in use. Before weighing any of the above oxides, it it decidedly preferable to burn the filter after shaking off as much of the substance as possible into a platinum crucible; to add the ashes, and then subtract their weight from that of the oxide. -Frank. Jour.; Mech. Mag. NEW METHOD OF DETERMINING THE CARBON CONTAINED TAKE five grains of cast-iron, reduced to filings when the cast-iron is soft, or pulverized in a mortar when it is brittle; and mix it with sixty to eighty grains of chromate of lead, melted previously. Take away about a third or fourth of this mixture, and put it aside. To the remainder add five grains of chlorate of potass, which contain the quantity of oxygen required to change the iron into peroxide; afterwards introduce the threefold mixture into a tube of glass, similar to those for organic analyses, but which may be much shorter. Add to this the portion of the mixture of cast-iron and chromate of lead, which had been put aside. Lastly, adapt to the tube the common Liebig apparatus, for the analysis of organic substances. The portion of the tube containing the mixture without chlorate is heated; and when it is red hot, begin to heat that part which contains the chlorate, and the fire thus is advanced successively, in proportion as the disengagement of gas diminishes. The cast-iron at first burns completely by the oxygen of the chromate, and only a small quantity of this gas escapes through the tube. Afterwards, the temperature becoming higher, combustion is finished by the chromate of lead, which, in melting, oxidates the last portions of cast-iron. It is convenient to envelop the tube with a sheet of copper, because at the end it is necessary to heat it very strongly in order to obtain a complete fusion of the chromate. The oxidation of the cast-iron is complete, as you may assure yourself by grinding, after the combustion, the matter contained in the tube-not a particle of matter remaining which is attracted by the loadstone. The analysis is so easy that the whole proceeding is finished in less than half an hour. Of the perfect concordance of the results we may judge from the three following analyses, made on the same grey cast-iron obtained by the hot air process : 1. Five grains have produced 0.582 of carbonic acid. 2. Five ditto 3. Five ditto Carbon, therefore, 1st, 3.22; 2nd, 3'23; 3rd, 3.25. When the cast-iron contains sulphur, not a trace of sulphuric acid is disengaged, all the sulphur remaining in the tube in the state of sulphate of lead. With the chromate of lead alone not all the carbon is obtained; the chromate, by losing much oxygen, becomes less fusible, and the oxidation penetrates with difficulty to the centre of the grains of a somewhat thick cast-iron. - Annales de Chimie. TO ASSAY GOLD. TAKE 6 grains of the gold, and place it in a small crucible, with 15 grains of silver, and from 8 to 12 grains of chloride of silver, according to the supposed impurity of the gold; lastly, add 50 grains of common salt, (chloride of sodium,) reduced to a fine powder, so as to prevent decrepitation; fuse the whole together for five minutes, and allow it to become cold; then take out the metallic button, beat it into a thin plate, and subject it to the action of dilute nitric acid, as in the ordinary mode of parting. By this plan, the tedious process of cupellation is avoided, the lower metals being wholly removed by the chlorine of the chloride of silver, and their place supplied by pure silver.-Mr. L. Thompson; Philos. Mag. SEPARATION OF LIME AND MAGNESIA. M. DÖBEREINER observes: if anhydrous chloride of magnesium be heated in the air, it absorbs oxygen and gives off chlorine. This decomposition, i. e., the conversion of chloride of magnesium into magnesia, is more quick and complete when chlorate of potash is used instead of air as an oxidizing agent. This property renders the separation of lime and magnesia very easy. A mixture or compound of these two bodies, dolomite, for example, is to be dissolved in hydrochloric acid; evaporate the solution to dryness, and heat the residue in a platina capsule, till it ceases to yield hydrochloric acid, when add gradually to the mass heated to low redness, small portions of chlorate of potash, till the disengagement of chlorine ceases. The residual mass will then be a mixture of magnesia, chloride of calcium, and chloride of potassium, which may be readily separated by treating the mixture with water, which dissolves the chloride of potassium and of calcium, while the magnesia is left; from the mixture of chloride of potassium and of calcium the lime is precipitated by carbonate of soda. Journal de Pharm.; Philos. Mag. Or, dissolve the combined earths in dilute nitric or muriatic acid, and precipitate the filtered solution by an excess of carbonate of soda; dry the precipitate, and place it in a coated green glass tube, so disposed that the whole can be heated to a dull red heat; when red, pass a current of well-washed chlorine through the tube for a few minutes: the lime will be converted into chloride of calcium, but the magnesia remain unacted upon. When