nitrogen, elementary carbon does not yield the same spectrum, no matter what the temperature may be; and lastly, that cyanogen gas burns with a flame of which the banded spectru.m is known as that of cyanogen by reason of the foregoing facts. Furthermore, I have found by recent experiments that when a condensed spark is passed between electrodes of gold in an atmosphere of cyanogen, the same spectrum is photographed.
If we admit that under conditions favourable to synthesis from its elements, cyanogen is capable of emitting a spectrum of its own, this emission should occur only at the moment of its formation, but while giving consideration to this view we are met by the difficulty that the flame of cyanogen burning in oxygen would less probably emit a spectrum of the compound substance itself, which is being burnt, than a spectrum of the products of its combustion, or of the separated elements of which it is composed, which are nitrogen and carbon; and for this reason, that the process it is passing through is not a synthetical but an analytical one. Indeed it has been shown by Liveing and Dewar* that when cyanogen is exploded with oxygen it gives a bright continuous spectrum, but no cyanogen spectrum, or carbon bands, or carbon lines.
I shall have to refer to these facts and adduce later evidence of the existence of the cyanogen spectrum in the latter part of this paper. Evidence derived from their Spectra, of the progress of Chemical Changes in Flames.—In support of the view that the flame of burning cyanogen ought to exhibit the spectrum of carbon, I may mention the following facts which have been recorded during a very careful examination of a number of photographs of the spectra of flames which were obtained by burning gases under normal atmospheric conditions.
The majority of these photographs were taken in 1882. The Combustion of Compound Substances. Hydrocarbons in oxygen. Sulphuretted hydrogen in air and in oxygen. Ammonia in air. Carbon disulphide in air. Carbon disulphide and nitric oxide. Carbon monoxide and oxygen. Components of the Spectra photographed. Carbon bands, cyanogen bands, watervapour lines.f Sulphur bands and water-vapour lines. Water-vapour lines. Sulphur bands only. Sulphur bands only.
Continuous spectrum of carbon monoxide. Faint lines due to carbon, very few in number.
- * Roy. Soc. Proc.,* vol. 49, p. 222. u On the Influence of Pressure on Flames.**
t When nitrogen is present, Liveing and Dewar have observed the formation of NO* Qoc. tit.),
