132 MANUFACTURE OF CHAECOAL. 



is claimed, with great uuiformity of result. It consists of a floor com- 

 posed of 48 irou plates resting iu a frame-work of iron upon the ground, 

 properly prepared by packing solid clay, or by masonry, so as to afford a 

 level circular area with a groove around the edge for receiving the iron 

 plates of the side. A series of IG plates of iron is arranged in a circle, 

 and above these two other tiers still above, forming a dome-shaped kiln 

 or oven, held together by iron bands and bolts, with an iron chimney at 

 tbe top, and eight smaller chimneys around the sides, communicating 

 with openings iu the base. A large door is provided below, and a 

 smaller one above, for filling with wood and for withdrawing the char- 

 coal. By a ladder and platform the workmen can reach the chimney 

 at the top for regulating the draught. The whole, when in use, is luted 

 with clay so as to be air-tight, except as air is admitted at will. Below 

 the iron floor is a flue with a fire-place opening externally. It should 

 be made of hard-burned bricks, and the fire-place may be large for 

 burning brush and other waste wood. This serves for kindling the kiln 

 and for assisting the process. The wood is piled vertically excepting 

 toward the top. The usual charge is 50 stores (about 14 cords), but it 

 may be raised to 70 where the ground is dry. The heaviest piece does 

 not weigh over 50 kilograms (110 pounds), so that it may be carried to 

 any i^lace in the woods. The whole weight for a 50-stere kiln is 4,500 

 kilograms (9,920.7 pounds), and one for '/O steres, 1,800 kilograms (3,908 

 pounds). For the former the base is 5'".2 (19§ feet) across. The re- 

 moval and putting up depends, of course, upon local circumstances; the 

 ^ costs, at a minimum, 180 francs. It is commonly moved about twice a 

 ' year. 



The time required for burning varies from 48 to 56 hours. It is 

 claimed that the^apparatus will last ten years in common use, except 

 that the lower side plates and doors may need renewal.^ 



Eed charcoal — Torrefied wt)od. 



About 1836, a method was introduced in France for the semi-carboni- 

 zation of wood, by placing it in chambers built at the mouths of fur- 

 naces and exposed to a heat by which the water and acetic acid were 

 expelled but the combustible gases left, which would contribute to the 

 heating properties of the coal thus partly produced, and a considerable 

 saving of fuel gained. This product is known as " red charcoal," and for 

 certain metallurgical processes, such as melting cast iron, it is said 

 about thirty per cent, is saved iu the cost of fuel over the amount re- 

 quired with charcoal fully carbonized. 



Torrefied wood is wood that has been heated enough to drive off the 

 hygroscopic water, and just to a point where carbonization begins. 

 In beech, this product resembles the wood itself, except in color. It 

 may be split, cut, or sawed, but is not so strong as the original wood. 

 It ignites easily, does not impair by keeping, and burns with a copious 

 flame and with intense heat. It is understood that some of the charcoal 

 furnaces in the Lake Superior region use wood not fully charred with 

 good results, but we have no precise account of their methods.^ 



' Ann. dea Mines, s. 3, 1837, xi, p. 527, aud s. 3, 1838, xiii, 487, 595, contain articles by 

 Sauvage npou this method. See, also, au article on " The Economy effected by the Use 

 of Ked Charcoal," by Bernard Frenow, in the Engineering and Alining Journal, N. Y., 

 March 2, 1878. 



3R. Freseuius, in Erdmann's Jour, far PraJctisch Chemie, 1863, ciii, 88. In 1839,_Eche- 

 ment, a Belgian, made brown charcoal in piles. See Ann. des Mines, a. 3, xvl, 654, and 

 Fercy's.Mctallurgij (lS<p), P- 410, where a description of the process is given. 



