RHEOI,OGICAL MEASUREMENTS IN THE COSMETIC INDUSTRY 97 physical properties of the continuous medium will not be the same as the medium per ,re since interfacial forces come into operation. The net result is that the viscosity of the liquid in between the particles is quite different from that of the bulk medium itself. If the film be thin enough and is compressed by virtue of the concentration of surface active substances, it can be rigid and, under such conditions, the whole will then, when forced through an orifice, have plug as distinct from streamline flow. There are, of course, other factors coming into play. The close-packing of particles brings in frictional forces which may be quite large, depending on shape and range of size, but also modified by a coating of protective colloid. How far these considerations have importance can be determined only by making the tooth paste in its completeness and under standard conditions of manu- facture and testing this for extrudability and rigidity. In other words, it really comes back to the dictum which is allegedly due to King Charles II at a meeting of the Royal Society of London in its very early days. He is said to have been drawn into a philosophical disputation on what would happen in a certain instance and his answer was "Take a bucket and try it." On the problem of how far the viscosity of one phase can affect the rhe- ological properties of a paste or of an emulsion, the only way to solve the problem, with our present knowledge, is not by calculation but by trial and error using the intuition which is to be found amongst those people who are what one terms "good formulators." All the theological data which one obtains outside that particular system have v•ry little moment except to act as rough guides and they are no more valuable if they are expressed in C.G.S. units. One gets the impression when one sees this mode of ex- pression employed, that the worker is creating a false environment and he begins to think that important accuracy is obtained. This is nothing more than deceiving oneself. Whilst it is obviously dishonest to attempt to deceive other people, it is sheer lunacy to deceive oneself. A good case in point is the paper by Heinrich and Clements (1oc. cit.) who, most sensibly, give their results in terms of Meter Readings. It could quite well be in the future that with the vast increase in knowl- edge which is being obtained, the time may come when the mathematics of reactions will be more or less complete and C.G.S. units come into their own. Thus with the aid of the electronic computer it may be possible to feed such a machine so that in the course of a relatively short space of time, a formula can be produced which will take care of all the rheological features without any formulation work having to be done. When this state of affairs comes to be, one may have reached the millenium when all the prod- ucts will be of the same basic formula. It might even lead to greater uni- formity in so far as all the colours and perfumes will also be standardised, based to suit the individual product rather than to appeal to the complex individualities of the consumers.

98 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS REFERENCES (1) de Waele, A., J. Soc. COSMETIC CHEMISTS, 7, 336 (1956). (2) Pryce-Jones, J., 9- Oil & Colour Chemists' Assoc., 26, 3 (1943). (3) Scarbrough, A. L., J. Soc. COSMETro CHEmSTS, 8, 306 (1957). (4) Meyer, R. J., and Cohen, L., Ibid., 10, 143 (1959). (5) Adler, L. S., "Cosmetic Science," London, Butterworths Scientific Publications (1959), pp. 143-160. (6) Heinrich, H., and Clements, J. E., Proc. Sci. Sect. Toikt Goods Assoc., No. 33, 16 (1960). (7) Scott Blair, G. W., "A Survey of General and Applied Rheology," 2nd edition, London, Sir Isaac Pitman & Son, Ltd. (1949). (8) "Texture in Foods," London, S.C. I. Monograph No. 7, Society of Chemical Industry (1960). (9) Marriott, R. H., Analyst, 74, 397 (1949). (10) •a•2ek, H., 9. Pharm. & Pharmacol., 12, 445 (1960). (11) Kynch, G. J., Brit. 9. Appl. Phys., Supplement No. 3, S. 5 (1954). DETECTION, ISOLATION AND IDENTIFICATION OF SURFACE ACTIVE AGENTS By MILTON J. ROSEN, Pa.D.* Presened September ZS-Z6, Z960, Seminr, Chicago, IlL Tu• L•TER^TUR• on this subject is voluminous. Hundreds of papers and a recent book (1) have been devoted to various aspects of this topic. As a result, the treatment in this paper will be highly selective and rather superficial. The term "surface active agents" or "surfactants" as used in this paper includes all types of synthetic organic materials, including soaps, presently commercially available for use as such. Inorganic materials and naturally occurring products with surface active properties, excluding soaps, are not covered in this discussion. DETECTION The detection of surface active agents has of late assumed considerable importance. Formerly, the presence of a surface active agent in such compositions as emulsions or hand creams was a foregone conclusion, since the very existence of these substances depended upon the presence in them of surface active agents with emulsifying properties. However, with modern emulsion technology and with the introduction of synthetic non- surface active dispersing and thickening agents, the presence of a surface active agent in such compositions can no longer be taken for granted. As a result, it is becoming more and more often necessary to test for the presence of a surface active agent in materials of this type. * Dept. of Chemistry, Brooklyn College, Brooklyn 10, N.Y.