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By George Rupp

THE Sunrise iron mine of The Colorado Fuel and Iron Corporation is in Platte County, Wyoming, about 110 miles north of Cheyenne. It is served by the company-owned Colorado and Wyoming Railway, which connects with the Chicago, Burlington and Quincy and the Colorado and Southern railways at Guernsey, Wyoming, a distance of 6 miles from the mine. The original Sunrise claims were staked mainly by United States Army officers and soldiers stationed at old Fort Laramie, because of small showings of copper in the Carboniferous limestones that form a horizontal capping overlying the Huronian iron ore. A small copper smelter was operated for about three years at Fairbanks, now an aban-doned town on the North Platte River. As many of the copper shafts and test pits near the present Sunrise mine were deepened, they pene-trated the capping and encountered iron. ore or gray sericitic schist, and were abandoned. Evidence of an early interest in iron ore was found when the Chicago claim was stripped for mining. A narrow, winding crevice was dis-covered, which led downward 20 ft. through the capping to the underlying soft red hematite, in which a room 10 by 14 by 7 ft. had been excavated. Stone hammers and wedges and a few rusted pieces of iron were found on the floor, and the evidence is conclusive that the excavation was used up to rather recent times by Sioux Indian medicine men, to provide war paint.

Jan 1, 1939

By Blamey Stevens

The object of this paper is to show how igneous intrusion is governed by definite mechanical laws. A distinction is made between dikes and fissures, and the various characteristics of intrusions are explained on an exact scientific basis. The modification of rock-stresses by intrusion is then considered and extensive isostress regions are recognized. Finally, a complete classification of intrusions is constructed covering all possible cases. The generalizations of observed data, taken from Geikie's Text-Book of Geology, confornl to the laws of intrusion herein stated, and the deductions based upon these lams. No authority, however, is quoted for the type which I hare named a corrugated intrusion. Its existence is a necessary deduction from the laws of intrusion, and even the entire absence of examples in technical publications cannot disprove its reality. In all probability, corrugated fissures would have remained undiscovered, but for the nrorking of mineral veins. As intrusions of tabular form are seldom worked for commercial purposes, it has been left for theory to anticipate the discovery of corrugated dikes. In the light of these laws of intrusion and the corresponding laws of fissures,' there seems to be a remarkable uniformity of stress-distribution in rocks at moderate depths. This renders possible the mathematical calculation which should help us to approximate exact science in this and kindred branches of applied geology.

Jan 1, 1911

By V. Lepetic, C. C. Harris

A systematic program of investigations covering all aspects of cell hydrodynamics,1-3 flotation kinetics,4,5 surface chemistry and their interactions has as a major objective the elucidation of the flotation micromechanism and the principles of cell design and scale-up.6 Purely from the scale-up point of view, a family of reactors should enable different throughputs of the same material to be similarly treated or, at least, to be treated in a manner which differs beween reactors in a predictable way. Thus, for the same material and residence time, the recovery and grade from differently sized cells of the same family should, ideally, be similar or, at least, be related to each other in a known way. It is well known, however, that different-sized cells do not always achieve similar results, and it is necessary to enquire into the reasons for these differences. For example, it may be that the relative dimensions of different-sized cells result in hydrodynamic conditions which preclude similarity; if so, different scaling may improve the situation. The major question concerns identifying the dynamic conditions and their associated geometric requirements which govern the flotation process, and the criteria which are necessary for their fulfillment. It is to answer such questions that the program referred to earlier was instituted. In connection with this program and in order to examine data concerning the physical features and operating conditions of existing flotation cells, the following survey was carried out. This work represents an approach which is complementary to experimental investigations, for it recognizes that the design of existing cells may embody several of the principles being sought. If data for enough cells, especially families of cells, are examined, some broad requirements common to all cells may emerge.

