advantage in this way, and some, where even the high temperature necessary in iron-works are thus produced. According to Tunner, gases from good lignites are capable of producing a temperature as high as 2,6000 C. The lignites of the West are eminently fitted for use in gas-generators; for the very fact that they break up into small pieces, when exposed to the heat, is an advantage, because it would be much the easiest, this way, to convert all the carbonic acid formed in the lower part of the generator into carbonic oxide, as a very large surface of glowing carbon is thus presented. They are not bituminous, and their contents in ash are so small that they will not interfere. It may be, indeed, necessary, and it is certainly highly advantageous, to use a blast under the grate in order to further a rapid development of the gases, but this has also the advantage that the danger of explosions will be lessened. It is my opinion that generators with stair-grates and under-blast will be found the most advantageous; and if still higher temperatures than can be produced by this means should be required, an increase can easily be obtained by using hot wind, both under the grate and for the combustion of the gases. But the use of the lignites in blast-furnaces is of far higher importance to the western mining districts than that in reverberatories. Experiments so far have proved unsuccessful, principally, I am sure, because with the blowing-engines in use the required pressure could not be attained. To burn that material in the blast-furnace, cylinder-blasts are required, and perhaps it would also be necessary to close the tops of the furnaces in order to smelt under a high pressure, which may be regulated by the damper in the flue. The extraordinary results thus attained in producing high temperatures by Bessemer are too new to require recalling. Nothing of this kind has, however, yet been tried in the West, but I hope that during the present year this subject will be thoroughly investigated. The coke produced from the lignites by the simple method employed is, as I have said before, not fit for the blast-furnace. But the coal used was, as far as I am aware, of the inferior kind occurring in Colorado and in the Wasatch near Coalville. The Rock Springs coal, which is by far the best lignite, has not been tried. And if, instead of trying to coke this material in imperfectly constructed bee-hive ovens and in pits, more perfect apparatus, like the Belgian oven or Appolt's oven, had been used, think the result, even with the poorer qualities of Rocky Mountain lignite, would have been more encouraging. The Rock Springs coal, I am confident, will make coke in good apparatus, and if it should not be quite as firm as required for the blast-furnace, its hardness might be increased according to experiments which I learn were made in the West several years ago, by coking it under pressure. To produce this pressure in the coking-ovens the escape of the gases need only be regulated; and the ovens themselves must be constructed with the special view of resisting a pressure from within. Success in this direction would of course be of the utmost moment; for even if we assume as a settled fact that the lignites can be used in the blast-furnace with the proper blowing-machinery, in a raw state, their high percentage in water will always be fatal to the production of very high temperatures and their maintenance. It is, besides, much more agreeable and economical to use coarse fuel than fine stuff, as every smelter well knows. Finally, I wish to draw attention to the importance which these lignite-beds have in regard to the vast magnetic-iron-ore deposits near Laramie, and the hematites of Rawlins. The latter are very pure, and rich in iron, and the former also contain nothing deleterious except a little sulphur, the precise amount of which I have forgotten. If a method is found in which good coke can be made from the coal, there is of course nothing in the way of the railroad companies making their own rails, but if this should not be the case, it seems to me highly desirable that the late experiments of Siemens and Pousard, for the purpose of making wrought iron and steel directly from the ore, and so avoiding the blast-furnace, should be continued with a special view to the utilization of the iron-ores and lignites of the far West. It is true that the respective means employed by these two gentlemen, though technically successful, have not been so economically. There are, indeed, at the present time experiments going on in this country with apparatus different from those used by the English and French engineers, which are very likely to solve this problem favorably, it being the special object of these experiments to produce large quantities of iron in a given time, and with the greatest possible economy in fuel. CHAPTER XVII. THE METALLURGY OF NATIVE SULPHUR. The discovery of large quantities of native sulphur, mixed more or less with earthy matter, in Nevada and Utah, and quite recently in the so-called Yellowstone region in Wyoming and Montana, induces me to say a few words in regard to the above subject. All those of the above sulphur-deposits, which I'have examined personally, owe their origin undoubtedly to the condensation of sulphurous vapors in the overlying colder