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The spirits distilled from different fermented 
liquors differ in their flavour : for peculiar odorous 
matter, or volatile oils, rise in most cases with the al- 
cohol. The spirit from malt usually has an empy- 
reumatic taste like that of the oil, formed by the 
distillation of vegetable substances. The best bran- 
dies seem to owe their flavour to a peculiar oily mat- 
ter, formed probably by the action of the tartaric 
acid on alcohol ; and rum derives its characteristic 
taste from a principle in the sugar cane. All the com- 
mon spirits may, I find, be deprived of their peculiar 
flavour by repeatedly digesting them with a mixture 
of well burnt charcoal and quicklime ; they then 
afford pure alcohol by distillation. The cognac 
brandies, I find, contain vegetable prussic acid, 
and their flavour may be imitated by adding to a 
solution of alcohol in water of the same strength, 
a few drops of the ethereal oil of wine produced 
during the formation of ether *, and a similar quan- 
tity of vegetable prussic acid procured from laurel 
leaves or any bitter kernels. 
I have mentioned ether in the course of this 
Lecture ; this substance is procured from alcohol 
by distilling a mixture of equal parts of alcohol and 
sulphuric acid. It is the lightest known liquid sub- 
stance, being of specific gravity 632 at 60°. It is 
very volatile and rises in vapour, even by the heat 
of the body. It is highly inflammable. In the 
formation of ether it is most probable, from the ex- 
periments of M. de Saussure, that the elements of 
* In the process of the distillation of alcohol and sulphuric 
acid after the ether is procured ; by a higher degree of heat, a 
yellow fluid is produced ; which is the substance in question. 
It has a fragrant smell and an agreeable taste. 
