Prep. From the rasped root, by the same method that is adopted for arrow-root or potato farina; or by boiling the sliced root in 7 or 8 times its weight of water, and after filtration,

whilst hot, allowing the decoction to repose for a short time.

Prop., &c. Only very slightly soluble in cold water; very soluble in boiling water, but is nearly all deposited as the solution cools; it is precipitated by alcohol.

Inulin is distinguished from starch by giving a yellow or yellowish-brown instead of a blue colour with iodine; in the decoction not being precipitated by either acetate of lead or infusion of galls; and by the precipitate formed in the cold decoction by an infusion of gall-nuts not disappearing until the liquid is heated to above 212°, whilst the precipitate from starch redissolves at 122° Fahr. It appears to be a substance intermediate between starch and gum.

I′ODATE′. Syn. Iodas, L. A salt of iodic acid. The iodates closely resemble the chlorates of the corresponding metals. They are recognised by the development of free iodine when their solutions are treated with reducing agents; thus, sulphuretted hydrogen passed into a solution of iodate of potassium reduces this salt to an iodide, iodine being liberated and sulphuric acid and water formed. They deflagrate like the chlorates when heated with combustibles. They are all of sparing solubility, and many are quite insoluble in water. They may be made by adding iodine to soluble hydrates or carbonates, and crystallising the sparingly soluble iodate from the very soluble iodide. See Iodic acid, Iodine, and Potassium.

IODHY′DRIC ACID. See Hydriodic acid.

IOD′IC ACID. HIO₃. Syn. Acidum iodicum, L.

Prep. 1. Iodate of sodium is dissolved in sulphuric acid in considerable excess, the solution boiled for 15 minutes, and then set aside to crystallise.

2. Decompose iodate of barium by dilute sulphuric acid.

3. (Boursen.) Iodine, 1 part; nitric acid (sp. gr. 1·5), 40 parts; mix, keep them at nearly the boiling temperature for several hours, or until the iodine is dissolved, then evaporate to dryness, and leave the residuum in the open air at a temperature of about 59° Fahr.; when, by attracting moisture, it has acquired the consistence of a syrup, put it into a place where the temperature is higher and the air drier, when in a few days very fine white crystals of a rhomboidal shape will form.

Prop., &c. Iodic acid is a crystalline solid, white or yellowish-white; it is decomposed into oxygen and iodine by a heat of about 450° to 500° Fahr.—a property of which we avail ourselves for the conversion of the salts of this acid (iodates) into iodides. It is very soluble in water, and is rapidly decomposed when heated with inflammable bodies. Iodic acid is used as a test for morphia and sulphurous acid. It has been employed as a tonic, stimulant, and alterative, in catarrhal hoarseness,

strumous cases, incipient phthisis, &c.—Dose, 3 to 6 gr.

Test. When iodic acid is mixed with an equal quantity of an alkaloid (preferably quinine), on a capsule or watch-glass, and a drop or two of water added, several distinct explosions occur, accompanied by the copious evolution of gas. No other substance exhibits a similar reaction. See Iodate.

I′ODIDE. Syn. Ioduret*, Hydriodate*, Iodidum, Ioduretum, Hydriodas, L. A compound of iodine with a metal or other basic radical. The iodides belong to the same class of bodies as the bromides and chlorides, and may be, for the most part, made in the same manner. All the principal iodides are noticed under the names of their respective bases. See Iodine, &c.

I′ODINE. I. Syn. Iodum, B. P.; Iodinium (Ph. L. & D.), Iodineum (Ph. E.), L.; Iode, Fr.; Iod, Ger. An elementary substance accidentally discovered in 1812, by De Courtois, a saltpetre manufacturer at Paris. It was first examined and described by M. Clement, in 1813, and its precise nature was soon afterwards determined by Sir H. Davy and M. Gay-Lussac. In 1819, some six years after its discovery, iodine was first employed in pharmacy. The merit of the introduction of this powerful curative agent into medicine is due to Dr Coindet, a physician of Geneva, who in that year commenced a series of experiments upon it as a remedy for bronchocele or goitre. It is found in each of the three kingdoms of nature, but exists in greatest abundance in the vegetable family Algæ (Seaweeds).

Prep. Iodine is principally manufactured in the neighbourhood of Glasgow, from the mother-waters of kelp known as iodine lye.

1. Kelp, the half vitrified ashes of seaweed, is exhausted with water, and the solution filtered; the liquid is then concentrated by evaporation until it is reduced to a very small volume, the chloride of sodium, carbonate of sodium, chloride of potassium, and other salts, being removed as they successively assume the crystalline form; oil of vitriol is now added, in excess, to the residual dark-brown mother-liquor (iodine-lye), and the evolved gases are either kindled or allowed to escape by a flue; the liquid, after standing some time, is decanted or filtered, heated to about 140° Fahr., and mixed with as much binoxide of manganese as there was oil of vitriol employed; the whole is then introduced into a cylindrical leaden still, furnished with a very short head and connected with 2 or 3 large globular glass receivers, and heat is applied, when fumes of iodine are evolved and condensed in the receivers. During the distillation very great care is taken to watch the process, and prevent the neck of the still becoming choked with condensed iodine. For this purpose the head of the still is usually furnished with a movable stopper, by which the process may be watched,

and additions of manganese or sulphuric acid made, if required. To render the product pure, it should be pressed between blotting paper, and then resublimed in glass or stoneware.

2. A solution of sulphate of copper, 4 parts, and protosulphate of iron, 9 parts, are added to the mother-liquid of the soda-works, as long as a white precipitate is thrown down; this precipitate (iodide of copper) is collected, dried, and mixed with its own weight of finely powdered black oxide of manganese, and distilled by a strong heat in a retort, when dry iodine passes over. By the addition of sulphuric acid with the manganese, a less heat is required, but the product is wet with water, like that of the last formula.

3. The residual liquor of the manufacture of soap from kelp (or other iodine lye), of the sp. gr. of 1·374, is heated to 230° Fahr., with sulphuric acid diluted with half its weight of water, after which the liquor is allowed to cool, and is either decanted or filtered; to every 12 fl. oz. of the filtrate 1000 gr. of black oxide of manganese, in powder, are added; the mixture is put into a glass globe or matrass with a wide neck, over which is inverted another glass globe, and heat is applied by means of a charcoal chauffer, when iodine sublimes very copiously, and condenses in the upper vessel; as soon as the latter is warm, it is replaced by another, and the two globes are thus applied in succession, as long as violet fumes are evolved. The iodine is washed out of the globes with a little cold water. A thin disc of wood, having a hole