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.

114 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Beckman Type E (Blue Glass), Beckman Catalog No. 4990-75. High alkalinity (low alkali error) electrode for measurements from pH 9 to pH 14. Temperature range: 5 ø to 40øC. OR Beckman Type E-2, Beckman Catalog No. 4990-72 for measure- ments over the entire pH range. Temperature range: 15 to 100øC. (3) Calomel reference electrode, such as the Beckman fiber type, Beckman Catalog No. 4970. Temperature range: -5 to 100øC. (4) Soft cotton string (at least 1/16 inch in diameter) saturated with potassium chloride solution and used while wet. Reagents Required Buffer solutions of pH 4.0, 7.0 and 10.0. Certified buffer solutions may be purchased from most laboratory supply houses in either solution form or as a fast-dissolving powder. Potassium chloride solution (KC1), saturated pH indicator test paper, such as Alkacid or Hydrion, sensitive to the nearest pH unit. Procedure Determine the approximate pH of the sample using indicator test paper. If the indicated pl-I is 9 or below, use general purpose glass electrodes designated #4990-80. If the pH is above 9, use the high alkalinity type E glass electrode designated #3990-75. The Beckman type E-2 glass elec- trode designated #4990-72 may be used as an alternate for either of the above electrodes and may be used anywhere in the pH range. P^RT I--STANDARDIZATION OF PH METER. See Note (a). (1) Attach the electrode system with the proper glass electrode described above and the calomel reference electrode to the pH meter. (2) Wash the electrodes thoroughly with distilled water and dry gently with clean absorbent tissue. See Note (b). (3) The temperature of all solutions to be tested, whether buffer or test solutions, shall be brought to 25 4- iøC. Electrodes shall be im- mersed in solution for several minutes, if necessary, to permit elec- trodes to reach same temperature as solution. (4) Buffer solution of pH 4 is used for initial standardization when the general purpose glass electrode (#4990-80) is used and pH 10 buffer solution is used for initial standardization when the high alkalinity type E glass electrode (#4990-75) is used. The pH 4 buffer solution is to be used for the initial standardization of the type E-2 glass elec- trode (#4990-72). See Note (c). (5) Place some fresh buffer solution in a beaker and in another beaker place a quantity of saturated potassium chloride solution. Set the