« PreviousContinue »
acids; and it must be remembered that what is dull white in silver, appears gray in platinum. If each commencement of this loosening is again destroyed, the crucibles will be preserved unaltered, otherwise they must gradually become brittle. Crucibles of the alloy of platinum and iridium are altered like those of platinum when they are ignited; it is, however, somewhat more difficult to reproduce the original polish of the metal, by means of sand, as might be expected from the greater hardness of the alloy. The sand used should be well worn; when examined under the microscope, no grain of it should exhibit sharp edges or corners, all the angles should be obtuse.-Journ, für praktische Chemie, March, 1860, lxxix, 117. 2. Safe and easy method of rectifying Sulphuric Acid ; ; by N. NEESE of Kiev.–“The rectification of sulphuric acid offers an example of how readily even the most practical matters may fall into oblivion in spite of the copiousness and the vigilance of our literature. Fifteen years ago, Prof. Siller, at that time filling the chair of Pharmacy at Dorpat, called my attention to an exceedingly ingenious device for rectifying sulphuric acid, which he had read in some journal. The retort in which the rectification of the acid is to be conducted, should be placed upon a bed of ashes about an inch in thickness, and sand then heaped up all around it; the distillation may then be proceeded with, without any further precautions. By this method I have twice rectified sulphuric acid, operating with a very bad retort, upon portions of 15 lbs weight; and have been astonished at the facility and tranquillity with which the distillation proceeded. The ashes evidently act as a non-conductor, so that the acid can boil only from the sides of the retort. Since then, manifold expedients have been proposed, all depending upon some peculiar apparatus, constructed for this particular purpose, but I have not yet met with any reference to the simple contrivance which has here been mentioned.”— From Archiv der Pharmacie, czly, 267; in polytechnisches Notizblatt, 1860, xv, 43. or [FREDERKING of Riga, (Archiv d. Pharm., Aug., 1859; in American Journal of Pharmacy, viii, 88,) corroborating the statement of Neese, states that he can recommend the process from his own experience,
* The author is evidently not aware that several devices almost as simple as the one which he describes have previously been proposed. Thus Otto, (in his Lehrbuch der Inorganischen Chemie, Braunschweig, 1855, i, 275,) directs that the retort be caused to rest upon an inverted crucible cover, which is placed upon a grate in an extemporaneous fireplace constructed of loose bricks, (figured in Otto.) so that the bottom of the retort may be less strongly heated than the upper portions by the charcoal fire which is built around it. Otto, however, considers it necessary to cover the retort with a thin coating of clay which has been mixed with a dilute solution of carbonate of soda or of borax, instead of water, so that it may adhere firmly to the retort when heated; urging that the danger of fracturing the latter is not only lessened thereby, but that a more rapid distillation is insured, since little or no condensation can occur within a retort thus protected. In Mohr, Redwood and Procter's Practical Pharmacy, Phila., 1849, p. 337, a somewhat similar proposal is made. A Hessian crucible being employed, however, instead of the cover used by Otto — moreover, the retort is not coated.
Possibly a more convenient method than either of the above would be to fill a sufficiently capacious crucible with ashes, or some other non-conducting substance-calcined gypsum, for instance,—as a bed upon which to rest the bottom of the retort. A charcoal fire similar to Otto's being then built around it. F. H. S.,
inasmuch as he has during the last twelve years, repeatedly rectified sulphuric acid in the manner indicated.—F. H. s. 3. Vulcanization of Caoutchouc, by means of mixed Sulphur and Hypochlorite of Lime.—GAULTIER DE CLAUBRY, having detected the presence of chlorid of calcium in many samples of vulcanized rubber, and suspecting that this salt might have been derived from hypochlorite of lime employed in some modification of Parkes' process of cold sulphuring, [English Patent of March 6, 1846. Repertory of Patent Inventions, (E.S.) ix,46,) to produce chlorid of sulphur in the rubber paste, was led to perform the following experiments: When flowers of sulphur and dry hypochlorite of lime, (bleaching powder) are shaken together, a very strong odor of chlorid of sulphur is immediately developed. If the mixture be somewhat forcibly rubbed in a mortar, elevation of temperature ensues, the sulphur softens and the mixture becomes solid while abundant vapors are evolved. When a much larger amount of sulphur than of the hypochlorite is used and friction is avoided when the two are blended, a mixture is obtained which being added to the caoutchouc paste—either with or without the addition of inert matters, such as chalk, oxyd of zinc, etc., serving to give “body” to the product—effects the vulcanization of the latter either at the ordinary temperature, or when gently heated. By this means, objects of any thickness can be uniformly vulcanized. - If instead of employing an excess of sulphur, an excess of the hypochlorite be introduced into the mixture, and this be agitated, so much heat will be developed that the vessel containing the mixture can no longer be held in the hands; if the flask be closed, the action becomes so violent that the cork will be blown out, or the flask broken by a violent explosion.—Comptes Rendus, May, 1860, l, 876. 4. Preparation of Cyanid of Barium, and of Ammonia with the Witrogen of the Air; by MARGUERITTE and DE SourDEVAL.-In a brief preliminary note, the authors claim :— That baryta when calcined in the presence of charcoal and of atmospheric air combines very readily with carbon and nitrogen, cyanid of barium being formed. That the cyanid of barium heated in a current of aqueous vapor is decomposed at a temperature of about 300° (C.) [572°F.] and disengages in the form of ammonia, all the nitrogen which it contains. Trials which they have made upon a tolerably large scale, have been eminently successful, leading them to hope that not only the various cyanids employed in the arts, but also ammonia and nitric acid may thus be economically produced.*—Comptes Rendus, June, 1860, l, 1100. 5. Gun-Cotton Filters; by Prof. BoETTGER.—Since gun-cotton—itself a product of the action of strong acids—when properly prepared is scarcely at all acted upon at the ordinary temperature, by chemicals, being capa
* To prepare baryta from its carbonate, M. and De S. ignite a mixture of the latter with the pitch (“asphaltum”) of coal tar. Each molecule of the carbonate being thus brought in contact with the reducing agent, carbon, excellent results are obtained, the decomposition of the carbonate being easy and the product of baryta abundant. From observing the odor of ammonia which was at times developed during their experiments upon this method of preparing baryta the authors were led to the important discoveries which are noticed in the text—Répertoire de Chimie appliq. June, 1860, ii, pp. 169, 170. - .
