100 FLUIDITY AND PLASTICITY

Commenting on the theory of v. Smoluchowski by way of
explanation he remarks, "II est probable que de pareilles h<§t£ro-
g6n&t6s produirairent une augmentation de la viscosit6 et
pourraient done expliquer la courbure, toujours de merne sens,
des courbes d'6gale concentration et par consequent les hearts &

101 d'additivite."

These researches make it perfectly clear that there is a decrease
in the fluidity near the critical-solution temperature as predicted
and that in some way this decrease is connected with the dis-
appearance of homogeneity in the mixture. Most of the in-
vestigators have concerned themselves with the explanation of
disappearance of homogeneity before the critical-solution tem-
perature is reached, rather than of the increase in viscosity.

FIG. 38.—Diagram illustrating the flow of emulsions.
But we are here only interested in the fact that heterogeneity
does occur simultaneously with the abnormal increase in viscosity,
and not in the cause1 of the heterogeneity itself.
Scarpa and Bose however offered explanations of the abnormal
increase in the viscosity. In. regard to Scarpa's assumption
that the decrease in fluidity is due to the formation of hydrates,
it is very possible that hydrates are formed between phenol and
water, with which he worked; but he has not given any facts to
prove that the hydration suddenly increases as the critical-
solution temperature is approached even in this favorable
case. In the cases studied by Drapier (cf. Fig. 34), such a,
chemical action seems to be out of the question, because if solva-
tion occurred the fluidity-concentration curves would be sagged
even above the critical-solution temperature.
In order to understand the explanation of Bose, we refer to
Fig. 38 which may be taken to represent the hypothetical
1 For an attempted explanation cf. Am. Chem. J., 33, 1273 (1911).