EVALUATION OF SHAMPOO 113 to flow birefringence and viscosity. Joly expressed the opinion that an analogous treatment could be applied to a general theory of thixotropy, to interpret perturbation due to flow in the second phase of sol-gel evolution a truly quantitative expression, however, would involve great difficulties in calculation, due to the relatively large number of parameters involved. The thing we generally want to know about a liquid cosmetic emulsion is its viscosity after a long period of rest, not its viscosity after it has been shaken or has been otherwise made to flow. To be specific, we want to know that it will flow from its container after long storage. We may be able to predict its ultimate viscosity from a curve made on the basis of successive readings taken over a few months. In order to draw such a curve accurately, our readings should be made with all pertinent factors uniform. The subcommittee's work indicates that there are factors affecting the viscosity of liquid emulsions which have not been covered in our specifica- tions. Our next effort will be to discover these factors and to include them in new specifications to be made the basis of another attempt to develop a standard method for determining the viscosity of liquid cosmetic emulsions. SUBCOMMITTEE ON CREAMS AND LOTIONS Dr. Paul G.I. Lauffer, Chairman Gabriel Barnett Dr. Saul Bell Dr. L. I. Conrad S. J. Strianse Report on the EVALUATION OF SHAMPOO SINCE THE report of this subcommittee was given in September, 1957, a tentative method has been approved and is published below. TENTATIVE METHOD PH DETERMINATION ./lpparatus Required (1) pH Meter: Any suitable instrument capable of obtaining a precision of q-0.1 unit. (2) Glass Electrodes such as: General Purpose, Beckman Red Label, Beckman Catalog No. 4990-80 for measurements of pH 9 or below. Temperature range: 5 ø to 100øC.

EVALUATION OF SHAMPOO 113 to flow birefringence and viscosity. Joly expressed the opinion that an analogous treatment could be applied to a general theory of thixotropy, to interpret perturbation due to flow in the second phase of sol-gel evolution a truly quantitative expression, however, would involve great difficulties in calculation, due to the relatively large number of parameters involved. The thing we generally want to know about a liquid cosmetic emulsion is its viscosity after a long period of rest, not its viscosity after it has been shaken or has been otherwise made to flow. To be specific, we want to know that it will flow from its container after long storage. We may be able to predict its ultimate viscosity from a curve made on the basis of successive readings taken over a few months. In order to draw such a curve accurately, our readings should be made with all pertinent factors uniform. The subcommittee's work indicates that there are factors affecting the viscosity of liquid emulsions which have not been covered in our specifica- tions. Our next effort will be to discover these factors and to include them in new specifications to be made the basis of another attempt to develop a standard method for determining the viscosity of liquid cosmetic emulsions. SUBCOMMITTEE ON CREAMS AND LOTIONS Dr. Paul G.I. Lauffer, Chairman Gabriel Barnett Dr. Saul Bell Dr. L. I. Conrad S. J. Strianse Report on the EVALUATION OF SHAMPOO SINCE THE report of this subcommittee was given in September, 1957, a tentative method has been approved and is published below. TENTATIVE METHOD PH DETERMINATION ./lpparatus Required (1) pH Meter: Any suitable instrument capable of obtaining a precision of q-0.1 unit. (2) Glass Electrodes such as: General Purpose, Beckman Red Label, Beckman Catalog No. 4990-80 for measurements of pH 9 or below. Temperature range: 5 ø to 100øC.