1888.] upon the Potential of Voltaic Couples. 



375 



With the astatic galvanometer, the electromotive force of the 

 couple in water began to change when the proportion of chlorine was 

 between 1 part in 17,000 million and 17,612 million parts of water ; 

 but with the reflecting one it was between 1 in 29,062 millions and 

 32,291 millions. 



The minimum proportion of chlorine required to change the poten- 

 tial of a zinc-platinum couple, when the astatic galvanometer was 

 employed, lay between 1 part in 1,264 millions and 1,300 million parts 

 of water (" Influence of the Chemical Energy of Electrolytes, &c," 

 ; Roy. Soc. Proc.,' June 7, 1888). 



Table XVII.— Cd + Pfc + Chlorine in 465 grains of Water at 19° C. 



Grains. 



Volts. 



Grains. 



Volts. 



Grains. 



Volts. 



1 '0695 

 1-0002 

 0-9309 

 '8616 

 -7923 

 0-723 



1 -71654 



1-730 



1-7683 



1-7453 



1-739 



-6537 

 0-5844 

 0-5151 

 -4458 

 -3765 

 0-3072 



1-7339 

 1 -7251 

 1-7223 

 1-7165 

 1-7022 

 1 -6885 



-2379 

 -1686 

 -0993 

 0-03 



1-7137 

 1 -7022 

 1 -6856 

 1 -6062 



Table XVIII.— Ditto at 19° C. 



Grains. 



Volts. 



Grains. 



Volts. 



Grains. 



Volts. 



03 



0-027 



0-024 



0-021 



0-018 



1 -6062 

 » 



1-5690 

 1 -5575 



0-015 

 0-012 

 0-009 

 0-006 

 0-003 



1 -5175 

 1-4889 

 1 -4603 

 1 -4346 

 1 3459 



-0003 

 -00010695 

 0-00005346 

 -00004806 

 water 



1 -1028 

 -7904 

 - 7589 

 0-7475 

 » 



The smallest proportion of chlorine necessary to change' the 

 potential lay between 1 part in 8,773,585 and 9,270,833 parts of 

 water. 



The following results were obtained by varying the kind of negative 

 metal : — 



Table XIX.— Zn + Au + Chlorine in 13,950 grains of Water at 



15° C. 



Grains. 



Volts. 



-000026928 

 -000025344 

 0-000024947 

 water 



1 -0371 

 1 -0228 



}3 



