136 Royal Irish Academy. 



sition that the potassium and the iron had conjointly decomposed the 

 nitrogen ? The latest experiments which bear upon this subject, and 

 from which I received the idea which led me to this investigation, 

 are those of Dr. Brown* " upon the conversion of carbon into silicon," 

 an explanation of phenomena which appears to me most unreason- 

 able, and contrary to all chemical analogy ; whilst the supposition of 

 the carbon having reduced the nitrogen is not only a simple but an 

 unavoidable conclusion to arrive at, if nitrogen be a compound sub- 

 stance. To determine, by experiment, the correctness or incorrect- 

 ness of this idea, it were only necessary to reduce nitrogen by some 

 other substance than charcoal ; and should silica result from its de- 

 composition, the problem might be considered to be solved. 



Exp. I. — A considerable quantity of ammonia-nitruret of potas- 

 sium was formed, by passing ammonia over potassium heated in an 

 iron tube ; the part which had not been in contact with the tube, 

 having been examined for silica, contained none. 



Exp. II. — Ammonia was passed for several hours over pure iron, 

 heated to a dull red heat ; examined for silica, it contained none. 



Exp. III. — Ammonia-nitruret of potassium was heated with pure 

 iron in an iron crucible, for one half hour, over a large Rose's lamp ; 

 the contents of the crucible, on examination, gave silicon and silica, 

 the weight of which was not registered, as it might have been said 

 to have derived a portion of silica from the inner surface of the 

 crucible. 



Exp. IV. — Twenty grains of ammonia-nitruret of potassium were 

 heated with twenty grains of pure iron in the same iron vessel for 

 one half hour ; when treated with nitric and muriatic acids there 

 remained insoluble a small quantity of a brownish colour, which, 

 when fused with carbonate of potash, gave of silica 0*10. The solu- 

 tion, supersaturated with potash, filtered, neutralized, evaporated to 

 dryness, gave of silica 1450 ; sum total of silica 1*550. 



From these experiments, together with those of Sir Humphry 

 Davy mentioned above, one might infer that nitrogen is either a 

 compound of silicon and hydrogen, or of silicon, hydrogen, and oxy- 

 gen ; to determine which, synthetically, a current of dry muriatic 

 acid gas was passed over siliciuret of potassium (formed by heating 

 silica with potassium), placed in a bent tube of Bohemian glass, the 

 extremity of which dipped into a cup of mercury, lying on the bottom 

 of a vessel filled with water. The atmospheric air had been pre- 

 viously expelled from the apparatus by a current of hydrogen. 



The gases insoluble in water having been collected, were found, 

 on examination, to be hydrogen and nitrogen, the relative propor- 

 tions of which varied in different experiments. 



In two experiments the proportions of hydrogen to nitrogen were 

 four of the former to one of the latter. 



In a third experiment, as six of hydrogen to one of nitrogen. 



In a fourth, as five of hydrogen to four of nitrogen. 



Observation. — White fumes appeared occasionally in the tube, 

 indicating the presence of muriate of ammonia. 



L* See Phil. Mag. S. 3. vol. xix. p. 295, 388 • vol. xx. p. 24.— Edit.] 



