Iodine was discovered in 1811, by Courtois, in the waste liquors produced in the man ufacture of carbonate of soda from the ashes of sea-weeds. A few years later, Gay Lussac discovered that it was a simple elementary body. It is obtained from the half fused ash of dried sea-weeds, which is known in this country as kelp (q.v.), and in Normandy as varek, and contains the iodides of sodium, potassium, magnesium, and perhaps calcium in considerable quantity. The iodine is liberated by the addition of .binoxide of manganese and sulphuric acid. Most of our commercial iodine is prepared in GlasgoW.
The preparations of iodine are employed.extensively in medicine and in photography (q.v ). Iodide of potassium, and the preparations of iodine generally, are almost entitled to be regarded as specifics in cases of goitre, bronchocele, or Derbyshire neck. Out of 364 cases (collected by Bayle) which were treated with iodine, 274 were cured. Manson, Lugol, and others have shown the value of the iodine-treatment in scrofula. The preparations of iodine are also eminently successful as resolvents in chronic indium tion, and enlargement of the liver, spleen, uterus, etc. In many forms of chronic rheu matism, and in certain affections of the osseous system, due to a syphilitic taint, iodide of potassium is of the greatest service; and its value in the treatment of chronic lead poisoning is not so generall•known, even in the medical profession, as it deserves to be. The iodide of potassium dissolves the compounds of lead with albumen, fibrine, etc., which abound in the body in chronic lead-poisoning; and these dissolved com pounds are excreted by the kidneys. In these cases, lead may often be detected in the
urine, almost immediately after the administration of the iodide. This salt has a simi lar action in chronic mercurial poisoning, and cases are recorded of mercurial salivation having come on during the use of iodide of potassium, in consequence of the liberation of mercury, which had been previously fixed in the system.
Iodide of iron, which may be given either in syrup or in the form of Blancard's pills (an excellent French mode of administering this salt), is especially serviceable in scrofulous affections of the glandular system, in which the.. use both of iodine and of iron is indicated. The• iodides of mercury have been prescribed with good effect in various forms of syphilis. They must be given with caution, on account of their energy, the average dose of the red iodide being a fraction to -1-) of a grain. Pure iodine is seldom preseribetiiuternally; but ,in Om form of tincture and ointment, it is a most useful topical application in cases of goitre, local enlargements, diseases of joints, chilblains, etc.
In large doses, iodine and most of the iodides act as irritant poisons; but very few fatal cases are on record. In the event of poisoning with the tincture of iodine, the first point is to evacuate the stomach; and the vomiting is assisted by the copious use of tepid liquids, containing starchy matter, as, for instance, starch, flour, or arrow-root boiled in water; the object being to form iodide of starch, which is comparatively inert.