860 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Vapor Pressure and Waving Performance of Bromate Neutralizers with Various Salts Vapor Pressure • 30øC Salt Molality mm Hg AW Rating ...... 30.1 Fair MgSO4 1.5 29.3 Excellent LiBr 1.5 29.0 Poor Mg Acetate 1.5 27.8 Excellent MgC12 2.0 25.0 Fair All neutralizers contain 0.67m sodium bromate. Table VI Effect of Application Sequence of Bromate and Magnesium Sulfate Waving Sequence Following Ammonium Thioglycolate Reduction (1) Magnesium Sulfate (2) Bromate (1) Bromate (2) Magnesium Sulfate Wave value 2 3 D2L, mm 17 14 WT 3 3 D2LW, mm 14 12 VLW, mm 37 37 ID, mm 7 7 AW value Poor to fair Poor Data represent the average measurements for six tresses. DISCUSSION Farnworth (6) suggested that permanent set in wool, which is anal- ogous to the permanent wave in hair, results from the breakdown and re-formation (italics, ours) of hydrogen bonds following the splitting of cystinc linkages. Concurrence with this view has been voiced by Whewell (7) and Walker (8). In waving with ammoniaeal thioglyeolate, followed by oxidation, two of these three mechanisms have been effected, namely, the cleavage of disulfide and hydrogen bonds. The salt- modified bromate neutralizer appears to give improved wave stability, in part at least, by augmenting hydrogen bond re-formation. To the ex- tent that this is true, the third of the proposed three prerequisites for permanent set has been provided. Whewell. in a remark appended to a subsequent study (9), held that

PERMANENT WAVE NEUTRALIZER 861 the role of hydrogen bond breakers was complex, but they did seem to increase disulfide scission by bisulfites. He described the action of di- sulfide breakers as that of a key which opens up the fiber so that hydro- gen bond breakers can be effective. The effectiveness of the modified neutralizer makes the reverse reasoning of the previous statement inter- esting to consider: namely, that the re-formation of hydrogen bonds seems to increase disulfide relinkage and that the substances that restore disulfide linkages act like a key which closes up the fiber so that hydrogen bond re-formers can be effective. It is our observation that the re- formation of both types of bonds must be done concomitantly for the pro- duction of the optimum wave stability. The simultaneous relinkage of both types of bonds has been given the term of "parallel waving." Bogaty showed by carefully chosen experiments (10) that the individ- ual participation of both primary and secondary bonds in the waving procedure could be demonstrated, and, furthermore, that the potential benefits to waving by an effective utilization of secondary bonds (along with sulfur cross links) was yet to be fully realized. Hopefully, this study demonstrates a manner by which this can be accomplished. SUMMARY Tresses were set with a bromate-based neutralizer modified by the addition of an amount of magnesium sulfate in excess of 24%. Com- pared to the results obtained with the unmodified bromate neutralizer, the tresses were superior in air- and water-stability did not lose their improved performance despite repeated waving and gave appreciably higher 20% index values when determined on the serigraph. A study of this neutralizer's possible mechanisms of action indicates that a combination of effects appears responsible for its beneficial action. Among these are: charge neutralization, uptake of the added salt, and re-formation of hydrogen bonds. To be effective, the added salt must Be applied concomitantly with the oxidant, thus re-forming both disulfide and secondary bonds at the same time, a process labeled "parallel wav- ing." AC•SOWI. EDCMEST The valuable suggestions and technical assistance of Dr. T. W. Gilbert are gratefully acknowledged. The authors also thank Mr. John Solaro for considerable technical aid and assistance. (Received December 8, 1967)