Jan 9, 1966

By B. Bryan

The tank car price of gasoline today is controlled by oil in the ground, rather than by stocks of gasoline or methods of refining. Previous to the commercial cracking of fuel oil, there was a normal and continuous relation between gasoline stocks, consumption and prices. From the beginning of the new cracking era in 1923 to the summer of 1926 there was a changing relationship, growing toward a correlation between the potential gasoline in storage and the price of gasoline. Since the development of large reserves of shutin production in Wyoming, California, Seminole, West Texas and Venezuela, the relationship between stocks of gasoline and gasoline prices has disappeared. The extreme depression of the Group 3 price can only be accounted for by oil which is not being produced but which we fear may be produced at any time. In Fig. 1, the curve of gasoline stocks is simply stocks of finished gasoline. The curve of potential gasoline is made by taking 40 per cent. of all stocks except gasoline, kerosene and lubricants, adding to that stocks of finished gasoline and dividing the sum by total gasoline con-sumption to get the months' supply of gasoline at the current rate of consumption. The price curve is the lower figure given by the National Petroleum News for the first quoted date of each month, with the price scale reversed. Stocks of potential gasoline have decrrased from 17 months' supply at the peak of 1924 to a low of 7 months' supply during the past summer, yet the low immediately precedes the lowest price for gasoline since it was a waste product. The tendency of the price curve to parallel the curve of potential supply is quite pronounced until the summer of 1926, since which time they have abruptly separated. The curve of gasolinct stocks is equally remarkable in relation to price when it is considered that total consumption for the year 1927 is almost exactly twice that of 1924. Clearly a new factor has been introduced. There is no possible factor to account for this distortion except known reserves of oil in ground storage, and therefore, until such time as the Bureau of Mines or the

Jan 1, 1928

By G. B. Pryde, R. M. Magraw

In laying out a new mine, provision should be made for the ultimate recovery of as much coal in any given bed as is consistent with safety and economic mining. Though each mining district, if not each individual mine, has problems that make the adoption of any hard and fast rule impossible, certain basic principles are adapted to practically all conditions. One of the most vital is the provision for barrier pillars of ample dimensions to protect all haulage and permanent airways during the life of the property. Where conditions permit, room or butt entries should be driven on the strike or slightly to the rise, and rooms turned at right angles to these entries. The width of rooms and room pillars is governed by conditions prevailing in the mines under consideration. A safe rule is: In advancing, extract not more than 25 to 35 per cent. of the entire seam; in exceptionally thick seams, considerably less than 25 per cent. should be taken. Rooms usually vary in length from 250 to 350 ft. (76 to 106 m.) with a barrier pillar of not less than 80 ft. between the last crosscut. in rooms and the back entry of the level above. All entries, rooms, and entry-and-room crosscuts should be driven .on sights and room crosscuts should be driven at, right angles to the direction of the rooms. In mines under excessively heavy cover or where roof conditions are bad, rooms should be driven narrow and a barrier pillar left at every fifth to tenth room. This barrier should be of such dimensions that one or more rooms, with pillars of usual dimensions, may be turned through it when the barrier is no longer required. Two of the advantages of such a barrier are the protection of the panel against peaking of roof load during pillar extraction and the easy closing of the entry in case of fire. Where economic conditions permit, it is preferable to follow the retreating panel system of mining. In the case of coal that outcrops, and even in cases where no outcrop is exposed, it is preferable to commence pillar extracting on the high side of the mine. Where the retreating

Jan 1, 1922

By R. A. Anderson, O. D. Sherby, J. E. Dorn

Solid solution alloying increases the plastic properties of aluminum at elevated temperatures by solid solution strengthening, by restraining recovery and recrystallization, and by a Cottrell effect. When binary aluminum alloys are strained and aged at 1940° to 300°K they develop a yield point. This is attributed to a migration of dislocations to solute atoms during aging. IN view of the ever expanding interest in applications of metals and alloys to high temperature service conditions, it becomes increasingly important to be cognizant of the effect of various metallurgical factors on the strength of alloys at elevated temperatures. One problem of wide interest, not only because of its engineering significance but also due to its fundamental scientific importance, is the elucidation of the effect of alloying elements on the plastic properties of homogeneous a solid solutions at elevated temperatures. It is indeed astonishing to note that in spite of its importance, and in spite of extensive random testing of alloys at elevated temperatures, no systematic investigation has been reported yet on the effect of alloying additions on the plastic properties of a solid solutions at elevated temperatures. This deficiency in our knowledge prompted the investigation described in this report. Rather extensive data are currently available on the effect of alloying elements on the plastic properties of a solid solutions at atmospheric and sub-atmospheric temperatures. Such data might be ex- trapolated to higher temperatures and reasonable guesses might be made regarding the influence of such factors as recovery and recrystallization in order to hazard a qualitative estimate of the effect of alloying elements on the plastic properties of a solid solutions at elevated temperatures. Such

Jan 1, 1952

By F. M. F. Cazin

Some twenty years ago the author of a book,* by which, for the first time, molecular action was made to account for nearly all phenomena in hydrodynamics, began his preface as follows: " It is contrary to all experience, that any branch of science should suddenly cut short its own line of reasoning, and drop all connection with its past, and yet as quickly re-establish itself on an entirely new basis. It is, therefore, not without justification that this book should be met with caution and even distrust." When the newly-discovered natural facts and laws presented in this paper were, in 1891, first laid before the officers of the American Institute of Mining Engineers, they might have been preceded by a preface to the same effect; and the expression would have found its justification by the actual experience these facts and laws met with. Since then, as the result of their publication in one of the most prominent

