Chemical Affinity in terms of Electromotive Force. 361 



Current, in 

 niicrowebers. 



Microwebers 

 per square 

 centimetre. 



E, in volts. 



CE. 



-e=-(E-CE). 



6-7 



0-78 



-•604 





■604 



9-8 



114 



-•589 





•589 



14-4 



1-67 



-•571 





•571 



23-2 



2-7 



-•547 



•001 



•548 



41-0 



4-8 



-•519 



•001 



•520 



58-5 



6-8 



-•493 



•002 



•495 



96-0 



11-2 



-•442 



■003 



•445 



135-6 



15-8 



-•395 



•005 



•400 



Evidently the value of — (E — CR)— that is, the direct 

 E.M.F. of the combination — decreases as the current increases, 

 but not at the same rate, the diminution in the E.M.F. being 

 less rapid than the increase in rate of flow. 



97. DanieWs Cell. — In order to verify the deductions above 

 made from the preceding experiments as to the variation of 

 the E.M.F. of a DanielPs cell with the current produced, and 

 so to amplify the observations of Waltenhofen and Beetz, the 

 following experiments were made with two such cells arranged 

 on the " gravity" principle — i. e. no porous cell being em- 

 ployed, but the copper plate being lowest and immersed in 

 a saturated solution of copper sulphate, the zinc plate being 

 uppermost and immersed in a solution of zinc sulphate of 

 lower specific gravity than the copper sulphate solution. In 

 the first cell the active surface of each plate was about 15 

 square centims., and the resistance of the column of fluid 

 between them was calculated, from the dimensions of the column 

 and Kohlrausclr's values for the specific resistances of copper 

 and zinc sulphate solutions, to be about 4 ohms. In the 

 second cell much smaller plates were used, exposing about 

 1 square centim. of active surface, the resistance of the column 

 of fluid being calculated to be about 40 ohms. 



First Cell. 



Current, in 

 microwebers. 



Microwebers 

 per square 

 centimetre. 



E, in volts. 



CE. 



-e=-(E-CE). 







o 



-1-090 





1-090 



10-9 



0-7 



-1-090 





1-090 



36-3 



2-4 



-1-090 





1-090 



107-7 



7-2 



-1-077 





1-077 



267-2 



17-8 



-1-069 



•001 



1-070 



530-5 



35-4 



-1061 



•002 



1-063 



1317-5 



87-8 



-1-054 



•005 



1-059 



Phil. Mag. S. 5. Vol. 11. No. 69. May 1881, 



2D 



