AMYG'DALOID (from ainygdalus, an almond), a rock, consisting of a basis of some kind of trap-rock, very frequently of greenstone, forming numerous roundish or oval cells, which are filled with nodules, often of calcareous spar or of zeolitic minerals. The cells are not of large size, but even those which arc almost adjacent differ much in this respect. The nodules are evidently the result, of a sublimation and imperfect crystallization, under the action of the formed the-cells. Empty cells often occur amongst those which are filled with minerals. The name A.. is sometimes extended to rocks of the same character, although the basis be not of trap.
AMYL is the fifth in the series of alcohol radicals whose general formula is and of which methyl and ethyl are the first two members. It. is obtained by heating amyl-iodide with an amalgam of zinc in a closed tube at a temperature of about 350°, and is one of the natural products of the distillation of coal. It is a colorless liquid,
with a sp. gr. of 32°, a boiling-point of 311°, and a somewhat aromatic odor, and it exerts a right-handed rotatory action on a ray of polarized light. It enters into a large number of chemical compounds, most of which—as, for instance, bromide, chloride, iodide, etc.—are derived from amylic alcohol, which bears precisely the same relation to amyl that ordinary alcohol bears to ethyl Amylic alcohol is sufficiently described in the article FUSEL OIL, which is the name given to the crude alcohol. It seems invariably to accompany ordinary alcohol when the latter is prepared by fermentation, and apparently occurs in largest quantity in those liquids which remain most alkaline during fermentation.