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THE J0GR:VAL OF I S D U S T R I A L Ai\-D
introduction of the present roller-disintegrators. Another application of the centrifugal principle is in sorting the chips. If the chopped wood is centrifuged in a suitable machine, the heaviest and largest pieces are separated from the lightest and smallest fragments. Mitscherlich’s tower plant, although it has been altered in details, is still largely used. His original towers were built up of casks with the heads and bottoms knocked out. They are now usually made of granite. The sulphurous acid is made by roasting iron pyrites in ovens such as are used in the manufacture of sulphuric acid. The hot gases pass from the ovens through brick channels into castiron pipes, which lead them into a set of vertical pipes, having about two-thirds of the height of the tower. From this set they travel downwards through another set of vertical pipes of the same height so that they enter the tower a t the bottom. The object of passing the gases through the two sets of vertical pipes is to cool them, and also to increase the current passing into the tower. The descent of the cooler gases in the second set of vertical pipes exerts a kind of suction which d r a m the hotter gases up the pipes of the first set. At the same time, the current of gas varies with the weather, being quicker in cold weather than in hot, and slower with a high than with a low barometer. The tower itself is, of course, filled m-ith limestone to absorb the sulphur dioxide and form the bisulphite for the treatment of the wood. This is delivered in the form of solution ready for use a t the bottom of the tower, water being continually sprinkled over the carbonate of lime from the top of the tower. Kellner’s attempts a t improving this plant were not very successful. They were directed chiefly to making the working of the tower uniform, or, in other words, independent of those atmospheric influences just mentioned. The only practical result took the shape of introducing intermittent artificial draught, used, of course, when the atmospheric conditions were adverse to the free passage of the gases. Another idea of his was to substitute, for the single lofty JIitscherlich tower, several lower ones. I n this type of plant the water is supplied to the last tower only, and the weak lye from the bottom of it is pumped to the top of the last tower but one. It arrives a t the bottom rather stronger, and is straightway pumped to the top of the last tower but two, and so on. This necessarily demands several acid-resisting pumps and much power.
PROBLEMS IN PAPERMAKING. Schwalbe calls attention (Paper, 9, No. 5 , 23) to the chemical problems which abound in the paper mill. There is the question of the influence of chemicals on the “beating” process. Cellulose is a colloid, and, as such, should be responsive in a physical sense to the action of very small quantities of chemicals in solution. The bleaching problem has been very little studied on the chemical side; it is not known what is the exact nature of the substances removed from the pulp by bleaching nor in what form they are eliminated. The problem of sizing remains full of unsolved points and chemists are not agreed even on the simplest question of the chemical reactions, while the physical reactions are still more obscure. The fixation of the loading materials is a physicochemical problem which should repay systematic investigation. All mineral loadings, especially clay, are colloidal and readily influenced by traces of soluble salts. The question of new sizing agents is waiting solution and the utilization of waste resins from the rubber industry appears t o be within sight. Under certain conditions engine-sized paper loses its resistance to ink after storage, and the chemical causes of this loss are still unknown. I n dyeing the pulp, the chemical relations of the dyestuff have t o be studied, not merely towards the fiber, but also towards the mineral loading materials. Finally, there is the
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problem of the clarification of the machine waste waters and the recovery of useful material from them;.there is every probability that the mechanical process of clarification might be materially assisted by suitable chemical additions.
THE AUTUMN MEETING OF THE INSTITUTE OF METALS. The autumn meeting of the British Institute of Metals took place a t the Institution of Electrical Engineers, in London, on September 2 5 and 26, 1912, and a number of interesting papers were presented. The report which follows was taken from .Vatitre, go, No. 2 2 4 2 , 199-201. Two papers dealt with the joining of non-ferrous metals and alloys. In these Carnevali and Tucker discussed the question of autogenous welding. Owing to the great extension of autogenous melding by means of oxygen and acetylene, the question as to hoiv far the results of this process can be depended upon is a n important one. Tucker appeared to regard a weld as satisfactory if it is found on testing it to destruction that the fracture occurs away from the weld itself; but Carnevali pointed out that the weakest portion oi‘ a v-elded joint is not the weld itself, but the region of injured metal on either side of it. According to Carnevali, the strength of welds in copper and its principal alloys can not be depended upon, and this conclusion agrees with the views on autogenous welds in iron and steel recently expressed by Fremont and others. With regard to pure aluminum, hon-ever, Carnevali found the method to give satisfactory results, but the efficiency of a weld was much reduced as soon as it was applied to one of the stronger light alloys of aluminum. To quote Suture: “Broadly speaking, these papers lead one to view the rapid development of autogenous welding practice with some suspicion.” X paper by Law dealt with oxygen and oxides as deleterious impurities in alloys. H e took the view t h a t progress in nonferrous alloys was largely a question of the better elimination of oxides, and this opinion mas supported in the discussion by Rosenhain. Turner appealed to chemists t o devise a satisfactory method for the determination of oxygen in brass. Johnson dealt with the effect of impurities, chiefly antimony, on the properties of tough-pitch copper, and here again the discussion centered around the part played by oxygen. The lenient view as to the deleterious effects of antimony put forward by Johnson was vigorously opposed by those who have to deal with copper on the large scale. Carpenter contributed two papers dealing in minute detail Tyith the inversion which he has discovered in a certain range of copper-zinc (brass) alloys at a temperature of 470’ C. I n one of these papers he dealt with the effect of impurities on this inversion and found that any addition of a third metal to these alloys tends to facilitate rather than to inhibit the transformation in question; since the change renders the metal weak and more brittlc, it is evident that the use of the purest copper and zinc is desirable in the manufacture of those varieties of brass containing the constituent. Rosenhain and Ewen presented a paper on the intercrystalline cohesion of metals. They advanced the view that the crystals of a pure metal are held together by the action of a thin layer of metal in the amorphous condition forming a kind of cement between the crystals. The conception of the existence of such a cement, we may note, had already been put forward by Bengough and by Osmond, but Rosenhain and Ewen claimed t o have used it as a working hypothesis in their own laboratory before others had published their views. Beilby discussed the phenomena of the solidification of metals from the liquid state in reference to the “foam-cell” theory of Quincke. The fundamental question, which goes beyond Quincke’s hypothesis, is, whether the metal in a liquid state undergoes any changes or separations before actual solidification commences, and, if so, whether there is really any formation of
