The mining and metallurgical laboratory, as we understand the term in this country, is a place in which mechanical and chemical working-tests are made on ores, fuels and furnace materials. It is of quite recent origin. The first laboratory of this kind to be used in connection with teaching was put into operation at the Massachusetts Institute of Technology. The laboratory was given from the first into the charge of Prof. R. H. Richards, who, by improving its methods and enlarging its scope, has brought it to the position which it occupies to-day as the leading representative of its class. Private laboratories for making tests upon ores had previously existed here and there, especially on the Pacific coast, for silver and gold ores; but in the educational field the Massachusetts Institute of Technology was the pioneer. Today there is hardly a school of mines in this country that has not a more or less complete mining and metallurgical laboratory. In European mining-schools there is very little laboratory-teaching. Most of them are located in mining-districts, where the students can personally see and engage in the practical work of mining, concentrating and smelting. Those which are in large cities, at a distance ….Read more
A recent paper by Prof. George P. Merrill, Curator of the Department of Geology of the U. S. National Museum, Washington, upon ” An Occurrence of Free Gold in Granite,” describes an interesting instance of the dissemination of this noble metal in the substance of granite of normal composition believed to be from Sonora, Mexico. He found the gold in small scales, rarely exceeding a millimeter in diameter, distributed through the scales of mica and apparently enclosed in both the feldspar and quartz granules. A number of thin sections of the rock submitted to examination with the aid of the microscope gave confirmatory evidence. Sulphides were not detected, nor any indication of a secondary impregnation, though the granite had undergone some alteration, apparently by weathering. Mr. Merrill concludes that ” there is apparently no way of accounting for the gold other than by considering it an original constituent of the rock, a product of cooling and crystallization from the original magma.”
We thus have another link in the chain of evidence showing that gold is a constituent of granite and of plutonic rocks, and that such crystalline rocks may be the primal source of the gold, which is concentrated in ….Read more
The accuracy of the silver-assay depends in great measure upon a careful regulation of the heat of the muffle furnace during the process of cupellation. At the beginning of the operation, a relatively high temperature is required to ” open ” the lead buttons, that is, to clear off the black film of oxide that covers the surface of the metal button immediately after fusion has taken place. The muffle furnace is usually closed up until the buttons are uncovered. As soon as a clear, free surface of molten metal is exposed to the oxidizing action of the air, the temperature should immediately be lowered to the minimum temperature at which the formation and absorption of litharge can progress freely, and the buttons still be kept from ” freezing.” The process, under satisfactory conditions, will be characterized by the formation of rings of litharge crystals (” feathers,” as they are styled), on the cupel, about the oxidizing globule; and the nearer these rings of litharge crystals can be made to approach the central oxidizing globule without interfering with the freedom of oxidation and absorption, the smaller will be the volatilization of silver, ….Read more
About six years ago the writer had occasion to visit a large magnetic iron-ore concentrating-plant, and then saw for the first time rubber belts employed for conveying-purposes. These Conveyor Belts were from 20 inches to 30 inches in width, and some of them were as long as 500 feet between centers. When I spoke of the enormous amount of material they handled with a small expenditure of power, the superintendent assented, but at the same time complained that although he bought the best quality of belts, the abrasion of the ore wore them out very rapidly, causing continually very large bills for repairs and renewals.
On close examination several interesting points were discovered
- It was noticed that the thin layer of rubber which covered the belt resisted the abrasion much longer than did a corresponding thickness of the cotton duck which formed the body of the belt; in fact, the life of the cover represented about one-half the life of the belt, although forming less than one- fifth of the total thickness.
- Each layer or ply of duck wore out more quickly than the one preceding it, showing that the fibers ….Read more
There has been considerable discussion of late as to the best method of determining the silver-contents of sulphides of silver resulting from the leaching of silver-ores, and also as to the relative merits of the crucible and the scorification method for the determination of the silver-contents of ores.
Owing to the great depression in the silver-market, these are questions of considerable importance, at the present time, to both the producer and the smelter and refiner.
