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Prof. A. Smithells on tin 



(III.) The Cyanogen Flame Spectrum. 



Occurrence. — (i.) The flame of cyanogen in air or, generally, 

 in oxidizing gases. 



Reputed origin. — The spectrum includes the Swan spectrum. 

 This part is therefore attributed to the same origin as the Swan 

 spectrum. The rest of the spectrum iucludes two distinct kinds 

 of groups : (i.) Those at the least refrangible end which fade in 

 brightness towards the red. These are commonly attributed to 

 cyanogen itself, (ii.) Those at the most refrangible end which 

 fade towards the violet. These are now attributed generally to 

 cyanogen. (A view has been held that the Swan components 

 plus the two most refrangible groups represent the compelte 

 carbon spectrum.) 



(IV.) The Cyanogen Electric Spectrum. 



Occurrence. — (i.) The electric discharge in cyanogen. 



(ii.) The ordinary carbon arc in air. 

 Reputed origin. — As stated above, either (i.) the spectrum of 

 carbon plus that of cyanogen, or (ii.) carbon at high temperature. 

 Differs from foregoing by absence of least refrangible groups (i.). 



(V.) The Carbon Line Spectrum (Carbon spectrum of the 

 second order). 

 Occurrence. — The condensed spark-discharge in gaseous carbon 



compounds in general. 

 Reputed source : 

 (i.) Carbon in the elementary state. 



(ii.) Carbon in a simpler state of atomic aggregation than that 

 corresponding to the Swan spectrum. 



Two other spectra have in the past held ground for some time 

 as pertaining to carbon compounds. What is now generally, if 

 not universally, admitted to be the " compound " or second line 

 spectrum of hydrogen was attributed to acetylene. According to 

 Pliicker (Pogg. Ann. cv. p. 77, 1858) carbonic acid is characterized 

 by a red line when the discharge is first passed through it. Salet 

 (Spectroscopies p. 239) states that this line is one of the carbon 

 line spectrum (v. supra), and my own observations agree with 

 this. 



The present investigation had its origin in researches on 

 the chemistry of names, which I began to publish in 1892, 

 when I was led to consider the source of the spectrum of the 

 inner cone of the flame of a Bunsen burner. At the same 

 time Sir Gr. G. Stokes, in referring to my papers, threw out 

 a suggestion that the Swan spectrum might be due to carbon 

 monoxide. As this was the view to which I was myself in- 

 clined, I was encouraged to subject the matter to a thorough 

 investigation and to undertake a critical study of previous 

 researches. I have accordingly, at intervals during the past 

 eight years, continued the study and have accumulated 