layers. They are situated in volcanic regions, in some of which the subterranean forces are still active, the deposition of sulphur going on continually at the present time. To determine the amount of sulphur which can be extracted profitably by the methods of beneficiation now in use, on a large scale, several simple tests are employed, one or two of which will be briefly mentioned. According to Anthon,* two grams of coarsely pulverized ore are heated in a glass tube of 10 to 16 inches in length and four lines in width, which is closed on one side, and into the open end of which another tube, also closed on one side, is introduced up to within 3 inches of the ore. When no more sulphur issues from the ore, that piece of the latter tube in which the sulphur has been condensed, is cut off and weighed. The sulphur is then removed, and the empty tube weighed again, the difference of the two weights giving the available amount of sulphur in the ore. To make the test on a larger scale, one or two pounds of the crushed ore are introduced into a good clay retort, which is put into a wind-furnace, so that its neck protrudes about 15 centimeters. To this a porcelain tube is luted, one end of which just dips into water. The retort is now heated to a strong red heat; the sulphur-vapors are condensed in the porcelain tube and the liquid sulphur drops into the water. When there is no more sulphur in the ore, the tube is taken from the retort, heated strongly over the water, and the sulphur, which has remained in it in solid form, will also be collected in the water. The whole product is then taken out, dried carefully, and weighed. For the utilization of the sulphur from the class of ores here under consideration various methods are in use, which can be classed under two main heads: 1. Eliquation of the sulphur in entirely open or partly closed apparatus. 2. Eliquation, sublimation or distillation of the sulphur in closed fur naces. The methods coming under the second head require considerable outlay of capital for apparatus, and greater expense for labor. They also require fuel. In their favor, however, is the more perfect extraction and utilization of sulphur which they effect; but the gain by these methods is not great enough to overbalance in our western Territories the increased expense of securing the product. In some regions the absolute want of a cheap fuel precludes their employment altogether. For these reasons I shall not dwell on them here, but rather present a description of a few of the methods belonging under the first head. a. Melting of the sulphur in cast-iron kettles.--This method can only be employed with profit in working the richest ores, containing over 70 per cent. of sulphur, because with poorer ores the unavoidable retention of sulphur in the dross would render the percentage actually saved proportionately too small, and the process would be unprofitable. Rich ores are treated in cast-iron kettles, of not over two cubic meters contents, which are heated by means of a separate fire-place. The heat maintained is over 1110 Centigrade, and must not rise over 150° Centigrade. The nearer the temperature can be kept to the melting-point of sulphur, (1090 Centigrade = 228° Fahrenheit,) the better is the result, because at such a temperature sulphur is most liquid and does not burn. The kettles are filled with ore, which is melted down, and occasional additions of raw ore are made, until the kettle is filled with the liquid mass. Meanwhile all the earthy parts which can be reached are taken out with perforated iron ladles. After the kettle is full, the mass is permitted to settle for a short time. The scum on top is then taken off, and the clear sulphur cast into molds, until the sediment at the bottom of the kettle is reached. A new quantity of ore is then introduced, and the process is repeated. After several operations the sediment is taken out of the bottom of the kettle, and either thrown aside or used with poorer ores in pits or furnaces. b. Eliquation of sulphur in furnaces or pits.-Formerly the sulphur was extracted from the ores of Sicily by means of shaft-furnaces, not over 4 to 5 feet high and 7 to 15 feet wide. They had an inclined bottom, at the lowest point of which a canal communicated with the outside. The largest pieces of ore were put on a bench on the inside of the furnace, near the bottom, and upon these as a base an arch was built, a small hole only being left in the center. Upon this arch smaller ore was thrown, until a small pyramid was formed protruding above the furnacewalls. This was finally covered with fine ore, upon which straw was thrown and ignited. The fire communicated to the sulphur and traveled from the outside toward the inside. After eight or ten hours the liquid sulphur had collected at the bottom, and was tapped into moistened molds or into water. This process furnished only from 40 to 50 per cent. of the sulphur in the ore, and is now nearly everywhere abandoned. At present pits, or rather stalls, called calcaroni, are almost universally used in Sicily, Spain, and elsewhere; the yield in these being, according to Professor B. Kerl, 67 per cent. of the sulphur in the ore. Mr. H. Sewell, who has had considerable experience with sulphur-ores in Spain, describes this method in the Engineering and Mining Journal as follows: The governing principle in this method is the working of large masses of.ore at low cost. Each calcarone works up per month from 800 to 1,000 tons of ore, the apparatus being constructed of common stone and plaster, and costing $300 apiece. No fuel is required, as one-seventh of the ore is used as combustible for reducing the rest; so that if the ore contained 23 per cent. of sulphur, 20 per cent. net would be produced.