Chemical Affinity in terms of Electromotive Force. 271 





Bi 





E 2 









D 











E x E 



R _ E 1 -E 2 





Observed. 



Interpo- 

 lated. 



Observed. 



Interpo- 

 lated. 





2-5xD' 



•000770 





•847 



•770 





•077 



4'00 ohros. 



•0006953 



•869 







•799 



•070 



4-03 „ 



•0003840 



■960 







•921 



•039 



4-05 





•0003708, 



•965 



•927 





•038 



411 





•0002036 1-018 







•997 



•021 



412 





•0001998' 



1019 



•999 





•020 



404 





•0001039 1 



1-050 



1-039 





•on 



4-24 





•0000845 1-056 







1-047 



•009 



4-28 



> 









Average 



.. 411 ohms. 



Taking 4" 11 okas as the average value of R, the following 

 numbers are calculated from the above observations, the values 

 of Ei and E 2 being obtained by interpolation: — 



Values from observations with 



Values 



from observations 



Average ■■ 

 value of R „ 

 EMF ■ bau * 





smaller plates. 





with larger plates. 



D. 



E r 



2-5 xDE. 



e i=Ej 

 +2-5DE. 



E 2 . 



5-0 XDE. 



* 2 =E 2 

 +5-0DE. 



of cell. 









1103 





1103 



1103 





1103 



1103 i 



•000001 



1103 





1103 



1103 





1103 



1-103 i 



•000002 



1100 





1.100 



1100 





1100 



1-100 -003 



•000005 



1-096 





1-096 



1-097 



■001 



1-098 



1-097 -006 



•00001 



1-092 



■001 



1-093 



1-092 



•002 



1-094 



1-094 |-009 



•00002 



1-086 



•002 



1-088 



1-086 



•004 



1090 



1-089 -014 



•00005 



1-072 



•005 



1-077 



1-065 



•010 



1-075 



1-076 -027 



•0001 



1-051 



•010 



1-061 



1-041 



•021 



1-062 



1-062 -041 



■0002 



1-019 



•021 



1-040 



•999 



•041 



1-040 



1-040 -063 



•0004 



•957 



■041 



•998 



•916 



•082 



•998 



•998 



•105 



•0007 



•868 



■072 



•940 



■798 



144 



•942 



•941 



162 



It is evident that the values of e x and e 2 accord so closely 

 that their average may fairly be taken as representing, with 

 but little error, the E.M.F. of a cell containing copper and 

 zinc plates in the condition of those experimented with in this 

 instance*. 



105. In various other analogous experiments the concord- 

 ance was usually not quite so close as in this example, a 

 smaller number of readings (one or two sets only) being made; 



* It might appear at first sight that a third valuation of the E.M.F. of 

 the cell might he deduced as follows: — Since e 1 =E 1 4-2"5DR, and also 

 e 2 = E 2 4-5-0DR, it results that e 1 =e 2 =2E 1 -E a ; but it is evident that this 

 -value Is such that e x is the arithmetical mean between e 2 and 2E X - E 2 , 

 and hence that the average of the three values must be identical with e 1? 

 and therefore less exact than the mean of e x and e 2 . 



