.l. Soc. Cosmet. Chem., 23, 525-531 (August 17, 1972) Evaluation of Powder Surface Properties by an Adsorption Method TAKEO MITSUI, B.S., SHOJI FUKUSHIMA, B.P., and SUSUMU TAKADA, B.S.* Presented November 25, 1970, Shikizai Kenkyu Happyokai, Tokyo, Japan Synopsis--ADSORPTION of various kinds of LIQUIDS on POWDERS was measured. The number of molecules adsorbed on a unit SURFACE AREA of powder increased with the SOLUBILITY PARAMETER (SP) of the liquids when powders were hydrophilic, but it did not change very much when hydrophobic powders were used. Liquid absorption and WETTABILITY of powders were also measured. In the case of hydrophilic powders, liquid absorption increased as the SP decreased and wettability increased as the number of ad- sorbed molecules increased. INTRODUCTION In order to evaluate the property of powder surface quantitatively, the amount of adsorption of various liquids having a different solubility parameter (SP) on powders was measured gravimetrically in vapor phase. Zettlemoyer (1) has proposed the concept that the ratio of specific surface area determined by water vapor adsorption (SR2o) to specific sur- face area determined by nitrogen gas adsorption (Sx,2) represents hydro- philicity of the powder surface. Murayama et al. (2) supported this con- cept and showed evidence that there was similar tendency between hy- drophilicity and heat of immersion. They claimed that the hydrophili- city could be used as a parameter which indicates affinity to water. •* Shiseid, o Laboratory, 1050, Nappacho Kohokuku, Yokohama, Japan 223. 525

526 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The present study has been undertaken from the point of view that this concept can be extended to other liquids--that an organic molecule also will be adsorbed on powder surface in the same manner as water. Liquid adsorption and wettability of powders were also measured and discussed in relation to SP and the amount of adsorption. EXPERIMENTAL Powder Samples Powders employed in this experiment are shown in Table I. Most of them are raw materials for cosmetics. They were selected widely from inorganic powders which are generally regarded as hydrophilic, and or- ganic powders which are regarded as hydrophobic. Liquids used are shown in Table II. These were selected, consider- ing SP, from water having a high SP to n-hexane having a low SP. Table I Powder Samples Used Specific Surface Area Powder Remarks (m2/g) Manufacturer Titanium dioxide (A) Rutfie-type 10.3 Titanium dioxide (B) Anatase-type 8.6 Iron oxide hydrate Goethite. a-FeOOH 14.5 Talc Manchurian 7.2 Carbon black (A) Channel-type 217.3 Carbon black (B) Channel-type 104.6 Lake Red C Ba salt 67.0 Typaque R-820, Ishihara Sangyo Ltd. Reagent E, Merck AG. Prepared for pigment Nihon Biryushi Ltd. Nittetsu Kagaku Kogyo Ltd. Cabot Corp. Toyb Ink Ltd. Table II Liquids Used in Study Solubility Liquid Parameter Water 23.2 6.00 15.3 16.7 Methanol 14.5 7.42 6.0 10.9 n-Propanol 11.9 7.75 3.3 8.5 Acetone 10.0 7.58 5.1 3.4 Benzene 9.15 8.95 0.5 1.0 Cyclohexane 8.2 8.18 0 0 n-Hexane 7.3 7.24 0 0 • The division of the solubility parameter into components representing dispersion inter- actions, •D, polar bonding, /Sv, hydrogen bonding, ba (5).