284 M. Karstcn's Observations and 



and this perhaps solely on account of thck great density. Dia- 

 mond, which is the densest kind of charcoal known, only burns 

 at a very high temperature, and by means of pure oxygen. 

 Glance coal and graphite are incomparably more easy to be de- 

 stroyed ; and the charcoal which is obtained on distilling black 

 coal, brown coal, and unaltered vegetable fibres in the dry way, 

 burns the more readily the looser the state of aggregation it 

 assumes during the process of carbonization, or the less the 

 quantity of carbon the body contains which has been employed 

 for producing the charcoal. A coal that is carbonised in a 

 furnace, or still better in a close vessel, affords a charcoal much 

 more compact and more difficult to be burnt, than that which 

 comes from the same coal carbonised in the open air. 



Elevation of temperature causes a decomposition of the com- 

 bustible, and the formation of new combinations. This process 

 has received the name of carbonization, because in this opera- 

 tion the residuum consists of pure charcoal. If hydrogen, oxy- 

 gen and carbon, on being subjected to different degrees of tem- 

 peratvire, also obey different laws of combination, the quantity 

 of pure charcoal which remains after the carbonization, must 

 depend, not only upon the state of the. body which is to be car- 

 bonised, but also upon the different degrees of temperature 

 which have been employed during this operation. This is actually 

 what takes places. Several resins and fats, which contain much 

 more carbon than vegetable fibres, leave no trace of charcoal in 

 their spontaneous decomposition at a high temperature ; and in 

 the same vegetable fibre, the quantity of charcoal residuum de- 

 pends entirely upon the degree of heat employed during the car- 

 bonization. 



It is not the quantity of the carbonaceous residuum alone that 

 must vary according to the different degrees of the temperature 

 employed. The same cause must render more variable still the 

 quantity and condition of the other combinations which are 

 formed during distillation in the dry way, that is to say, during 

 carbonization. This is the case precisely, because the quantity 

 of the charcoal residuum is but a consequence oi* the nature and 

 condition of the gaseous combinations and fluids, or vapours, 

 which are formed during the operation. This difference in the 

 manner in which organic combinations are affected under the 



