This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The particular use to which alcohol is devoted in the bottling business, is that concerning the preparation of flavoring extracts and essences, as it is one of the best solvents known in chemistry; but by the dilution of water this property is much diminished. As a menstruum or solvent for certain drugs or materials entering into the manufacture of carbonated saccharine beverages, its strength should be at least 93 or 94 per cent., as a weaker alcohol will not produce the best results; and this holds true for "cutting" oils. Alcohol of this purity is a transparent, colorless, mobile and volatile liquid, of a characteristic pungent and agreeable odor and a burning taste, the same as the anhydrous kind, though the latter is more intense in its effects.
Alcohol is too expensive a material to be used other than in the most stringently economical manner, and should be preserved in well-closed vessels, in a cool place, remote from lights and fire. It is the waste in alcohol that renders the preparation of extracts such a costly undertaking to the bottler ignorant of the means for its recovery, to say nothing of his extravagance in connection with essential oil solutions.
It should not change the color of blue or red litmus-paper previously moistened with water; is readily inflammable, giving a blue flame without smoke. If a portion (at least an ounce) be evaporated to dryness in a glass vessel, no residue or color should appear. If mixed with its own volume of water and one-fifth its volume of glycerine, a piece of blotting paper, on being wet with the mixture, after the vapor of alcohol has wholly disappeared, should give no irritating or foreign odor (fusel oil). If a portion be evaporated to one-fifth its volume, the residue should not turn reddish upon the addition of an equal volume of sulphuric acid (amyl alcohol). When treated in a test-tube with an equal solution of potash, there should not be an immediate darkening of the liquid (methyl alcohol, aldehyde and oak tannin).