316 J. Trowbridge — Spectra of Hydrogen 



with continuous currents, which will be described later. In 

 general, with condenser discharges, all these spectra are the 

 same; the differences which occasionally appear may be due to 

 changes in pressure, time of exposure, etc. 



The line 4268 in all these cases is by far the most prominent 

 line present in the region studied, and may be taken as charac- 

 teristic of hydrogen, oxygen, and nitrogen in tubes with car- 

 bon terminals, and of gaseous carbon compounds in tubes with 

 metallic terminals. This line does not usually appear in 

 hydrogen in tubes with metallic terminals ; occasionally it 

 appears very faintly. It appears, however, very strongly in a 

 tube provided with platinum terminals which is filled with 

 hydrogen and heated for two hours during exhaustion to a 

 temperature of 350° C. The spectrum, in this case, appears to 

 be identical with the spectrum of hydrogen in a tube provided 

 with carbon terminals. Were it not for this fact, it would 

 seem as if this line were due to carbon in some form ; but even 

 with this fact, it is possible that there was enough foreign car- 

 bonaceous matter present in the platinum tube to produce the 

 result noted. 



Eder and Yalenta* find, among others, the following lines in 

 the spectrum of an induction coil between carbon terminals: 



4268 

 3921 



Apparently these are the same lines found in the tubes pro- 

 vided with carbon electrodes; and also in tubes with metallic 

 electrodes which are filled with carbon compounds. Observed 

 visually, with a straight-vision spectroscope, all the above cases 

 appear identical. When, for instance, hydrogen was put into 

 the tube with carbon terminals and submitted to discharges 

 from an induction coil, at first the line spectrum of hydrogen 

 appeared. Alter the discharge had passed for some time, this 

 gradually changed into the characteristic band spectrum of car- 

 bon. To the eye alone the change was equally noticeable; the 

 light being, at first, reddish, and then changing to a white. 

 Similar changes were noticed when nitrogen and oxygen were 

 used in the carbon tube. 



It seems to me that the following conclusions can be drawn 

 provisionally from the above: When various elementary gases 

 are introduced into wide tubes with carbon electrodes and 

 exhausted to a pressure of l-2 mm , and submitted to condenser 

 discharges, compounds of carbon with the various gases are 

 formed. With nitrogen this compound is probably cyanogen; 

 with hydrogen acetylene; but when a photograph of the spec- 

 trum in each case is taken, we get, not the spectrum of the 



* Beiblatter, xviii, 1894, p. 753. 



