion as thickening or stiffening agents for preparations based on synthetic detergents or liquid soaps. They have the power to increase the viscosity of liquid compositions, or to lend greater rigidity to paste or cream prepara- tions. They show great advantage over the colloids and waxes previously used for these purposes in that, of course, they augment rather than cancel the efficiency of the detergent on which the preparation is based. Naturally, it is necessary to choose the best fatty acid alkylolamide for any specific purpose, and the amount of the more insoluble products which can be incor- 177

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS porated into liquid compositions, which must remain clear in the cold, is restricted. In general, fatty acid alkylolamides tend to raise the viscosity of detergent solutions less than they do that of pure water, but in some cases an increased thickening effect can be achieved when polyphosphates are present also. It has been possible here only to indicate the types of fatty acid alkylo- lamides which are available, and to give a brief idea of the purposes for which they are used. The number of possible compounds is very large and the emulsion chemist should find a range of compounds even more extensive and more valuable to him than the wide range of esters of polyhydric alco- hols with fatty acids. The detergent chemist has already come to regard -[atty acid alkylolamides as essential in many of his formulations, and .doubtless much still remains to be discovered. VISIBLE REGION ABSORPTIOMETRY IN COSMETIC ANALYSIS By T. T. GORSUCH, B.Sc., A.R.I.C.* IN A paper in Volume II of the Journal, G. R. Clark •, writing on the use of spectrophotometric methods in cosmetic analysis, dismisses the visible region in one short paragraph. While it must be agreed that its dependence on colour is a limitation, it by no means follows that this restricts its useful- ness to colour matching and the standardisation of dyes and pigments, as is there suggested. Any matehal which can be converted to a coloured deriva- tive is potentially amenable to absorptiometric estimation, and a large number of substances of considerable interest to cosmetic chemists can be estimated by the measurement of the colour or turbidity produced by various general or specific reagents. It must also be borne in mind that the ultra- violet and infra-red regions have difficulties and limitations of their own: by no means all substances will give an absorption in the ultra-voilet while in the infra-red it is more a case of an embarrassment of riches, with interference from solvent absorption becoming a major factor, greatly limiting the number of systems which will give satisfactory results. One great advantage of visible region absorptiometry, as opposed to ultra-violet or infra-red spectrophotometry, lies in the comparative cheapness of the apparatus required: a visible region spectrophotometer costs, perhaps, * County Laboratories, Ltd., Stanmore, Middx. 178