1882.] On the Origin of the Hydrocarbon Flame Spectrum. 427 



acid and ether bath. By this method of condensation any easily 

 liquefiable substances are isolated, and any permanently gaseous 

 substance escapes. The samples were sealed up in glass tubes into 

 which different reagents were inserted. After snch treatment the 

 cyanogen was nsed for the production of the flame in dry air or 

 oxygen. The liquid cyanogen was left in contact with phosphoric 

 anhydride, Nordhausen sulphuric acid, and ordinary sulphuric acid. 

 By means of a special arrangement of glass tubing surrounding the 

 flame dry oxygen conld be supplied, or oxygen made directly from 

 fused chlorate of potash could, by means of a separate nozzle, be 

 directed on to the flame, and thus perfectly dry and pure gases used for 

 combustion. Liquid cyanogen which had remained in presence of the 

 above reagents gave only the single green hydrocarbon line faintly in 

 dry air, all the cyanogen violet sets being strong. When oxygen 

 made directly from the chlorate of potash was directed on to the 

 flame, all the hydrocarbon flame sets appeared with marked brilliancy. 

 The set of lines which we have formerly referred to as the three lines 

 or set of three flutings of the cyanogen spectrum, show marked altera- 

 tion of brilliancy with variations in the oxygen supply. Thus liquid 

 cyanogen, purified by the action of the above reagents, does yield the 

 spectrum of hydrocarbons on combustion in pure oxygen. From 

 the great precautions we have taken we feel sure that the amonnt of 

 combined hydrogen in the form of water or other impurities in the 

 combining substances must have been exceedingly small, and that 

 the marked increase in the intensity of the flame spectrum when 

 oxygen replaces air is essentially connected with the higher tempera- 

 ture of the flame, and is not directly related to the amount of hydrogen 

 present. This being the case, it must be admitted that the hydrocarbon 

 flame spectrum requires a higher temperature for its production during 

 the combustion of cyanogen than that which is sufficient to cause a 

 powerful emission of the special spectrum of the molecules of cyanogen. 

 Now the two compounds of carbon which give the highest temperature 

 on combustion are cyanogen and acetylene. Both of these compounds 

 decompose with evolution of heat, in fact they are explosive compounds, 

 and the latent energy in the respective bodies is so great that if kinetic 

 in the separated constituents it would raise the temperature between 

 three and four thousand degrees. The flames of cyanogen and 

 acetylene are peculiar in respect that the temperature of individual 

 decomposing molecules is not dependent entirely on the temperature 

 generated by the combustion which is a function of the tension of 

 dissociation of the oxidised products, carbonic acid and water. We 

 have no means of defining with any accuracy the temperature which 

 the particles of such a flame may reach. We know, however, that the 

 mean temperature of the flames of carbonic oxide and hydrogen lies 

 between two and three thousand degrees, and if to this be added that 



