GALLATES; salts consisting of gallic acid combined with bases; the most important being that with oxide of iron, constituting a principal part of the black dye.
GALLIC ACID, is the peculiar acid extracted from [gall-nuts]; which see.
GALLIPOLI OIL, is a coarse olive oil, containing more or less mucilage; imported from a sea port so named, of the province of Otranto, in the kingdom of Naples.
GALL-NUTS, or GALLS; (Noix de Galle, Fr.; Galläpfel, Germ.;) are excrescences found upon the loaves and leaf-stalks of a species of oak, called Quercus infectoria, which grows in the Levant. They are produced in consequence of the puncture of the female of the gall wasp, (Cynips folii quercus), made in order to deposit her eggs; round which the juice of the tree exudes, and dries in concentric portions. When the insect gets fully formed, it eats through the nut, and flies off.
The Levant galls are of two different appearances and qualities; the first are heavy, compact, imperforated, the insect having not been sufficiently advanced to eat its way through the shell; prickly on the surface; of a blackish or bluish green hue; about the size of a musket ball. These are called black, blue, or Aleppo galls. The second are light, spongy, pierced with one or more holes; smooth upon the surface, of a pale grayish or reddish yellow colour, generally larger than the first, and are called white galls. Besides the galls of the Levant, others come from Dalmatia, Illyria, Calabria, &c.; but they are of inferior quality, being found upon the Quercus Cerris; they are smaller, of a brownish colour, and of inferior value. The further south the galls are grown, they are reckoned the better.
Galls consist principally of three substances; tannin or tannic acid; yellow extractive; and gallic acid. Their decoction has a very astringent and unpleasant bitter taste. The following are their habitudes with various reagents:—
Litmus paper is powerfully reddened.
Stannous chloride (protomuriate of tin), produces an isabel yellow precipitate.
Alum; a yellowish gray precipitate.
Acetate of lead; a thick yellowish white precipitate.