of recovering the metallic zinc so as to be re-employed in a continuous process, has been again brought into operation at Tarnowitz, in Silesia. The argentiferous zinc crust is now allowed to cool in an iron basin, then placed in the liquating furnace, where, by gentle heating, with full access of air, it is deprived of the greater part of its lead. By this means the zinc is thoroughly oxidized and converted into the so-called zinc dust, which is then distilled between layers of powdered coke, with the production of metallic zinc, free from silver, on the one hand, together with a residue containing the whole of the silver, along with any lead remaining in the zinc dust. -18 A, April 9, 1875, 89.

ON THE FUSIBILITY, ETC., OF ALLOYS OF SILVER AND

COPPER.

Mr. Roberts, chemist to the English Mint, has communicated to the Royal Society the result of a detailed elaborate investigation into the liquidation, fusibility, and density of certain alloys of silver and copper. The melting-point of the several alloys experimented upon by him varied from 840° Centigrade to 1330° Centigrade, the most fusible alloys being those that contain from sixty to seventy per cent. of silver; and the fusibilities vary very much as to the electric conductivities. The density of pure silver, when fluid, is 9.46; its density when solid is 10.57. This alloy, therefore, on becoming fluid, expands at nearly double the rate that it expands when at ordinary temperatures. Mr. Roberts has also succeeded in obtaining excellent results in the electrodeposition of iron, for which purpose he employs a solution of the double sulphate of iron and magnesia. The iron thus obtained possesses a higher electric conductivity than any commercial iron, and occludes thirteen times its volume of hydrogen. The tube of the metal, which was a vacuum tried at the ordinary temperature, allowed hydrogen to pass through it freely at a dull red heat.

A NEW TEST FOR GOLD,

M. Sergius Kern, of St. Petersburg, in studying the behavior of certain double salts of gold, made the observation that the sulpho-cyanide of potassium was a most sensitive reagent of this metal, which, as experiment proved, would

indicate the presence of less than the 0.001 of a gramme of gold. He proposes the following procedure: The gold of the sample under analysis is first separated in the usual manner from foreign metals, and next converted by means of sodium chloride into sodio-gold chloride (NaAuCI); the solution is then concentrated by evaporation. In order to detect the presence of gold, an aqueous solution of potassium sulpho-cyanide (KCyS) is employed, which should contain, for one part of the salt, about fifteen to twenty parts of wa ter. About six grammes of this solution are poured into a test-tube, and some drops of the suspected gold solution, treated in the manner above described, are added. If gold is present, a red-orange turbidity is at once obtained, which soon falls in the form of a precipitate. On gently heating the contents of the test-tube, the precipitate dissolves, and the solution becomes colorless. This reaction is said to be so delicate that one drop of a solution of the sodio-gold chloride (one gramme of the salt in forty grammes of water) affords a decided reaction. The reaction indicates, according to the observer, the formation of a double sulpho-cyanide. —1 4, XXXII., 171.

PURE PLATINUM AND IRIDIUM.

Deville and Debray, obtaining pure platinum and iridium in quantity, have found for these metals rather higher densi ties than are commonly ascribed to them. The platinum has a specific gravity of 21.5, while that of iridium is 22.421. An alloy containing eighty-five per cent. of platinum to fifteen of iridium, with density 21.618, was found to be very ductile and malleable, and yet quite rigid. Probably it would be useful in the arts. An alloy containing only 66.67 per cent. of platinum, on the other hand, was not malleable.-Supplement to 7 A, December, 1875.

OSMIUM.

According to Deville and Debray, osmium is the heaviest substance known, having a specific gravity of 22.477. They have prepared the metal in a crystalline form by passing the vapor of osmic acid over red-hot charcoal. The crystals ap parently belong to the first or regular system, and are hard enough to scratch glass. The color is grayish-blue, becom

ing even violet when the light is reflected several times upon the surface of the metal.-6 B, May 8, 1876.

CONVERSION OF BRUCINE INTO STRYCHNINE.

Sonnenschein has shown that brucine may be converted into strychnine by the action of nitric acid, and calls attention to the fact that this discovery may be of practical interest in toxicological investigations, since brucine might be converted into strychnine in course of the examination.— 35 C, 1875, IV., 212.

OLEANDRINE.

It has long been known that oleander leaves contain an active poison, which was first examined by Lukowski in 1861. This body, oleandrine, has lately been reinvestigated by Bettelli, who obtained it in an imperfectly crystalline condition. It is pale yellow, soluble in water, alcohol, ether, chloroform, fusel-oil, and olive-oil. At 56° C. it softens, becomes a greenish liquid at about 70°, and at 170° it undergoes partial decomposition. Bettelli also succeeded in forming the chlorhydrate of the alkaloid.-35 C, September 27.

BISULPHIDE oF CARBON AS AN ANTISEPTIC.

