On October I O , 1910,three of the nine chamber plants were destroyed b y fire. In planning for rebuilding, the director decided t o adopt the essential will afford a n explanation for the phenomenon. features of the so-called Moritz system of chamber construction, as not only promising economy in future cost of production, but also offering exceptional facilities for rapid replacement of the missing units, even during the winter season. He was able to use the first series of chambers on March 15th and the second on April 4th of this year. The construction of the third unit did not begin until July. The Moritz system was brought to the attention ol technical chemists about four years ago. It was first introduced a t Wasquetal, northern France, by the SociCt6 anon. des Etablissements Eyken e t Leroy, with which the inventor, R. Moritz, is connected. The results obtained in a chamber system of 4,500 cubic meters were so satisfactory t h a t several French and Belgian works utilized the new method when increasing their chamber capacity. At present a large system of 8,000 cubic meters is under construction a t Hainaut, Gelgium, a smaller one of 4,000 meters a t Elberfeld, Germany, and the P third unit of the "Union" works ( 5 , 2 0 0 meters). From the equation R = K-, it would be expected As a rule, in chambers constructed according to V" t h a t K would vary inversely with the viscosity, but. prevalent methods, the sides, the top, and the bottom the effect of the above-mentioned variation in n is of a lead chamber are suppdrted b y strong wooden so great t h a t the reverse is true. The calculated beams. These timbers, while showing externally values of K are a s follows: no change, are seriously affected b y the radiation of Viscosity. K. heat from the adjacent lead walls. The temperature 0.0124 1310 of the walls may attain g o o and even 100' C., and as a 0.0109 635 result the wood rapidly loses its strength, becomes 410 0.0096 These values of K are interesting chiefly a s a n in- brittle, and is warped. This leads t o a dangerous dication of what may be expected t o develop on further strain upon the flaps along the walls. They are frequently torn off and the wall loses its shape. This investigation of the subject. The purpose of this article is twofold: First, t o tendency is heightened b y the great difference bepoint out that, despite the popular theory, the rate tween the coefficients of expansion of lead and wood. of flow of a liquid through a filter cake is not as a The thoroughly dry timber offers also an undesirable rule directly proportional t o the pressure and inversely amount of very combustible material, as shown b y the proportional to the thickness of cake, but can be extensive fire a t Kratzwieck in 1910 and the conflagration a t the Wasquetal works in 1907. P" expressed by the equation R = K -- in which the Much more serious, however, is the increased V" ' constant and coefficients can be quickly and easily corrosion of the lead chambers, due t o the use of determined; and secondly, by outlining some pre- wooden supports. Those portions of the lead walls liminary experiments carried out in this laboratory adjacent t o the timber supports are prevented from t o stimulate further investigation which will be able radiating heat freely. This retards the oxidizing t o explain the very interesting and unexpected re- reaction in the immediate vicinity, while allowing lationships which apparently exist between the vis- the lead to be corroded more rapidly. Careful measurements of the thickness of the wall in different parts cosity of the filtrate and the values of n and K. of a lead chamber, after the fires mentioned, showed RESEARCH LABORATORY OF APPLIED CHEMISTRY, MASSACHUSETTSINSTITUTE OF TECHNOLOGY, t h a t the portions of wall screened b y a timber were BOSTON. on a n average half a millimeter thinner than other sections of the chamber. This was in spite of the fact IMPROVED SULPHURIC ACID CHAMBERS.' t h a t the timbers were separated by spaces of 8-10 cm. By THOMAS H . NORTON. from the lead walls. While visiting the extensive works of the Union An additional disadvantage results from the more Fabrik Chemischer Produkte a t Kratzwieck, near Stettin, I was afforded a n opportunity t o examine rapid corrosion of the lead behind a beam, as leaks minutely two series of sulphuric-acid chambers re- occur thereby most frequently a t points where the cently constructed b y the company. These are re- repairs are difficult t o execute I n some few works garded as embodying the most advanced ideas of the day. iron instead of wooden beams have been introduced. This obviates the distortion of the chamber walls, Special report to Bureau of Manufacturers, Department of Commerce due to the warping of the wood, but does not diminish ;md Labor. proportionality, other
investigators will be led t o
try more exhaustive and accurate experiments which
