244 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1200 o : elasticity 5 % wt/wt 70 ppm ß : viscosity 70Oc.__40oc I• ]: specific volume 1.5 hours 1000 - 10•000 rpm l•18.3] I• 16.1 ] ....,._.• 8oo u l•14.6] / " J•10.6] • 600 J• 10.0 '• 400 - 30 o 200 0 • • I • • 0 3.8 4.6 5.4 6.2 7.0 flow rate, cc/min Figure 7. Effect of flow rate of the soap solution (to the foam-generator) on the viscoelasticity of the soap foam obtained from a 5 % (wt/wt) toilet soap aqueous solution. The specific volume of the foam is designated in brackets 500 to 800 dynes/cm 2 with increasing flow rate, while the viscocity scarcely depended on the flow rate. On the other hand, a close relationship is probable between elasticity of foam and its specific volume, as is evident from Figures 5, 6 and 7. The comparison of the viscoelastic moduli of the foam prepared by using deionized water with those of the foam prepared by using the aforementioned water is shown in Figure 8. The elasticity of the foam was much larger with the deionized water than that with the artificial tap water. Figure 9 shows the influence of a soap composition on the viscoelastic moduli of the foam. The elasticity of the foam prepared from soap manufactured by mixing coconut oil with tallow in the ratio of 20 to 80 was larger than that of the foam from soap in which the ratio of coconut oil to tallow was 15 to 85. CONCLUSION The storage shear modulus increased from about 500 to 850 dynes/cm 2 as the specific volume of the foam increased from about 10 to 25 cma/g. On the other hand, the dy-

1200 lOOO 8OO 600 400 200 [19.2] 5% wt/wt 70øC --• 40øC 1.5 hours 10,000 rpm 6.2 ccJmin 0 : elasticity ß : viscosity [ ] : specific volume [9.3] I 3O 20 o lO 8 o deionized artificial water tap water Figure 8. Influence of a hardness of water on the viscoelasticity of the foam from toilet soap. The hardness of the water was 70 ppm (as CaCO•) 1200 1000 800 600 400 2OO 3O 20 •' lO • 0 : elasticity 5% wt/wt ß : viscosity 70 ppm 70øC --• 40øC [ ] : specific volume 1.5 hours 10,000 rpm 6.2 cc/min [•o.71 [9.3] I l 15 : 85 20 : 80 0 0 ratio of coconut oil to tallow Figure 9. Influence of soap composition on the viscoelasticity of the foam from toilet soap