MR. H. BRERETON BAKER ON COMBUSTION IN DRIED OXY< 



577 



monoxide, and that this, unless prevented by drynees, as in this case, or by some 

 other influence, then produces carbon dioxide. 



This conclusion is strengthened by the fact that when a piece of charcoal is heated 

 in a rapid stream of ordinary oxygen a long flame is seen to issue from the glowing 

 solid in the direction of the current of gas. This is probably the second stage in the 

 burning of the charcoal. 



It has been shown (C. J. BAKER, ' Chem. Soc. Journ.,' 1887) that a small quantity 

 of carbon monoxide is produced by the slow absorption of oxygen by charcoal. This 

 was given out by heating to 45 in vacuo. The amount was not more than 5 c.c., 

 given out by heating half a gram of charcoal for two hours. Though such a small 

 amount was not likely to vitiate an experiment made at more than atmospheric 

 pressure, and lasting not more than two minutes, it was thought advisable to use 

 precautions to obviate any possibility of error from this source. The following method 

 .was then tried. 



The oxygen was contained in a gas pipette with a stop-cock. Phosphorus pentoxide 

 was introduced, and the gas was left drying for a week. The aperture of the pipette 

 was connected by a piece of dried and paraffined india-rubber tubing with the tube 

 containing the carbon. In this india-rubber tube phosphorus pentoxide was placed. 

 The carbon had been heated to redness in vacuo to free it from any carbon monoxide 

 which might have been occluded. The tube containing it was drawn out in the 

 middle, and phosphorus pentoxide placed in the part remote from the pipette. To 

 prevent the formation of carbon monoxide in the charcoal while the oxygen was 

 drying, the tube was exhausted as completely as possible and the free end drawn out 

 to a point and sealed. 



Fig. 3. 



The oxygen was to be driven out by mercury which had been boiled and cooled in 

 an atmosphere dried by sulphuric acid. After a week's drying the gas was admitted 

 to the vacuous tube. The sealed tip was broken and connected with a set of GEISSLER'S 

 potash bulbs. These would absorb the carbon dioxide produced. Next in series was 

 another set of weighed potash bulbs which would indicate whether all the carbon 

 dioxide had been absorbed by the first set. Connected with these bulbs was a hard 

 glass tube containing copper, oxide heated to redness in a small gas furnace. In this 



MDCCCLXXXVI1I. A. 4 E 



