On seme Chemical Agencies of Electricity . 17 



or tlepositions were formed, as in common galvanic expe- 

 riments, on the negative wire, and oxide was likewise de- 

 posited round it; and a great excess of acid was soon found 

 in the opposite cup. With solutions of iron, zinc, and tin, 

 this effect took place, as well as with the more oxidable me- 

 tals : when muriate of iron was used, the black substance 

 deposited upon the wire was magnetic, and dissolved with 

 effervescence in muriatic acid; and when sulphate of zinc 

 was used, a gray powder possessed of the metallic lustre, 

 and likewise soluble with effervescence, appeared ; and in all 

 cases acid in excess was exhibited on the positive side. 



Strong or saturated saline solutions, as might have been 

 expected, afforded indications of the progress of decompo- 

 sition much more rapidly than weak ones; but the smallest 

 proportion of ncutrosaline matter seemed to be acted on with 

 energy. 



A very simple experiment demonstrates this last principle. 

 If a piece of paper tinged with turmeric is plunged into pure 

 water in a proper circuit in contact with the negative point, 

 the very minute quantity of saline compound coniained in 

 the paper affords alkaline matter sufficient to give it instantly 

 a brown tint near its point of contact; and acid in the same 

 manner is immediately developed from litmus paper at the 

 positive surface. 



I made several experiments with the view of ascertaining 

 whether in the decompositions by electricity the separation; 

 of'the constituent parts was compkte from the last portions 

 of the compound ; and whenever the results were distinct, 

 this evidently appeared to be the case. 



I shall describe one of the most conclusive of the experi- 

 ments : — A very weak solution of sulphate of potash, con- 

 taining twenty parts of water and one part saturated soln- 

 tion, at 64", was electrified in the two agate cups by the 

 power of fifty pairs of plates for three days: the connecting 

 amianthus, which had been moistened with pure water, was 

 removed, washed with pure water, and again applied, twice 

 every day ; by this precaution the presence of any neutral 

 salt that might adhere to it, and disturb the results, was 

 prevented. 'I'he alkali obtained in this process in the sohi- 



Vol. 'JS. No. lOy. June lb07. B ""U 



