JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS cyanol Chloride and Rhodamide 6G for anionic agents, and Sky Blue FF eosin and fluoroscein for cationic agents. The disappearance of Micelies is determined by a sharp change in colour or sharp reduction of fluorescence. They observe that w/thin each class of detergents the depression of the critical concentra- tion brought about by equal amounts of salt is greater the lower the critical concentration of the detergent. In the case of Potassium Laurate the critical concentration is 2.3 x 10 -• M, in the case of Na Dodecyl sulphate it is 6.02 x 10- 3 M. Dodecyl ammonium chloride has a critical concentrate of 1'31 x 10 The major outlet for surface- active agents in the cosmetic industry is in the preparation of shampoos, although considerable quantities are used in the preparation of liquid and semi-solid emulsions, and as minor constituents in permanent waving solutions and other cosmetic pre- parations. In this country and in Europe in general at present the liquid, paste and powder shampoos appear to have the largest proportion of sales, in America the accent is on liquids and creams, powders being rarities. Liquid products sold by retail are based chiefly on the fatty alcohol or olefine sulphates--triethanolamine or other amine lauryl sulphates, or Teepol, being preferred. Normally the liquids represent about 12 per cent to 15 per cent of fatty alcohols (that is a concentration of about 60 per cent to 75 per cent of the mater- ials as bought) although some manu- facturers keep around 5 per cent of fatty alcohol (about 25 per cent dilutions of materials as bought). Cream shampoos are usually based on the sodium fatty alcohol sul- phates, bought as powder, pastes or needles, and cut with water to about 15 per cent fatty alcohol content and thickened either with sodium stearate or other soap or with colloids such as ' C.M.C., methylcellulose and alginate. The powder shampoos are often totally spray-dried--this form pos- sessing many advantages such as ease of solubility, greater packing volume, cheap packing and increased homogeneity. The fatty alcohol contents vary from about 15 per cent to 45 per cent, and often builders such as sodium sulphate, borax, phosphates are added, following in some cases fairly closely to the older soap powder shampoo formulae. Liquid cream shampoos represent one of the latest presentations and have achieved considerable popu- larity, particularly in the U.S., due to the very attractive packaging used and to the adoption of the aerosol bomb principle of packaging, using freon under pressure as the propel- lent: liquid cream shampoos are often formulated w/th either trieth- anolamine, ammonia or sodium neutralised lauryl sulphates thick- ened and opacified w/th C.M.C. soap, glycerin or glycolesters, magnesium stearate, etc. Zussman, in a paper previously published in this Journal, dealt with the question of the so-called "defatting" action of synthetic sur- face-active agents and brought out, 214

among others, the following points' !i?•11!:?i• • 1. The defatting of the skin pro- duced by synthetics is not the same as true defatting caused by the use of organic solvents. 2. The short chain alkyl naphtha 4 lene sulphonates, which are not good detergents or fat emulsi- fiers, produce the same type of effect on the skin as do the high molecular weight alkyl aryl sulphonates, whereas oleic acid soaps, generally considered to be good fat emulsifiers, do not "dry" the skin. Zussman likens the effect of syn- thetics on the skin to the "scroop" finish to textiles, characterised by a high coefficient of friction and rustle on rubbing. He puts forward the suggestion that the artionic agents should rinse better at slightly alkaline pH's, the cationics at slightly acid pH, and that harshening of the hair, un- manageability, and difficulty in combing after shampooing may very well be the result of increases in friction as a result of absorption of surface active ions on the skin, and that adjustment of pH may over- come these difficulties. The effect of conditioners in sham- poo formulations does not in my experience have much effect on the suppression of harshness produced by some shampoos, notably by anionics having an aromatic ring in their constitution. The aromatic character of these surface •active agents (alkyl aryl) is known adversely to affect lubrication (incidentally, this is also brought out in packaging SYNTHETIC DETERGENTS problems connected with household detergents based on alkyl aryl sul- phonates) and is particularly notice- able at the high concentration used in shampoo techniques, and although considerable work has been done on the additions of conditioners such as nonionic esters, lanolin fractions, etc., the problem of the harshness of the alkyl aryl sulphonates under sham- poo conditions has not yet been overcome (otherwise these are excel- lent and cheap products). Before leaving the question of shampoos, a further point, not directly concerning surface-active agents, is noteworthy--this is the use of small amounts of lime and magnesium sequestering agents of the ethylenediamine tetra-acetic acid type (available as Sequestrene, Irga- Ion, etc.) these are finding applica- tion in the preparation of shampoos based on both soap and some syn- thetic agents, to improve their hard water stability. With regard to the use of the water-soluble and oil-soluble surface- active agents in the preparation of cosmetic emulsions, the number and variety of these products on the market is considerable, the main ones being the fatty acid esters of glycerol, the glycols and condensed glycols, sorbitol and mannitol and pentaerythritols--the products are often available either non-self-emul- sifying, or rendered self-emulsifying by the addition of soap, or anionic products such as sodium lauryl sulphate, or a cationic such as Sapa- mine. The fatty alcohols--cetyl and ceto-