Jan 1, 1895

By Howard S. Bryant

The year 1928 has recently.passed from the picture and it is at this time that the various divisions of the oil industry are giving thought to plans for the present year. The outstanding characteristic of the industry in 1928 was the successful curtailment of oil production to the market's needs. It has been thought advisable to look ahead and endeavor to anticipate the oil demand for the coming year, and thus determine the volume of oil that can be safely produced without causing major additions to surface stocks. The year has been one of smaller additions to stocks than in 1927, a record demand for oil products, and a further developed spirit of cooperation among oil producers, as well as various other achievements. It is well to pause and take stock of ourselves. Present Status of Crude Oil Supply and Demand The total daily new supply of oil is at this time1 about 2,960,000 bbl. per day, made up of 2,585,000 bbl. domestic crude production, 125,000 bbl. casinghead gasoline, and 250,000 bbl. of imports. With the present low consumption, due to the falling off in the winter season demand, it is estimated that about 150,000 bbl. a day are now being run to storage, and that the first three months in 1929 will see large-sized additions to storage. Consumption plus exports of oil have increased at a regular rate from year to year, and although oil production in 1928 passed the 1,000,000,-000 bbl. mark for the second time in the history of the United States, with a production of 25,000,000 bbl. more than in 1927, only 30,000,000 bbl. were added to storage during 1928. This is compared to an addition of 65,500,000 bbl. in 1927.

Jan 1, 1929

By William C. Brice

Minnesota is involved in planning controversies related to taconite and potential copper-nickel mining. Mine facility planning includes the Reserve dining on-land tailings disposal issue and the potential for a new copper-nickel mining district. Both provide a unique opportunity for innovative planning in the attempt to be responsive to public and private interests. Concerns that emanate as a result of mineral resource activities include environmental protection, land use competition, land exchanges, highway and utility extensions, and legal constraints on public or private lands. The purpose of this newly-developed planning approach is to anticipate such issues and provide a rational information base for dealing with them. The result will be a framework plan for guiding public planning, and an impact assessment for reviewing the implications of industrial project proposals. The approach uses a computer-stored resource inventory of natural and cultural information. Geographic data is mapped and entered into a computer storage and retrieval system. This enables systematic analysis of mineral resources along with environmental and land use considerations. Computer mapping describes the relationship of each activity and allows identification of potential conflicts; it also shows geographical extent in the form of statistical compilations. Resource data is being collected and compiled using a standard metric grid (Universal Transverse Mercator). Individual cells are 100 m. squares and represent areas of about 2.5 acres. The study area contains about 145,000 cells. Data inventories are being compiled in 25 natural and cultural resource categories. Geologic variables include Bedrock Geology, Taconite Reserves and Potential Resources, Depth to the Duluth Complex Contact and two soil inventories. Topographic and hydrologic variables include elevation, slope, slope orientation, surface hydrology, and watersheds. There are also 6 biological data variables and 7 land use inventories.

Jan 1, 1977

By N. A. Ziegler

THE present publication is a continuation of the work on gas analysis, described in a paper presented before the Institute of Metals Division a year ago.1 While that paper was largely descriptive in character, dealing with the various parts of the apparatus and method of operations, the present one gives numerical data obtained as a result of a series of experiments with iron-carbon alloys. The apparatus and the methods applied are essentially the same as previously described, changes being only in minor details. Attention should be called to the fact that in the present work we are dealing with the gaseous mixtures obtained as a result of vacuum melting of various ferrous alloys. It should be understood that when the terms "degasified sample" and "products of degasification" are used, they refer to the sample remaining after the vacuum fusion of the alloy and the gaseous products removed therefrom, respectively. The writer does not wish to create the impression that the metallic products of this process are absolutely free from any gaseous elements, nor that the gases obtained are present as such in the original sample. These two points are not yet definitely known and are subjects for future investigation. The point, however, which has been established beyond doubt, is that all the gases dealt with come from the metallic charge and are present either in the charge as such, or are produced as a result of chemical reactions going on within the charge. The suggestion that the gases are due to the reactions between the metallic charge and the refractory materials has no valid basis.

