128 Mr, Grove 07i Voltaic Series and the 



be seen, materially from those of Sir H. Davy on unimetal 

 series. Having constructed two troughs in the manner 

 described in my last letter, one of alternate plates of iron 

 and unglazed porcelain, the other of plates of copper and 

 poi'celain, I poui'ed into the alternate cells of the first a 

 saturated solution of sulphate of ii'on and dilute sulphuric 

 acid. With this arrangement, as was to have been expected, 

 little electric action was manifest ; equally trifling were the 

 effects when sulphate of iron and dilute muriatic acid were 

 the electrolytes ; when however nitric acid was employed 

 with sulphate of iron a tolerably active current was gene- 

 rated : with twelve plates acidulated water was decomposed 

 and a slight shock felt in the moistened hands. I now tried 

 the copper trough with sulphate of copper and the same 

 three acids respectively : with the sulphuric and nitric the 

 electric development was but slight; but with the muriatic, 

 diluted with about twice its quantity of water, a most energetic 

 series was formed. With twelve plates acidulated water was 

 rapidly decomposed * : with a pair of copper plates each ex- 

 posing about 36 square inches of surface, a Ritchie's rotating 

 magnet was whirled rapidly round, exhibiting small but 

 brilliant sparks ; its revolution continued for several hours 

 without the addition of fresh acid ; in fact the energy was 

 fully equal to that displayed by similarly sized arrangements 

 of zinc and copper, excited b}' muriatic acid but without dia- 

 phragm: a strong solution of common salt, substituted for 

 muriatic acid, produced effects not far interior. On ex- 

 amining the batteries when exhausted, I found the sides of the 

 copper which had been exposed to the sulphate of copper 

 covered with a fine coating of that metal ; the affinity between 

 the chlorine and the copper had consequently (according to 

 the principle of preponderating affinity established by Dr. 

 Faraday,) been sufficiently powerful to cause the solution of 

 copper to be de-oxidated by the transferred hydrogen and to 

 produce vigorous electro-motive action without the presence 

 of a dissimilar metal. 



It would appear from this that the diaphragm is of more 

 practical importance in voltaic combinations than as a mere 



* It is more expensive but much more satisfactory, if,in these experiments, 

 series, as in the text, be employed instead of single combinations. I have 

 frequently imagined I had obtained results from a single pair with the gal- 

 vanometer, but have found them entirely negatived when the same combi- 

 nation was used in series. This was most probably owing to the many in- 

 terfering circumstances to which the magnetic galvanoscope is liable, or 

 perhaps to superficial differences in the two plates of metal. 



