524 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS with the heteropoly-acids phosphomolybdic acid is preferred, as the pre- cipitate can readily be analysed to determine the surfactant content which varies with different compounds. Ampholytic surfactants of the amino- carboxylate group are usually analyzed by the methods employed for catiordcs, with special attention to reactions in acid solution. Those of the aminosulphonate group are analyzed by the methods used for anionics. Ampholytics containing a sulphate group are subjected to acid hydrolysis to yield an amine which is analyzed as a true cationic compound. CONCLUSION A great deal of work on new methods of detergent analysis is being undertaken in this country and abroad, but most of this falls into two classes. The first is a thorough examination of the traditional methods in endearours to draw up national and international standards, and the second is concerned with new types of detergents, mainly biodegradable anionic surfactants, and a wide range of ampholytics. Most of this paper has been confined to a discussion of analytical methods that have stood up to the recent scrutiny and that are likely to be issued as standards in the near future. Among these procedures are two that have hitherto survived severe criticism, but which have such inherent defects that they are liable to be superseded in the second generation of standards. The first is the large group of analyses by solvent extraction. Each operation is limited by an equilibrium partition coefficient and, though series containing up to a dozen extraction and washing steps have been recommended, the overall accuracy and precision of many is barely acceptable. With chromatographic pro- cedures on the other hand, using columns of ion-exchange resins, of alumina, cellulose, and silica, separations may involve hundreds of theoretical equi- librium stages with no more than a few minutes' attention of the analyst. Such methods will become widely used in the future, but a great deal of tedious study is needed before results can be accepted as reliable and reproducible, especially among different laboratories. The second procedure is the two-phase cationic-anionic titration using methylene blue and this suffers from the same limitations of equilibrium partition as the first method. The best hope for improvement lies in the synthesis of a cationic indicator designed specially for this application. The ideal indicator will probably contain only one basic group, this being a quaternary nitrogen, and will have an intense colour, preferably blue. Nevertheless, an ideal indicator may not overcome the inherent defects of the competing equilibria, for many investigators seem to ignore the extracta- bility of both anionic and cationic surfactants, in the absence of indicator, in solvents such as chloroform. The factors appear to be more serious in

THE ANALYSIS OF SYNTHETIC DETERGENTS 525 alkaline solutions, which underlines the need for a better indicator that is usable at low pH values. The other field of much current endearour is the development of analytical methods to deal with newer types of surfactants. The search for a detergent that is readily decomposed in sewage treatment plants is to a large extent concerned with derivatives of natural fats, particularly of tallow which is available in larger quantities than coconut and palm kernel oils derivatives are being made and tested at a faster rate than the necessary methods of analysis can be devised. The field of ampholytic surfactants is another in which new compounds are frequently appearing. When commercial con- siderations have led to a more stable pattern of supply and demand of both types of surfactant, then the analyst can develop procedures that are worthy of publication. This situation is not likely to be reached within the next year or two. (Received: 27th May 1963) REFERENCES Many references given in the first paper below have not been listed again. The books referred to under 4 and 7 below are useful general works, and the former contains a good guide to the literature, excluding the anionic-cationic titration. • Smith. W. B. Analyst 84 77 (1959) 2 Holness, H., and Stone, W.R. Analyst 82 166 (1957) a Rosen, M.J. Anal. Chem. 27 787 (1955) 4 Rosen, M. J., and Goldsmith, H.A. Systematic Analysis of Surface-Active Agents (1960) (Interscience, London) 5 Drewry, J. Analyst 88 225 (1963) 6 Gaspari6, J., Borecky, J., Obruba, K., and Hanzlik, J. Collection Czechoslovak Chem. Commun. 20 2950 (1961) * Longman, G. F., and Hilton, J. Methods for the Analysis of Non-soapy Detergent (NSD) Products (1961) (The Society for Analytical Chemistry, London) 8 House, R., and Darragh, J.L. Anal. Chem. 20 1492 (1954) 9 Voogt, P. Rec. tray. chim. 78 899 (1959) •0 Voogt, P. Proceedings, $rd World Congress on Surface Active Agents III 78 (1960) (University Press, Mainz) • Jones, J. H. J. Assoc. O.l•c. Agr. Chemists 28 398 (1945) •a Abbott, D.C. Analyst 87 286 (1962) •a Silverstein, R.M. Anal. Chem. 35 154 (1963) •4 Cullum, D.C. Proceeding, $rd World Congress on Surface Active Agents III 42 (1960) (University Press, Mainz) •5 Dolezil, M., and Bulandr, J. Chemicke Listy 51 255 (1957) •6 Schwerdtner, H., Teztil u. Faserstofftechnik 5 569 (1955) •? Marron, T. V., and Schifferli, J. Ind. Eng. Chem. Anal. Ed. 18 49 (1946) •8 Blank, E. W. Soap Chem. Specialties $4 41 (January 1958) •9 Chinnick, C. C. T., and Lincoln, P. A. Proceedings, 1st World Conference on Surface Active Agents I 209 (1954) (Chambre Syndical Tramagas, Paris)