EVALUATION OF SHAMPOO 115 temperature adjustment dial of the meter to the temperature of the buffer (25øC). (6) Insert the glass electrode into the beaker containing the buffer solu- tion and the calomel electrode into the beaker containing the saturated potassium chloride solution. (7) Connect the buffer solution and the saturated potassium chloride solution with a 3-inch piece of string saturated with potassium chloride (wet). See note (d). (8) Check and adjust, if necessary, the pH reading with the known pH of the buffer solution used following the manufacturer's instructions. (9) Remove the glass electrode, wash thoroughly with distilled water and dry gently with clean absorbent tissue. Insert the glass elec- trode into a beaker containing fresh pH 7 buffer solution. (10) Connect the buffer solution and the saturated potassium chloride solution with a new piece of string, saturated with potassium chlo- ride, and check the pH reading. If the pH value obtained on the latter is not within +0.1 unit of the correct value for the pH 7 buffer, a faulty electrode is probably to blame and new electrodes should be installed and checked as described above. See Note (e). P^• II--DETEltMINATION OF PH (1) Wash the electrodes thoroughly with distilled water and dry gently with clean absorbent tissue. The type of electrode and standardization are based on a preliminary test for pH using indicator paper. See Part I. (2) Insert the glass electrode into the sample being tested and insert the calomel electrode into a beaker containing saturated potassium chloride solution. (3) Connect the sample being tested and the saturated potassium chloride solution with a 3-inch piece of string saturated with potassium chloride (wet). See Note (e). (4) Read the pH of the sample in accordance with the manufacturers in- structions for the instrument used. Notes (a) The pH meter should be standardized daily or before each series of tests. If a number of determinations are being made, check the meter against the two buffer solutions after every 5 determinations. (b) The pH meter should be switched to a neutral or check position when the electrodes are being handled or are not immersed. This will pre- vent the possibility of polarization of the glass electrode which will cause the pH readings to be a few tenths high and a reading drift for several minutes after re-immersion.

116 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (c) The electrode reaction of the type E-2 glass electrode may be improved by soaking the electrode in pH 10 buffer solution prior to use. (d) The string may be prepared in the following manner. A ball of cot- ton twine is placed in a beaker, covered with distilled water, and the water heated to boiling. Heating is continued for several minutes, then the water is replaced with fresh distilled water and the operation repeated. This is done a number of times until visually the water is free of sizing or other material which may be leached from the cotton twine. This twine is then cut into appropriate lengths and stored under a saturated KC1 solution. (e) Each piece of string must be used only once. Reference Beckman General Instructions, "Type E-2 Glass Electrodes," Bulletin No. 361, May, 1955, Beckman Division, Beckman Instruments, Inc., Ful- lerton, Calif. We have also made a start on two other problems we originally set 'for ourselves, that of shampoo viscosity or consistency. Here we have pro- gressed only to the point of asking the members of the subcommittee for sug- gestions and ideas. As might be expected there is not the same meeting of minds as on the pH procedure thus far, we have received suggestions for use of viscosimeters of various kinds, as well as flowmeters and penetrom- eters. A cursory examination of the problem leads to the opinion that we may need not one but several methods for viscosity measurements, perhaps one for cream or paste shampoos, one for thin liquids and one for viscous liquids. Additional problems become evident on further con- sideration. For example, shall we consider the initial resistance to flow or the resistance after application of a shearing stress? Which experimental technique will tell us the most about the flow characteristics of the sham- poo? Perhaps the most cogent observation which has been made thus far is that we consider which attributes of the complex quantity we call "viscosity" we are most concerned with before we attempt to set up any procedures for its measurement. Standardized procedures for pH, viscosity, and other physical proper- ties of cosmetic products are extremely desirable so that we may, in dif- ferent laboratories, be able to speak the same language and have the same frames of reference. I believe that we have already considered some of the necessary benchmarks for such procedures. Among the most im- portant are reproducibility, simplicity, and use of readily available equip- ment. Important as such procedures are I feel that the need is even greater for standard evaluation techniques for the performance properties of shampoos and related products. I say that the need is greater because