SECTION III. 



Empyreumatic Oils and Aromatic Products of 

 Destructive Distillation. 



Destructive distillation is a very ancient industry, whose 

 intricate ancj numerous problems have been from time to time 

 investigated by the ablest chemists. In the sixteenth and 

 seventeenth centuries it came to be the principal work in chemical 

 laboratories. 



Destructive distillation is the decomposition by heat of a 

 substance in a closed vessel, in such a manner as to obtain liquid 

 products. 



By a 'product is meant a body not originally present in the 

 substance distilled. A body merely extracted without change by 

 distillation is termed an edud. 



As stated by Dr. Mills in his very useful Manual,* " the nature 

 of the products depends, — 1st, on the composition of the substance 

 heated ; 2nd, on the degree of heat applied ; but not to any serious 

 extent (when working on the large scale), on the material of 

 the retort. If an organic substance contain much infusible 

 mineral matter, the latter will hold down the former, and compel 

 recourse to a higher temperature. Thus gum-benzoin, when 

 distilled alone, yields benzoate : when mixed with sand it produces 

 benzene. In cases of this kind, the fine state of division or porosity 

 of the earthy constituent contributes, with the higher temperature, 

 to a change in the nature of the prevailing re-action." ... At 

 a very high temperature, the products from coal and shale are 

 carbon and carbonised gases of low illuminating power, with Init 

 little liquid distillate ; at a low temperature there is much liquid 

 product, and comparatively little gas, but of high illuminating 

 power. 



* " Destructive distillation," by E. J. Mills, London. (Van Voorst). 



