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EXPERIMENTAL GENERAL SCIENCE 



liquid with the lowest boiling point would come off first, fol- 

 lowed by others in the order of their boiling points, as the tem- 

 perature is increased. This is called fractional distillation. 

 Naphtha, benzine, gasoline, kerosene, coke, and a large number 

 of other substances are obtained from crude petroleum by this 

 process. Occasionally solids may be broken down, by means 

 of heat, into one or more new products, gaseous, liquid, or 

 solid. This is called dry or destructive distillation. By this 



A 



V\ 



FIG. 49. Distillation of coal in test-tube. 



means wood alcohol, acetic acid, and charcoal are derived from 

 various hard woods, and coal is made to produce coke, tar, 

 illuminating gas, and other substances. From the coal tar are 

 also derived a large number of useful products among which are* 

 numerous dyes. The wood alcohol obtained by dry distilla- 

 tion of wood, differs from ordinary alcohol in being very 

 poisonous. Denatured alcohol is ordinary or grain alcohol 

 to which has been added a small quantity of wood alcohol or 

 other substance to render it unfit for internal use. 



