DISCUSSION OF EVIDENCE. 165 



tivity minima were found in mixtures of the alcohols with water and 

 acetone with water. Conductivity maxima were obtained with lithium 

 bromide in mixtures of methyl or ethyl alcohol with acetone. Cobalt 

 chloride in mixtures of acetone with ethyl alcohol also showed a maxi- 

 mum. Jones and McMaster reached the same conclusion from their 

 work that had been reached by Jones and Bingham. Change in the 

 complexity of the solvate formed by the ion in different mixtures of 

 solvents is an important factor in determining the conductivity maxima. 



A point of interest brought out by the work of McMaster was in 

 connection with the temperature coefficients of conductivity in non- 

 aqueous solutions. The bearing of temperature coefficients of con- 

 ductivity on the solvate theory of solution has already been discussed. 

 With rise in temperature the hydrates about the ions became simpler. 

 The mass and probably the size of the ion thus became less, and it moves 

 faster the higher the temperature, thus increasing the conductivity. 



McMaster found that cobalt chloride in certain mixtures of acetone 

 with the alcohols showed, at ordinary temperatures, negative temper- 

 ature coefficients of conductivity. What does this mean? The solvent 

 becomes less viscous with rise in temperature, thus increasing the 

 velocity of the ions; and the solvates become simpler, which also 

 increases the velocity with which the ions move. 



With rise in temperature, on the other hand, the association of the 

 solvent, and consequently its dissociating power, becomes less. 



The above two influences work counter to one another. Negative 

 temperature coefficients of conductivity mean that the latter influence 

 overcomes the former. The alcohols used and acetone are highly 

 associated liquids. Rise in temperature diminishes their association 

 and consequently their dissociating power. 



A solution of cobalt chloride in a 75 per cent mixture of acetone with 

 methyl alcohol, the solution being -^^ normal, had a zero temperature 

 coefficient of conductivity. 



A number of points of interest were brought out by the next investi- 

 gator, Veazey. 1 He worked with solutions of salts in water, methyl 

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

 with one another. The minimum in conductivity was found to be a 

 more general phenomenon than had been supposed from the earlier 

 work. It had long been known that mixtures of methyl alcohol and 

 water or ethyl alcohol and water, are more viscous than either of the 

 pure solvents alone. A rational explanation of this phenomenon was 

 suggested alcohol and water are strongly associated liquids. When 

 two associated liquids are mixed each diminishes the association of 

 the other. The larger molecules are thus broken down into smaller 

 molecules, which increases the frictional surfaces when these molecules 

 move over one another as they do in measuring viscosity. The result 



iAmer. Chem. Journ., 37, 405 (1907). Zeit. phys. Chem., 61, 641 (1908); 62, 44 (1908). 