the whole is cool, remove the mass from the tube, and boil it for a minute or two in water, filter the liquid, and wash the insoluble portion, (which is magnesia,) with water, and precipitate the lime from the mixed liquor by carbonate of soda. The heat should not exceed a dull red; else the mass may become vitrified at the part which touches the tube. - Mr. L. Lewis ; Philos. Mag.. MANUFACTURE OF SODA. PROF. GRAHAM has observed that, in the history of the useful application of Chemical Science to the Arts, the past year will be memorable for various improvements connected with the Soda Process. Sulphuric acid, which is the key to so many important chemical products, had been chiefly prepared from the sulphur of Sicily; the supply of which was suddenly much reduced by some fiscal regulations of the Sicilian government. This has led to the invention of several new processes for soda, which possess considerable merit as chemical discoveries. The most interesting is that of M. Gosage, in the neighbourhood of Birmingham, for the recovery of the sulphur from soda-water; which promise not only a great saving of material, but a benefit of another kind, in abating, or entirely removing the nuisance of the escape of muriatic acid into the atmosphere in the ordinary soda process.-Proceedings of the British Association. NEW SAFETY LAMP. THE BARON EUGENE DU MESNIL has given to the British Association a description of a safety-lamp, invented by him in 1834. He stated that he had presented it to the French government in 1837, and that it had been now adopted, after a favourable report upon it by M. Ch. Combes. This lamp consists of a body of flint glass, defended by a dozen of iron bars. The air is admitted by two conical tubes, inserted at the bottom, which are capped with wire gauze, and enter by the side of the flame. The latter rises into a chimney, which has a piece of metal placed in the form of an arch over its top; the chimney, however, being quite open. The consequence of this construction is, that a strong current is constantly passing up the chimney. When carburetted hydrogen passes in, the fact is discovered by numerous small explosions, and the whole glass work is thrown into vibrations, which emit a loud and shrill sound, which may be heard at a very considerable distance. Prof. Graham stated, that the novelty in Baron du Mesnil's lamp was the circumstance of the chimney being quite open. He considered that the lamp of Davy was left almost perfect by that philosopher, and that all accidents proceeded from carelessness. He alluded to the deleterious effects of the after-damp, or carbonic acid left in the atmosphere of a mine after an explosion, which is believed to occasion often greater loss of life among the miners than the original explosion, and often prevented assistance being rendered in case of accidents. In many cases, it was certain that the oxygen of the air was not exhausted by the explosion, although, from the presence of 5 or 10 per cent. of carbonic acid, it was rendered irrespirable. The atmosphere might, therefore, be rendered respirable by withdrawing this carbonic acid, and he suggested a method by which this might be effected. He had found that a mixture of dry slaked lime and pounded Glauber's salts, in equal proportions, has a singular avidity for carbonic acid, and that air might be purified completely from that deleterious gas, by inhaling it through a cushion of not more than an inch in thickness, filled with that mixture, which could be done without difficulty. He suggested the use of an article of this kind by persons who descended into a mine to afford assistance to the sufferers, after an explosion: indeed, wherever the safety-lamp was necessary, and the occurrence of an explosion possible, the possession of this lime-filter would be an additional source of security.-Proceedings of the British Association. IMPROVED MANUFACTURE OF PRUSSIAN BLUE. THE Gold Isis Medal was last year awarded by the Society of Arts to Mr. Lewis Thompson, of Lambeth, for the following improved mode of manufacturing Prussian blue; extracted from the last publication of the Society's Transactions: "In the usual mode of manufacturing Prussian blue, the requisite carbon and nitrogen are obtained by decomposing animal matter in contact with potash. In this process the potash, being reduced to the metallic state, causes the formation of cyanogen, in consequence of its affinity for that substance. The quantity of nitrogen furnished by a given weight of animal matter is not large, and, in the material employed by manufacturers, seldom perhaps exceeds 8 per cent.; and of this small quantity at least one half appears to be dissipated during the process, thus producing an enormous waste of material, and at the same time increasing the size of the apparatus. Mr. Thompson conceiving that the atmosphere might be made to supply, in a very economical manner, the requisite nitrogen, if allowed to act on a mixture of carbon and potash under favourable circumstances; the experiment proved correct; for the carbonaceous matter employed may