1895.] in the Flames of Hydrocarbon Gases. 455 



a detonator containing one-tenth of a gram of mercuric fulminate 

 suspended in it by two copper wires, which were connected by a thin 

 platinum wire in contact with the fulminate, and on firing the 

 detonator by the electric current the flash of the fulminate was 

 found to emit but a feeble light. 



The same charge was fixed in a similar tube filled with pure 

 acetylene collected over mercury, the result being a flash of intense 

 white light and the shattering of the tube, the pieces of which were 

 thickly coated with the carbon produced by the decomposition of the 

 acetylene. 



Moreover, the small piece of white tissue paper used to contain the 

 fulminate was only scorched at the points where the explosion of the 

 fulminate had burst through it, showing that in the instantaneous 

 decomposition which had taken place, the intense heat which had 

 been developed either was confined to the products of decomposition, 

 or else had not had time to scorch the paper. 



The experiment at first sight seemed conclusive evidence that it 

 was the endothermic nature of the acetylene which, during its decom- 

 position in the flame, endowed the particles of carbon with the 

 necessary incandescence, but the objection presented itself that, when 

 exploding mixtures of oxygen and hydrogen in the eudiometer, a 

 distinctly luminous flash is produced, and, although the light so 

 obtained is feeble as compared with the intensity of the white light 

 produced by the detonation of the acetylene, still further proof is 

 necessary before this action can be accepted as the prime factor in 

 producing luminosity. 



It is also manifest that it would not do to assume that the rapidity 

 of the decomposition of the acetylene in a flame was nearly so great 

 as when the undiluted gas was detonated, and the question arose as 

 to whether it would be possible to obtain evidence as to acetylene, 

 when exposed to heat alone, liberating carbon in a luminous con- 

 dition. 



Although the instantaneous liberation of heat on the decomposition 

 -of the gas by detonation appears to confine the temperature to tho 

 products of its decomposition, it was to be expected that, on being 

 decomposed by heat, and probably, therefore, at a slower rate, the 

 increase in temperature might be detected. 



To try this, pure acetylene was passed through a platinum tube 

 :2 mm. in diameter and 40 cm. long, in which the Le Chatelier 

 thermo-couple was arranged as follows : The two wires were twisted 

 together for a length of 3 mm., and the wires on either side of the 

 twist are then passed through thin glass tubes, which are fused on to 

 them; having been in this way coated with glass so that only the 

 twist is exposed, they are passed through the platinum tube, the 

 glass insulating the wire from the metal of the tube, and also keeping 



