from their Solutions by the Galvajiic Current, 439 



salts of metals into protosalts favours strongly, by analogy, the 

 same opinion. Such evidence is amply sufficient, but 1 have 

 now to detail some direct experiments in which hydrogen 

 alone reduces metals from various salts. 



13. The mode in which this satisfactory result is obtained 

 is very simple. The metallic solution to be examined is placed 

 in a glass, a test-tube filled with the same solution is then pro- 

 cured, into which a slip of platinum, platinized as for the con- 

 struction of my battery, is then placed. The whole is then 

 placed within a glass of metallic solution, and a current of 

 hydrogen introduced sufficient to extend half-way up the pla- 

 tinized platinum. It will be seen that the arrangement is 

 similar to that of one of the tubes of Prof. Grove's elegant gas 

 battery, and the various results obtained by this mode of exa- 

 mination it will be my duty immediately to explain. 



14. If the solution employed be chloride of platinum the 

 hydrogen disappears gradually, and the black powder of pla- 

 tinum is coated here and there by a beautiful bright layer of 

 reguline metal. 



15. With a solution of chloride of gold the same result is 

 seen, the platinum being gilt with a beautiful deposit of metal. 

 With this salt the action is immediate. 



\6. With nitrate of palladium the hydrogen is rapidly ab- 

 sorbed and bright palladium deposited. 



17. With nitric acid and platinized platinum the hydrogen 

 is gradually absorbed and the acid decomposed. 



18. A solution of sulphate of copper under similar exami- 

 nation yields a plentiful crop of small crystals of copper in a 

 short period. 



19. A solution of persulphate of iron yields rapidly its 

 oxygen and becomes converted into the protosulphate. 



20. A solution of nitrate of silver yields slowly small cry- 

 stals of silver, but the action with this metal is not so rapid. 



21. The hydrogen was slowly absorbed when exposed to a 

 solution of muriate of tin in contact with platinized platinum. 



22. Nickel was slowly deposited from the chloride, when 

 exposed under similar circumstances, as a white deposit. 



23. Hydrogen, contrary to my expectations, did not appear 

 to reduce iodine from iodic acid. 



24". From the solution of protosalts of iron I could not de- 

 termine that the metal was reduced. 



25. I next subjected to experiment the extraordinary com- 

 pounds of cyanogen forming the metal lo-cyanides. From the 

 aurocyanide of potassium I obtained metallic gold. 



26. The argento-cyanide of potassium, in a similar way, 



