CHARCOAL. 



'['In- value i>r charred wood-fibre, deprived of its liquid and volatile portion 

 l, v destm distillation, for smelting and heating purposes, has long been 



,,".,.,, Tihui^li now in England, Belgium and other coal producing countries, 



cheapness of |>i->duci.i<m outweighs considerations of quality, the value of Swedish 

 iron is, |>rol.;iMv with justice, attributed to its being smelted with charcoal; and 

 nianv of (he furnaces of the United States are as dependent upon the wood 

 sui'i'lv. as were those of Sussex in the sixteenth and seventeenth centuries. For 

 charcoal making, tin- hard woods are mainly used; beech charcoal being preferred 

 in the miiKTa logical laboratory. 



In (livat llritain the chief use of charcoal is in the manufacture of gun- 

 |io\viler, for which purpose a highly inflammable quality, which is obtained from 

 light spongy woods of various broad-leaved species is generally required: it 

 requires to be as free from earthy or mineral matter as possible, though no char- 

 i is absolutely pure carbon, generally retaining as it does, some hydrogen and 

 oxvgen, as well as mineral ash. For this reason, though still largely pre- 

 pare. 1 by the primitive method of pits or heaps covered with turf, charcoal 

 i> preferably manufactured in iron cylinders or retorts a method which is- 

 far more economical and yields a more uniform result. The inflammable gases 

 distilled from the wood are conveyed by pipes into the furnaces below the 

 retorK so that an immense saving in fuel is effected, while the tar, pyro- 

 1 igneous acid, etc., are condensed and collected. The temperature at which 

 the wood is charred exercises a great effect upon the properties of the charcoal. 

 The higher the temperature the more completely are the hydrogen and oxygen 

 of the wood driven off, and the denser and blacker is the resulting charcoal, 

 while its temperature of ignition is also higher in proportion. Slack-burnt 

 charcoal retains more volatile matter, is softer, reddish, more readily inflamm- 

 able and more hygroscopic. 



It has been found by experiment that, with sixty grains of saltpetre, 

 twelve grains of each of the following kinds of charcoal give the number of 

 cubic inches of gas (CO 2 ) in the table : 



Dogwood (Rkamnus frangula') 82 cubic inches. 



Willow (Salix alba) '. 77 



Alder 74 " 



Filbert 72 



Fir, chestnut, hazel 66 " 



The three first named species are accordingly preferred for the purpose, 

 though Gornus sanguinea, Euonymus europceus, Rhamnus catharticus, and 

 perhaps other species are not uncommonly substituted for the alder-buckhorn, 

 berry-bearing alder, or true " dogwood " of gunpowder manufacturers. Rkamnus 

 frangula ; this is a slow-growing shrub, being cut, when about an inch 

 in diameter and under ten years of age, in lengths of not more than six 

 i grown in Prussia, Belgium, and Sussex. It forms a very explosive 

 powder, used for military small arms, and for sporting purposes. Willow and 

 alder are of quicker growth, especially, the former, and are cut when about four 



\Vith reference to the use of the two last named species an 

 that they can be cut in the spring, when their bark is in the 

 t condition for tanning purposes. Charcoal is also of great value as a filtering 

 and deodorising agent. 



