70 Mr. Binks on the Laws of Action of Voltaic Electricity, 



Let a sheet of common rolled zinc, carefully selected for its 

 apparent uniformity of surface and thickness, be amalgamated 

 in such a way as to secure the greatest uniformity in the distri- 

 bution of the mercury over its surface. Let plates be cut from 

 this sheet, exactly of the same size, and then associated with 

 corresponding copper plates ; and however well this may have 

 been done, and however exactly alike the plates and every at- 

 tendant circumstance may be, it will be found that no two of 

 the couples will give the same results in the same time, when 

 arranged as simple galvanic circles and acted on by acids in 

 the usual way. Whilst one zinc plate will lose 10 grains in 

 a certain time, another compared with it and apparently ex- 

 actly similar will lose perhaps only 6 grains, or, on the other 

 hand, as much as 15 grains. Out of innumerable instances I 

 have never been able to select two exactly alike, and in the 

 closest approach to perfect similarity in the amount of action 

 of any two which I have found there has still been between 

 them a difference of ^th of the whole amount. 



Again, any one plate, associated with a copper plate as a 

 simple circle, will lose less the first time of its immersion than 

 during the second, of which the following is one taken out of 

 many such examples: 



A plate of amalgamated zinc, arranged with copper as a 

 simple voltaic circle, and immersed (the acid being each time 

 renewed) during periods of 30 minutes each : 



Table No. 1. 



In the 1st time lost 8*8 grains 

 2nd 90 — 



3rd 9-s — 



4th 11-2 — 



5th 13'0 — 



6th H-3 — 



And when at the end of these the plate was amalgamated 

 afresh and reimmersed, the action was reduced below its 

 first amount, namely, to 6*7 grains in the 30 minutes. 



These sources of error, in cases where such elements are 

 used, are independent of many others well known to experi- 

 menters, such, for instance, as accidental differences in the 

 distance of the plates from one another, and the varying con- 

 ditions of their surfaces. 



Again, the common rolled zinc of the shops is very impure, 

 and before undertaking investigations of phaenomena in which 

 comparisons of effects with the quantities of zinc consumed 

 and hydrogen evolved are needed, the proper equivalent of 

 the zinc actually employed must be determined. 



In the midst of so many sources of error, against which the 



