RHEOLOGIC AGING OF COSMETIC LOTIONS 155 IOO 0.0 4 0.1 0.4 I 4 I0 40 I00 400 ELAPSED TIME (DAYS) Figure 7.--Aging of a lotion prepared with different ratios of 98% and of technical grade triethanolamine. It is intended later by the study of the equation of flow to attempt to derive parameters from such equations that will recognize the likelihood of this type of behavior before it is clearly established. Our first efforts in this regard are promising, but considerably more work will be necessary before it can be clearly established. 40,000 20,000 4,ooo C)• •. •ooo 6OO 4OO 200 i0• tooc •25øC ¾.e50•C 5oc 0.04 0.1 0.4 I 4 I0 40 I00 ELAPSED TIME {DAYS) Figure 8.--Effect of temperature on the aging properties of an antiperspirant fi)rmulation,

156 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS SUMMARY The use of plots of the logarithm of time with the logarithm of the various extensive properties examined in an aging program is suggested as the best way to evaluate the normality of the aging process. Deviations from linearity may be used as guides in anticipation of untoward behavior. The linearity of the logarithmic plot of time and extensive property permits safe prediction of properties for two to three age periods beyond the last observation. Its utilization in the course of process and formulation studies permits a compacting of considerable data for comparison into one or more con- venient graphs. (Received September 18, 1962) REFERENCES (1) J. H. Wood, Arm. Perruiner, 76 (10), 37 (1961). (2) E. Menczel, M. Rabenovitz, and A. Madjor, Arm. yt. Pharm., 132, 315 (1960). (3) J. B. Appino, J. E. Christian, and G. S. Banker, 5 t. Pharm. Sci., 51, 254 (1962). (4) J. H. Wood, G. Catacalos, and S. V. Lieberman, Ibid., accepted for publication. (5) G. Levy and J. M. Rutowski, Ibid., accepted for publication. (6) C.W. Chong, S. P. Eriksen, and J. V. Sintosky, •t. Arm. Pharm. Atssoc., Sci. Ed., 49, 547 (1960). (7) C. W. Chong, personal communication. (8) G. Levy and J. M. Rutowski, y. Pharm. Sci., accepted for publication. (9) A. H. Geisler, in "Phase Transformations in Solids," ed. by R. Smoluchowski, J. E. Mayer, and W. A., Weyl, New York, John Wiley & Sons, Inc. 1957, p. 387 if. (10) L. G. Harrison, I. M. Hoodless, and J. A. Morrison, Discussions Faraday $oc., 28, 103 (1959). (11) F. P. Clarke, Ibid., 23, 141 (1957). (12) W. G. Burgers and L. J. Groen, Ibid., 23, 183 (1957). (13) M. Avrami, y. Chem. Phys., 7, 1103 (1939) 8, 812 (1940). (14) L. E. Fryk16f, Svensk Farm. Tidskr., 62, 697 (1959). (15) J. H. Wood, G. Catacalos, and S. V. Lieberman, y. Pharm. Sci., accepted for publica- tion.