FLUIDITY. 109 



inflection-points in the curves, but no simple relation between the viscosity 

 coefficients of a mixture and those of its constituents could be deduced. 



Linebarger 1 found that the observed viscosities, in general, were less than 

 those that were calculated by the mixture rule, except, perhaps, in the case 

 of mixtures of benzene and chloroform, and mixtures of carbon disulphide 

 and benzene, toluene, ether, and acetic ether, where, according to Dunstan, 

 the temperature of observation, 25, was possibly too near the boiling-point 

 of the carbon disulphide to make any specific influence which that liquid 

 might exert at lower temperatures perceptible. 



Dunstan 2 makes the significant statement that " the law of mixtures is 

 never accurately obeyed, and divergences seem to be more clearly marked in 

 the case of viscosity than with other properties, such as refractive index." 



These discrepancies are explained if our view be accepted, since the diver- 

 gence in every abnormal case thus far investigated is smaller for the fluidity 

 curves than for the corresponding viscosity curves, and the mixtures with 

 carbon disulphide, which give "normal" viscosity curves, also give fluidity 

 curves that are equally satisfactory. In the particular case of acetone and 

 methyl alcohol or ethyl alcohol, the fluidity is a straight line, nearly to within 

 the limits of experimental error, so that these two pairs of liquids may be 

 considered as perfectly normal. 



It must be stated explicitly that many of the conclusions arrived at by the 

 above-mentioned workers are not changed by this new method of comparing 

 results, especially since, in many cases, they obtained curves with actual 

 maxima and minima. These effects are reproduced in the fluidities as minima 

 and maxima, respectively, which are generally less prominent than before. 



When most of the organic solvents worked with up to this time are mixed 

 with water, there is a very large increase in viscosity. In general, there is also 

 a contraction on mixing these solvents and water. Some of those that give a 

 pronounced maximum of viscosity are methyl alcohol, ethyl alcohol, propyl 

 alcohol, isopropyl alcohol, acetic acid, propionic acid, butyric acid, isobutyric 

 acid, and acetone. The workers in this field have attributed the increase in 

 viscosity to increase in the size of the molecular aggregations. 



This decrease in fluidity retards the movement of the ions, hence there is a 

 fall in molecular conductivity, which explains the minimum in conductivity 

 heretofore observed by Zelinsky and Krapiwin, Cohen, Jones and Lindsay, 

 Jones and Carroll, and ourselves. This relation between viscosity and con- 

 ductivity, as has been shown, has long been recognized. Wiedemann, 

 Stephan, Dutoit and Friderich, and Jones and Carroll have been connected 

 with the development of the exact relation between them. 



1 Amer. Journ. Sci. [4] 2, 331 (1896). 



2 Journ. Chem. Soc., 85, 817 (1904.) Ztschr. phys. Chem., 49, 590 (1904). 



