438 Prof. Graham on the Composition of the 



The theoretical density of this gas, deduced from its com- 

 position, is 0*6308. 



The Hebburn gas was of specific gravity 0'6327. 



Seventy-nine measures of the Killingworth gas, mixed with 

 an equal volume of chlorine, left in the dark for eighteen 

 hours, and afterwards washed with alkali, were reduced to 

 75 measures ; from which the presence of 4 measures of de- 

 fiant gas might be inferred. But in a comparative experi- 

 ment made at the same time on 25*3 measures of pure gas of 

 the acetates, mixed with an equal volume of chlorine, a con- 

 traction occurred of 1*3 measure; that is, in exactly the same 

 proportion as with the fire-damp. 



It was observed that phosphorus remains strongly luminous 

 in these gases, mixed with a little air, while the addition to 

 them of one-four-hundredth part of defiant gas, or even a 

 smaller proportion of the volatile hydrocarbon vapours, de- 

 stroyed this property. Olefiant gas itself, and all the allied 

 hydrocarbons, were thus excluded. 



Another property of pure light carburetted hydrogen, ob- 

 served by myself, enabled me to exclude other combustible 

 gases, namely, that the former gas is capable of entirely re- 

 sisting the oxidating action of platinum black, and yet permits 

 other gases to be oxidated which are mixed with it even in 

 the smallest proportion, such as carbonic oxide and hydrogen, 

 the first slowly and the last very rapidly; air or oxygen gas 

 being, of course, also present in the mixture. Now platinum 

 black had not the smallest action on a mixture of the gas from 

 the mines with air. No moisture appeared or sensible con- 

 traction, and no trace of carbonic acid could be discovered 

 after a protracted contact of twenty-four hours; while, with 

 the addition of one per cent, of hydrogen, the first effects were 

 conspicuously evident in three minutes, and with the same 

 proportion of carbonic oxide, the gas became capable of affect- 

 ing lime-water in half an hour. These experiments were re- 

 peated upon each of the three, specimens of fire-damp. 



Potassium fused in the fire-damp did not become covered 

 with the green fusible compound of carbonic oxide, nor occa- 

 sion any contraction. Indeed, however carefully the heat was 

 applied to the potassium by means of an oil-bath, a slight 

 permanent expansion always ensued. The same thing oc- 

 curred in pure gas of the acetates. It appeared that potas- 

 sium could not be heated above 300° Fahr. in pure carbu- 

 retted hydrogen, without causing a decomposition and the evo- 

 lution of free hydrogen gas. 



The gas was also inodorous, and clearly contained no ap- 

 preciable quantity of any other combustible gas than light 



