Ohfervations of Galvanic Proceffks. 399 



The Giver flips in pump water almoft always became incrufted with a white matter, which 

 was never notable in diftilled water, and which was foluble, without cloudinefs, in 

 nitrous acidt 



In one experiment, when a filver flip, forming part of a powerful feries, was 

 introduced into a fmall veflel, containing folution of muriate of magnefia* (connected 

 with the next zinc glafs by means of mufcular fibre, to prevent the interference of the oxy- 

 dating metal with the refills), in the courfe of a night much gas was given out from it, 

 and it became incrufted with a white matter, which diflblved with flight fiffervefcence in 

 marine acid. A precipitation had taken place in the fluid. 



Thefe refults afl'ord ftsong probabilities in favour of the produftion of ammoniac on all 

 the filver excitnrs of the feries formed with common water : and compared with the fafts 

 before mentioned, they amount almofl; to demonftrations. Whether the nitrogen of at- 

 mofperic air diilblved in water is the agent which forms with the hydrogen ammoniac, 

 future experiments made in vacuo muft determine t. 



6. The power of the feries with filver wires, was much lefs than that of the feries with 

 plates. Suppofing the formation of ammoniac, it was probable, that the larger quantity 

 produced upon the plates, might be in feme meafure the caufe of their greater powers; and 

 if fo, it vi'as likely that the condenfasion of nafcent hydrogen upon^ the wires would be con- 

 ne£^ed with increafe of power. From the following fails it appears that this is the cafe. 

 A feries of thirteen plates of zinc, with their filver wires, conftrudled in glafles,, containing 

 weak folutions of red fulphate of iron, mingled with a little folution of common fulphate 

 ©f iron and nitrous gas, atVed full as powerfully as the common feries of twenty plates. 

 The wires gave out no hydrogen, but occafioned a brown precipitation in the fluid, and 

 the zinc plates foon became covered with green oxide of iron. The phanomenon was the 

 fame with other mixed metallic folutions, capable at the fame time of abforbing hydrogen 

 and oxydating zinc. 



7. The flrongeft analogies would induce us to believe, that all the galvanic feries com- 

 pofcd of eafily oyydable metals and diflicultly oxydable metals muft follow the fame laws in 

 producing changes in their connefting fluid as zinc and filver. But as from the interefting 

 faCts of Colonel Haldane, it appeared that iron and ?.inc as a combination were poflefied of 

 very confiderable powers, and as iron is but Httle inferior to zinc in its aflSnity for oxygen, 



* Muriate of magnefia was ufed in preference to nitrate or fulph.ite, becau.e there was a pollibility of the 

 dscompofitisn of the acids in thsfe falts by the nafcent Iiydrogen, which alone would occafion a precipitation 

 of earth. 



f Mr. Cruicklhank, who fiift noticed the probable formation of ammoniac on the filver wire of the p!l<, 

 has offered forae ingenious arguments to prove that nitrous acid is formed at the 7inc wire. Analogy, 

 would induce us to conjt6lure, that if it was formed on one of the oxydatiiig furfaces, it ought to be 

 formed on all. That no diange of colour takes place in cabbage j«ice, in contail with the oxydating zinc 

 plates, may be owing to the grcal extenfion of their furfaces. It is worth oWerving, that the filver oxy- 

 dates as rapidly in water in vacuo as in the atmolphere, when the pile is in the atmofphere j or when nitrous 

 , .ar fulphuric acid is ufed in the cells in vacuo, 



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