nitre to be made in a crucible made of alumina or aluminate of soda. G. Buchner states that commercial aluminium contains considerable quantities of silicon, which by treatment, when melted, with hydrogen, evolves hydrogen silicide. This does not result if arsenic is present. Mallet made chemically pure aluminium by treating the commercial metal with bromine, purifying the resulting Al2Br by fractional distillation, and then reducing it with pure sodium. By repeatedly melting the metal upon aluminium leaf, he obtained it chemically pure. Although this method is quite ȧpplicable when studying the properties of the pure metal, yet it cannot serve on an industrial scale. USES OF ALUMINIUM. "Since aluminium was prepared by Devillet on a large scale it has received numerous applications. Its beautiful color, its lightness, its unoxidizability in contact with air or sulphuric acid, its harmlessness to the health, the ease with which it may be worked, are some of the properties which assure for it a place among the useful metals. On account of its very high price the first articles made of it were those of ornament and luxury. The very first article * Wagner's Jahresb., 1884. made of it was a baby rattle, intended for the young Prince Imperial in 1856. Afterwards there were made of it jewelry, medals, inlaid work, and carved mouldings for inlaid work and rich furniture. It is very well suited for fine jewelry by reason of its adaptability to being cast and carved, the beautiful reflections from a chased surface, its color, which matches well with gold, and its absence of all odor. Later on, the lightness of aluminium leads to its use for telescope tubes, marine glasses, eye-glasses, and especially sextants. In delicate physical apparatus, where it is necessary to avoid the inertia of large masses, aluminium replaces the other metals with advantage. It is used for beam's for delicate balances and for very small weights. There have been made of it sabre sheaths, sword handles, and the imperial eagles for the French army. Finally, made into fine wire, it is worked into lace, embroidery, etc. For all these purposes aluminium answers better than silver, for the objects are much lighter and do not tarnish. The resistance of aluminium to most of the agents which attack the useful metals has led to its employment for culinary articles; a large number of which were seen at the London Exhibition in 1862. But the advantages of aluminium vessels have not yet been sufficiently comprehended, and this use of it has at present been entirely discontinued. Likewise, aluminium jewelry is not seen any more; so that the metal seems reserved for little more than optical and surgical instruments. But the aluminium industry is nevertheless established on a permanent basis and will continue, because of the numerous applications of its alloys." M. Dumas made a helmet of aluminium, gilded and ornamented, which weighed complete only one and one-fifth pounds. Aluminium leaf, beaten very thin, may be used anywhere in place of silver leaf. It is applied in the same manner, and is more durable. Aluminium wire has been proposed for telegraph lines. The conductivity of aluminium is double that of iron, and as it is so much lighter, thinner wire can be used. As its high price is a practical difficulty, an alloy of iron and aluminium has been suggested. "One of the most likely applications of aluminium is probably as a material for statuettes and small works of art of this description, especially if the means could be found of giving to it a richer color and appearance either by a kind of bronzing or some alloy. “Aluminium makes very bright reflectors, not tarnished by the products of combustion, while the slight bluish tinge of the metal corrects the yellowish tinge of the flame. For culinary uses it is well adapted, because of its lightness and the little tendency it has to become corroded by any of the liquids likely to come in contact with it. It is necessary to observe, however, that this power of resisting the action of corroding agencies, and more especially the atmosphere of large towns, is exhibited only by the pure metal. Most of the metal of commerce is very impure with iron and silicon, not having been properly freed from slag. Aluminium thus contaminated soon becomes tarnished, and much disappointment has been experienced from this cause by those who have used it for ornamental purposes. According to Deville, the impurities just mentioned are found to the greatest amount in the metal obtained from cryolite." In the 'Scientific American,' vol. xii. pp. 31 and 51, is a long article on plating with a luminium, giving complete directions for preparing articles, solutions, etc. A large collection of articles of aluminium was shipped from England to Calcutta in Oct. 1883, intended for exhibition there. The exhibit consisted of wire, pens, pencil-cases, railway-carriage fittings, locks and bolts, harness furniture in great variety, chandeliers, cutlery, and ships' fittings, and illustrated very well the various uses to which the metal can be put. It is being used for the lighter parts of such instruments as galvanometers, etc., for suture wire, and perhaps its most promising field is for engineering, astronomical, and optical instruments. "Aluminium is sold as leaf in books, like gold leaf, for decorations, at from 40 to 50 cents per book, and is being experimented with by manu facturers of jewelry. In Germany, experiments have been made with it as a coating for iron, to be applied for ornamental purposes, and as an improvement on tin plate. Its use is extending slowly but surely, its cost being at present the principal obstacle to its wider employment."* Experiments were made in the U. S. Mint in 1865, on alloys of aluminium for coins. The results were not sufficiently successful to induce the Government to adopt the metal for that purpose. SOLDERING ALUMINIUM. At the time Deville wrote his book, the difficulty of soldering aluminium properly was one of the greatest, if not the greatest, obstacle to the employment of the metal. His views on the question may be, therefore, very interesting; they are as follows: "Aluminium may be soldered, but in a very imperfect manner, either by means of zinc or cadmium, or alloys of aluminium with these metals. But a very peculiar difficulty arises here, we know no flux to clean the aluminium which does not attack the solder, or which, protecting the solder, does not attack the aluminium. There is also an obstacle in the particular resistance of aluminium to being wetted by the more fusible metals, and on this account the solder does not run between * Mineral Resources of the TT. S. 1883-4. |