218 Prof. W. N. Hartley. On the Spectrum of Cyanogen 



By the combustion of ammonia in oxygen, water vapour lines are 

 produced, and new bands and groups of lines attributed by Eder and 

 Valenta to ammonia. Some of these are, however, due to a compound 

 other than ammonia. 



It will be observed that compounds during combustion as a rule 

 show the spectra of one or other of their constituents, or of both. In 

 the case of hydrogen compounds they show the product of the com- 

 bustion of hydrogen, which is a substance of great stability, and can 

 therefore exist at a high temperature. 



In the nitric oxide and carbon disulphide spectrum, the sulphur 

 bands, which are very strong, probably obscure those of carbon. 

 There is a strong continuous band of rays which would likewise serve 

 to obscure them. 



C. Bohn* has examined the spectra seen in a Bunsen burner of the 

 form devised by Tecluf (which is simply a modification of that 

 described by Smithells), and compared the spectra with that obtained 

 by Swan, and with the discharge in Geissler tubes containing various 

 hydrocarbon gases. He concludes that it is impossible to define a carbon 

 band spectrum, as the differences observed were greater than could 

 be accounted for by alterations in temperature and pressure. He 

 also states that sulphur, hydrogen, and carbon disulphide, also 

 carbon monoxide, were burnt, but that all these flames yielded con- 

 tinuous spectra. This statement is incorrect, or at least inaccurate. J 

 Bohn's observations were evidently made on too limited a region of 

 the spectrum, and without the aid of photography. On Bohn's paper 

 Eder has made some observations, quoting both his measurements 

 in the visible and ultra-violet spectrum, which he observes must have 

 been unknown to Bohn. 



He describes in what manner and by what causes the edges of the 

 carbon bands are altered in position or in character. 



The observations of Eder on the spectra of hydrocarbon flames are 

 quite in agreement with those previously communicated by me to the 

 Royal Society on the oxyhydrogen flame spectrum and the oxy-coal 

 gas spectrum. 



On certain Chemical Changes occurring in the Spark and in Flames. 



Though it is now accepted as a fact that the arc in air yields the 

 spectrum of cyanogen, and that the evidence of this is, first, the 

 identity of certain bands observed in the flame of burning cyanogen 



* ' Zeitschrift fur physikal. Chemie,' vol. 18, p. 219, 1895. 



f ' J. prak. Chemie ' [2], vol. 52, pp. 145160, 1895. 



J " .Flame Spectra at High Temperatures " (' Phil. Trans.,' A, vol. 185, pp. 161 

 212, 1894). 



" Ueber Flammen und leuchtende Q-ase " (' Zeitschrift fur physikal. Chemie, 

 vol. 19, p. 1, 1896). 



