OBTAINING THE CONSTITUENTS OF WOOD. 527 



Cubic meters. Cubic feet. 



Birch .... 35 1,225 



Oak 34 1,190 



Beech . . . .33 1,155 



Spruce . . . .33 1,155 



Larch .... 32 1,120 



Wood therefore yields 2J times as much gas as does coal, 

 and the lighting power of wood-gas is to that of coal as 

 118: 100. 



Broillard states (Rev. des E. et F. 1900) that Biche, by 

 passing out the wood-gas through glowing charcoal, has 

 succeeded in obtaining from 350 to 400 cubic meters of gas 

 from 100 kilos of wood. Any wood, coppice-shoots, etc., will 

 do, and the apparatus is so simple that it can be set up in 

 any village or farm where there is plenty of refuse wood. 



Neutral (non-acid) tars are used for making dyes, for which 

 hitherto chiefly coal-tar lias been used. Acid tars (creosote 

 and carbolic acid) are powerful antiseptics. At ordinary 

 temperatures solid naphthaline is a constituent and is a 

 certain remedy against the clothes-moth, also paraffin, but 

 the latter is obtained usually from raw petroleum. 



Charcoal is a residual product from distillation in stoves 

 and retorts, but is the chief product in the woods from char- 

 coal-kilns and pits, whilst the gaseous and liquid products 

 are then either neglected or only of secondary importance. 

 In the following pages the process of charcoal-making will be 

 described shortly. 



SECTION II. CHARCOAL-KILNS.* 



A charcoal-kiln is a heap of firewood of a regular shape, 

 and with a covering as effective as possible for keeping the 

 fire inside the kiln and excluding atmospheric air. 



The shape is generally that of a paraboloid and only in 

 certain cases that of a horizontal prism. Wood may be piled 

 in kilns either vertically or horizontally, and as these methods 

 of piling the wood, as well as the external form of the kiln, 



* Th' best work on charcoal-kilns is -v. Berg's ' Anleitung zum verkohlen des 

 " Sided., 1880. 



