132 Dr. Ure on Gunpowders 



three-quarters of an inch in thickness, and the larger ones 

 should be divided lengthwise into four, so that the pith may be 

 readily burned away. 



Wood is commonly carbonized in this country into gunpowder- 

 charcoal in cast-iron cylinders, with their axes laid horizontally, 

 and built in brick- work, so that the flame of a furnace may cir- 

 culate round them. One end of the cylinder is furnished with a 

 door, for the introduction of the wood and the removal of the 

 charcoal ; the other end terminates in a pipe, connected with a 

 worm-tube for condensing the pyrolignous acid, and giving 

 vent to the carburetted hydrogen gases that are disengaged. 

 Towards the end of the operation, the connexion of the cylinder 

 with the pyrolignous acid cistern ought to be cut off, and a 

 very free egress opened for the volatile matter, otherwise the 

 charcoal is apt to get coated with a fuliginous varnish, and to 

 be even penetrated with condensable matter, which materially 

 injure its qualities. 



In France, the wood is carbonized for the gunpowder-works 

 either in oblong vaulted ovens, or in pits, lined with brick- 

 work or cylinders of strong sheet-iron. In either case, the 

 heat is derived from the imperfect combustion of the wood 

 itself to be charred. In general, the product in charcoal by 

 this method is from sixteen to seventeen parts by weight from 

 one hundred of wood. The pit-process is supposed to afford a 

 more productive return, and a better article ; since the body of 

 wood is much greater, and the fuliginous vapours are allowed 

 a freer escape. The surface of a good charcoal should be 

 smooth, but not glistening. 



The charcoal is considered by the most scientific manu- 

 facturers to be the ingredient most influential, by its fluctu- 

 ating qualities, on the composition of gunpowder; and, there- 

 fore, it ought always to be prepared under the vigilant and 

 skilful eye of the director of the powder-establishment. If it 

 has been kept for some time, or quenched at first with water, 

 it is unsuitable for the present purpose. Charcoal extinguished 

 in a close vessel by exclusion of air, and afterwards exposed to 

 the atmosphere, absorbs only from three to four per cent. of mois- 

 ture ; while red-hot charcoal quenched with water may lose by 

 drying twenty-nine per cent. When the latter sort of charcoal 

 is used for gunpowder, a compensation in weight must be made 



