Araroba Powder; Goa Powder. - The medullary matter of the stem and branches of Andira Araroba, dried and powdered.

Characters. - A light brownish-yellow, minutely crystalline powder, tasteless and inodorous.

Solubility. - Very sparingly soluble in water, but almost entirely soluble in 150 parts of hot rectified spirit.

Reactions. - On heating it melts and partially sublimes in yellow vapours, leaving a charred residue, which entirely disappears on ignition in air. It dissolves in sulphuric acid to form a yellow to orange-red solution, and in solution of caustic potash to form a yellow to reddish fluorescent solution, which becomes carmine by absorption of oxygen from the air.

Composition. - It contains more or less chrysophanic acid according to age and condition, and yielding much chrysophanic acid by oxidation.

Dose.- 1/5 to 2 grains.

Preparation, B. and U.S.P.

Unguentum Chrysarotoini. Chrysarobin Ointment (Chrysarobin 1, benzoated lard 24, B.P.; Chrysarobin 10, benzoated lard 90, U.S.P.).

Uses. - It is used in psoriasis and parasitic affections of the skin. It may be simply applied to the skin moistened with vinegar or saliva, or used in the form of ointment (of the strength of 1 in 50 to 1 in 10). It should never be applied to the head, as it may cause extensive erythema and oedema of the face. It colours both the skin and clothing, and it is better not to use it over too large a surface at a time, as it may cause much irritation. In 2 per cent. ointment it is useful in eczema after exudation has ceased, especially in that of the genitals and anus. It is an excellent application in fissured nipple, and is useful in tylosis of the palms and soles after the epidermis has been removed by salicylic acid plaster (vide p. 821). It may also be given internally in eczema, impetigo, acne, psoriasis, urticaria, and other skin diseases.