if a Bunsen cell was employed, in which the carbon element was of a porous character, (such, for example, as the common imported form manufactured by Deleuil,) the mercury salt might be dispensed with, and the battery (charged with a solution of glaubersalt only) would give for several hours a constant current, quite sufficient to operate a medical coil with all the energy desirable. In this case not only is all inconvenience from acids and fumes avoided, but we also get rid of the poisonous and expensive mercury salt, using one harmless and cheap in the extreme, (5 cents per pound.) The necessity of using porous carbon, arises from the fact that hydrogen is liberated in the action of the battery, which would collect on the surface of a dense carbon, so directly impairing the efficiency of the couple, or by occasioning a deposit of metallic zinc in its place, (after that substance had been dissolved in the fluid,) attaining the same end quite as effectually. The porous carbon, however, absorbs this hydrogen to a wonderful extent under these conditions, as has been proved by Daniell, Grove, and others, and thus keeps the couple in efficient action for some hours. The oxide of zinc formed, is dissolved by the solution of sulphate of soda, which has this power when in galvanic connexion, as was shown by Millon in 1645. See his paper, Comptes Rendus, T. 21, page 37. We see, therefore, that a battery thoroughly efficient for medical purposes may be prepared by placing a cylinder of porous gas-coke within one of zinc, (which should come as near as convenient to it without touching,) and immersing both in a solution of glaubersalt. (A battery of this sort was here exhibited.) We have also to show you another modification of this widely used Bunsen battery, from the same source as the preceding, i.e., Chester & Co., of New York. The change here consists in the substitution of a solution of chromic acid, for the nitric acid usually employed in the above apparatus. This solution is sold under the name of electropoion fluid, and may be prepared by dissolving 5 ozs. of bichromate of potash in half a gallon of water, and adding to this 6 ozs, by measure, of oil of vitriol. In this case, part of the sulphuric acid combines with potash, setting free the chromic acid, which remains in solution. As hydrogen, is liberated in the working of the battery, it takes oxygen from the chromic acid, forming water, and reducing the chromium to the condition of a sesquioxide, which is then taken up by another part of the sulphuric acid, and we have at last a solution of chrome alum or double sulphate of chromium and potassium. We have found by experiment that this fluid works well in a battery which is not called upon for a large and continuous supply of force. Thus with the Ruhmkorff coil, where the contact is being continually made and broken, it gives results little if at all inferior to those obtained with the usual arrangement employing nitric acid. For the electric light, where there is a great resistance interposed, which materially cuts down the quantity, its working is very good; but where a full connexion of the circuit is maintained, as in electro-magnetic experiments, it runs down rapidly while in contact, recovering, however, when the circuit is opened for a few minutes. The reason of this is obvious. The solution of chromic oxide, formed around the carbon by the action of the battery, is not decidedly different in density from the rest of the liquid; it is therefore sluggish in giving place to fresh liquid which is required to continue the action. Time must therefore be given for this circulation, or if this is denied, the force will rapidly decrease by the accumulation of this inactive material where an energetic one is demanded. For this reason it is that "carbons" of a porous character and large surface are desirable in this battery, the French giving better results than the harder (and otherwise much more desirable ones) manufactured in this country. For the same reason this solution will not act well in a Grove's battery, unless some mechanical means is employed to keep it in constant circulation. Such a battery, stirred by blowing air into it, was introduced some time since in France, but on the large scale cannot be conveniently applied. Chemistry. A new process for plating glass mirrors has lately been introduced by a M. Dode. Neutral chloride of platinum is dissolved in water, and oil of lavender is added, by which the platinum is separated in a state of fine division. Litharge and borate of lead are then added, and the mixture is painted over the surface of the glass, which is then heated to redness in an appropriate furnace. If this plan is practically successful, it would afford a material capable of useful applications in some optical instruments, where the double reflection incident to a glass plate "silvered" at the back is injurious; such, for example, as the kaleidoscope for the magic lantern, in which, otherwise, mirrors of the expensive and troublesome speculum metal must be employed. M. de Chaubry presented to the Academy of Sciences, March 27, a note, describing a new solvent for aniline colors. This is simply a decoction of common soap-bark, (quilläia saponaria,) or the Egyptian soap-root, (Gypsophila