JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS some waxes are emulsifiable, others (particularly the hydrocarbon waxes) are not. A further reason for omitting emulsifiability is that it is not a typical wax characteristic, although wax emulsions are of considerable importance as polishes and for industrial uses (paper coating, textile impreg- nation, etc.). So far as the emulsifiable types of wax are concerned, the ease of emulsi- fication differs greatly. Various waxes often require different emulsifying agents and the resulting emulsions may exhibit a different degree of fluidity, particle size, stability and compatibility with additives. With a few excep- tions, wax emulsions are primarily used where gloss production is aimed at. For the manufacture of cosmetics, the anionic and nonionic emulsifying agents listed under the heading of "related materials" are, as a rule, superior to waxes as a basis for emulsions. On the other hand, the incorporation of a suitable wax often leads to considerable improvements. The Spans, Tweens, and similar non-ionic surface-active agents are marketed in a wide variety of types with different hydrophilic/lipophilic balances, which make it fairly easy to produce either oil-in-water or water-in- oil emulsions. As mentioned above in connection with waxes, the stability of emulsions and their compatibility with medicating additives greatly depends on the emulsifying agent used. Finally, it should be recorded that even hydrocarbon waxes can relatively easily be emulsified with modern emulsifying agents. MODERN CONCEPTS OF WAX ANALYSIS AND EVALUATION The old-established physico-chemical fat-constants remain very useful so long as their limitations are properly understood and the results not simply recorded but correctly interpreted. In the majority of cases they provide circumstantial evidence only, as materials with identical or very similar constants may widely differ in chemical composition and/or technological properties. With the help of the "constants" only clumsy adulterations can be detected and, by the same token, their identifying value is limited and often misleading. For materiMs of a complicated and/or not fully known chemical com- position and for the analytical evaluation of hydrocarbon waxes, the "con- stants" are of very little use, and physical, physico-analytical, and specific performance and keeping tests have proved to be much better tools than those provided by fat-analytical examinations. The determination of the retention number and the retention effect, in conjunction with that of the paste index, paste consistency, and viscosity, permits the evaluation of hydrocarbon waxes, microcrystalline waxes and the like. The same procedure will be found useful also in the case of other waxes. Retention-number and -effect measure the binding and homogenising 138

WAX AND THE COSMETIC CHEMIST power of microcrystalline waxes for oils, solvents and crystalline waxes (such as, for instance, paraffin wax). Various types and grades of micro- crystalline wax and of paraffin wax show great differences in this respect and thus in their commercial value. The paste-index and -consistency methods evaluate the hardness (firm- ness) and consistency of pastes made from a particular wax. This, too, is of technological and commercial importance. The viscosity of a wax relates to its molecular (or particle) size and shape, and serves as a further identification and evaluation test. The determination of melting and setting points of a wax (both of them appropriately chosen from the great number of available methods) and of its hardness provide further useful information. The same tests should or could be carried out with a seri•s of mixtures of the wax concerned with paraffin wax. The physico-analytical examination comprises mainly the use of chroma- tography and of urea-complex formation. By means of chromatographic methods it is often possi. ble to separate a wax into its major components and/ or to detect adulterants (for instance, added hydrocarbons in carnauba wax). Urea selectively forms complexes with certain types of compounds (for instance, with straight or little branched chai•s, but not with others). Thiourea has the opposite effect. It is hoped that both methods will be further developed, but already, although only fairly recently applied to waxes, they have been found most useful. Repeated freezing and thawing of emulsions (and preferably estimating also changes, i.e., increase, of particle size by means of turbidimetric examina- tions) will inform about their keeping properties. A similar effect can be achieved by placing emulsions for several hours in an incubator (say, at 35 ø C.) examining them warm and after cooling to room temperature. Regarding details of the methods discussed, reference must be made to published literature. s In connection with the definition of wax, it was stated that they form gels, pastes or mixture masses in conjunction with organic solvents. These three physical systems are representative of specific types of wax, namely (in the same order of listing) microcrystalline wax, paraffin wax and car- nauba wax wax mixtures give rise to further characteristic systems. For details reference must be made to published work.* • Ivanovszky, "Waxes in the Cosmetic Industry," S.P.C. Year Book, 1954. • Ivanovszky, "Wachs-Enzyklopaedie," Volume I, Augsburg, 1954. a Ivanovszky, "Wax Chemistry and Technology," London-Bridgend, 1952 {and the references listed therein) "Wachs-Enzyklopaedie," Volume II (in preparation) in addi- tion, J•ette u. S•ifen, 54, 275-279, 559-562 {1952) 55, 224-229, 302-308, 384-388, 444-448 (1953) Erdoel u. Kohle, 6, 787-791 (1953). • Particularly "Wachs-Enzyklopaedie," Vol. I, and Fette u. Seifen, 55 (1.c.). 139