the trouble arising from rapid corrosion and the difYiculty in carrying out repairs. With regard t o the bottom of chambers, observation shows t h a t corrosion is very pronounced along the lower edge, where the lead is bent upward Her% n zone of about 6 inches is peculiarly liable to rapid attack; and the same is true of the lower part of the side walls, which form the hydraulic joint. The direct cause of this quick corrosion is the thick flooring of wood necessary t o support the weight of the acid, b y retarding the radiation of heat from the surface of the lead. The tops of chambers are ordinarily flat The lead sheets are attached b y flaps t o overhead beams or hung upon iron rods or tubes. I n both cases the same disadvantages exist as have been previously mentioned. A flat roof also favors the accumulation of dust, which in turn retards radiation. As a rule it is a matter of great difficulty to clean thoroughly the ordinary flat roof of an acid chamber. The prevalent method of attaching the various sections of a lead chamber t o its supports prevents almost entirely any uniform expansion of the different parts. I n consequence of the heavy weight of the lead, and of the uneven expansion, there is a constant tendency toward strain about the flaps, and cracks that are exceedingly awkward t o mend appear along the soldering lines. All of these defects of the customary construction seem t o be avoided in the Moritz chambers. The essential feature of such a chamber unit is a strongly built skeleton of structural iron, enclosing the chambers, which are suspended from overhead beams. The skeleton serves also as a support for the roof. The main columns of this skeleton, which bear the weight of the roof, have been constructed in some cases of concrete or masonry. Preference is, however, given t o iron, a s involving less time in preparation and assuring greater strength. A tile roof is used. The outer walls of the structure are built of brick, laid between the upright columns. The bricks are placed edgewise, so t h a t the walls are exceedingly light, 2.36 inches in thickness. No windows are required. An abundant use of panels of wire-net glass and of ordinary glass tiles in the roof affords all needed light. Some additional light and abundant ventilation are assured b y numerous series of openings in the brick walls, the bricks being arranged in a latticelike manner a t distances of 3.937 inches from each other. Such a n arrangement suffices t o keep out snow and rain, while affording a maximum of air circulation for cooling purposes. At Kratzwieck two units are located side by side, separated from each other b y a n aisle about 4 feet wide, and under a single roof. In other forms of construction there is a separate roof over each unit. Great ingenuity is displayed in the manner of suspending the chambers from the skeleton framework. At intervals of 3 1 . 5 inches along the top edges ( 2 7 . 5 inches on the end sides) hooks of half-inch iron are attached firmly to the lead sheets. These hang b y iron rods (1.57 by 0 . 2 4 inches) from the T girders
overhead, and thus insure a complete, unhindered exposure of the side walls t o the cooling action of the air. There is, however, a further addition necessary, in order t o obviate a n y danger from expansion or contraction. Along the walls, likewise a t distances of 31.5 inches (or 27.5 inches on theencl walls), vertical flaps are soldered on tightly. Light iron rods, round or flat, pass through these, and are connected above with the pendant supports, while below t h e y are attached, by means of spring hooks, to the upturned edge of the chamber floor. They givt, a ribbed appearance to the chamber walls and increase the coolingsurface. While imparting a certain amount o f rigidity, and preventing undue swelling outward, or inward depressipn, they still permit of free play for ordinary contraction, or the reverse, without any undue strain falling upon the soldered fastening of the ribs. The effectiveness of this rib construction is heightened b y numerous horizontal connections, b y means of iron rods, with the skeleton frameworks. A similar principle is applied in the case of the top of a chamber. Here there is also a ribbed construction, and hooks a t frequent intervals are connected b y round iron bars with the girders overhead. All exposed iron parts are carefully protected from corrosion b y a special paint. I n the shape of the chamber top we encounter one of the most striking innovations of the Moritz system. It is of a semicylindrical form t o prevent the accumulation of dust, while avoiding "dead corners'' inside the chamber, and their liability t o frequent repairs, and assuring a more perfect circulation of air about its upper surface. The lead floor of the chamber rests upon an under floor of iron plate 0.197 inch in thickness, and this in turn is supported b y brick columns about 8 feet high. I n some instances the constructors have used woocl or ferro-concrete. I n all cases, however, the upturned edge of the floor consists of iron plate, bent underneath t o a distance of 9.8 inches. This is to insure the most rapid cooling a t the weakest point in the construction of a chamber, where corrosion is most pronounced, and repairs involve a complete stoppage of manufacture. An identical method is used in supporting the lead mantles of the Glover and Gay-Lussac towers. Details are naturally ~ n u c l i simpler, on account of the smaller size of the tmvers. Each tower shows eight vertical ribs. There are certain theoretical considerations connected with the use of the rounded roof t h a t deserve mention. I n addition t o the advantages attendant upon this particular shape, the inventor claims that it is a powerful factor in equalizing temperature, and consequently in insuring uniform chemical activity and production in all parts of a chamber. While there is little movement of air over a flat roof, there is, on the contrary, an active current over the surface of a curved roof, thus bringing about a more rapid cooling. In a chamber of rectangular construction the hotter gases accumulate a t the t q ) . IVitl-i LL curved roof the volume of such gases is reduced to a minimum. T h e y are constantly drawn off by the 5
