ABSTRACT
In spite of the difficulty in definitely characterizing alkaloids by definition, they do have a surprising number of physical and chemical properties in common. For the most part, the alkaloids are insoluble or sparingly so in water but form salts (by metathesis or addition) that are usually freely soluble. The free alkaloids are usually soluble in ether or chloroform, or other immiscible solvents, in which, however, the alkaloidal salts are insoluble. This permits the isolation and purification of the alkaloids as well as their quantitative estimation. Most of the alkaloids are crystalline solids, although a few are either amorphous (
coniine
,
nicotine
,
sparteine
) or liquid. It is interesting to note that the liquid alkaloids have no oxygen in their molecules. Alkaloidal salts are invariably crystalline, and their crystal form and habit are often useful in their rapid microscopical identification (Sollmann, 1944).