ble of withstanding the most corrosive agents; it affords a material for filtering strong acids, and the like, as well as liquids which would be decomposed by contact with the organic matter of ordinary filters, the excellence of which cannot be too highly extolled. Besides employing it for removing from strong nitric acid the chlorid of silver which is precipitated in the common method of purifying this acid by means of nitrate of silver, (as has recently been advised in the Berlin polytechnisches Intelligenz-Blatt, No. 4, p. 30); Boettger affirms that, he has for several years past, found it of special use in filtering off the slimy precipitate, containing selenium, which is gradually deposited, when fuming sulphuric acid is mixed with a little water; in separating crystallized chromic acid from the sulphuric acid of the mother liquor; and in filtering concentrated solutions of permanganate of potash, in order to separate suspended peroxyd of manganese. He has even found the gun-cotton well suited for filtering concentrated alkaline lyes, aqua-regia, and concentrated solutions of chlorid of zine, not to allude to many other instances. In using the cotton a small bit of it is pushed loosely, like a stopper, into the throat of a funnel. The materials which have heretofore been used for similar purposes, viz.: garnets, asbestos, powdered glass, &c., are very much inferior, as filters, to the loose, fibrous gun-cotton.—From polytechnisches Notizblatt, 1860, No. 7; in Dingler's polyt. Journal, clv, 463. 6. Preservation of Flesh ; by VERDEIL.—Having been separated from the bones, and, as far as possible, from fat, the flesh is cut into slices from one to five centimetres, (one centimetre =0-3937 inch,) in thickness; the slices being cut as nearly as possible across the grain of the flesh. These are now laid upon hurdles of basket-work, which are subsequently placed in a chamber. As soon as a sufficient number of the trays have been introduced into the chamber, it is closed, and steam under a pressure of three or four atmospheres, consequently of 135° to 145° C. [=275° to 293°F.] is admitted through several openings. The chamber, which may be of lead or iron, must not be absolutely tight, a small outlet for the steam being necessary, in order that the pressure may not become too great. After from six to ten or fifteen minutes, according to the kind of flesh and the thickness of the slices, the steam is shut off, this part of the process being finished. The flesh is now very nearly in the condition of boiled meat, but has retained all of its ingredients, the albumen having been coagulated: its taste recalling that of roasted meat. It presents a wrinkled appearance, is of a gray color, and may be readily divided. Being removed from the steam chamber the flesh is now placed upon trays, or hung upon hooks, in another chamber which is warmed, but in which the temperature is never allowed to exceed 40° or 50° C. [=104° to 122 F.]. The drying process is completed in the course of eight or twelve hours. Packed in tight casks or in tin boxes, so that it may be protected from the action of moisture, and from insects, the flesh thus prepared may be preserved for any length of time which may be desirable. It is never. theless well to place a layer of salt in the casks, in order that it shall absorb any moisture which the flesh may have retained. Before using this meat it must be soaked for an hour or two in warm water in which it softens and regains its original condition. When boiled with water it affords an excellent soup, and passes into a condition, in which it cannot be distinguished from fresh meat.—From Le Génie Industriel; in BoETTGER's polytechnisches Notizblatt, 1860, xv, 71. 7. Magnesium as a Source of Light.—Prof. A. SCHMITT calls attention to the practicability of employing metallic magnesium for purposes of illumination, as had already been suggested by Bunsen. From the researches of the last named chemist, it is known that when magnesium is ignited it readily takes fire and burns with an exceedingly brilliant flame. The intensity of the light thus produced, as determined by Bunsen and Roscoe in one of their photo-chemical researches (Pogg. Annalen, cviii, 261, et seq.) is only some 525 times less than that of the sun. Compared with an ordinary candle, it appeared that a wire of magnesium 0.297 millimetre [1 mm. =0.0394 inch] in diameter, produced as much light in burning as 74 stearine candles, five to the pound. In order to support this light during one minute, a piece of wire 0.987 metres long, weighing 0-1204 gram [l grim. = 15:4325 grains], was required. Only 72.2 grams of magnesium, therefore, would be needed, in order to maintain during ten hours an amount of light equal to that of 74 stearine candles, consuming about 10:000 grams of stearine. According to Bunsen, magnesium wire is readily obtained, by forcibly pressing the metal through a hot steel die by means of a steel piston. Bunsen's arrangement for burning the wire was made, by connecting spools of it with rollers moved by clock-work so that the wire should be unrolled like the ribbon of paper in Morse's