* The dimensions of a calcarone differ much, according to the percentage of the ores; that is, the poorer the ore, the larger must be the furnace. When I commenced to use them in Spain, I found that stalls about 15 feet in diameter were the most successfully managed by workmen not versed in the process; but I found, also, that for economy, and a greater production in the liquation, a larger diameter, say 33 feet, gave the best results, and this is the size of the stall in the accompanying drawings. The height at X, on the front or tapping door, varies from 6 to 8 and 12 feet, (though seldom the latter,) and that at L, the aperture for loading, is about 4 feet. At XX, also, in the ground and vertical plan, an aperture reaching from the bottom to the top of the stall exists. This is also used for loading; but after that operation *This yield, as claimed by Mr. Sewell, is very high, and at variance with the statements of other authorities. Mr. Sewell seems to allow nothing for the sulphur retained in the ore after treating it. has been concluded, the aperture is closed with a cast of plaster of Paris, (or pieces put together,) the thickness being only 2 inches. This thin door is built up new every time, and destroyed for discharging. It is used as a pyrometer, the heat easily Calcarone-Vertical section. Calcarone-Horizontal section. are filled with brush-wood, and in this way the ore is made to ignite. These hollows are left while piling the ore and building the cone. The object of placing the small ore at the top is simply to prevent any of the earth and sifted stone from falling through the large crevices that would be left, if large bowlders were placed at the top. The earth and sifted stone or gravel play an important part in the manipulation. At K K K K we have, immediately in contact with the small ore, a stratum of about 6 inches of small sifted gravel, about the size of a nut, and on this again, at N N N N, we have a coating of earth; this is to make the interior of the stall as impermeable as possible to z the oxidizing action of the air, and this coating is increased or decreased according to the amount of heat required, which in turn depends on the strength of the winds and their direction. The brushwood ignited, the ore commences to burn, and the chimneys are kept open for about twenty hours, at the end of which period the ore has ignited all over the surface of the heap, and to the depth of, say, some 15 or 20 inches. The chimneys are then all closed as follows: bricks are placed over them, as at point P; and should the burning of the ore be too rapid, earth is then thrown over the bricks; but these chimneys are opened toward the middle of the operation, to increase the heat, and closed again, according to circumstances, to decrease it. After forty-eight hours, the melted sulphur begins to trickle down through the interstices of the stone, and congeals, forming, as it were, a conglomerate with the ore; the heat also travels downwards, and so we have remelting and congealing consecutively, till the sulphur arrives at the bottom of the furnace, forming a massive conglomerate of sulphur and ore; for it fills the interstices up to the point where the first tap-hole is drilled, through the thin door of plaster at point Z. The lines across the stall denote the lines or levels of tapping; and this commences naturally at Z, and so downwards, as the congealed sulphur is remelted with the descending Leat. Every twenty-four hours a fresh tapping takes place, the former holes are plastered up, and a new hole drilled lower down, and so on till we get down to the lowest point or bottom of the furnace. At the end of the operation, that is, during the last three days, nearly all the chimneys are left open, so that the air shall descend to the lower part of the furnace, and aid the combustion of the ore. The jet of sulphur is received into wooden molds, as at point B. These have been soaked in water, to prevent the sulphur sticking to the wood, and are shaped wheelbarrow fashion, in order that the block of sulphur may easily fall out, without breaking. During the carrying away of a mold that has been filled, and the bringing of an empty one to be filled, the jet runs into a reservoir made for the purpose at A. Öne of the principal reasons for placing large blocks of ore, from the middle of the furnace downwards, is to leave sufficient interstices for receiving the sulphur, otherwise the first tap-hole would be too high, and near the ignited ore, thus setting fire to the stream of sulphur. Two of the principal things to be guarded against are overheating the apparatus, and, on the other hand, carrying on the process so slowly, by the complete closing of the chimneys, that the operation would take two months instead of four weeks from the commencement. In the former case, instead of the sulphur congealing between H. Ex. 211 -29 |