ELECTRICAL CONDUCTIVITIES, ETC. 79 



other salts in Table II. Its temperature coefficients of conductivity are of the same 

 order of magnitude as the other compounds included in this table. 



The halogen salts of copper present apparent exceptions to the above relation. 

 The chloride crystallizes with only two molecules of water, and yet has temperature 

 coefficients of conductivity that are nearly as large as the salts with six molecules of 

 water of crystallization. It might be inferred from this that this salt has much less 

 hydrating power than the other compounds in Table II. The work of Jones and 

 Bassett,* however, shows that this is not the case. Copper chloride has almost as 

 great hydrating power as the compounds in this table which crystallize with six 

 molecules of water. When we take this fact into account its temperature coeffi- 

 cients of conductivity are not surprisingly large. 



Aluminium chloride crystallizes with six molecules of water, and aluminium 

 nitrate with eight. They are, however, quaternary electrolytes, and their temper- 

 ature 1 coefficients are therefore larger than those of the ternary electrolytes. The 

 hydrating power of these salts has been worked outf and has been found to be of the 

 same order of magnitude as that of the ternary electrolytes in this table. 



A third point brought out by the above tables is the following. The temperature 

 coefficients of conductivity for any given substance are greater at the higher dilution than 

 at the lower. This is satisfactorily explained on the basis of the above suggestion. 

 The complexity of the hydrates at the higher dilutions is greater than at the lower, as 

 has been shown by Jones and his co-workers, on the composition of the hydrates 

 formed by different substances at different dilutions. X 



The hydrates being more complex at the higher dilutions, the change in the com- 

 position of the hydrates with change in temperature would be greater at the higher 

 dilutions; and, consequently, the temperature coefficients of conductivity would be 

 greater the more dilute the solution. 



To summarize the above three points: 



(a) The temperature coefficients of conductivity of aqueous solutions of salts, ex- 

 pressed in conductivity units, are greater the greater the hydrating power of the salt. 



(b) The temperature coefficients of conductivity of aqueous solutions of electro- 

 lytes are of the same order of magnitude for those substances having approximately 

 the same hydrating power. 



(c) The temperature coefficients of conductivity for any given salt increase with 

 the dilution of the solution, and this increase is greatest for those substances with 

 large hydrating power. 



All three of these conclusions are necessary consequences of the assumption that 

 the large change in conductivity with change in temperature is due, in part, to the 

 decreasing complexity of the hydrates formed around the ions, with rise in temper- 

 ature. As these conclusions are verified by the experimental results, and as there 

 seems to be no other assumption which would lead to these conclusions, we must 

 accept the assumption which led to them as containing a large element of truth. 



*Carnegie Institution of Washington Publication No. 60, pp. 84 and 85; Ainer. Chem. Journ., S3, 

 577, 1905. 



tCarnegie Institution of Washington Publications No. 60, pp. 67 and 88. 

 tCarnegie Institution of Washington Publication No. 60. 



