This is obtained by distilling with water bitter almonds, previously deprived of their fixed oil by expression. it is of a yellowish colour, with a strong odour of the kernels, and a bitter, acrid, burning taste. It is soluble in alcohol and ether, and slightly so in water. it consists mainly of hydrocyanic acid, dissolved in or combined with a volatile oil, upon which its peculiar odour and taste chiefly depend. When freed from the former ingredient, it has the ordinary properties of the volatile oils, and retains its smell and taste, but is no longer poisonous. When taken internally in its original state, it produces on the system all the effects of hydrocyanic acid, and has the advantage, as a medicine, over the pure diluted acid, that it will keep for a long time without any material deterioration; the oil being a preservative to the active ingredient. it is, indeed, a very convenient form for the administration of the acid. The dose is from one-quarter of a drop to a drop, given at the ordinary intervals, and cautiously increased, if necessary, until some effect is experienced. it is most conveniently administered in emulsion with gum arabic, loaf sugar, and water, and may be applied externally to irritating cutaneous eruptions, either in the same form, or dissolved in water, in the proportion of one minim to the fluidounce, through the intervention of a little spirit. it is so poisonous, that four drops of it are said to have killed a dog of medium size. A patient who was supposed to have taken two drachms of it, died in twenty-one minutes. {Lancet, Dec. 1863, p. 447.)