MANUFACTURE OF WOOD-NAPHTHA. 
47 
tion of the tarry and oily matters held mechanically in suspension 
by the acid liquor will be returned. 
The next process depends upon the method of working adopted 
at each particular manufactory ; but without individual reference 
we may class them all under two heads. First, those who distil 
the pyroxylic spirit direct from the crude acid liquors ; and, sec- 
ondly, those who first neutralize the acid liquors with lime and then 
distil off the spirit. The first class employ copper stills of a capa- 
city of about 500 gallons ; into these the crude acid liquor is 
pumped, and heat applied either by means of steam made to tra- 
verse a coil of well-connected copper pipes placed within the still, 
as at Pitchcombe Works, or the stills are heated externally as at 
Cwm Avon Works. In the second case sheet-iron stills or boilers 
are employed, and the previously neutralized acid liquor run into 
them, and external heat applied as at the Melancrythan and other 
works. In each case about 100 gallons, or one-fifth of the contents 
of the still, are distilled off and put by as containing all the pyrox- 
ylic spirit, the further distillation and purification of which we shall 
hereafter speak of. In the first case the remaining acid is next 
distilled off, and the residuary tarry liquor run off through a cock 
placed in the lower part of the still ; or if distilled acid be not re- 
quired, the remaining 400 gallons are run off into a suitable tank 
or reservoir, in which the tar settles to the bottom, and the acid 
liquor may be drawn off or pumped up for further use. In the sec- 
ond case the remaining 400 gallons of neutralized acid liquor, or 
acetate of lime solution, is run out of the still, and employed as 
will be hereafter described. 
The tarry product of the distillation of wood is also distilled in 
copper or cast-iron stills, and the crude spirit obtained therefrom 
is added to that obtained from the distillation of the acid liquor 
above-mentioned. 
Manufacture of Pyroxylic Spirit or Wood Naphtha. — The 
crude and weak spirit procured in the distillation before mentioned, 
is next subjected to repeated distillations in order to obtain the 
spirit in a more concentrated form, which is then rectified by distil- 
lation, first with lime alone, and lastly with a mixture of lime and 
caustic potash. In some works chalk is employed, and in others 
lime and bicarbonate of soda. For this purpose copper stills are 
employed, and steam heat applied either through a coil of lead 