A few ounces of silver sulphide were prepared by dissolving quite pure silver chloride in sodium hyposulphite and precipitating the silver as a sulphide by the addition of sodium sulphide to the solution. After filtration and slight washing, the precipitate was dried, ground, and thoroughly mixed; and the percentage of silver was then determined by carefully weighing out several portions of 0.05 A. T. each, on the assay-balance used for weighing the silver buttons resulting from assays; dissolving each portion in nitric acid of 27° Beaume; boiling to expel the red fumes; diluting with distilled water to 200 c.c., and titrating with a standard solution of potassium sulphocyanate; adding about 1 c.c. of a strong solution of ammonium ferric ….Read more
Rittinger, having found that jigs save galena of smaller sizes than his formula, worked out in his appendix of the theory of acceleration to account for that fact, showing that a particle of galena which is equal-settling with a particle of quartz reaches its maximum velocity in perhaps one-tenth the time required by the quartz. The oft-repeated pulsations of a jig give the galena particles a decided advantage over the quartz, placing beside the quartz, when equilibrium is reached, a much smaller particle of galena than we should expect according to the law of equal-settling particles. He concludes that the excess of jigging-power over that indicated by the law of equal-settling particles is due to acceleration. Unfortunately, he has not given a ratio of diameters of quartz and galena, which represents equilibrium with regard to acceleration.
To test this question of acceleration, I have designed a pulsion- jig or modified Setzpumpe, which is shown in Fig. 8. It consists of a tin funnel, a, with overflow, b, connected by rubber connector, c, to a glass tube, d, cut apart at h for the insertion of a disk of sieve- cloth. ….Read more
The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe.
In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper.
In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger’s work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal.
The laws that have been claimed as the laws of jigging by the several authorities are:
- The law of equal-settling particles.
- The law of interstitial currents.
- The law of acceleration.
- The law of suction.
The first of these ….Read more
Since the introduction of the improved method of precipitating gold from chlorine solution by SO2 and H2S at the Golden Reward chlorination-works, Deadwood, S. D., this modern method has been further adopted in the chlorination-works. It has proved practically most successful in the handling of large quantities of gold solution, and constitutes up to date, the most important improvement, namely, barrel-leaching under hydraulic pressure, the principal progress made in gold chlorination.
The method of refining the gold sulphides which result from this method of precipitation. It has not suffered any changes during the last three years, and is substantially as described below.
Drying and Roasting
The gold sulphides collected are dried already as far as practicable in the filter-press by passing compressed air through them, and are then transferred (care being taken to avoid loss in handling) to light sheet-iron pans, 20 inches wide, 36 inches long and 4 inches high.
Precipitate and filter-cloth are kept separate as much as possible. If dried well in the press, the precipitate is easily detached from the filter-cloth in pretty hard black-brown cakes. The pans, with precipitate and filter-cloth, are now introduced into the muffles of the ….Read more
In the use of the apparatus purchased for the new chemical laboratories of the university, no piece has given us more satisfaction, or has been a greater success, than a new still which is the subject of this paper. In the designing of this still I had two definite objects in view ; one, the utilizing of steam from the large 60 horse-power boiler used in heating the building, and the other, a provision for making distilled water with gas, when steam from the heating-plant was not available. The still is encased in wrought-iron, with a lining of asbestos, and is provided with a float which automatically regulates the flow of water from the supply-pipe. It was made for me by G. J. Murrle, Pforzheim, Germany, and was imported by Messrs. Eimer & Amend, of New York City. It is a beautiful piece of apparatus, and the workmanship is excellent in every detail. The essential parts of this apparatus will be understood by consulting the accompanying figures, but a few words of explanation may be appropriate. The still has a capacity of seven gallons, and is made of heavy copper, tin-lined. It has a water-gauge showing the height of the ….Read more
Owing to certain inexplicable failures of tires, The Standard Steel Works authorized us to make a series of experiments to determine, if possible, the cause of the trouble. As a result of numerous analyses and physical tests, both from defective and experimental tires, we are able to present the following facts concerning piping and segregation, as they exist in the original ingot, and their effect upon the finished tire. At the autumn meeting of the Iron and Steel Institute, in a paper on segregation, after giving analyses from various parts of different-sized ingots, makes the following statement: “It may be fairly assumed that ordinary ingots are not seriously affected by this redistribution,” that is, by the segregation of the elements.
We think the following data show conclusively that this is not the case, and that there are conditions under which ordinary ingots are seriously affected by this redistribution of the elements.
Our opinion is that segregation and the existence of piping in the ingots used are the causes of by far the larger percentage of failures of steel tires. If this opinion can be substantiated, then, as the two evils of piping and segregation ….Read more