310 J. Trowbridge — Spectra of Hydrogen 



Art. XXXIV. — The Spectra of Hydrogen and some of its 

 Compounds; by John Trowbridge. (With Plate VI.) 



In a late paper I expressed the conviction that the so-called 

 line spectrum of hydrogen cannot be considered apart from 

 the spectrum of water vapor ; and that one can never be sure 

 that one is observing with a condenser discharge a pure spectrum 

 of hydrogen. I am convinced from further experimentation 

 that this conclusion is correct ; and I am also led to the con- 

 clusion that a certain amount of water vapor is essential in all 

 electrical discharges through gases. Just as aqueous vapor 

 seems to play an important role in most chemical reactions, so, 

 it seems to me, its presence in raritied gases contained in ordi- 

 nary glass tubes, enables a dissociation to take place which 

 determines the strength and character of the electrical dis- 

 charges. 



I am led, moreover, to the conclusion that pure hydrogen is 

 a perfect insulator, and that the passage of electricity through 

 a gas depends upon the dissociation of the hydrogen and 

 oxygen, by means of which change in the distribution of 

 energy the gases are made luminous. Before proceeding to an 

 account of my experiments, I will state some of the grounds 

 upon which I base my belief that pure hydrogen is an insula- 

 tor of electricity. 



V. Schumann, in an important paper, has shown that a 

 column of pure hydrogen at atmospheric pressure transmits 

 the ultra-violet rays as well as the most perfect vacuum he has 

 been able to obtain. Now Maxwell's electromagnetic theory 

 of light demands that the space between us and the sun, or in 

 other words the vacuum of space, should be a perfect insulator, 

 otherwise the electromagnetic waves would be completely 

 absorbed and the earth would remain in darkness. This 

 observation of Schumann seems to me one of the most impor- 

 tant in physical science, for it proves, I believe incontestably, 

 that hydrogen cannot be a conductor. 



Professor Dewar has also shown that liquid hydrogen is an 

 insulator. The experiment sometimes shown, in which a wire, 

 rendered incandescent by a current of electricity and sur- 

 rounded by an atmosphere of carbonic dioxide, is suddenly di- 

 minished in brilliancy by supplanting this atmosphere by one of 

 hydrogen, can be explained, in my opinion, not by the better con- 

 ductibility of hydrogen for heat, but by the increased resistance 

 of platinum due to the occlusion of this gas by platinum. A 



*Ann. d. Physik, No. 3, 1901, p. 642; this Journal, May, 1901, p. 394. 



