Chemical Affinity in terms of Electromotive Force. 381 



described were ordinarily made) ; but with two opposed Da- 

 rnell cells, containing pairs of solutions of the same strengths 

 in each severally, the differential current sometimes passed in 

 one direction on first setting up, sometimes in the opposite 

 direction : sometimes it increased in intensity as time elapsed, 

 and sometimes it diminished : in the latter case occasionally 

 it diminished to nil, and then flowed in the opposite direction 

 with gradually increasing intensity. Thus, for instance, the 

 following numbers were obtained in one set of observations 

 where the density never exceeded '02 microamperes per square 

 centimetre, and was usually much less, so that '•polarization 4 ' 

 errors were eliminated (§ 150). The total resistance in cir- 

 cuit (including galvanometer and cells) was 107,100 B.A. 

 units. The sign + indicates that the E.M.F. of the cell con- 

 taining the stronger solutions was higher than that of the 

 other; the sign — indicates the opposite. Readings were 

 taken every minute for 15 minutes after setting up ; the 

 plates were then exchanged (after rinsing with the appropriate 

 solutions), and another similar series of readings taken : a 

 second, and then a third exchange was similarly made, readings 

 for 15 minutes being again taken in each case : the readings 

 are translated into millivolts, every scale-division being equal, 

 in these experiments, to 85*7 elassoamperes, and consequentlv 

 representing 85*7 x 10" 12 + 107,100 ='00000895 volt -^ 8-95 

 microvolts. 



Minutes 

 after first 

 setting up. 



Before plates 

 exchanged. 



After first 

 exchange. 



After second 

 exchange. 



After third 

 exchange. 



I 



-1-3 



-2-0 



+•±•5 



+ 5-4 



2 



-1-4 



-2-0 



+ 3-2 



+ 3-4 



3 



-T5 



-2-1 



+21 



+2-0 



4 



-1*5 



-24 



+ 1-3 



4-1-0 



5 



-l-o 



-2-1 



+ -7 



+ -5 



6 



-1-5 



-2-2 



+ '4 



— 7 



7 



-T5 



— 2*2 



+ 'I 



-1-3 



8 



-16 



-22 



- -3 



-1-7 



9 



-1-6 



— 22 



— 



-2-0 



10 



-1-6 



— 2*2 



— '7 



-22 



11 



-1-6 



_.>o 



- -s 



-24 



12 



-1-6 



-2-1 



— -9 



-2-5 



13 



-1-6 



-2-1 



-1-0 



-2-6 



14 



-1-0 



-2-1 



-1-0 



— 27 



15 



-1-0 



-21 



-10 



-2-7 



Average ... 



-1-5 



-2-1 



+ '4 



— -6 





General 



irera^e 



. =-09. 







In precisely the same way the following numbers were 

 obtained in a duplicate experiment : — 



