This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Iodine. I =126.53.
Obtained from the ashes of sea-weed and from the mother-liquor of Chilian Sodium Nitrate.
Heavy bluish-black, dry and friable rhombic plates, having a metallic lustre, a distinctive odor, and a sharp and acrid taste. Solubility.- In 5000 parts of water; in 10 parts of Alcohol, freely in Ether, slightly in Glycerin, freely in a solution of Potassium Iodide or Sodium Chloride.
Iodine cyanide and iron.
Dose, 1 to 10 m.; .06 to .60 c.c.
Tinctura Iodi. Tincture Of Iodine. Iodine, 70; Alcohol to 1000. Strength. - 7 per cent.
Dose, 1 to 5 m.; .06 to .30 c.c.
Unguentum Iodi. Iodine Ointment. Iodine, 4; Potassium Iodide, 1; water, 2; Benzoinated Lard, 93. Strength. - 4 per cent.
The actions of iodine applied externally are the same as those of chlorine, that is to say, it is powerfully disinfectant and irritant. The latter action is the most important Iodine applied to the skin produces a yellow stain, which can be removed by an alkali or sodium hyposulphite. At the same time it causes a sensation of heat and burning, dilatation of the vessels (rubefaction), some cedematous swelling, and some exudation of leucocytes, to which its energetic absorbent action is probably due. There often is an accumulation of fluid under the epidermis forming a vesicle. Preparations of iodine are rarely used strong enough to produce more powerful irritation than this. The external application of them probably reflexly contracts the vessels of the subjacent organs, and this may explain their use as counter-irritants. If they are too strong, the irritation set up by them will proceed to the formation of vesicles, and even pustules, and deep inflammation with scarring. They usually destroy the superficial cuticle, so that after the use of them the skin peels. Iodine may be absorbed from the skin, and the alkalies in the blood serum lead to the formation of sodium iodide and iodate; thus, 6NaHco3+3I.2=5NaI+NaIo3+ 6Co2+3H2O. These, when they meet an acid, undergo double decomposition; thus 5NaI+NaIo3+H2O=6NaHO + 3I2. Thus free iodine is formed in the stomach and kidneys, and so if iodine has been applied to too large an area we get gastro-intestinal irritation and vomiting. The same may happen if it is taken by the mouth, and it may cause precisely the same symptoms of iodism as potassium iodide. Iodine preparations are parasiticides to the various vegetable and animal parasites which infest the skin.
Minute doses of the tincture occasionally stop vomiting. The vapor B. P., which is tincture of iodine, 1; water, 8; to be gently heated is very irritating to the respiratory passages.