Marcus Balls Table Charcoal. 



147 



Botanical Names of the foregoing kinds of Trees and Shrubs. 



589. Charcoal is a slow conductor of heat and a non-conductor 

 of electricity. When exposed to the most intense heat, without ac- 

 cess of air, it remains unchanged, but it burns freely without flame 

 or smoke in the open air, leaving as ashes a part of the mineral 

 constituents of the wood from which it was made. 



590. It absorbs and holds moisture with great readiness, and is 

 an active absorbent of gases. It will take up many times its bulk, 

 but this amount is much greater with some gases than others. 1 It is 

 for this reason a most valuable disinfectant, and a material for filters. 



591. The chief use, however, of charcoal is as a fuel in smelting 

 ores, and in forges, furnaces, and other metallurgical operations, 

 and for these uses immense quantities of wood are annually re- 

 quired. 



592. The wood for charcoal should be cut only in winter, and it 

 is generally piled for partial seasoning till the next autumn. It is 

 found, as is shown elsewhere under the head of " seasoning," that 

 wood acquires its greatest dryness in about eighteen months, but 

 practically a single summer's drying is found sufficient. 



593. There are several modes of charring wood in use, but by 

 far the most common one is that in " metiers" or " coal-pits." For 



1 De Saussure found that boxwood charcoal would absorb 90 times its 

 bulk of ammonia, 55 times of sulphuretted hydrogen, 35 times of carbonic 

 acid gas, 9} times of oxygen, 1\ times of nitrogen, and If times of hydro- 

 gen. The absorbing power is greatest when the wood has been charred at a 

 low temperature in a damp atmosphere, and with a high barometric pressure 

 of the air. The absorption of gases is attended with an increase of tem- 

 perature. 



