378 W. G. Mixter — Deportment of Charcoal ivith 



formed, although the oxygen largely exceeded the amount 

 required for the complete oxidation of the carbon. To prove 

 that the increase was not due to heating the wires passing the 

 stopper, the wires were repeatedly heated by an electric current 

 and the gas in all cases returned on cooling to its original vol- 

 ume. Nor could any air have passed in by the stopper for the 

 pressure in the apparatus was greater during the combustions 

 than that of the atmosphere. 



The above results throw no light on the question of the 

 burning amorphous carbon in dry oxygen, as charcoal contain- 

 ing O07 per cent of hydrogen and upwards was used, which 

 would yield water. It is evident, however, that dense charcoal 

 must be intensely heated before it will burn in dry oxygen. 

 When such charcoal ceases to burn after. having been ignited 

 at one point it may be that the temperature of the part burn- 

 ing falls below the point of ignition owing to the dense coal 

 conducting heat from it. Charcoal even of the densest variety 

 when burning rapidly in oxygen is surrounded by a small flame 

 which may be due in part to the incandescence of carbon di- 

 oxide and oxygen about the piece, but the flame is chiefly that 

 of burning carbonic oxide, which formed in the reaction 

 between the oxygen and glowing carbon, as the latter is in ex- 

 cess in the limited space where the reaction occurs. Carbonic 

 oxide is formed either by the direct union of oxygen with car- 

 bon or by the reduction of carbon dioxide. Carbonic oxide, 

 as Meyer* has shown, burns when mixed with dry oxygen 

 only when intensely heated by a powerful electric discharge, 

 and carbonic oxide mixed with air or with an excess of oxygen 

 not dried burns with difficulty and ignites only at a high tem- 

 perature. In order then that charcoal may continue to burn 

 in oxygen the temperature must be maintained sufficiently 

 high to ignite the carbonic oxide. Rapid combustion will do 

 this while slow combustion will not, as the following results 

 show : 



Experiment 12. — A piece a centimeter thick of dense char- 

 coal having 0*126 per cent of hydrogen was placed in a glass 

 tube and a rapid current of oxygen was passed in, the gas 

 being dried as for organic analysis. The charcoal was heated 

 by one burner until it began to glow. It then rapidly became 

 hotter and in a few seconds there was a slight puff, flame pass- 

 ing 20 or 30 centimeters through the tube, after which the 

 charcoal burned brilliautly with a slight flame surrounding it. 

 This result has been attained many times, not, however, with- 

 out failures. 



Experiment 13. — A piece of dense wood charcoal a centi- 

 meter thick and three centimeters long when heated in a rapid 



*Berichte der deutsch. chem. Gesellsch., xix, 1099. 



