The following is Bucholz’s analysis of ipecacuanha root:—
| Emetic extractive (emetina) | 4·13 |
| Soft resin | 2·43 |
| Wax | 0·75 |
| Gum | 25·17 |
| Starch | 9·00 |
| Woody fibre | 10·80 |
| Bitter extractive | 10·12 |
| Sugar | 2·00 |
| Extractive, gum and starch extracted by potash | 34·80 |
| Loss | 0·80 |
| ——— | |
| 100·00 |
The annexed process for the determination of the emetina in ipecacuanha is by Zenoffsky:—Take 15 grammes of the root, mix with 15 drops of dilute sulphuric acid, and so much of 85 per cent. alcohol that the volume shall be 155 c.c. Digest 24 hours, filter, measure 100 c.c. of the filtrate, evaporate the alcohol, and add a deci-normal solution of iodo-hydrargyrate of potassium until no more reaction takes place. The number of c.c. of the reagent used multiplied by 0·0189 (1⁄10000th of an equivalent of emetine) gives the amount of emetine in the 10 grammes of root to which the 100 c.c. of liquid corresponds. The deci-normal solution of iodo-hydrargyrate of potassium is made by dissolving 13·546 grammes of mercuric chloride and 49·8 grammes of potassium iodide in water, and making up to 1 litre.
Quantitative determination showed that one c.c. of such a solution corresponds to 0·0189 gramme of emetine. To perform the volumetric estimation, the standard solution is added to the liquid containing the alkaloid, until no more turbidity is produced. To determine the end of the reaction, filter a few drops on to a watch-glass (placed on black glazed paper) and touch with a glass rod previously moistened with the standard solution. To prevent loss both filter and filtrate should be returned to the liquor.
IRID′IUM. Ir. A rare metal discovered by Descotils in 1803, and by Tennant in 1804, in the black powder left in dissolving crude platinum. This powder is an alloy of iridium with osmium. The metal is also found native and nearly pure amongst the Uralian platinum ores.
Prep. The native alloy of iridium and osmium remaining after dissolving crude platinum in aqua regia is reduced to powder, mixed with an equal weight of dry chloride of sodium, and heated to redness in a glass tube, through which a stream of moist chloride gas is transmitted. The further extremity of the tube is connected with a receiver containing liquor of ammonia. Chloride of iridium and chloride of osmium are produced; the former remains in combination with the chloride of sodium; the latter, being volatile, is carried forward into the receiver, where it is decomposed into osmic and hydrochloric acids, which combine with the ammonia. The contents of the tube, when cold, are treated with water to dissolve out the double chloride of iridium and sodium; the solution thus formed is mixed with an excess of carbonate of sodium, and evaporated to dryness. The residue is ignited in a crucible, boiled with water, and dried; it then consists of a mixture of sesquioxide of iron and a combination of oxide of iridium with sodium hydrate. It is reduced by hydrogen at a high temperature, and treated successively with water and strong hydrochloric acid, which remove the alkali and the iron, leaving
metallic iridium in a divided state. By strong pressure and exposure to a welding heat, a certain degree of compactness may be given to the product.
Prop., &c. Brittle, white, very hard, only fusible by the strongest heat of Deville’s gas furnace. In its pure state it is not acted upon by any of the acids, but it is oxidised by fusion and nitre, and by ignition to redness in the air. An ingot of iridium, weighing 273⁄4 oz., melted by Deville’s process, was displayed in Messrs Johnson and Matthey’s case at the International Exhibition of 1862. An alloy of iridium and osmium (artificial or native) has been employed for tipping the nibs of gold pens (everlasting pens).
Iridium, Chlo′rides of. Dichloride. IrCl2. An olive-green powder formed by transmitting chlorine over powdered iridium, heated to a dull red, or by digesting the hydrated protoxide in hydrochloric acid. Sesquichloride, Ir2Cl6, obtained by calcining iridium with nitrate of potassium, digesting in nitric acid, washing with water, and solution in hydrochloric acid. Tetrachloride, IrCl4, obtained in solution by adding hydrofluosilicic acid to the tetrachloride of iridium and potassium (formed when chloride is passed over a heated mixture of iridium and chloride of potassium). Hexachloride, IrCl6, obtained in combination with potassium by heating iridium with nitrate of potassium, dissolving in aqua regia, and evaporating to dryness.
Iridium, Ox′ides of. Monoxide, IrO, prepared by adding potassium hydrate to the hexachloride of iridium, and digesting the precipitate in an acid. It is a heavy black powder, insoluble in acid. Sesquioxide, Ir2O3, is best prepared by fusing in a silver crucible a mixture of carbonate of potassium and the double chloride of iridium and potassium, and boiling the product in water. Bluish-black TRIOXIDE, IrO3, is produced when carbonate of potassium is gently heated with hexachloride of iridium. A greyish-yellow hydrate, containing alkali.