1894.] Thermo-electric Properties of Salt Solutions. 363 



is due to the superposing of a salt effect on that due to the water 

 itself. 



We see from these observations that for any given salt the value 



of $, starting from some value independent of the nature of the salt, 



tends to come to some value depending on the salt, and which does 



| not vary much for solutions of moderate strength. The latter result 



i was that obtained by M. Bouty ; the former is believed to be new. In 



; one of his series of experiments M. Bouty used very strong solutions of 



zinc choride, and he found that as the strength of these was increased 



i the value of $ rapidly diminished. This taken with the above results 



I seems to show that, if we could trace the entire curve for this salt, 



; taking the value of $ for all concentrations down to pure zinc choride 



at one end and pure water at the other, we should have a curve with 



a point of inflexion somewhere about its middle. It would, of course, 



be well-nigh impossible to trace such a curve for any salt, but we can 



do something very nearly identical without any great difficulty. If 



we take two solvents, and while keeping the salt a fixed quantity use 



different mixtures of the solvents, we can get a complete curve for 



#, as it varies with the change of solvent. I made a large number of 



experiments on 1 per cent, solutions, or rather 1 gram per 100 c.c. 



solutions of cadmium bi'omide ; these gave very good results with all 



the mixtures used. The electrodes were the exposed ends of sticks 



of cadmium, the sides being coated with glass. In each set I started 



with the solutions in pure solvents, and then mixed them so as to get 



the required mixture for each experiment. 



With solutions of 1 gram per 100 c.c. in methyl alcohol and ethyl 

 alcohol with their mixtures the following results were obtained : 



Methyl alcohol. Ethyl alcohol. $ (see fig. 3). 



100-0 11-3 



90-0 10-0 11-0 



81-3 18-7 10-76 



70-0 30-0 10-410-5 



50-0 50-0 10-27 



30-0 70-0 9-86 



18-7 81-3 9-64 



10-0 90-0 8-9 



1000 8-15 



This gives us a curve with a point of inflexion similar to that 

 suggested above as the probable shape of the complete curve for 

 water and zinc choride. 



