204 On certain Products oltained 



mon tar. My connection nitli the Ordnance powder-mills 

 liasing compelled me to examine some of the properties of this 

 substance, which is obtained in large quantities in the proces of 

 making charcoal, I was induced to extend mv inquiries, in con- 

 sequence of finding that the nature of the compound has not 

 hitherto ijeen understood. 



As it is commonly called tar by the workmen, I shall use this 

 term for want of a better. 



This tar is very inflammable, and so liquid that it may be burnt 

 ill a lamp. 



Although it appears to be an uniform fluid, it contains a great 

 quantity of acetic acid, in a state of loose combination or mix-' 

 ture. For, by washing with water, a great part of this is se- 

 j)arated ; the water at the same time acquiring a colour from a 

 jjortion of the tar which is retained in solution bv the acid. 

 Boiling water takes up a larger portion, and the tar acquires 

 from this operation a thicker and more pitchy consistence. 



Lime and the carbonated alkalies separate the acid with ease, 

 carrying away also a portion of the tar which continues united 

 to the solution. With subcarbonate of jiotash it thus forms in 

 the first instance an uniform solution of a brown colour ; but a 

 continuance of trituration or boiling renders it pitchy and tena- 

 cious, after which it forms no further union with the mild al- 

 kalies. 



It is perfectly and readily soluble in alcohol, in ether, in the 

 pure alkaline lixivia, in acetic acid, and in the mineral acids. The 

 fat oils and the new essential oils dissolve only a small portion 

 of it ; but the drying oils and the latter when thickened by age 

 act more readily. Coloured oil of turpentine dissolves a good 

 deal of it. Naphtha hardly exerts any action, acquiring a scarcely 

 sensible brown colour. If heat be applied to assist the solution, 

 the portion taken up is again deposited on cooling. 



When it is sulijected to distillation in a heat sufficient to keep 

 it in a gentle ebullition, an oily-looking matter passes over in 

 considerable proportion, which sinks to the bottom of tlie water 

 into which the tube is inserted. It is first of a pale colour, re- 

 seuibling oil of peppermint, but becomes graduallv darker as the 

 operation advances, till it acquires a deep brown hue. 



If the operation be pushed by increasing the beat of the re- 

 tort to redness, there remains at length only a mass of spungy 

 charcoal, and the substance is totally converted into the follow- 

 ing new compounds, namely, the residuary charcoal, the oily 

 matter, and the matter held in solution in the water of the appa- 

 ratJi-'. This latter proves to consist of a large portion of acetic 

 acid, with which is combined a very little ammonia. 



Tlicre is no inflammable gas given out in this process unless 



the 



