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:

272 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (1) The bar should be the equivalent of a good toilet bar with respect to detergency, foam power, solubility and stability toward normal additives, such as perfume. (2) It should behave physically like a toilet bar with respect to wash down, lumpiness, sanding effect, cracking and wasting away on the soap basin. (3) The density should be reasonably close to soap say, 1.00 to 1.15. (4) It should have a precipitable curd with hard water that remains dispersed in reasonably hard water up to say 250 p.p.m. (5) The pH should lie between 7 and 8. To attain these conditions it is suggested that a formulatot should endeavor to choose his basic raw materials in such a way that they will resemble one another as closely as possible. Soap, for example, is a mixture of fatty acid salts of similar series. The formula should have plasticity so that it can be worked in standard or heavy duty milling equipment so that clean-cut, well-pressed bars can be made at temperatures below the decomposition points of the various ingredients. Soap, for example, is generally plodded at 100-106øF. A synthetic should be ploddable at say not over 135øF., and preferably lower. The formulatot should not be handicapped by having to work with standard soap equip- ment. Other methods are available. With respect to basic raw materials, the detergent or detergent mixture should be solid, odorless, nontoxic and light colored. Chemically it must have high detergency, foam power, be reasonably priced at less than 40 cents per pound, and be readily available from at least two or more suppliers. If the formulatot is using soap as an extender, then anionic and nonionic detergents of the generally accepted types may be used. The ones most frequently used are the alkyl aryl sulfonates, alkyl methyl taurides or alkyl sulfates. The binder is generally soap but sometimes dextrinated starch, natural gums, polyethylene glycols and other special condensation products (3) are used extensively. The manufacturing drawbacks are numerous. Moisture content and temperature are very critical. Often a difference of only 1/2 per cent moisture can cause a firm easily milled product to deteriorate into a slush, or become an impossible rubber-like mass. Sensitivity to moisture is particularly true of alkyl aryl sulfonates and frequently plodding temperatures are established on the basis of this factor (4). These latter have exceptional lime soap dispersion power but lack the full lathering qualities of the substituted amides or the fatty alcohol sulfates. The sulfated alkylolamides are also useful as foam boosters. A few typical formulations for their use are given in the refer- ences cited (3, 4) but the technical detail necessary to interpret them is beyond the scope of this paper. Another class of detergents are available or can be made available,