2 Dr. Mac Culloch on certain products 



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 In 

 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 mixture. 

 For, by washing with water, a great part of this is separated ; the 

 water at the same time acquiring a colour from a portion of the tar 

 which is retained in solution by 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, car- 

 rying away also a portion of the tar which continues united to the 

 solution. With subcarbonate of potash 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 tenacious, after which 

 it forms no further union with the mild alkalies. 



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 subjected to distillation in a heat sufficient to keep it 

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

 able proportion, which sinks to the bottom of the water into which 

 the tube is inserted. It is first of a pale colour, resembling oil of 

 peppermint, but becomes gradually darker as the operation advances, 

 till it acquires a deep brown hue. 



