part n,

Materia Medica.

303

aromatic odour, and a warm, pungent, bitterish taste;are semifluid, tenacious, translucent, combine readily withfixed oils, and are inflammable, burning with a white flameand much smoke. Alcohol and ether dissolve them entirely,leaving the impurities; but water takes up only their flavour.When distilled with water a volatile oil comes over, and resinremains in the retort; the turpentines being compounds ofdiese two substances. But each sort of turpentine has cha-racteristic qualities which require to be noticed; 1. Commonturpentine has a strong somewhat fragrant odour, and a bitterdisagreeable taste; its consistence is greater than that of ho-ney ; its colour whitish, and it is more opaque than the othersorts. 2. Venice turpentine is more fluid, having the consist-ence of new honey, a yellowish colour, and is less unpleasantto the smell and taste than the common. 3. Canadian balsam(or more correctly turpentine) has a strong not disagreeableodour, and a bitterish taste; is transparent, whitish, and hasthe consistence of Copaiva balsam. 4. Chian or Cyprus turpen-tine (see Pistacia) is very fragrant, but almost insipid, nearlytransparent, thick, tenacious, and of a whitish colour.

Oil of Turpentine has a strong, penetrating, peculiarodour, and a hot, pungent, bitterish taste. It is perfectly lim-pid and colourless: extremely light, volatile, and inflammable;and dissolves completely in six parts of sulphuric ether; butalthough hot alcohol readily dissolves it, yet it again separatesin drops as the spirit cools, and is very sparingly soluble in thecold in the strongest alcohol. In all other respects it agreeswith the other essential volatile oils. A stream of oxymuriaticgas passed through it converts it into a yellow resin.

Tar has a strong odour familiar to every body; a resinous,subacid, bitterish taste; and a coarse thick consistence, with a'deep brown colour approaching to blackness, derived from thecharring of the wood during its formation. It consists prin-cipally of empyreumatic oil, resin, and acetic acid; is partiallysoluble in water; and inspissated by boiling into pitch.

Yellow and White resin are varieties of the same substance.They are nearly inodorous when cold, but heated emit a slightterebinthinate odour. Their taste is slightly acrid and bit-terish.; and the colour a dull whitish yellow, or a greenish yel-low. The mass of resin is semipellucid, brittle, breaks witha true vitreous fracture, and adheres moderately to the fingers.Its specific gravity is 1 - 0742. It melts when heated, then in-flames, and burns with a yellow flame giving out much smoke.It is insoluble in water, but entirely soluble in alcohol, ether,the fixed oils, and the alkalies. The acids also dissolve resin,and convert it into artificial tannin: with the exception of the