144 



Prof. H. L. Callendar and Mr. H. T. Barnes. 



pendently checked. If we liad ourselves foreseen a simple relation 

 of this character, we should have taken even greater pains in verify- 

 ing the observations about this point. As it is, we hope shortly to 

 be able to investigate the subject further, and in particular to 

 ■endeavour to find similar relations in the case of other solutions. 



Fig. 3. 



-050 



■040 



-050 



-020 



■0/0 

































i 



7 



y 



' form 



u/a 











of 3ei 

 (cfotd 



xf) 





X V 



V 



oCaA 



X Ldi 



'eno/ar q 

 woy. 



Barnes. 



/Ibsc/ssae . Ife/ues of w pd/too. 



§ 22. Change of E.M.F. with Strength of Solution at Constant 



Temperature. 



A number of Clark cells of the B.O.T. pattern, but without 

 crystals, were set up with the solutions above described, of which 

 the density and composition had been carefully determined. Due 

 precautions were taken in each case to avoid evaporation. The 

 difference of E.M.F. from the standard at 15° C, and also at other 

 temperatures, was carefully determined in the case of each of these 

 cells. On plotting the results, we could not find any simple relation 

 between the change of. E.M.F. and the density or the percentage 

 strength of the solutions. But on expressing the observations in 

 terms of w, the weight of ZnS0 4 per c.c, and not per gram, of solu- 

 tion, we found that the values of cZE, the difference of E.M.F. from 

 the standard at 15° C, fell very nearly on a straight line, represented 

 by the formula : — 



dE = 42-0-88-Om? (millivolts). 



The following table contains the observations for each solution 

 tested : — 



