32 



KOYAL SOCIETY OF CANADA 



fcnine wihether the change ia the density curves for these salts could 

 he accounted for by a change in dissociation of the hydrated salt. 

 Such a change was indicated in the case of MgCl^, but before basing 

 any conclusions on these results we desired to study the matter further 

 Our apparatus difEered from that previously described by us only in 

 the addition of a continuous electrical heating device, by means of 

 which the temperature in our water bath could be maintained constant. 

 We show a diagram of this apparatus in figure I. 



A glass tube TH is fitted with a heating spiral of platinoid or 

 manganin wire, which is connected at each end with heavy copper lead.<5, 

 A continuous current of water flows through the tube into the tank 

 "from a constant level device at H. Tliis constant level device is fed 

 from the mains through the tube M and overflows at 0. The water, 

 which is cooler than the desired temperature m the tank, is heated 

 by the passage of a current from the 100-volt experimental circuit E. 

 Eheostats at R serve to adjust the current which is read ofl: on the 

 ammeter at A. Two adjustments are possible, and Ijoth alter the 

 temperature of the tank. The head H may be raised or lowered, and 

 the current in TH may be adjusted at E, and observed on the ammeter. 

 By knowing what a change in head or current will produce on the 

 temperature of the tank, it was possible to compensate quickly for the 

 changes in temperature of the tap water. 



The salts we used in our work were Merck's best, and solutions 

 were made with the purest distilled water. The strength of each 

 solution was adjusted roughly by means of a hydrometer, and then after 

 the measurements of resistance had been made, it was obtained accu- 

 rately by a pyknometer. 



Table 1 contains our results for K.^SO^ which we obtained at a 

 ■constant temperature of 25-5° C. 



Table I. KoSO^ at 25- 5° C 



