464 Prof. V. B. Lewes. The Cause of Luminosity [Mar. 21, 



would probably have a diluting and cooling action, the cyanogen 

 would burn directly without liberating any carbon which could emit 

 light. 



In order to see if the temperature of the cyanogen flame when 

 burnt from an ordinary flat flame burner differed much from that 

 of hydrocarbons when consumed in a flame of the same size and 

 kind, the temperatures were experimentally determined by the same 

 method employed, and in the same parts of the flame as had before 

 been done with acetylene, ethylene, and coal gas. 



Portion of the flame. Temperature. 



Centre of inner zone 1377 C. 



Top of inner zone 2085 



Near top of outer zone 1645 



Showing that the cyanogen flame was actually hotter than the 

 acetylene and ethylene flames, and about the same as the coal gas 

 flame, but that the heat was differently distributed, the inner zone 

 being far hotter than in the other gases, whilst the maximum 

 temperature of the flame was at the apex of the inner zone, instead 

 of being nearer the top of the flame. 



An experiment was now made to ascertain if it were possible to 

 decompose cyanogen with luminous deposition of carbon, by passing 

 it through a hard glass tube heated by means of the blowpipe ; but at 

 the highest temperature attainable no trace of any deposition of carbon 

 took place, showing how far more stable cyanogen is under the influence 

 of high temperatures than acetylene. 



The structure and characteristic appearance of the cyanogen flame 

 have been explained by Smithells* and Dent, who conclude that the 

 inner zone of peach blossom tint is caused by the combustion of 

 the cyanogen to carbon monoxide and nitrogen, whilst the outer blue 

 cone is formed by the oxidation of the monoxide to dioxide, the green 

 fringe to the outer cone being attributed to the presence of small 

 quantities of oxides of nitrogen ; and if this explanation be accepted, 

 it is clear that we could not obtain luminosity in the portion of the 

 flame immediately above the inner zone, as all cynogen has been 

 destroyed without decomposition before that point is reached. It is 

 conceivable, however, that although no luminosity can be detected 

 in a cyanogen flame, and although the temperature which can be 

 obtained in a glass tube is insufficient to break up the compound with 

 luminous separation of carbon, yet if cyanogen could be heated to a 

 considerably higher temperature, it might be possible to decompose 

 it in such a way as to develop luminosity. 



In order to try this point, a hydrogen flame was burnt from the 

 end of an open platinum tube 9 mm. in diameter, and a thin platinum 



* ' Chem. Soc. Jour.,' 1894, p. 603. 



