_Copal._—The concrete juice of a tree growing in South America and the East Indies. Strictly speaking, it is not a gum or a resin, but rather resembles amber. It may be dissolved by digestion in linseed oil with heat little less than sufficient to boil the oil. The solution, diluted with oil of turpentine, forms a transparent varnish. It also dissolves in ether, and the ethereous solutions may be mixed with alcohol. _Copperas._—Sulphate of iron or green vitriol. A salt made by the decomposition of iron or iron pyrites in oil of vitriol. Dissolved in water, is the basis of black dyes, and is used in making ink, &c. _Copper, Sulphate of._—Called blue vitriol, which see. _Corrosive Sublimate._—Chloride of mercury. A salt prepared by the decomposition of sulphate of mercury by common salt. It is a deadly poison. It is soluble in alcohol, ether, in two or three parts of hot water and in about 15 parts cold water. It melts and sublimes about 600°. The white of eggs is an antidote for the poison. _Damar or Dammar._—A gum obtained from the agathis or dammar tree, allied to the pine trees, growing in the East Indies. It is soluble in alcohol and in oil of turpentine. _Dragon’s Blood._—The inspissated juice of various plants, of a red color, used for tinging varnishes, tooth tincture, staining marble, &c. _Ether, Nitric._—Mode of distilling equal parts of strong nitric acid and alcohol with a few grains of urea. It is liquid, colorless, of sweet taste, and insoluble in water. It boils at 185° F. The vapor explodes at moderate heat. _Elemi._—A resin obtained from plants grown in the East Indies and South America. In making lackers, it is used to give toughness to the varnish. _Fustic._—The wood of a tree growing in the West Indies. Used for dyeing yellow. _Gallic Acid._—See Acid, gallic. _Green Copperas._—Sulphate of iron. See Copperas. _Green Vitriol._—Copperas, which see _Hydrochloric Acid._—Muriatic Acid, which see _Iron, Chloride of._—See Muriate of Iron. _Iron, Muriate of._—See Muriate of Iron. _Iron, Sulphate of._—See Sulphate of Iron. _Iron, Sesqui-Chloride of._—Perchloride of iron or permuriate of iron. Made by dissolving rust of iron in muriatic acid and then crystalizing. It forms red crystals. Soluble in water, alcohol and ether. Very corrosive. _Logwood._—The wood of a tree growing in Central America. The extract is used in dyeing black color. _Madder._—A plant of the genus Rubia, one species of which is used in dyeing red. _Manganese, Sulphate of._—A beautiful rose-colored salt, used to give a fine brown dye. _Mastic._—A resin exuding from the mastic tree. It is in yellowish-white, semi-transparent tears. Used as an ingredient in varnishes.