

Dr. W. M. Watts on the Spectra of Carbon. 251 



pounds : — olefiant gas, cyanogen, carbonic oxide, naphthalin, car- 

 bonic disulphide, carbonic tetrachloride, amylic alcohol, and 

 marsh -gas. 



It may be obtained from olefiant gas either by burning the gas 

 with oxygen, as already described, or by taking the spark of an 

 induction-coil in the gas at the ordinary pressure. In the lat- 

 ter case, however, carbon is rapidly set free and the spectrum 

 becomes continuous. The electric discharge in olefiant gas under 

 diminished pressure gives a different spectrum, which will be 

 afterwards described. 



The spectrum obtained from cyanogen varies with the mode 

 of production. The flame of cyanogen in oxygen exhibits y, 8, 

 and e. The red group is replaced by a series of bands which 

 show an opposite character to the rest of the spectrum, inasmuch 

 as each band is brightest at the most refracted edge. If cyano- 

 gen be burnt in air instead of in oxygen these bands are more 

 numerous^ extending nearly to 8, and replacing y, which is 

 then not to be seen*. Instead of the group / we have two very 

 brilliant groups of lines — £ which includes seven lines (105-113), 

 and 6, which is composed of six lines (136-142) . Fig. 1 e is a 

 reduction of Dibbits's drawing of the spectrum of cyanogen burn- 

 ing in air (De Spectraal Analyse), and agrees well with my own 

 observations. 



If the cyanogen, instead of being burnt, be rendered incan- 

 descent by the discharge of an induction-coil in the gas at the 

 ordinary pressure, a spectrum is obtained which contains y, 8, e, 

 f, and 0, but which does not exhibit /. The red group a may 

 be obtained precisely the same as from the olefiant-gas flame ; 

 but when the intensity of the spark is increased a different aspect 

 comes out, which is represented in the Plate, fig. Id. 



Precisely the same spectrum is obtained from a Geissler's tube 

 enclosing cyanogen of a few millimetres pressure. The spectrum 

 consists of «, 7, 8, e, JJ and 6. 



When a Ley den jar is included in the circuit, the relative in- 

 tensity of the lines is altered, but the spectrum is essentially the 

 same, with the addition of the nitrogen-lines obtained from the 

 spark in air. 



The flame of carbonic oxide gives only a continuous spectrum ; 

 but if the induced spark be taken in the gas at the atmospheric 

 pressure, we obtain again the carbon-spectrum, comprising 

 sometimes y, 5, e, and/, and sometimes y, 8, e, f, and 6. The 

 red end is too faint to determine. The replacement of the 

 group /by f and 6 is very curious, but I have been unable to 



* These hands are thus obtained more completely developed at the lower 

 temperature of the flame in air, and are doubtless due to the compound 

 cyanogen itself. 



S 2 



