Disappearance of Gas in the Electric Discharge, 605 



at liquid-air temperature, Carbon dioxide was naturally 

 suspected. Accordingly the apparatus was rearranged so thai 

 the cooled tube in which the gas condensed could be sealed 

 off from the rest of the apparatus. Gas to the total pressure 

 of 1*02 mm. was then caused to disappear in the discharge, 

 representing a volume at N.T.P. of 1*34 o.c, The sealed-oflE 

 tube was opened under mercury and 0*74 c.c. of gas found 

 to be present in it. All but a few per cent, of this gas was 

 proved to be carbon dioxide by letting up a solution of 

 l>arimn hydroxide and showing by chemical tests that the 

 white precipitate formed when the gas was absorbed was 

 indeed barium carbonate. 



The result was surprising. If a tungsten filament is 

 heated in carbon dioxide, it is well-known that it absorbs 

 oxygen and reduces the gas to the monoxide ; it could hardly 

 have been expected that in the presence of so powerful a 

 reducing agent as incandescent tungsten this action would 

 be reversed. If oxygen had been present, the formation of 

 some dioxide by combustion of the monoxide might have 

 been anticipated : but there was no free oxygen present in 

 sufficient quantity, and the ratio of dioxide to monoxide 

 indicates that the change is effected, not by the addition of 

 oxygen, but by the abstraction of carbon : it appears to 

 occur according to the equation 2wCO = raC-f wC0 2 *. The 

 destination of the carbon abstracted has not been traced 

 completely. It is almost certainly not taken up by the 

 tungsten, for the filament showed none of the known charac- 

 teristics of a carbonized filament. It may be deposited on the 

 walls and give rise to some of the blackening, but it is 

 suspected that it passes to the nickel of the anode; for the 

 anode was found to be blackened and the surface layer 

 undoubtedly contained carbon, detected by burning it. 

 Unfortunately, however, it was found later that the metal 

 itself contained some carbon ; and the examination was not 

 sufficiently accurate to determine whether the carbon found 

 was in excess of that contained in the original metal. The 

 loss of weight of the filament during the disappearance of the 

 quantity of carbon monoxide mentioned was 0'45 mgm. ; it 

 is thought that this loss is merely due to the bombardment 

 of the filament by the positive ions, or, in other words, 

 merely represents cathodic spluttering ; as has been said, it 



* It is not easy to explain the occurrence of numbers greater than half 

 in the third column of Table I. ; those less than half may be due to gas 

 absorbed on the glass. But it is not yet certain that the deviations 

 from half are real. 



