MR, H. BRERETON BAKER ON COMBUSTION IN DRIED OXYGEN. 575 



Tlie Products of Combustion of Charcoal ,,. 



In the course of the experiments on the combustion of carbon in dried oxygen, :i 

 gas-bolder was constructed to contain oxygen dried by phosphorus pentoxide. The 

 only liquid which could be used for driving out the gas was mercury, and, as the amount 

 of gas required was about eight litres, its use would have been inconvenient. The 

 following apparatus was fitted up. 



Fig. 2. 



A large bottle was graduated and fitted with an india-rubber stopper, through 

 which a large tap-funnel was passed. Through another hole in the stopper a narrow 

 upright tube was fixed. This passed to the top of an inverted two-litre flask, also 

 provided with an india-rubber stopper. A bent tube also passing through this stopper 

 was connected with a second flask arranged in the same way as the first. A third 

 flask, similarly fitted, completed the gas-holder. It resembled three inverted wash- 

 bottles, with the exit tube of one connected with the pressure tube of the next. The 

 whole, including the large bottle, was heated for several hours by Bunsen burners 

 playing on the sides, while a current of air, dried by sulphuric acid, was drawn 

 through the apparatus. 



In order that no moisture should be given off from the india-rubber stoppers in the 

 three flasks, each was covered with a little mercury previously boiled. On the surface 

 of the mercury in each flask five or six plugs of phosphorus pentoxide were placed. 

 A current of oxygen was passed through six long, nearly horizontal, tubes filled with 

 concentrated sulphuric acid, and then through the apparatus described above. After 

 passing for an hour a sample of the gas was collected as it issued from the last flask. 

 It was found to be pure oxygen. A hard glass tube containing dried charcoal was 

 drawn out at both ends. One end, bent upwards, was passed through the opening in 



