270 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS tion must be given to the absence of metallic contamination. The use of EDTA in the acid form solubilized with the desired base for compatibility should prevent this darkening with age and also assist in the cleaning function of the preparation. Simply add the EDTA acid before the addi- tion of the base. This brings up the question of the toxicity of EDTA and DTPA. In the concentration necessary to accomplish the ends described previously in this paper, and within the pH limitations of cosmetic products, neither of these materials presents any toxicological problems. Actually the utility and amounts used in cosmetic products place their relative toxicity far below that of alkalis, reducing or oxidizing agents commonly used by the cosmetic industry. Chelation is spreading into many new cosmetic formulations but old products and soap preparations are areas where chelation can improve the end-use performance and make such products very competitive with syn- thetics. When employed correctly, either EDTA or the new chelating agent, DTPA, should be the solution to problems involving trace metal ions. The cosmetic chemist should look to these two chelating agents for the solution of problems dealing with interplay of metal ions and competing anions as well as enhancement of many soap-based cosmetic preparations. The writer gratefully acknowledges the foam protection data proved by Dr. A. K. Prince and Mr. Norman Picard of the Technical Service and Development Department, The Dow Chemical Company, Midland, Mich- igan. THE PRESENT ROLE OF DETERGENTS IN TOILET BAR MANUFACTURE BY JOHN W. McCuTCHEON* Presented •Yune ¾, 1955, New York City IT Is ^ mistake to think that the introduction of synthetic detergents into bar form is a recent innovation. Experiments along these lines have been carried out over a quarter of a century. The fact that during most of these years they met only limited success under special conditions indicates the enormity of the problem. The initial attack was to incorporate the detergent with binders and to frame and cut the product as a laundry bar. The salt water bar used by the Navy during World War II is an example. The use of synthetics in toilet bars made its appearance about a dozen * John W. McCutcheon, Inc., New York 17, N.Y.

DETERGENTS IN TOIIiET BAR MANUFACTURE 271 years ago as a fairly salt-free product combining sulfated monoglyceride and soap. This product lathered well in normally hard water, prevented the objectionable bathtub ring anti was quite good with respect to resistance from wasting away on the washstand. It was priced within the range of such a specialty product. In fact there seemed every indication that the product would be a fine success. It failed however, on two counts, it defatted the skin and it was not free rinsing. Defatting of the skin is a complex phenomenon (1) requiring special means of testing (2). Free rinsing requires some amplification. When a soap is rinsed from the skin, the hardness of the water causes the residual traces of soap to be pre- cipitated as calcium and magnesium soaps thereby removing them from action and causing the skin to have a "snappy" feel. With detergents these trace residues are not so destroyed, thereby causing the skin to have a slimy or sticky feeling. Prolonged rinsing must be carried out before the skin again feels snappy free of detergent. This was a drawback from an unexpected quarter, but real enough to warrant heavy thinking on the part of the formulatot. Since all detergents by the very definition of their function have soluble lime salts, the first direct approach might be to use more soap in the product to diminish this effect. Another approach would be to use a product which would not conform to the general conception of a detergent but would yield insoluble lime salts of a nonsticky or dense nature that would avoid the formation of a bathtub ring. Other bars appeared on local test markets within the last half dozen years that did meet these general requirements but which were received with only mediocre success. Within the past year or so, however, progress in formulation has reached a point where several products are now being nationally distributed with more to follow. They may be considered as specialty products priced from 25 to 200 per cent above their competitive soap analogues. With an available toilet soap market of some 300,000 tons a year and the modest price structure above, the future would seem to be very promis- ing indeed. This is of extreme concern to the detergent manufacturer who wants all the business, the renderer who may lose what he has and the toilet soap manufacturer who may be by-passed in the process. The ideal product must do something better than soap. It must cleanse better, it must not form unsightly scum in hard water and it must be milder than soap on the skin. In addition to these attributes it must maintain all of soap's good points. This presents an extremely difficult formulation job that has reached one high level plateau, but has still a long way to go. A few specifications for an ideal synthetic bar may be briefly stated as follows: