By the combustion of ammonia in oxygen, water vapour lines are produced, and new bands and gronps 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 combustion 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 continuous spectra. This statement is incorrect, or at least inaccurate.^
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 fiir physikal. Chemie,’ vol. 18, p. 219, 1895.
f ‘ J. prak. Chemie ’ [2], vol. 52, pp. 145—160, 1895. J “ Flame Spectra at High Temperatures ” (‘ Phil. Traus.,’ A, vol. 185, pp. 161 —212, 1894). § “ Ueber Flammen und leuchtende G-ase” (£ Zeitschrift fur physikal. Chemie,’ vol. 19, p. 1, 1896).