I
gyratory movement of the chamber's contents, due to external cooling, and descend steadily downward along the walls. An instance is cited from the observations made at Wasquetal upon the temperatures a t three different points in the first chamber of a plant. Under similar conditions of external temperature, with the same pyrites, the same ovens, and the same towers, the temperatures observed a t the three points in a rectangular chamber were 9 0 ° , 8 8 O , and 86' C. In the chamber with curved top, which replaced the former, they were 7 5 " , 7 j o ,and 74' C. The more rapid cooling and the close approach to uniformity are noteworthy. The director of the works a t Kratzwieck is, however, of the opinion that a more gently curved roof is quite as effective as one of semicircular shape and more desirable from several standpoints. In the plant now under construction he plans to modify this feature. At the outset i t must be noted that the cost o f construction, per unit of cubic chamber space, is higher than by the old method. At Kratzwieck the additional cost was found to be about 33 per cent. 'l'his figure would vary according to local factors. 'There seems t o be no doubt of the manifest economy in space, frequently a n important factor where chemical works are hampered in their development by lack of. sufficient available area for building. At Kratzwieck the two units already built on the Moritz system occupy b u t two-thirds of the area formerly covered by three separate units before the fire. Yet these two units produce more sulphuric acid than the three units that were destroyed. The next important economy is in the amount of nitric acid required to produce the maximum effect in the lead chambers. The newly erected plant of the "Union" yields daily about 7 kilograms of acid (50" Baume) per cubic meter of chamber space. Formerly, a t this rate of production, 0.7-0.8 kilogram of nitric acid (36' Baumi.) was consumed for each I O O kilograms of chamber acid of the above strength. This consumption has now fallen to very nearly 0.5 kilogram. I t is to be noted that 0.9 kilogram is ;L very common figure in German acid works. In 1900 the average consumption was 1.4 kilograms in American acid works burning pyrites. This loss of nitric acid is an important item in the cost of producing sulphuric acid. I n Germany i t constitutes 4-8 per cent. o f the total cost. I t is obvious that a saving ( ~ If or 2 per cent. in this direction constitutes a notablr csconomy. The inventor guarantees a maximum loss o f 0 . 6 kilogram where chambers are producing 7 kilograms daily per cubic meter. I t may be mentioned in this connectiqn that in the " Union" system water in the form of spray is admitted to.the chambers in summer and in the form of steam during the winter. Apart from the direct saving on the daily cost of production, the director of the "Union" works is confident from his study of the plant during the few months that i t has been in operation that there will be ultimately a very material saving in the item of depreciation, through the prolonged life o f the chambers, and the ease and simplicity with which any necessary eventual repairs can be executed.
A MODIFICATION OF THE FRARY ELECTRODYNAMIC STIRRING DEVICE. B y J. hf. KNOTEAND W. R. WORK.
Received March 14. 1912.
The use of a solenoid for the rapid determination ot' metals in the electrolytic way was proposed by Frary (Jozrrizul o j tht, A m e r i c a n (-'hemica1 Society, Ko'vember, 1907, and in other publications). He employed the usual form of solenoid which is a coil of copper nire cylindrical in shape and hollow, and enclosed in an iron case. The beaker containing the electrolyte is put into the hollow space in the center of the coil and :i current passed through the electrolyte in the usual way. At the same time a current through the solenoid produces a magnetic field in the region of the beaker which in conjunction with the electrolyzing current causes a rapid circulation in the electrolyte. The disadvantages of this form of apparatus are that the electrolyte is not in sight and an inspection of the electrodes during the process of electrolysis is not easy. The solution becomes quite hot and in some common determinations this is not desirable. The use of a rooling coil complicates the apparatus. .
MODIFICATION
By actual tneasurements the magnrtic field pro ducecl by a solenoid was shown to be practically as strong at the top of the coil as i t is at any point in the interior, and an inch above the top it still amounts to 40 per cent. of this strength, gradually decreasinn as the distance increases. a s shown by Fig. T . The lines I
o f force which constitute the field pass without hindrance through glass, paper, wood, brass, etc., so it is a simple matter t o put the coil of the solenoid around an iron core, cover the top with a suitable material and place the beaker containing the electrolyte on it. By using electrodes with bent stems a very simple
