Voltaic Batteries^ Sfc. 67 



action. It was now remembered that this particular plate 

 had been cut from a piece of copper which had been employed 

 in some former experiments, during which it had been partly 

 amalgamated, and had had one of its sides covered with bee's 

 wax, to remove which and the mercury previously to adopting it 

 to its present use, it had been thrown on the surface of a bright 

 fire, and afterwards, whilst nearly red hot, had been plunged 

 in a trough containing dilute sulphuric acid. The same plate 

 was the agent in another curious phaenomenon, to be men- 

 tioned subsequently. (See Section VIII.) But confining my- 

 self to my present purpose, and without further alluding to 

 this circumstance, or to the suggestion it affords of a means 

 of increasing the power of voltaic arrangements, by some such 

 treatment of the plates, it is necessary here to remark that so 

 soon as this condition of the plate was detected, both the whole 

 of the plates, and the results of the experiments in which they 

 had been engaged, were dismissed as uncertain, and the whole 

 repeated with the use of new plates prepared with every pos- 

 sible regard to uniformity in their condition in every par- 

 ticular. 



44. VI. The copper plate of any voltaic arrangement very 

 speedily has its surface so affected as to be greatly diminished 

 in its amount of action ; an effect arising in some case from a 

 partial action upon the copper itself, but caused more fre- 

 quently by a deposition of matter upon its surface, derived 

 from the solution it is acting in ; and consequently differing 

 in kind and degree according to the nature of that solution, 

 and to the intensity of the voltaic action itself. If a copper 

 plate be so used through a period of 30 minutes, and its 

 amount of action be examined during every five minutes of 

 that time, it will be found that this diminishing in effect will 

 proceed much more rapidly during the latter than the former 

 portions of that time, as is shown in the following table : 



No. 1. 



Periodsoftimeof 5 minutes') , . „ i „ -, .^i ^,, ^,, 

 ggjjjj^ > 1st. 2nd. 3rd. 4th. 5th. 6th. 



Measures of gas in 50ths of ^ 



a cubic inch yielded in > 35. 33. 29. 24. 17. 9. 

 each time. J 



And when at the end of these periods the surface of the cop- 

 per was again brightened, its action was restored to the first 

 amount, or to 33 measures in the same time. 



45. This table is not unimportant, inasmuch as it might 

 have occurred that the accelerated action which takes place 



F2 



