EMULSION STABILIZATION BY GUMS 337 70 , 6o o o o x o -- o 5o 4o 50- 20- 10 0 0 2 4 6 EMULSIFIER CONC. (• W/W) Figure 5. Effect of emulsifier concentration on total number of particles in emulsions containing no polymer. gestive of coalescence, so that the percentage of larger particles is increased at the expense of the smaller ones. As would be expected, the process is accompanied by a decrease in the total number of particles. Viscosity data for the emulsions are summarized in Tables III and IV. The viscosity of emulsions containing no polymer was too low to be measured accurately under the Table II Effect of Xanthan Gum on Median Particle Size at 1% (w/w) Emulsifier Concentration Emulsifier Conc. (% w/w) Median Particle Size (micrometer) Xanthan Gum Conc. (% w/w) Aging (days) 0 0.1 0.2 0.3 0.4 1.0 1 4.30 4.30 4.40 4.15 4.10 28 4.35 4.40 4.60 -- -- 56 4.65 4.65 4.85 4.85 4.80 214 4.50 4.65 4.80 4.85 4.65 308 4.35 4.60 -- 4.60 427 4.30 4.50 -- 4.40

338 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Effect of Xanthan Gum on Apparent Viscosity at 3 rpm and 25øC Apparent Viscosity (cp) Xanthan Gum Conc. (% w/w) Emulsifier Aging Conc. (% w/w) (days) 0 0.1 0.2 0.3 0.4 0 1 -- 67.1 170 297 303 0.25 3 -- 107 275 314 371 59 -- 99.4 272 318 374 399 -- 36.3 212 504 817 0.5 55 -- 93.0 248 374 417 409 -- 22.8 271 584 872 1.0 7 -- 82.6 243 381 474 56 -- 74.9 240 394 500 472 -- 15.1 201 522 832 3.0 7 -- 47.8 176 457 613 60 -- 40.0 165 452 610 462 -- 4.9 154 647 698 5.0 7 -- 47.3 168 333 549 53 -- 48.5 168 332 * 455 -- 11.5 116 368 * * Indicates mold growth. conditions we used. For emulsions that contained a polymer, viscosity within each group was directly related to polymer concentration, as expected. The viscosity of the freshly prepared emulsions was also dependent on emulsifier con- centration. We would anticipate that emulsion viscosity should increase as we raise the emulsifier concentration because the particle size decreased under the same conditions. However, in many cases, just the opposite was observed (Figure 6). Table IV Effect of NaCMC on Apparent Viscosity at 3 rpm and 25øC Apparent Viscosity (cp) NaCMC Conc. (% w/w) Emulsifier Aging Conc. (% w/w) (days) 0 0.5 1.0 1.5 0 1 -- 44.4 336 1290 1.0 7 -- 107 775 1290 57 -- 99.4 755 1280 448 -- 19.3 76.9 152 3.0 7 -- 38.7 300 1210 61 -- 19.4 192 865 445 -- 4.1 49.5 165 5.0 7 -- 37.4 265 968 61 -- 27.1 151 768 445 -- * 34.4 99.0 * Indicates viscosity too low to be measured.