192 APPENDIX. [No. X. 



20. A solution of nitrate of silver yields slowly small crystals 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 determine that 

 the metal was reduced. 



25. I next subjected to experiment the extraordinary compounds of 

 cyanogen forming the metallo-cyanides. From the aurocyanide of potas- 

 sium I obtained metallic gold. 



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

 silver, the hydrogen becoming at the same time lessened. 



27. These last two results are interesting to the chemist, for it appears 

 to open a path for investigation on the nature of these very curious and 

 now highly important combinations. 



28. Such were my results with platinized platinum and hydrogen ; the 

 hydrogen becoming absorbed and the metals being reduced. It was found 

 that chloride of platinum, chloride of palladium, persalts of iron, chloride 

 of gold, and nitric acid yielded the oxygen most rapidly. It next became 

 my endeavour to ascertain how far other metals, or different conditions 

 of the same metal, might be used ; and smooth platinum was next the 

 subject of experiment. With sulphate of copper or persalts of iron no 

 absorption, however, took place. , 



29. Palladinized platinum was made the subject of experiment ; and 

 when employed with hydrogen in a manner similar to platinized platinum 

 in sulphate of copper, it caused that metal to be reduced. 



30. The effects of silver were then examined, and for that purpose a 

 piece, carefully cleaned by nitric acid, was immersed in a solution of copper 

 in contact with the hydrogen, but no change occurred even after many days. 



31. No better result attended the employment of silver sponge used 

 for the same purpose. 



32. Nor did the black deposit of silver answer better to effect the 

 absorption of the hydrogen, and the reduction of the metal from a solution 

 of sulphate of copper did not occur. 



33. Copper, both in its bright and spongy states, was next examined ; 

 in its blight state, cleansed by nitric acid, no change occurred. 



34. In the spongy state it appeared to be of no greater efficacy to 

 cause the reduction of the metal. 



35. Considering the interest attached to carbon in the cinder experi- 

 ment, detailed in a former part of this paper, a piece of carbon was exposed 

 to the action of hydrogen and a solution of copper, but, singular to state, 

 no deposit of copper took place, nor was any hydrogen absorbed. In fact 

 I have no mechanical method of charging coke with hydrogen, by which 

 it can be made to cause the reduction of the metals. 



36. The last set of experiments which I instituted upon the reduction 

 of the metals by hydrogen was the value of bibulous paper to effect that 

 object. In dilute chloride of gold apparently no action after two or three 

 days took place. 



