Disappearance of Has in the Electric Discharge. 607 



without pumping out the residue of the previous charge, the 

 same limit was reached once more. 



The side tube A oil the lamp was now cooled in liquid air 

 in the expectation that C0 2 would have been formed and 

 that much of the gas would condense. But it was found 

 that there was no decrease of pressure due to the cooling, or 

 rather none that would not follow from the mere temperature 

 change of incondensible gas. Though the carbon monoxide 

 had disappeared under the discharge it had not now been 

 converted in any appreciable quantity into the dioxide. 

 With A still cooled, the discharge was started once more, 

 and now, as before, the pressure fell rapidly to 00008 mm., 

 when the glow ceased. If the liquid air was now removed 

 from A and the tube allowed to warm up, some of the gas 

 was restored and could be condensed again by cooling A once 

 more. But at the first trial the restored gas was found to 

 be markedly greater than half that which had been removed 

 in the presence of the cooled tube. The decrease in pressure 

 during the discharge was 0*007 mm., the increase on warming 

 the tube 0*006 mm. Further investigation showed that the 

 qtiantiry restored on warming A depended on the time that 

 the discharge was continued while A was cooled, and that in 

 suitable circumstances the gas restored might be as great as 

 half the total that had disappeared both with and without 

 the side tube cooled. That is to say, if we start with gas at 

 a pressure of jt^, and, by passing the discharge with A warm, 

 reduce this pressure to p 2 ; further, with A cooled, reduce 

 the pressure to j> B ; then the gas restored on warming A 

 again may be as great as -J (jt?i — ]h) an( ^ n °t merely J (p 2 — p») 

 as would be expected. The discharge can convert into 

 carbon dioxide, so long as the tube A is cooled, not only the 

 gas that disappeared while the tube was cool, but also the 

 gas that disappeared while it was warm, although the dis- 

 charge while A was warm did not at the time convert the 

 gas into dioxide. 



Explanation of the Observations. 



11. A very simple and, to our minds, plausible theory will 

 explain these facts. We have only to suppose that the 

 effect of the discharge is to cause several reversible chemical 

 actions to take place between the gas and the other materials 

 in the lamp. Of these actions, one consists of the abstraction 

 pf carbon from the monoxide, resulting in its transformation 

 into dioxide, together with its reverse, the combination of 

 the dioxide with carbon to form monoxide. Another of 



