Plumbi Iodidum. Lead Iodide. Pb12=430.46.

Source

Mix solutions of Lead Nitrate and Potassium Iodide and dry the precipitate. Pb(No3)2+ 2KI=2Kno3+PbI2.

Characters. + A heavy, bright-yellow powder, without odor or taste. Solubility. - In about 2000 parts of water.

Preparation

Unguentum Plumbi Iodidi

Ointment of Lead Iodide. Lead Iodide, 10; Benzoinated Lard, 90.

Action of Lead Salts

External

The action of lead salts on the unbroken skin, if they have any, is very slight; but when applied to the abraded skin, to sores and to ulcers, they coagulate the albumin of the discharge, thus forming a protective coat; they coagulate the albumin in the tissues themselves; and they contract the small vessels; for these three reasons they are powerfully astringent. They also soothe pain, and are therefore excellent local sedatives. It is obvious that substances so markedly astringent will be haemostatics. Any salt may be irritant and caustic if enough be used, and it is sufficiently concentrated.

Internal

Lead salts act on mucous membranes precisely as on the unbroken skin, and are therefore powerfully astringent and haemostatic to all parts of the alimentary canal, from the mouth downwards. In the stomach they are converted into a chloride. (For other actions see Toxicology.)

Therapeutics of Lead Salts

External

Lead salts are applied as lotions or ointments in many conditions for which an astringent, sedative effect is desired, as in weeping eczema and many varieties of ulceration. The glycerin of the subacetate B. P., lead acetate, 10; lead oxide, 7; glycerin, 40; water, 24; boiled together diluted fourfold with glycerin or milk is useful for these conditions. The lotions may be injected in vulvitis, leucorrhcea, gleet and otorrhoea, but should not be applied for ulceration of the cornea, lest the white precipitate formed should lead to permanent opacity. The sedative effect is well seen in their use in pruritus; but of course the cause of the itching should, if possible, be removed. The Liquor Plumbi Subacetatis is rarely used, as it is strong enough to irritate; the diluted form is that usually employed when a lotion is desired. It is often applied to bruises when the skin is unbroken, but is doubtful if it is absorbed. The ointment is an excellent remedy, and a lotion of lead and opium is a favorite preparation. It may be made by mixing 5 gr. .30 gm. of extract of opium with 1 oz. 30. c.c. of Liquor Plumbi Subacetatis Dilutus and 1 oz. 30. c.c. of water. Diachylon ointment mixed with an equal quantity of zinc oleate and mercuric oleate ointments forms a transparent ointment excellent for many purposes.

Internal

The chief uses of lead salts (the acetate is the only one given internally) are as astringents in severe diarrhoea, such as that of typhoid fever, and as haemostatics, as in gastric ulcer, or in haemorrhage from the intestine, especially if severe, as in typhoid fever or tuberculosis. For these purposes the Pilula Plumbi cum Opio B. P., lead acetate, 3 gr.; .20 gm.; opium, 1 gr.; .06 gm. is very valuable, and suppositories containing the same amount of the ingredients may be employed for rectal haemorrhage. Lead salts produce marked constipation. Other preparations are generally preferred, but lead subacetate may be used as a gargle when an astringent effect on the mouth or pharynx is desired.

Toxicology