650 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Continuous Phase Inlet Dispersed phase Inlet Water chamber :• Dispersio LLI STATIC MIXER © section • Camera Figure 9. Schematic set-up of the contacting experiment Table II Materials Used for the Dispersed Phase" Interfacial Tension Density (g/ml) Viscosity (cps) • (dyne/cm) Anisole 0.99 1.32 26 Benzene 0.87 0.65 40 Benzyl alcohol 1.04 5.8 5 Cyclohexane 0.T8 1.02 46 Oleic acid 0.89 26.0 16 Toluene 0.87 0.59 32 From Middleman (11). face of the glass pipe was corrected. Materials of different physical properties used in the experiment as the disperse phase are listed in Table II. Water was used as the continuous phase in the experiment. }•ESULTS AND DISCUSSION The drop size of the dispersed phase can be controlled merely by changing the flow rates in the device. For a given size of the device and the material for the dispersed phase, the higher the flow rate, the smaller the drop size. Figure 10 shows the dispersions at three different flow rates in the aA-in. device. The photographs were taken at 3000 frames per sec. The drop size measurements were made from the photographs taken at the chamber. The measurements were classified into size groups of 10-/x or 50-/x intervals, depending upon the range of sizes resulting from each run. The Sauter mean diameter was calculated from the equation (10): N • ni D, a • n• D? i=1

CONTINUOUS MIXING AND PROCESSING 651 ...... "."•:• .: ::'•'• 7"" ' % •:"' :. :..': .': '"' "?' .:'• .,, '".% ... ß •a ... :.'•,:•,!•}!-?}• f .. ....... :":'::! .... '•:'.':.•::',•:.:'::.".':.. '. ':'.' '. '":.:::•'.:'.': ...... ß .. •,:.• :•:-•':: :•.' ..... ß :: :. .:' Figurd 10. D•erent &op s&es are provided in •e same Static Mixer u•t by va•ng the •veloci• (70% of dispersed ph•e fo• drops xvithin 20% of mean drop size) W•eYe D = Sauter mean diameter N = number of size intervals D• = diameter of a drop in the i-th size interval N• = number of drops in the i-th size interval