Chemical Affinity in terms of Electromotive Force* 385 



strengths, the difference being sometimes very considerable. 

 Thus the following tables represent the results thus calculated 

 when solutions MS0 4 2aH 2 and MS0 4 26H 2 are inter- 

 mixed so as to form MS0 4 (a + 6)H 2 when b = 200, and 

 consequently when /? 2 = 0. The " observed " values quoted are 

 those obtained with electro-coated plates throughout, save in 

 the case of zinc chloride, where amalgamated plates were em- 

 ployed; all the electromotive forces are expressed in millivolts. 



Zinc Sulphate. 



2a. 



a+b. 



* P 



2* 3 . 



H. 



Corre- 

 sponding 

 E.M.F. 



Observed 

 E.M.F. 



Excess. 



20 



210 



375 



O 



375 



8 



27 



19 



25 



212-5 



175 







175 



4 



22 



18 



33-3 



216-7 



100 







100 



2 



17 



15 



50 



225 



50 







50 



1 



13 



12 



100 



250 



















8 



8 



Copper Sulphate. 



50 



225 



50 







50 



1 



17 



16 



100 



250 



















12 



12 



200 



300 



















6 



6 



Cadmium Sulphate. 



16-7 



208-3 



1075 



25 



1025 



23 



34 



11 



20 



210 



825 



25 



775 



17 



28 



11 



25 



212-5 



625 



25 



575 



13 



23 



10 



33-3 



216-7 



450 



25 



400 



9 



18 



9 



50 



225 



275 



25 



225 



5 



14 



9 



66-7 



233-3 



200 



25 



150 



3 



9 



6 



100 



250 



75 



20 



35 



1 



4 



3 



Zinc Chloride. 



4 



202 



9000 



790 



8210 



181 



264 



+83 



5 



202-5 



8050 



790 



7260 



160 



225 



+65 



10 



205 



6100 



780 



5320 



118 



149 



+31 



20 



210 



4800 



760 



4040 



89 



65 



-24 



25 



212-5 



4400 



750 



3650 



80 



57 



-23 



333 



216-6 



3800 



730 



3070 



68 



52 



-16 



50 



225 



2700 



700 



2000 



44 



40 



- 4 



100 



250 



1250 



600 



650 



14 



23 



+ 9 



Cadmium Chloride. 



20 



210 



100 







100 



2 



32 



30 



100 



250 



















14 



„ 



