WORK OF E. G. MAHIN. 



125 



be the same as Walden's constant for aqueous solutions. It is probable that, if 

 complete dissociation could have been obtained in acetone, the product for this 

 solution would have been found to be nearly 0.70, and that the product for mixtures 

 of acetone and water would conform to the rule of mixtures. We have no explan- 

 ation to offer for the fact that water differs so strikingly from the organic solvents 

 with respect to the numerical value of the product of maximum molecular conduc- 

 tivity and viscosity. 



Table 92. Molecular Weight of Lithium Nitrate in Acetone. 



In order to test the assumption that the low conductivity shown by ordinary 

 solutions of lithium nitrate in acetone is due to association of the salt, the molecular 

 weight of lithium nitrate in acetone was determined by the boiling-point method. 

 The apparatus used was that designed by Jones, 1 the thermometer being the Beck- 

 mann instrument, graduated to 0.01. The boiling-point constant for acetone was 

 taken as 17.25, which is that found in a redetermination by Jones. 2 The usual cor- 

 rections were made for changes in barometric pressure. The results are shown in 

 table 92, and the molecular weights are plotted against concentrations in fig. 53. 



Fig. 53. Conductivity of cad- 

 mium iodide in mixtures of 

 acetone and methyl alcohol 





Fig. 54. Conductivity of 

 cadmium iodide in mix- 

 tures of acetone and 



50 75 



Per cent, of Acetone 



Per cent, of Acetone 



The normal molecular weight of lithium nitrate is 69.07. The fact that, even in 

 the most dilute solution which could be used with accuracy (0.09 N.), the molecular 

 weight is greater than this number, is significant. If it be remembered that a portion 

 of the salt is also ionized, and that the molecular weight as obtained by the boiling- 

 point method is the average weight of associated molecules, single molecules, and 

 ions, existing simultaneously in the solution, it will readily be surmised that there 

 must be a certain degree of association at much greater dilutions. This would 

 explain the departure from the dilution law in those solutions in which the associa- 

 tion has not entirely disappeared. 



It has already been stated that cadmium iodide was found by Jones to be asso- 

 ciated when dissolved in acetone. We have studied the conductivity of cadmium 



Amcr. Cliem Jour 



.^1(1897); Zeit. phys. Chem., 31, 119 (1899). "-Ibid., 27, 16 (1902). 



