200 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS giving the product as a fine free-flowing powder. The polyvinylpyrrolidone recovered from the dryer has a water content normally in the region of 1'2--1'7 per cent. As the polymer is hygroscopic, it must be packed hot into heat-sealed polythene liners enclosed in stout outer kegs. At each stage of the synthesis, the intermediates are carefully purified by vacuum distillation to avoid side reactions at subsequent stages, as these would make eventual purification much more difficult. The illustrations in the text show various items of the plant at various stages in the synthesis. 3. GENERAL PROPERTIES Polyvinylpyrrolidone is a rather' unique polymer in that it is soluble in both water and a very wide range of organic solvents. POLYVIN•LFYRROLIDOIqE SOLUBILITY ALCOHOLS Methanol El/hanoi Isopropanol N l•utanol Sec butanol Isobutanol N amyl alcohol Isoamyl alcohol N hexanol Sec hexanol Cyclohexanol Diethyl ethanol Ethylene glycol Glycerine Propylene glycol Diacetone Methyl isobutyl carbinol ETHERS Cellosolve ACIDS LACTON•ES Acetic anhydride Glacial acetic acid •,Butyrolactone Oleic acid ESTERS Ethyl acetoacetate Butyl tartrate HALOGEN COMPOUNDS Methylene chloride Ethylene dichloride Ethylene dibromide Ethylene chlorhydrin Chloroform ALDEHYDES XND I•ETONES Acetone Methyl ethyl ketone Acetyl acetone Cyclohexanone Glyoxal Crotonaldehyde Benzaldehyde ]NITROGEN COMPOUN'DS •Pyrrolidone Vinyl pyrrolidone Pyridine Morpholine Nitrobenzene Acrylonitrile Based on the preparation of 10 per cent solutions at room temperature. Certain substances, for example acetone, can give rise to some difficulty as, although anhydrous polyvinylpyrrolidone will dissolve in anhydrous acetone, in the presence of only a little water the polymer tends to separate as a sticky second phase and for this reason such solvents are best avoided. Although polyvinylpyrrolidone itself is insoluble in hydrocarbons, solutions

POLYVINYLPYRROLIDONE IN COSMETICS 201 EFFECT OF DILUENTS ON POLYVINYLPYRROLIDONE SOLUBILITY MI. of Diluent added to Procure a Cloudy Mixture with 20 mi. of P.V.P. Solution Solvents -- Benzene Xylene White Ether AR Ethyl Spirit Acetate Chloroform (AR.) ß. 23 11 7 16 -- I.M.S ..... 32 15 6 26 -- Cellosolve .. 100 100 20 46 200 .. Nitrobenzene .. 18 5 4 unsuitable 22 Methancl (Tech.) .. 100 49 unsuitable 52 2 100 Based on 10 per cent solution of P.V.P. Fig. 12. Solubility of polyvinylpyrrolidone in organic solvents. Fig. 5, General view of the purification section with a vacuum receiver shown in the foreground. in powerful solvents will tolerate considerable dilution with hydrocarbons this is useful in certain applications. Apart from its unique solubility p, operties, the polymer has the novel property of forming complexes with many substances very varied in chemical structure•for example, dyestuffs, iodine, antibiotics, insulin, etc.--and many industrial and pharmaecutical applications have been developed which take advantage of this property.