Mr. Davy on a new Gaseous Compound 0/ Carbon and Hydrogen. 87 



— Whereas, after about one-fourth of the preceding number of discharges, were 

 passed through an equal quantity of fticariwre^ of hydrogen ; the tube was quite 

 obscured by a blackish crust of carbon deposited on it, but there was only a very 

 slight contraction of the original volume of the gas. 



In another experiment, made in a tube, in which the wires were placed three 

 times farther from each other, than in the tube used in the preceding experiments ; 

 and a very large Leyden phial was employed; the first strong discharge through 

 the bicarburet of hydrogen, occasioned a considerable deposition of carbon, on the 

 platina wires and tubes; and a half dozen similar discharges, greatly increased 

 such deposition, but there was no change of volume in the gas. On similar dis- 

 charges being passed, separately, through olefiant and carburetted hydrogen 

 gases, no apparent effect, in either case, took place. 



I made some experiments, with a view to ascertain whether I could make the 

 bicarburet of hydrogen combine with an additional quantity of hydrogen. — 

 Thus, I mixed those two gases in nearly equal volumes over dry mercury, there 

 was no immediate effect, nor any change after they had been in contact about 

 fifteen minutes. On letting up a globule of the mixed gases into a small glass 

 of chlorine, a loud explosion took place, and carbon was deposited. Through a 

 part of the above mixture, I passed about a dozen discharges from a small Leyden 

 phial, but there was no apparent change ; on letting up a globule of chlorine, 

 inflammation instantly took place, and a second globule of chlorine produced a 

 similar effect, with deposition of carbon in both instances. The mixture of the 

 bicarburet of hydrogen and hydrogen, burned with a dense bright flame. 



The bicarburet of hydrogen, appears to offer an exception to the principle 

 established by the able researches of the late Dr. Henry, on the then known 

 aeriform compounds of charcoal and hydrogen ; namely, " that the fitness of 

 those gases for artificial illumination is greater, as they require for combustion 

 a greater proportional volume of oxygen ;"* for that gas, requires less oxygen 

 for its combustion than olefiant gas, yet it illuminates much more powerfully 

 than this gas. The superior illuminating power of the bicarburet of hydrogen 

 is in strict conformity with the principle, that the degree of light emitted by the 

 carburets of hydrogen, is dependent on the quantity of carbon they contain; the 



* Phil. Trans. Royal Society, 1808 and 182], 



