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XI. On the Spectrum of Carbon. By John Attfield, Esq., F.C.S., Director of the 
Laboratory of the Pharmaceutical Society; lately Demonstrator of Chemistry at 
St. Bartholomew's Hospital. Communicated by Dr. Feankland, F.B.S. 
Eeceived June 19, — Eead June 19, 1862. 
It is weU known that a mixture of coal-gas and air burns with a flame of slight lumino- 
sity. When such a flame is prismatically examined under favourable circumstances, as 
by the ordinary spectroscope, the light it emits is found to consist of four groups of rays 
of difierent refrangibility. These rays appear in the field of the instrument as faint 
yellow, light green, bright blue, and rich violet bands of light. 
In 1856 Swan* found that the spectrum thus obtained was common to all hydro- 
carbon fiames. He showed that they were best seen in an olefiant gas-flame fed with 
air by a blowpipe jet, measured and recorded their distances from each other, searched 
for, but did not find, corresponding dark bands in the solar spectrum, and gave no 
theory in explanation of their origin. 
On recently reading Swan’s paper by the light that Professors Bunsen and Kiechhofp 
have thrown on the subject, I came to the conclusion that these bands must be due to 
mcandescent carbon vapour ; that, if so, they must be absent from fiames in which carbon 
IS absent, and present in flames in which carbon is present ; that they must be observable 
equally in the flames of the oxide, sulphide, and nitride as in that of the hydride of carbon ; 
and, finally, that they must be present whether the incandescence be produced by the 
chemical force, as in burning jets of the gases in the open air, or by the electric force, as 
when hermetically sealed tubes of the gases are exposed to the discharge from a powerful 
induction coil. 
Experiment has fully confirmed the truth of this theory, and the following are the 
details of the investigation : — 
To obtain intimate acquaintance with the spectrum in question Swan’s experiments 
were repeated. On feeding the flames with undiluted oxygen, instead of with air, still 
brighter spectra than he describes were obtained. The heat thus produced, however, 
volatilized potassium, sodium, lead, &c. from glass jets, and zinc and copper from brass 
jets ; and this result ensued whether the oxygen was directed into the centre of, or made 
to surround the hydrocarbon flame. Finally, a mixture of olefiant gas and oxygen, or 
of coal-gas, saturated with benzole, and oxygen, was burned at an ordinary platinum 
oxyhydrogen safety-jet. In this way a cylindrical fiame, half an inch in length and one- 
MDCCCLXII. 
* Edinb. Phil. Trana., vol. xxi. p. 411. 
2 Q 
