1880.] Compounds of Carbon with Hydrogen and Nitrogen. 159 



Dibbits, and three given by PKicker and Hittorf. These ultra- violet 

 bands are well developed in the flame of cyanogen . burning in air and 

 are readily photographed, and easily seen when quartz lenses and 

 calcite prisms are employed. 



The flame of hydrocyanic acid burning in air showed very much the 

 same as that of cyanogen. 



In the flame of a mixture of hydrogen and carbon disulphide, 

 made by passing purified hydrogen through a tube containing carbon 

 disulphide so as to be nearly or quite saturated with the vapour, and 

 burning it in air, no hydrocarbon bands at all could be detected. 



Nor could any hydrocarbon bands be detected in the flame of a 

 mixture of carbonic oxide and hydrogen burnt in air. 



When a mixture of hydrogen with carbon tetrachloride vapour was 

 burnt, hydrocarbon bands made their appearance, but were rather 

 weak. 



The flame of carbonic oxide mixed with vapour of carbon tetra- 

 chloride showed faint traces of hydrocarbon bands occasionally, but 

 not continuously. 



On the other hand, chloroform, carefully prepared from chloral and 

 fractionated, when mixed with hydrogen, gave, when burnt in air, the 

 hydrocarbon bands very strongly. When it was mixed with carbonic 

 oxide instead of hydrogen it still gave the hydrocarbon bands, but 

 not nearly so strongly as with hydrogen. 



On a review of the whole series of observations, certain points stand 

 out plainly. In the first place, the seven blue, the violet, and ultra-violet 

 bands, characteristic of the flame of cyanogen, are conspicuous in the 

 arc taken in an atmosphere of nitrogen, air, nitric oxide, or ammonia, 

 and they disappear, almost, if not quite, when the arc is taken in 

 a non-nitrogenous atmosphere of hydrogen, carbonic oxide, carbonic 

 acid, or chlorine. These same bands are seen brightly in the flames of 

 cyanogen and hydrocyanic acid, but are not seen in those of hydro- 

 carbons, carbonic oxide, or carbon disulphide. The conclusion seems 

 irresistible that they belong to cyanogen ; and this conclusion does not 

 seem to us at all invalidated by the fact that they are seen weakly, or 

 by flashes, in the arc or spark taken in gases supposed free from 

 nitrogen, by reason of the extreme difficulty of removing the last traces 

 of air. They are never, in such a case, the principal or prominent part 

 of the spectrum, and in a continuous experiment they are seen to fade 

 out in proportion as the nitrogen is removed. This conclusion is 

 strengthened by the observations of one of us, that cyanogen (or 

 hydrocyanic acid) is generated in the arc in atmospheric air in large 

 quantity. Also in the experiment above described with the arc in 

 nitrogen, we have found that when the current of nitrogen issuing 

 from the globe is passed through a solution of potash the solution soon 

 gives the reactions of a cyanide. 