strutium.) Among the advantages of this menstruum enumerated is the equality in tone obtained with mixed colors, which, in the ordinary solutions of mingled alcohol and water, changes as the proportions of these ingredients change, through the evaporation necessarily attending their treatment in use. A paper on the utilization of brine from salted meat by application of dyalisis was read before the London Chemical Society by William Marcet, M.D., and will be found in the journal of that institution, Dec., 1864, page 405. From experiments made by this author it appears that the material obtained by the above means is very poor in nutritious matter, wanting the crystalloid constituents of flesh, such as phosphates, lactates, kreatine, and kreatinine. This fact should be remembered in connexion with the statements contained in papers quoted in this Journal, vol. xlviii, pages 22 and 143. A new material is manufactured under the name of Linoleum, which is stated to possess many of the valuable qualities of india rubber. It is prepared by oxydizing linseed oil and then combining it with resins, &c. It is said to admit of vulcanizing. An excellent and cheap ink may be prepared by any one after the following recipe: Dissolve in about 4 gallons of hot water 3 ozs. of solid extract of logwood; to this add oz. of bi-chromate of potash, dissolved likewise in a little hot water. As soon as the liquids are mingled they assume an intense purplish-blue color, and the ink thus prepared may be used at once. It acquires a black color on the paper while drying. It does not corrode steel pens. It does not fade, as we know by personal experienae during six years, for which time we have used it exclusively. The cost of materials is about 3 cents per gallon. It is often used to mark packages and boxes. Specimens of writing with this ink, six years old, were here exhibited, and bottles filled with it were presented to all the members present. Metallurgy. An improvement in the character of the product is said to result from the introduction of sulphate of iron and oxide of lead, in the ordinary iron puddling furnace. (Mechanic's Magazine, April 1865, page 216.) The Academy of Sciences at Brussels have awarded a gold medal to M. Caron for an essay on steel. In the course of this paper occurs this statement: "Iron in becoming steel does not absorb nitrogen." In our own Journal last year, vol. xlviii, page 283, will be found a very full description of a new form of iron furnace, known as the Rachette furnace. In the German Miners' and Metallurgists' Journal, published at Berlin, we find some account of one of these furnaces erected at Mülheim, from which great results were expected in the direction of economy of fuel and amount of product. As this is a matter of great practical interest, we insert here a translation of the article above mentioned, kindly prepared by R. H. Lamborn, Secretary of the American Iron and Steel Association. Translated from the Berg und Huettenmaennische Zeitung, for Jan. 8, 1865. Of the various advantages that have been hoped for from the Rachette furnace, viz: lower first cost, high daily production, and economy of fuel, only the first mentioned has been realized at the works at Mühlheim. The furnace cost only one-half to two-thirds as much as a common blast furnace. While many coke furnaces produce 60,000 lbs. of iron per 24 hours, the Rachette furnace produced only 30,000 to 35,000 lbs. of white cast iron in the same period. At Concordia furnace 0.37 lb. of coke is necessary to smelt 1 lb. of charge; at Mühlofen, 0.34 lb. of steel 0.28 lb., while the Rachette furnace requires 0.42 lb. coke to do the same work. Without doubt the Rachette furnaces present eminent advantages in possessing a large hearth and an excellent distribution of the blast, but the common furnaces have made great advances towards excellence by widening their hearths and increasing the quantity of air thrown in. Mr. Nystrom then presented several papers by Messrs. Antony Pamfilli and C. Latimer, which were referred to the Committee on Publications. In reporting the proceedings of the Institute at the stated meeting, April 20, an error was made in describing the alloy prepared by the U. S. Composition Iron Co., New York. It is there stated to consist of zinc, lead, and tin, while it is in fact composed of zinc, copper, and tin. HENRY MORTON, Secretary. A Comparison of some of the Meteorological Phenomena of JUNE, 1865, with those of JUNE, 1864, and of the same month for FOURTEEN years, at Philadelphia, Pa. Barometer 60 feet above mean tide in the Delaware River. Latitude 39o 574 N.; Longitude 75° 10' W. from Greenwich. By J. A. KIRKPATRICK, A. M. Rain-Amount, No. of days on which rain fell, 11 7 Prevailing Winds-Times in 1000, s30°39′ w.188 s78°30′w 343 s74°22′W 222 * Sky, one-third or less covered at the hours of observation. 11.6 OF THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA, FOR THE PROMOTION OF THE MECHANIC ARTS. DEVOTED TO MECHANICAL AND PHYSICAL SCIENCE, Civil Engineering, the Arts and Manufactures. EDITED BY PROF. JOHN F. FRAZER, Assisted by the Committee on Publications of the Franklin Institute. VOL. 80. No. 476. THIRD SERIES. Vol. L.-AUGUST, 1865.-No. 2. PHILADELPHIA: PUBLISHED BY THE FRANKLIN INSTITUTE AT THEIR HALL. 1865. |