1895.] in the Flames of Hydrocarbon Gases. 463 



this having been so arranged that the holes were buried in the flame 

 just at the top of the inner zone, acetylene was then gently allowed 

 to flow through them into the flame. 



At the points where the acetylene issued into the flame, small areas 

 of intense luminosity were produced, whilst the liberated carbon 

 streaming up between the flame walls of the upper zone produced 

 dull red bands of very low luminosity. It may be suggested that 

 the carbon particles supplied in this way to the flame may have 

 agglomerated and formed masses larger than those produced in the 

 ordinary way, but I do not think this, as they were completely 

 consumed, and no smoke escaped from the crown of the flame, 

 whereas if a flat flame is interfered with in such a way as to cause 

 the carbon particles to roll themselves together, smoking of the flame 

 is produced. 



I think the inference to be drawn from this experiment undoubtedly 

 is that it is the heat of decomposition which gives the high incan- 

 descence and light emitting value to the carbon particles, and that 

 the temperature of the combustion of the other flame gases and finally 

 of the carbon itself plays but a secondary part. 



In considering these results, it seems remarkable that if acetylene 

 owes its power of rendering hydrocarbon flames luminous to its 

 high endothermic properties, that cyanogen, which is still more 

 endotbermic, should burn under all conditions that have at present 

 been tried with a non-luminous flame. 



Heat of formation. 



Acetylene C 2 H 2 -47,770 



Cyanogen C 2 N" 2 -65,700 



It is clear that if the rapidity of decomposition localises the heat 

 evolved to the products of decomposition, and that this renders the 

 liberated carbon particles incandescent, whilst the hydrogen plays at 

 best a very subsidiary part, it ought not to matter whether it be 

 hydrogen or nitrogen which is combined with the carbon. 



Berthelot showed that cyanogen like acetylene could be detonated 

 by a small charge of mercuric fulminate, but he notes that the test is 

 not always successful, which points to the decomposition of this 

 body requiring a greater expenditure of energy to break up the 

 molecule than is the case with acetylene, and known facts would 

 lead us to expect that this would be the case, as although exothermic 

 compounds become less and less stable with rise of temperature, 

 endothermic bodies on the other hand become more stable, 

 and the eiidothermicity of cyanogen being greater than that of 

 acetylene, would lead one to expect that temperatures which would 

 decompose acetylene would have no effect on cyanogen, and that, 

 as during the combustion of cyanogen, the liberation of nitrogen 