telegraph, the end of the wire thus gradually pushed forward, passed into the flame of an ordinary alcohol lamp, where it took fire. It is evident that a magnesium lamp of this sort must be much simpler and more compendious than any of the existing arrangements of the electrical, or of Drummond's light; for light-houses, &c.; where an intensely brilliant illumination is required it can hardly fail to rival either of these. Where an extraordinary amount of light is needed, it could readily be produced by burning large wires, or several thin ones at the same time. Another important consideration is the fact that the spools of wire, as well as the clock-work and spirit lamp, are easily transportable. It is not, however, to the intensity alone of the magnesium flame that these lamps owe their utility, for the photochemical, (i. e., photographical) effect of the light is also very great. According to Bunsen, the photochemical power of the sun being only 36-6 times greater than that of the magnesium flame. The latter must therefore be useful in photographing by night or in any dark or subterranean locality; the evenness and remarkable tranquillity of the flame, especially commending it for this purpose. The present high price of magnesium, it is true, must prevent any extended use of it for technical purposes. For example, Lenoir of Vienna charges 3 Florins, [l Fl. =51 cts.] for a gram of it, hence the cost per minute of the light just described, would be 36 Weukreutzer, El ktr.— about 3 of a ct...] and the cost during ten hours, would amount to 216 Florins, while the ten kilogrammes of stearine could be procured for less than 14 Florins. But even at this price, it could still be used by photographers, since it would only be required for exceedingly short intervals of time, and all unnecessary consumption of the wire might be prevented by stopping the clock-work—From Stamm's Illustr. Zeitschrift, 1859, p. 332; in polytechnisches Notizblatt, 1860, xv, 56. #. 8. Method of employing carbonic acid in connection with the hypochloorite of lime used for bleaching paper-stock—An apparatus devised by FIRMIN DIDOT and BARRUEL of Paris, for introducing carbonic acid, prepared by burning charcoal, into the solution of hypochlorite of lime, (bleaching salt.) while the latter is in contact with the fibre which is to be bleached, is described in the Nov., (1859,) No. of Barreswil's Répertoire de Chimie, Appliquée, vol. i. p. 457. The carbonic acid on being introduced into the solution of bleaching salt, unites with the lime, thus setting free hypochlorous acid, the decolorizing action of which is infinitely more energetic when it is at liberty than when in combination with a base. This process, says Barreswil, is of extreme simplicity, and one is at a loss to 'comprehend why it had not been sooner invented, in view of the fact that each and all of its phases have been so long and so well known. In order to judge of the practicability of the new process—in so far as concerns difference of price, strength, and whiteness of the paper, and the duration of the operations in the two systems, (new and old,) of bleaching—comparative experiments were instituted, by the Messrs. Firmin Didot, upon carefully assorted rags. The cost of the chemicals and labor, and the amount of time required, having been exactly noted. After bleaching, the pulp was converted into paper. The different papers were then carefully tested. As the result of these experiments, it appeared that the new process was more energetic and more rapid than the old method, au chlore, chlorure ?] liquide, [with solution of bleaching salt, and that in many cases it is also equally energetic with the process in which chlorine gas is employed. Over the latter it has the advantage of not destroying to so great an extent, the fibre of the pulp. Since the details of the process, which for that matter consists merely of arrangements for thoroughly washing and cleansing the carbonic acid employed—the latter being then introduced into the bleaching vats, just as if it were steam, through coils of pipe pierced with holes, which are placed at the bottom of the vats, cannot well be explained without a diagram, we must refer the reader who may desire these to the original article, in which the apparatus is figured. F. H. S.
9. New “fusible metal.”—Dr. B. Wood of Nashville, Tenn., has secured a patent (Weekly Scientific Artizan, Cincinnati, May 5th, 1860,) for an alloy composed of cadmium, tin, lead and bismuth, which fuses at a temperature between 150° and 160°F. The constituents of this fusible metal may be varied according to the other desired qualities of the alloy— viz.: cadmium one to two parts; bismuth seven to eight parts; tin two parts; lead four parts. It is recommended as being especially adapted for all light castings requiring a more fusible material than Rose's or Newton's “fusible metal,” it having the advantage of fusing at more than 40°F. lower temperature than these alloys, and owing to this property may replace many castings heretofore made only with amalgams. Its fusing point may be lowered to any extent by the addition of mercury, which