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.
This oil is obtained from the berries of juniper, therefore also called oil of juniper-berries, which are found in most all hemispheres, throughout Europe and the United States. The ripe berries are bruised, mixed with table-salt and water, and distilled, preferably by the aid of steam, yielding from one-half to one per cent. of volatile oil. The latter is colorless or pale greenish-yellow, limpid, "but on exposure rapidly thickens and turns yellow, and ultimately reddish-brown". - N. D. Fresh distilled oil from juniper berries is thickish and light-yellow, specific gravity varying from 0.850 to 0.900, commences to boil at 155° C. (311° F.), if obtained from ripe berries at 205° C. (401° F.) (Blanchet), has the peculiar taste of the berries, and a warm, aromatio taste, is slightly soluble in alcohol.
"The similarity of oil of juniper and oil of turpentine in specific gravity, boiling-point and behavior to solvents and reagents renders the detection of an adulteration with the latter rather difficult, except by the formation of a solid compound with hydrochloric acid gas, and by its different odor, particularly after exposure". - N. D.
"One drop of the oil, triturated with sugar and agitated with one pint of water, should not impart a sharp taste to the latter". - P. G.
Essence and tincture of juniper are prepared as directed for those of cloves.