Hugo Schiff calls attention to the remarkable antiseptic properties of carbon disulphide. A dissected frog, which had served for physiological experiments, was sealed up in a glass vessel, with a few cubic centimeters of the antiseptic, as long ago as 1869; the specimen as yet shows no trace of putrefaction. A similar trial with the entrails of poultry, and another with a small lizard, have resulted likewise. Two hundred grammes of beef, treated with bisulphide, remained for months unaltered; and then, after cooking, was readily eaten by a dog.-35 C, IX., 828.

MANUFACTURE OF CARBOLIC ACID.

The following process for separating carbolic acid from the cresylic and other liquid tar acids was recently patented by Lowe and Gill in England. The partially or wholly hydrated mixtures of tar acids are submitted for a sufficiently prolonged time to a temperature varying between 15° and 56° Fahr. The carbolic acid crystals thus formed are sepa

rated from the mother liquors containing the liquid tar acid and a residue of carbolic acid dissolved in them. Complete purification of the carbolic-acid crystals thus obtained is effected by recrystallization, either by partial fusion or solution in water, with subsequent refrigeration. Carbolic acid of high degrees of purity is obtained by dehydrating these carbolic-acid crystals.-Practical Magazine, Dec., 1874, 437.

DETECTING ADULTERATIONS IN COFFEE.

Wittstein, in a paper published in "Dingler's Polytechnic Journal," gives a detailed method for testing coffee, which is treated in a great variety of ways for the purpose of impart ing greater strength or weight, a better color, or some other desired quality. He remarks that roasting, and still more grinding, coffee renders it almost impossible to apply the necessary tests. The principal vegetable substances used in adulterating coffee are chicory, beet-root, carrot, figs, corn, malt, etc. A simple method of testing coffee for a mixture of chicory is to shake it with water; if pure it remains floating for an hour together, whereas chicory sinks. An infusion of burned chicory, diluted with much water and treated with potassium bichromate, undergoes no visible change; but coffee assumes a deep brown tint, causing a resemblance to porter. This is only observed, however, where the substance is either entirely coffee or entirely chicory. To detect a mixture of the two, the decoction is diluted with eight times its bulk of water, filtered, and the dilution increased to twelve parts. If the decoction contains pure coffee, on adding to thirty drops of it two drops of concentrated hydrochloric acid, boiling for a few seconds, then adding fifteen drops of a solution of one part of potassium ferrocyanide in eight parts of water, and boiling as before, the solution becomes first green, then dark green. Six drops of potash are next added, and the whole is boiled for two minutes, the solution becoming first brown and then clear pale yellow, with a slight dirty-yellow precipitate. With chicory alone, the solution. finally remains brown and turbid, and after long standing a precipitate falls, the supernatant fluid retaining its brown color. With a mixture of twenty-four drops of coffee and six of the chicory decoction, a final brown turbid solution is obtained. A decoction of coffee of average strength contains.

one per cent., and of great strength barely two per cent., of the dry soluble matter. The evaporation residue consists of a deep brown, shining, varnish-like mass, feeling quite dry to the touch after two days. If the ordinary substitutes are present, however, this residue becomes sticky after one or two hours' standing, and quite damp in twenty-fourhours.

ON THE GASES INCLOSED IN COAL.

An examination of the gaseous substances contained in coal, and also of the gases which are evolved from fissures in coal-mines, has been made by Thomas. The coals which he examined were of three sorts: the bituminous or house coals, the semi-bituminous or steam coals, and the anthracite coals. The samples examined all came from the South Wales coalbasin. In obtaining the gas from the coal, slices were first sawn from the middle of large cubical blocks, and a strip cut from the centre of each of these six or eight inches long, and five eighths of an inch square. This was then placed in a hard glass tube, connected with a mercury pump, and exhausted. Very little gas, however, was obtained in this wayonly two or three cubic centimeters in 100 grammes of coal. On placing the tube in boiling water, the exhaustion being continued, gas was freely evolved. When it ceased, the temperature was raised to 200° and even 300° Centigrade, whereby additional quantities of gas were obtained. On analyzing the gas, it was found to be composed of marsh gas, carbon dioxide, nitrogen, and oxygen. The bituminous coals give the minimum amount of gas, but the quantity of carbon dioxide contained in it is large. Steam coals come next, as much as eighty-seven per cent. of the gas obtained from them being methyl hydride, or marsh gas. Anthracite coals give more gas than the others, one specimen giving 600 cubic centimeters of gas from 100 grammes of coal when heated to 100°. But at 200°, 1000 c. c. were given off, and at 300°, 1875 c. c. In composition, the gas from anthracite closely resembles that from steam coal. The examination of the gas collected from fissures in the mine, as well as that obtained by boring the blocks of coal, was almost pure marsh gas, the amount present rising sometimes even to 97.65 per cent.-21 A, II., xiii., September, 1875.