Origin. - It is found in the ashes of sea-weeds, and is prepared from the mother liquor obtained in the purification of Chili saltpetre.

Description and Properties. - Heavy, bluish-black, dry and friable, rhombic plates, having a metallic luster, a distinctive odor, and a sharp and acrid taste. It imparts a deep-brown, slowly evanescing stain to the skin, and gradually destroys vegetable colors. Iodine is soluble in about 5000 parts of water and in 10 parts of alcohol, with a brown color; also freely soluble in ether and in a solution of potassium iodide, with a brown color, and in chloroform or carbon disulphide, with a violet color. It should be kept in glass-stoppered bottles, in a cool place.

Dose. - About 1/4 grain (0.016 Gm.) [1/10 grain (0.005 Gm.), U. S. P.], although seldom given in substance.

Official Preparations

Liquor Iodi Compositus - Liquoris Iodi Compositi - Compound Solution of Iodine (Lugol's Solution). - Iodine, 5; potassium iodide, 10; distilled water, to make 100 parts. Strength, 5 per cent.

Dose. - 1-10 minims (0.06-0.6 Cc.) [3 minims (0.2 Cc), U. S. P.].

Tinctura Iodi - Tincturae Iodi - Tincture of Iodine. - Iodine, 70; alcohol, to 1000. Strength, 7 per cent.

Dose. - 1-5 minims (0.06-0.03 Cc.) [1 1/2 minims (0.1 Cc), U. S. P.].

Unguentum Iodi - Unguenti Iodi - Iodine Ointment. - Iodine, 4; potassium iodide, 4; glycerin, 12; benzoinated iard, 83. Strength, 4 per cent. For external use.