Properties : Iodin is a heavy, bluish-black, dry and friable solid crystallizing in rhombic plates, having a metallic luster, a distinctive odor and a sharp and acrid taste. It is readily volatile. It is very slightly soluble in water (1:5,000), but soluble in alcohol (1:10). It is also soluble in solutions of iodids.

Incompatibilities: Iodin is incompatible with alkalies and alkali carbonates, the alkaloids, with tannin and other vegetable astringents and with most volatile oils, particularly the terpene-containing oils.

Action and Uses: Cutaneous: Iodin irritates the skin, causing a sensation of heat and itching. In concentrated solutions it may cause blistering, or even corrosion, but it acts more slowly than many other irritants. It penetrates into the deeper layers of the skin and small quantities are absorbed.

Iodin is applied to the skin for the purpose of exciting congestion of the underlying tissues. This congestion is supposed to cause the absorption of exudates. Its action is probably overrated. It is also used by surgeons for the disinfection of the skin, for which it is considered to be the most desirable agent. The application is made by painting the tincture over the part to be disinfected. The skin must be dry; wet applications should not be used previously. It is also used in various skin diseases for the purpose of producing an acute inflammatory reaction in the skin, and to cause the destruction of bacteria. Its effect on bacteria below the epidermis is probably due to the inflammatory reaction which it excites rather than to any direct action on the bacteria. For the prevention of tetanus it is recommended to apply to the skin about the wound a 3 per cent, alcoholic solution of iodin and to the wound pieces of gauze soaked in the same solution.

Internal: Iodin is more irritating to mucous membranes than to the skin. It is seldom used internally because of the irritating action on the stomach and intestines. This irritation may be so great as to excite a suppurative gastritis. The irritating action on the intestines may cause diarrhea. Small quantities of iodin are converted in the intestines into iodids and absorbed in this form. In some cases there is formed, also, a protein compound of iodin. After absorption iodin acts like the iodids (see potassium iodid). In cases of iodism, produced by the use of elementary iodin, there is tachycardia and irritation, of the nervous system, but not so much affection of the skin and respiratory tract as is seen after the administration of the iodids.

Iodin should rarely be used internally; in treatment of obstinate vomiting the tincture has been recommended in doses of from 0.03 to 0.05 c.c. or from ½ to 1 minim combined with the same quantity of phenol, given in a little water.

Local Uses: In the diseases of the eye iodin is sometimes used as a caustic agent and germicide to corneal ulcers of the simple type. It should be applied by means of a pointed toothpick soaked in the solution and used very cautiously.

For the treatment of chronic granular pharyngitis, in acute follicular tonsillitis, and in cases of middle ear catarrh associated with granular pharyngitis, it may be applied mixed with glycerol and combined with other remedies. The following formulas may be used:

c.c.

R Tinct. iodi ............... 3| m xlviii

Glycerini ................. 30| oz j-m

R, Tinet. iodi

R, Tinct. ferri chlor.

Glycerin! âà ...........q. s.

In gynecology the tincture is often applied directly to the interior of the cervix and painted over the mucous membrane of the vagina. This application is especially recommended in acute gonorrheal endocervicitis. Solutions of iodin have been much used in surgery. The tincture is often injected into cysts to cause the adhesion of their walls. Such applications should be made with caution. It is applied in a similar way to fistulous canals. A diluted solution is useful as a stimulant to ulcers.