Characters. - Small orange-coloured crystals.

Solubility. - Readily and almost entirely soluble in water and in rectified spirit.

Reactions. - Its aqueous solution has a neutral reaction, and gives a yellow precipitate with sulphuretted hydrogen. Heated in a test-tube it almost entirely volatilises, violet vapours of iodine being set free. . Preparation. - By the direct combination of iodine and metallic arsenic, or by evaporating to dryness an aqueous mixture of arsenious and hydriodic acids.

Dose. - 1/30 gr.

Use. - In skin diseases.

Liquor Arsenii et Hydrargyri Iodidi, B. and U.S.P.

Solution of Iodide of Arsenic and Mercury. Donovan's Solution.1 Iodide of arsenium, AsI3, and red iodide of mercury, HgI2, of each 45 grains (1 per cent. of each by weight), water up to 10 fl. oz., B.P. Iodide of arsenic, 1; red iodide of mercury, 1; water up to 100, U.S.P.

Characters. - A pale yellow liquid, with a metallic taste. Incompatibles. - Solutions of opium or morphine. Dose. - 5 to 30 minims (0.3-1.8 c.c). Uses. - In skin diseases, syphilis, rheumatism, and nocturnal pains.