204 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Fig. $. The co•ro! room of the •cetyle•e high-pressure building. would expect, give solutions of extremely high viscosity, and these may find application as special-purpose thickening agents, etc., but they are otherwise of relatively little commercial interest in this country at the present time. 4. COSMETIC AND TOILET PREPARATION USES OF POLYVINYLPYRROLIDONE (a) General Apart from the general properties of polyvinylpyrrolidone reviewed above, the cosmetic chemist will be interested to know that it is a stable substance, uniform in its properties and, as far as we know, without harmful physiological effects, although clearly in any new application it is essential to check this by the usual methods. The study of the possible uses of polyvinylpyrrolidone in cosmetics and toilet preparations appears to have originated from work carried out in America by Shelanski, Shelanski and Cantor, ø who demonstrated that polyvinylpyrrolidone is substantive to human skin and hair. The resultant films leave the skin smooth and soft to the touch, and when the polymer, suitably formulated, is applied to the hair it imparts a conditioning effect, enhancing its appearance and manageability.

POLYVINYLPYRROLII)ONE IN COSMETICS 205 •ig. 9. View of the spray dryer for the final recovery of solid polyvinylpyrrolidone. The combination of these somewhat remarkable properties has encour- aged cosmetic chemists to evaluate polyvinylpyrrolidone for a wide variety of uses employing these special characteristics. It is not suggested that polyvinylpyrrolidone be used simply as a water-soluble binder and thickening agent, although it is suitable for use in this way. The polymer is clearly too expensive to compete with the older materials, and it must be pointed out that the lengthy synthesis of the product rules out the possibility of it ever becoming very much cheaper. Attention has therefore been primarily directed to developing those uses where the polymer's special properties can be used to advantage as a bonus over its more normal properties as a water-soluble film former and binder.