358 



Dr. C. R. A. Wright on the Determination of 



the conclusion that either the freshly deposited copper had a 

 higher power of " condensing '* copper on its surface than 

 rolled copper, thereby increasing the value of n x in the for- 

 mula 



e={h'+{l-n l )B. i +h") X 3, 



and that this power became lessened on standing, or else that, 

 on standing, the surface of the copper altered in such a way 

 as to cause the value of h" to increase, or, possibly, that both 

 changes took place together. 



Precisely analogous results were obtained in other experi- 

 ments with different voltameters : with considerably stronger 

 currents up to some 5000 microwebers per square centimetre 

 of electrode surface, values of 0*2 volt and upwards have been 

 obtained for e by a method now being elaborated in conjunc- 

 tion with Mr. E. H. Rennie. Admitting that in these instances 

 the values of 7/ and W are negligible compared with (1— -rtx)^ 

 (which probably is not quite the case), it results that the value 

 of H^J must exceed 0*2 volt, i. e. that H l3 the heat of trans- 

 formation of " nascent " into ordinary copper, is greater than 



0-2 xlO 8 , Rnn , . . , 



—T7j7] — =4500 gramme-degrees per gramme-equivalent. 



94. In precisely the same way the following values were 

 obtained on electrolysing a solution of zinc sulphate with 

 bright zinc electrodes, the area of each of which was 8' 6 square 

 centims., the value of R being close to 250 ohms. 





Microwebers 









Current, in 

 microwebers. 



per square 

 centim. of 

 electrode 

 surface. 



E, in volts. 



OE. 



e=E-CE. 



14-3 



1-7 



•023 



•004 



•019 



28-2 



3-3 



•031 



•007 



•024 



39-4 



4-6 



•039 



•010 



•029 



69-8 



8-1 



•050 



•017 



•033 



87-9 



10-2 



•068 



•022 



•046 



1364 



15-9 



•085 



•034 



•051 



1671 



19-4 



•094 



•042 



•052 



3100 



36-0 



•131 



•078 



•053 



647-0 



75-2 



•232 



•162 



•070 



1147-0 



132-5 



•365 



•287 



•078 



The curves traced out with zinc- and copper-sulphate solu- 

 tions and zinc and copper poles respectively exhibit resem- 

 blance in general characters to those obtained with acidulated 

 water and non-oxidizable electrodes : they indicate that e in- 

 creases with the current but not so rapidly, so that the curves 

 are concave downward. 



