POLYVINYLPYRROLIDONE IN COSMETICS 197 have been developed in the textile industry, photographic industry and so on. It is with one group of such uses, in the formulation of cosmetics and toilet preparations, that we are now concerned. It should be emphasised at the outset that special grades of polyvinyl- pyrrolidone are required for internal medical use, and materials supplied for industrial and cosmetic purposes should not be used in pharmaceuticals. 2. SYNTHESIS SYNTHESIS OF POLYVINYLPYRROLIDONE LIMESTONE I I • CARBON LIME DIOXIDE I I C.•LCIUM CARBIDE ACETYLENE CH•CH COKE WATER METHYL [• • ALl-_9 HOL AIv•MONL• FORMALDEHYDE 0,.•. CH 2 BUTYN•[-1:4 DIOL HOH 2 • C---C C CH 2 OH BUTANE 1:4 DIOL ..• c-•. c.• c.•o. • BUTYROLAC tONE HC,,. /CO 20 • l • PYRR(•LIDONE I I N VINYLPYRROUDONE CH = CH::) POLYMER ISATION AIR NITROGEN OXYGEN PO LYVINYLP.YRROLIDONE Fig. 2. Synthesis of Polyvinylpyrrolidone. Polyvinylpyrrolidone is primarily derived from limestone, coke, water and air, and is therefore potentially available in unlimited quantities. As it is completely synthetic there is little variation in the properties or quality of the material, which can be controlled during manufacture. The polymer is prepared by the following series of reactions, two of which involve the use of acetylene under elevated pressures. It is perhaps worth mentioning that in handling acetylene, explosive

]98 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS decompositions can readily be initiated at pressures above 0-6 arm. above atmospheric pressure, and special precautions and techniques have to be adopted to avoid the associated hazards. Indeed, such operations are governed by legislation issued under Orders in Council, which only permit the handling of acetylene at pressures up to 9 lb. per sq. inch normally very special precautions are called for at higher pressures. For chemical purposes, pressures up to 20 atmospheres may be used, subject to the approval by H.M. Chief Inspector of Explosives of the equipment and the techniques used. The equipment illustrated, particularly in Fig. 8, has been designed to meet these requirements. This equipment is probably amongst the most advanced in design with regard to safety existing at this time. •,• .:• •?"•'•. . •. ,- . ß . .•-:. •':• '• ....• ß • • •-•'.•.• :•.:.: 2• •:. .} -•.. .:•,• ..q. :.:..:.:.: j.'•:. ?5 ':'. :• :. -: . j..-',. , . •' .•: .-•...•.:.• • ..... ...?. '•:-.. :- ...: •:..•:.-. :':.. [ :..::•:.: ß .'j .j• • •.-, ..:.: :.:. ..:'. • • ::- •. . •.-.. --• :.... . .. ,, .•:•.... -¾•.•(• .... -• ... :: ... Fig. 3. View of the reactor and vessel used in the production of gamma butyrolactone.