1887.] On the Development of Feehle Currents. 



271 



A. Acetic acid solution, approximately of strength 



l-iC.H.O^lOOHoO. 



B. Ditto also containing sodium acetate, approximately of strength 



10C 2 H 4 O 2 ,10XaC 2 H 8 O 2 ,100H. 2 O. 



C. Ammonia solution originally of strength 10XH :3 .100H 2 O, but 



considerably weakened during the experiment by evapora- 

 tion. 



D. Ammonia solution also containing ammonium sulphate ; origin- 



ally 10NH 3 ,2-5(XH 4 ) 2 SO 4 ,100H 2 O. 



E. Ammonia solution also containing sal-ammoniac ; originally of 



strength 10NH 8 ,5NH 4 Cl,100H 2 O. 



F. Dilute sulphuric acid, 4H 2 SO 4 ,10l»H 2 O. 



Time in 

 hours. 



Silver dissolved 



Silver 

 deposited 

 in volta- 

 meter. 



Per cell per 24 hours. 



Differ- 

 ence. 



In 4 cells 

 jointly. 



Per cell. 



Silver 

 , deposited. 



Silver 

 dissolved. 



A. 180 



0-003 



0-00075 



-0025 



0-00033 







o-oooio 



0-00023 



B. 130 



0-0045 



0-001125 



0020 



; 0-00037 



0-00021 



00016 



C. 68 



-015 



00375 



0060 



; 0021 



0014 



0007 



D. 136 



0-1095 



-027375 



037 



1 0-0065 



0-0048 



0-0017 



E. 44 



0-086 



0215 



027 



0147 



0117 



0030 



F. 96 



0-343 



087 



097 



0242 



-0217 



0025 



The difference between the silver dissolved and that deposited by 

 the current is thus relatively much larger with the weakest currents, 

 representing 43 — 69 per cent, of the latter in cases A and B ; 26 — 33 

 per cent, in cases C and D ; and 10 — 20 per cent, in cases E and F. 



It is obvious that if silver will dissolve in acids, &c, under the com- 

 paratively feeble oxidising inOuence of an aeration plate, much more 

 rapid solution might be anticipated by substituting for such a plate 

 platinum immersed in a powerfully oxidising fluid such as strong 

 nitric acid, or sulphuric acid solution of chromic anhydride. In point 

 of fact, we have found that on setting up such cells where the silver 

 was immersed in dilute sulphuric acid (i.e., Grove's cell with silver 

 instead of zinc, and so on), electromotors of notable power are 

 produced, at any rate until the silver plate becomes coated with 

 sparingly soluble sulphate. Even in these cases, however, perfect 

 correspondence between the amount of silver dissolved and that 

 deposited in a voltameter included in the circuit does not subsist, the 

 latter being always measurably the greater. Thus in several experi- 

 ments with such cells, when the current was so regulated by interpos- 



