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.

IDENTIFICATION OF SURFACE ACTIVE AGENTS 99 The most general and versatile method of detecting surface active agents depends on their ability to solubilize dyestuffs in solvents in which these dyestuffs are usually insoluble. For example, water-insoluble dyestuffs will dissolve in water if a surface active agent is present in the water, and this is the basis for the most general test for detecting surfactants, devised by Hoyt in 1947 (2). In this test, the unknown composition is first treated with a polar organic solvent, such as chloroform or 50 per cent alcohol, to extract any surfactant. The extract is evaporated to dryness, and the residue thereby obtained is dissolved in a few milliliters of water. This aqueous solution is then treated with a well-pulverized mixture of salt and the water-insoluble dyestuff, Brilliant Oil Blue BMA. If a surface active agent is present, the dyestuff dissolves in the aqueous solution, imparting to it a distinct blue color. In the absence of a surfactant, the color of the aqueous solution is unchanged. All types of surfactants, anionic, cationic and nonionic, can be detected by this test. Since this test is so general, further tests are required if any knowledge of the nature of the surfactant present is desired. The first type of informa- tion concerning the surfactant which is usually desired is its ionic type i.e., is it anionic, cationic, nonionic or one of the recently introduced ampholytic types? A number of tests are available for obtaining this in- formation. They fall into two categories: (1) Color change tests (2) Dye transfer tests. In the Color Change tests, an ionic type of surfactant reacts with an indicating dyestuff to produce a change in the color of the dyestuff. The presence of the ionic type of surfactant is thereby indicated by the change in color. R-Na* q- In --• RIn- Anionic Indicating Dyestuff-Anionic Surfactant Dyestuff Surfactant Complex (Color I) (Color II) RN•Cl - q- In-• InRN •- Cationic Indicating Dyestuff-Cationic Surfactant Dyestuff Surfactant Complex (Color T) (Color IT) (I) (TT) Two tests based on this principle are the Bromophenol Blue test for cat- ionics of Kortlandt and Dammers (3) and the Thymol Blue test for anionics of Peter (4). In the Bromophenol Blue test, a buffered solution of Bromo- phenol Blue is treated with a few drops of a neutral, dilute aqueous solution of the surfactant. If a cationic surfactant is present, the reddish color of the Bromophenol Blue solution changes to a sky-blue. Ampholytic sur- factants, such as betaines and long-chain amino acids, can also be detected by this test, since they change the color to a light blue with a distinct violet fluorescence. Anionics, nonionics, and nonsurfactant short-chain amines