Appendix.

919

eight fluid ounces of the brown liquid, which drains from the salt which the soap-makers, who employ kelp, boil up and evaporate to dryness, heat it to 230° Fahrenheit,and add one fluid ounce of sulphuric acid diluted with its own bulk of water.When the mixture cools, separate the crystals of the salts,* which will form in itby filtration through a woolen cloth, and add to the fluid poured into a matrass,830 grains of black oxide of manganese in powder. A glass globe is then to beinverted over the mouth of the matrass, and the heat of a charcoal chaffer beingapplied, Iodine will sublime in great abundance. It must be washed out ofthe globe with alcohol, then drained and dried on plates of glass; and purifiedby a second sublimation from dry quicklime. 2

Iodine has been procured from sponge by M. Straub of Hofwyl; 3 and fromvarious sea plants; for instance, Fucus sacckarinus, digitatus, serratus, vesicu-losus, sUiquosis,JUum, rubens, cartilagineus, membraiuiceus, scaAJUamentosus ; Ulvapavonia, and U. linza.

The discovery of Iodine is due to M. Courtais, a French chemist, who first ob-tained it in 1811; but its nature was not known to the philosophical world till18IS, when it was announced to the French institute by M. Clement. Its pro-perties and chemical affinities were afterwards determined by the experiments ofGay Lussac, 4 Sir H. Davy, b Vanquelin, 6 Colin, Gaulthier de Claubry, 7 andM. Pelletier. 8

Qualities. Iodine, when properly prepared, is a crystallized substance of a greyishblack colour, having a specific gravity of 4.948, and a metallic lustre : its smell isdisagreeable, not unlike that of chlorine, and its taste acrid and hot. It is usuallyobtained in rhomboidal plates, which show a lamellated fracture; are scarcelysoluble in water, but more so in alcohol, and still more in sulphuric ether. Itmelts at 224'Fahrenheit, and is volatilized at a temperature between 347" and356'. Its vapour is of a beautiful violet colour, (whence its name from /a>5fcviolet).

Medicinal Properties. From the fact that burnt sponge forms the basis of allthe remedies that have been productive of any benefit in the treatment of broncho-celc, Dr. Coindet of Geneva, supposing that Iodine was the active principle of thesponge, proposed to employ it in different combinations for the cure of that die-tase. lie gave it in the form of tincture, made by dissolving forty-eight grainsof Iodine in a fluid ounce of alcohol; and, also in the form of hydriodatc of pot-ass. 'Die hydriodatc is made by dissolving Iodine in a solution of pure potass.Both an iodate and a hydriodate are formed; the first of which being much lesssoluble than the second, falls to the bottom of the solution in the form of smallgrains; the second (the hydriodate J remains dissolved in the liquid, which assumesa bright yellow colour if the Iodine be not in excess, but a deep, brownish yellow,if it be in excess. Numerous cases of the beneficial results of the exhibition ofboth these preparations of Iodine in bronchocele and in scrophulous swellings,have been published by Dr. Coindet and others : but, in this country, the remedyhas been too little used to determine its real value. The hydriodate of potass istbe form of the medicine now generally preferred.

Much caution is requisite in the administration of Iodine. In delicate, nervoushabits, it is apt to bring on palpitations, dry cough, tremors, and other febrilesymptoms.

Die dose of the tincture is from ten to fifteen drops for an adult, given in aglass-ful of sugared water, or of syrup of capillaire and water, three times a day,and of that of the hydriodate, from six to ten drops, in the same vehicle.

Besides the use of Iodine as a curative agent, it has been employed as a test ofthe presence of oxide of arsenic and of corrosive sublimate. Brugnatelli, who first

1 These are sulphate of soda, sulphate of potass, hydriodate of soda and sulphur.3 Phil. Magazine, 1. p. 161.

3 Journ. of Science and the Arts, vol. x. p. -1J6.

4 Gay Lussac's experiments were published in November 1813. Vide Amude Chim. t. 88. p. 319.

s Sir H. Davy's experiments were published in December 1813.

6 Ann. de Chimic. t- 91.

7 Journ. de Phijh. Aout. ISM.

8 Bulletin de Pharmacie, t. vi.

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