A gum-resinous exudation obtained by incision from the living root of Convolvulus Scammonia, hardened in the air. Chiefly in Asia Minor. B.P. A resinous exudation from the root of Convolvulus Scammonia, U.S.P.

Characters. - In irregular, angular pieces or circular cakes, ash-grey and rough externally; fresh fracture, resinous, splintery, shining, black when dry; odour and flavour cheesy; causes, when chewed, a slight prickly sensation in the back of the throat; easily triturated into a dirty-grey powder, and converted with water into a smooth emulsion.

Composition. - Gum and resin.

Adulterations. - Chalk, starch, wood-ashes, and gum.

Tests. - It does not effervesce with hydrochloric acid (no chalk). Boiling water agitated with the powder, cooled and filtered, does not strike a blue colour with tincture of iodine (no starch). Ether removes from 80 to 90 per cent. of resin; and what remains is chiefly soluble gum, with a little moisture (no wood ashes).