Compound Line-Spectrum of Hydrogen* 341 



to be very similar to that mentioned by Trowbridge and 

 Richards (Phil. Mag. [5] xliii. p. 137); the continuous 

 discharge from their high-tension accumulator gave a whitish 

 glow in the capillary which gave the second spectrum : — 

 "A large capacity is needed to change this spectrum into the 



familiar 4-line spectrum The change is marked by a 



sharp alteration in the colour of the glow from white to dee]) 

 red." It seems possible, therefore, that the presence of 

 oxygen alters the electrical conditions, and that this alone 

 accounts for the sudden change. 



It is not easy to find from Cornu's paper exactly how pure 

 a spectrum he obtained ; however, he says: — " Dans ces tubes 

 ainsi purifies l'eclat des raies de l'hydrogene est vraiment 

 admirable." But in this connexion it should be noted that this 

 may have been due to the presence of traces of oxygen, since 

 Cornu washed out his tubes with ionized oxygen, and the 

 arrangement which he used makes it quite possible that the 

 hydrogen afterwards admitted might become contaminated 

 with traces of this gas ; at any rate precautions to guard 

 against this contamination are not described in his paper. 



Stas has noted, in one of the papers published since his 

 death, that extraordinary precautions have to be taken to 

 remove a trace of some impurity which is present in all 

 hydrogen prepared by the usual methods (see J. S. Stas, 

 (Euvres Completes, Bruxelles, 1894, iii. pp. 216, 225); and 

 the possibility of this unknown impurity having some influ- 

 ence upon the spectrum needs perhaps to be considered. 



I was sorry to be unable to continue the work upon the 

 influence of oxygen upon the hydrogen spectrum, as probably 

 some more conclusive result might have been arrived at. 



4. Spectrum of Hydrogen prepared by a different Method. 



On studying the work which has been done not only on 

 the spectrum, but also with regard to the other properties of 

 hydrogen, one cannot help being struck by the fact that very 

 few workers have attempted to prepare this gas except by 

 methods which are essentially the same, in nearly all cases 

 by the decomposition of water or of a solution of an acid in 

 water ; and, so far as I can find out, the gas prepared from 

 sources quite different has not been worked with. Various 

 methods suggested themselves by which at least small 

 quantities of hydrogen might be prepared, but the one I 

 adopted recommends itself more by its dissimilarity from that 

 usually employed than by its simplicity. I decided to pre- 

 pare hydrogen from pure ammonia gas, generated by heating 

 ammonium chloride purified by Stas' method with lime pre- 

 pared from marble. The ammonia thus formed remained in 



Phil Mag. S. 5. Vol. 46. No. 280. Sept. 1898. 2 B 



