216 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



the atomic volume the smaller the value of y, just as we should anticipate in 

 terms of our hypothesis. 



The small values of t\ for cadmium and mercury are due to the fact that the 

 salts of these metals are only slightly dissociated. 



Thallium seems at first glance to present an exception, but it is to be re- 

 membered that it is the thallous salt which produces the negative viscosity. 

 The atomic volume curve deals with thallium in the thallic condition, 

 and, consequently, thallium can not at present be considered as a test of our 

 hypothesis. 



CONCLUSIONS. 



(1) We have measured the conductivities of various concentrations of cop- 

 per chloride in water, methyl alcohol, ethyl alcohol, and in binary mixtures of 

 these solvents. We have also measured the conductivities of various con- 

 centrations of potassium sulphocyanate in water, methyl alcohol, ethyl 

 alcohol, acetone, and in binary mixtures of these solvents. 



(2) Further, we have measured the fluidities of the above-named solvents 

 and mixtures of these with one another; also the fluidities of solutions of 

 potassium sulphocyanate in these solvents. 



(3) A minimum in conductivity was observed in certain of the mixtures of 

 the solvents. The hypothesis of Jones and Lindsay as substantiated by the 

 work of Jones and Murray has been discussed. 



(4) It has been shown that in nearly all cases where actual minima do not 

 occur, there is nevertheless a decided dropping of the conductivity curves 

 below the values as calculated from the rule of averages; and that this drop 

 is most pronounced in the 25 per cent and 50 per cent mixtures, which are the 

 points at which the actual minima usually occur. It has also been shown 

 that these cases of dropping of the values below the values calculated from 

 the rule of averages constitute cases of virtual minima, and we have extended 

 the hypothesis of Jones and Lindsay to such cases, and have shown that the 

 hypothesis when applied to the problem of conductivity in mixed solvents is 

 perfectly general. 



(5) A minimum in the fluidity curves of the above solvents has been ob- 

 served, and the cause of this minimum has been explained as follows : It has 

 been shown that viscosity and fluidity are largely frictional phenomena; and 

 that since when two associated liquids are mixed they mutually decrease the 

 association of one another, they thus increase the number of molecules pres- 

 ent, and, consequently, increase the total frictional surface, thus causing an 

 increase in viscosity (or decrease in fluidity). Further, it has been shown 

 that the point of maximum viscosity is the point where the effect of the sol- 

 vents upon each other is greatest; and, consequently, is the point at which 

 we have the greatest number of simple molecules present. This has been 



