206 Effect of Hydrogen on the Lines of the Carbon Spectrum. 



Several other series of experiments with mixtures of car- 

 bonic oxide and hydrogen were made, and the results agreed 

 together, and with the corresponding results obtained with 

 mixtures of carbonic acid and hydrogen so far as could be 

 estimated by the conditions of the experiments. 



C. Spark in Coal-gas. 



The spark in coal-gas showed the red hydrogen line 

 strongly — the other hydrogen lines were not attended to — 

 the violet carbon line well, but the red carbon line was hardly 

 visible. Taken as a whole, the appearance of these three 

 lines was much the same as in a mixture of carbonic acid and 

 hydrogen containing 50 per cent, of hydrogen. 



The effect of mixing coal-gas with carbonic acid was then 

 tried with the following results : — 



(i.) 5 per cent, coal-gas in the mixture. [Carbon red line slightly the stronger.] 

 (ii.) 10 ,, ,, [Hydrogen line slightly the stronger.] 



(iii.) 33 „ ,, [Carbon red line faint, but quite distin- 



guishable.] 

 (iv.) 50 „ ,, [Carbon line very faint, but more readily 



seen than with 50 per cent, hydrogen.] 



It will be seen that the red line of carbon is more per- 

 sistent than in the case of corresponding mixtures of carbonic 

 acid and hydrogen ; this is only to be expected, as the coal- 

 gas brings carbon as well as hydrogen into the mixture. 



From these experiments the conclusion seems certain that 

 though the red carbon line may not be completely destroyed 

 by the presence of hydrogen — at any rate when the propor- 

 tion of hydrogen does not exceed 50 per cent. — yet it is 

 influenced in a way totally different from the other strong 

 line of carbon in the violet, whereby it suffers a very rapid 

 quenching, as the proportion of hydrogen is increased, to 

 which the violet line is not subject. 



It might, perhaps, be thought that the effects observed are 

 due to the faint carbon line being rendered invisible owing 

 to the strong glare of the hydrogen red line in its neigh- 

 bourhood. But this possible objection is, I think, completely 

 met by the consideration of the following facts. 



Firstly, the two lines were well separated by the instrument 

 used, and the screen fixed in the eyepiece enabled either one 

 of them to be covered up ; secondly, when a mixture con- 

 taining a mere trace of hydrogen was examined the very faint 

 persistent hydrogen line was seen without any difficulty 

 by the side of the very bright carbon line ; and, lastly, when, 

 with 50 per cent, hydrogen, the carbon red line appeared to flash 



