Chips or turnings of the heartwood of _G. officinale_ (_guaiaci lignum_) are employed in the preparation of the _liquor sarsae compositus concentratus_ of British pharmacy. They may be recognized by being either yellow of greenish-brown in colour, and by turning bluish-green when treated with nitric acid, or when heated with corrosive sublimate, and green with solution of chloride of lime. They are occasionally adulterated with boxwood shavings. Lignum vitae is imported chiefly from St Domingo, the Bahamas and Jamaica. The bark was formerly used in medicine; it contains much calcium oxalate, and yields on incineration 23% of ash. Guaiacum resin, the _guaiaci resina_ of pharmacopoeias, is obtained from the wood as an exudation from natural fissures or from incisions; by heating billets about 3 ft. in length, bored to permit of the outflow of the resin; or by boiling chips and raspings in water to which salt has been added to raise the temperature of ebullition. It occurs in rounded or oval tears, commonly coated with a greyish-green dust, and supposed to be the produce of _G. sanctum_, or in large brownish or greenish-brown masses, translucent at the edges; fuses at 85 deg. C.; is brittle, and has a vitreous fracture, and a slightly balsamic odour, increased by pulverization and by heat; and is at first tasteless when chewed, but produces subsequently a sense of heat in the throat. It is readily soluble in alcohol, ether, chloroform, creosote, oil of cloves and solutions of caustic alkalies; and its solution gives a blue colour with gluten, raw potato parings and the roots of horse-radish, carrot and various other plants. The alcoholic tincture becomes green with sodium hypochlorite, and with nitric acid turns in succession green, blue and brown. With glycerin it gives a clear solution, and with nitrous ether a bluish-green gelatinous mass. It is blued by various oxidizing agents, e.g. ozone, and, as Schonbein discovered, by the juice of certain fungi. The chief constituents are three distinct resins, _guaiaconic acid_, C19H20O5 (70%), _guaiac acid_, which is closely allied to benzoic acid, and _guaiaretic acid_. Like all resins, these are insoluble in water, soluble in alkalies, but precipitated on neutralization of the alkaline solution.