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 United States and England are great producers of peppermint and peppermint oil. It is principally grown in Michigan, New York and other States of the Union, and in'England by Cambridge and Mitcham. The oil is used in medicine, confectionery, perfumery, and in preparing carbonated drinks. The herb is distilled with water, or .preferably with steam, and usually rectified by steam-distillation. The oil separates from the water and is filled into tin cans, or glass demijohns. The latter are preferable when the oil is kept for any length of time, as its good qualities are more fully retained, and it is less liable to discoloration It is a colorless, or more frequently yellowish or greenish-yellow, liquid, which on exposure becomes brownish and viscid. Its specific gravity is usually near 0.900, but varies between 0.840 and 0.940, at 60° F. Steam rectified and re-distilled oil of peppermint is of a slightly higher specific gravity than natural oil, but should not be less than 0.905, nor more than 0.915 at 60° F The decrease in weight is caused by the separation of the oleoresin. It commences to boil near 190° C. (374° F ) and at a low temperature sometimes deposits crystals of menthol (mint camphor). It has a peculiar pungent odor, and a warm, aromatic, and when old also bitterish, taste, followed by a sensation of cold, which is most noticed on drawing air into the mouth. After the N. D it dissolves clear in from one to three parts of 80 per cent, alcohol, the solution usually becoming opalescent with more alcohol, and depositing slowly a minute white precipitate.
Proceed as follows. Mix oil of peppermint one ounce; alcohol sixteen ounces.
We append the followiug Formula. Oil of peppermint one ounce; alcohol and water, of each eight ounces; cut the oil in the usual way to obtain the soluble essence. For the sole purpose of admixture to other syrups a weaker essence is usually prepared.
Where the herb of peppermint is growing and easily obtainable a tincture may be prepared by macerating one pound of herb with five pints of diluted alcohol. This may be serviceable for many a purpose.
Oil of peppermint is to a considerable extent adulterated with castor oil, oil of turpentine, hemlock, and alcohol, but these adulterations can be detected without much difficulty in applying the tests we have given on page 639 and following pages.
The following general test for adulterations has been recommended: Mix thoroughly about one pint of snow or finely crushed ice with a like quantity of finely powdered salt (or in summer produce artificial cold, by mixing sal ammoniac 5 ozs., nitrate of potassium, 5 ozs., water, 1 pint), and put this into any convenient quart-holding open container (pot, measure, box, etc.); into this place a corked test tube not quite filled with the oil. After ten or fifteen minutes, the oil, if pure, will have become cloudy, translucent, thick, or of a jelly-like consistency; then add four or five small crystals of pure menthol (mint camphor), recork and shake thoroughly. Replace the tube into the freezing mixture, and after a short time the pure oil will present a solid frozen mass of crystals. If the oil remain limpid or partially so, it has either been adulterated, or had its menthol extracted, and should unhesitatingly be rejected. This test will, in the hands of one who has used it a few times, detect so small an adulteration as five per cent, of any other oil, so that it will be found a test for adulterations as well as of the abstraction of menthol.
Distil one pound herb of peppermint with ten pints of water, until one gallon is received; or distil one drachm of the oil with ten pints of water, until one gallon is received; or triturate one drop with sugar, and dissolve and agitate with one pint of water; clarify and filter.