obtained from Hood and Pit- coal. 31 1 



self: or should its operation continue in temperatures when 

 we cease to perceive any material change, its progress Inost 

 probably would be so slow as to require ages before the 

 second portion of oxygen was set free. This last will be regu- 

 lated by the nature of the affinities betwixt carbon and oxy- 

 gen, and the progress of their action upon each other during 

 the exposure. 



If the affinity of de-oxidation is supposed once to be 

 established, and the carbonaceous matter to be approaching 

 to the state of diamond, by sacrificing part of itself in com- 

 bination with the oxygen, its tendency to do so will be di- 

 minishing; in the ratio of its continuance, unless some new 

 action, by increase of temperature, affinity or otherwise, be 

 excited. The ultimate period. of de-oxidation will therefore 

 most likely-be retarded by both a want of time and means. 

 The difficulty arising from the . former, and want of tem- 

 perature to extract or give both an additional affinity that 

 would clear the oxide of its second and third portions of 

 oxygen, are evidently so great as to leave little hope of form- 

 ing any thing in this way purer than a highly incombustible 

 coal. 



The combustion of wood or of pit-coal to form coke or 

 charcoal may be considered as a principal step towards de- 

 oxidation. In the natural state of wood and pit-coal, the 

 carbonaceous matter appears to be highly surcharged with 

 oxygen, which is in part carried off in burning. 



If the ignition has been performed in open fires exposed 

 to external air, a greater portion of the original oxygen will 

 remain fixed. On the contrary, when distillation is per- 

 formed so as to secure the product from the contact of at- 

 mospheric air, the portion of carbonaceous matter, which in 

 all cases is unavoidably lost, is here combined with the oxy- 

 gen of the oxide, which is left in a state of comparative 

 purity, in place of being carried off in simple combustion by 

 the external air. 



-Every oxide of carbon that has hitherto been examined 

 contains a portion of foreign matter in the state of earths or 

 salts, and it appears by experiment that even the diamond is 

 not entirely ii^ from such an alloy. 



U4 100 parts 