be worked over again many times, and is even improved by each operation. To produce Prussian blue: Take of potash or pearlash, 2 parts; 2 parts; 1 part. Grind the whole together into a coarse powder, and place it in an open crucible or other convenient vessel, and expose the whole for half an hour in an open fire to a full red heat, stirring the mass occasionally. During the process, little jets of purple flame will be observed to arise from the surface of the mixture; when these have almost ceased to appear, which will happen in about the time specified, the whole must be removed from the fire, and allowed to cool; water is now to be added, so as to dissolve the matter soluble in that fluid, and the black matter remaining put aside for another operation. The solution, after being filtered, is to be mixed with one part of copperas, and muriatic acid added in the usual way to brighten the colour of the precipitate. The quantity of Prussian blue produced from a given weight of pearlash or potash is generally about one-fourth of the weight of the pure potash contained in the salt; but the larger the quantity operated upon at one time, the larger is the relative produce. Thus six ounces of pearlash, containing 45 per cent. of alkali, yielded only 295 grains of Prussian blue, whilst one pound of the same pearlash yielded 1355 grains. The Prussian blue here spoken of is the pure perferrocyanate of iron. "In this process the potash is decomposed by the iron, producing potassium, which, being volatile, rises and combines with the carbon of the coke and with the nitrogen of the atmosphere, the oxygen of which has been removed by passing through the fire, or by the coke or cinders. In the mixture, the cyanide of potassium thus formed is next dissolved in water, and furnishes ferrocyanite of iron on the addition of sulphate of iron, and muriatic acid." WHITE PRUSSIATE OF IRON. Mr. R. PHILLIPS, in a series of valuable experiments, has proved the so-called White Prussiate of Iron to be really a combination of ferrocyanide of potassium, with cyanide of iron, or Prussian blue; and that this, by the action of water, becomes resolved into these two salts, of which the ferrocyanide of potassium, being soluble in water, is removed by washing; and the residual cyanide of iron, or Prussian blue, presents the ordinary tint of that beautiful pigment. - Proc. Brit. Assoc.; Literary Gazette. NEW ACID AND COMPOUND. Mr. L. PLAYFAIR has described to the British Association the true constitution of Chlorochromic Acid, and methods of procuring others of a similar class; together with a new compound called Iodosulphuric Acid. The latter may be obtained by mixing two atomic proportions of iodine with one equivalent of sulphate of lead, and subjecting the mixture to distillation; or, by a more easy method, by sending a stream of pure sulphurous acid through a solution of iodine in pyroxilic spirit to complete saturation. It may be procured from this by distillation, drying over sulphuric acid, &c. It has a powerful acid taste, and acts violently on the cuticle, being analogous in composition with the chlorosulphuric acid of Regnault.-Literary Gazette. VERATRIC ACID. PROF. SCHRÖTTER has obtained a new and peculiar acid, by treating the seeds of Cevadilla, in the manner directed by Couerbe, with alcohol and sulphuric acid, for preparing veratria: add hydrate of lime to the alcoholic tincture, and distil the alcohol from the filtered liquor. The water liquor remaining with the residue on the separated veratria will separated then contain the new acid in combination with lime, and it will be requisite only to supersaturate it with sulphuric acid to separate the veratric acid, which, if the liquor be sufficiently concentrated, will crystallize in a few hours. The crystals are completely purified by washing them repeatedly with cold water, dissolving them in boiling alcohol, and treating them with purified animal charcoal. The property of subliming is the only one which this new acid has in common with that which MM. Pelletier and Caventou found in the seeds of Cevadilla, and which ought not, therefore, to be confounded with the acid discovered by Schrötter. - Journal de Pharm.; Philosophical Magazine. CONVERSION OF CHLORATES. On Jan. 24, was read to the Royal Society, a paper "On the Conversion of the Chlorates," &c., by Mr. Penny. This communication is insusceptible of analysis: we can only present one or two of the author's results. After mentioning the steps by which Mr. Penny found his equivalents, he gives an account of many experiments with oxygen, nitrate of potassa, nitrogen, chlorate of soda, nitrate of soda, and other substances: he points out the discrepancies which exist between Thomson, Turner, and himself, which appear to be in some instances considerable. The experiment by which he effected the conversion of silver into chlorate, presented, for 100 parts of the former, 157-441 of the latter; and 100 parts of nitrate presented 84-374 of chlorate. Oxygen is the only substance on the equivalents of which chemists are agreed.- Literary Gazette. |