Menthol. - C10H19OH=155.66. A stearopten (having the character of a secondary Alcohol), obtained from the official oil of peppermint (from Mentha piperita Smith), or from Japanese or Chinese oil of peppermint (from Mentha arvensis Linne, var. piperascens Holmes, and Mentha canadensis Linne, var. glabrata Holmes; nat. ord. Labiatae).

Source

By fractional distillation of the volatile oil and feezing the higher boiling product, and crystallization.

Characters

Colorless, acicular or prismatic crystals, having a strong and pure odor of peppermint, and a warm, aromatic taste, followed by a sensation of cold, when air is drawn into the mouth.

Solubility

Slightly soluble in water, but imparts to the latter its odor and taste. It is freely soluble in Alcohol, Ether, Chloroform, Carbon Disulphide, or glacial Acetic Acid. When it is triturated with about an equal weight of Camphor, Thymol, or Chloral hydrate, the mixture becomes liquid.

Impurities

Glass and magnesium sulphate.

Dose, 1/2 to 2 gr.; .03 to .12 gm.

Action And Therapeutics Of Menthol

Menthol is chiefly employed externally, for it produces local anaesthesia, a feeling of coldness and numbness, and thereby alleviates the pain of neuralgia, especially if it involves a superficial nerve. It is very efficacious in some cases. The solid menthol, in the form of a cone, may be drawn over the skin, or an alcoholic solution may be painted on, or a plaster; menthol, 3; yellow wax, 1; resin, 15; spread upon rubber cloth may be applied. In very hot weather this may be too fluid, and then more wax should be added. A solution made by heat with oleic acid 1 to 2.4 is an excellent preparation, and a good liniment is formed of menthol, 3; chloroform, 4; olive oil, 9. The local application often relieves itching. Menthol has been applied locally to carious teeth, and has been inhaled with advantage for the relief of the symptom asthma. For teeth it is best rubbed up with an equal part of pure carbolic acid, camphor or chloral hydrate. The oily liquid formed in either case may be put in the tooth. For the symptom asthma it is readily volatilized by the addition of hot water. Solutions of it have been painted upon the throat in diphtheria. A pigment of 1 to 4 in olive oil is employed for painting the larynx in tuberculous ulceration. It has been used internally in small doses (1/10 gr.; .006 gm.) to relieve nausea and vomiting. It is a powerful antiseptic, and is excreted in the urine, rendering it aseptic and giving it a pleasant smell. Menthol should be preserved in closed tin boxes.