Oils of Mint.
Although all the mints possess an agreeable odor, only three varieties find extensive application. There are the oils from Mentha piperita, peppermint; Mentha viridis, spearmint; and Mentha crispa, crispmint. The oils of English manufacture are highly esteemed, but the United States also produces them of excellent quality. At one time the cultivation of mints, particularly peppermint, was greatly extended, with the expectation of deriving satisfactory profit from the enterprise. It has, however, been conclusively shown that the market cannot absorb more than a certain quantity of these products; and that any over-production brings loss and disappointment to the investor. Beside the three kinds of mint above mentioned, there is another species, Mentha arvensis, a native of Japan, which is extensively cultivated there, and is the chief source of the menthol of commerce, so well known as an efficient remedy for neuralgia, migraine, etc., in form of menthol cones. The three varieties of the mint oils previously mentioned are distinguished, aside from their pleasant odor, by the property of leaving a very refreshing and cooling taste in the mouth, and for this reason they form the most important constituent of all fine mouth washes.
True oil of peppermint, Oleum Menthæ piperitæ, when pure is colorless, very mobile, of a burning sharp taste which is followed by a peculiar coolness. The commercial product is usually pale green. Oil of crispmint, Oleum Menthæ crispæ, which in Europe is often sold to novices as oil of peppermint, has always a more or less yellow color and resembles the oil of peppermint in its properties, but it is less fine and cheaper. The same is true of the oil of spearmint, but this has a very characteristic odor and taste, distinctly different from peppermint.
As above stated, the oils of mint are extensively used for mouth washes, also for scenting soap, in liqueurs and pastils, but rarely in handkerchief perfumes.