Jan 1, 1929

By Carl H. Samans

THE INFORMATION AVAILABLE on the rolling characteristics of the precious metals-gold, silver, the platinum metals and their alloys-is incomplete and mostly from scattered sources. In the present paper an effort has been made to assemble and correlate it and to fill in some of the gaps that exist. GENERAL ROLLING CHARACTERISTICS SOME EFFECTS OF IMPURITIES Gold and its alloys are generally considered to be hot short and hence are usually rolled cold. Cold rolling of the yellow, green, and pink gold alloys. Which customarily contain gold, silver, copper and zinc and frequently some nickel as well, introduces no new problems since reasonable reductions are quite feasible and the alloys show little tendency to fire crack in subsequent annealing. The white gold alloys. which usually contain little or no silver and 10 pct or more nickel, are very susceptible to fire cracking1 and hence wrist he given relatively heavy reductions, i. e., 8-10 pct or more per pass with a total reduction of about 50 pct between anneals, to minimize this tendency. In addition, it is preferable to keep the bar as flat as possible during rolling. Although no comprehensive study appears to have been made of the effects of impurities on the cold rolling characteristics of gold alloys, the observations of Nowack2 on the effects of small

Jan 1, 1948

I. The Property. The Homestake Mining Co. has acquired through consolida tion the ground and equipment of the Father De Smet Con solidated Gold-Mining Co., the Deadwood-Terra Mining Go., the Caledonia Gold-Mining Co. and the Highland Mining Co., at and near Lead, Lawrence county, South Dakota, in the northern portion of the Black Hills. The company owns or controls 250 claims, comprising 2,616 acres and covering about 8,000 ft. along the strike of the lode. At the surface there are several veins, of which three have united in depth, where the main vein ranges from 300 to 500 ft. in width. The 1,100-ft. level is the lowest at present. The rock of both walls is, so far as known at present, carboniferous alate, and the country is penetrated by a system of porphyry dikes, and in some places capped with porphyry. The output of the company up to January, 1903, has been, approximately, $70,000,000. II. The Ore. The oxidized, open-cut ore is nearly all treated in the three mills on the northern part of the property, which are as follows : The Mineral Point (formerly the De Smet), of 100 stamps, the Monroe (formerly Caledonia), of 100 stamps, and the Pocahon tas (formerly the Deadwood-Terra), of 160 stamps. A cyanide plant, to treat the leachable portion of the tailings from these North End mills, has recently been installed and put into oper ation at Gayville, or Blacktail as it is now known. The Homestake lower-level ore, which comprises the greater part of that being milled at Lead, may be described as a horn blende, garnetiferous schist or slate, which has been crushed and infiltrated with free silica and pyrites, the latter being

Jan 1, 1904

By Reamy Joyce

Conditions in underground mining are so variable that in approaching the problem of the economies effected by the use of pressure-treated mine ties and mine timbers, it is necessary to secure specific data for each mine. Facts must first be dug out to show the service life of untreated timber and the reason for its failure. Generally speaking, decay is the usual cause of failure, but in some mines mechanical destruction is an important factor. Occasionally the two causes combine to produce fail-urrs, and it is difficult to determine positively which factor is responsible. In making comparisons, it is always necessary to start with the cost in place and for this reason there must be accurate information covering the labor cost of installation and the labor cost of renewals. When treated timber is used, it is necessary to know the specifications for the treating process, whether the timber was painted, dipped, treated open tank, or impregnated under pressure according to standard specifications. It is also necessary to know the preservative used and the amount of the preservative that was retained by the timber after treatment. It is also well to know whether the timber was thoroughly air-seasoned before treatment or was green at the time it was treated. The kind of timber available, both untreated and treated, must be known and all of the factors listed above must be taken into consideration in the study of any problem. Variable Conditions A study was made recently of the untreated mine ties used by a bituminous coal company in two of its mines, which are about 20 miles apart. The mine ties were secured from the same sources for both mines. A careful check was made over a 10-yr. period on the life of untreated main-haulage ties, and it was found that in the mine where the haulage roads were on intake air the average life was approximately 5 yr., while in the other mine, where the haulage roads were on return air, the average life was 2 yr. A similar variability in untreated timber

Jan 1, 1940

By C. H. Mathewson

MY first reflection on the subject assigned to me by the officers of this symposium was that a critical description of these lesser characters in the cast of inanimate actors now before us under the title "The Role of Metals in New Transportation" would be about as well received as the description of a horse race in terms of harness buckles and jock-ey's buttons. The word "new" in the title of this symposium seems to shout strong aluminum and stainless steel, unless we transfer our attention to transpor-tation on another planet where the strength-density ratios may require very different engineering treatment. To load a speaker with the "heavier nonferrous metals" amidst the airy consideration of flying or 20th century gliding along the earth and through water, like Hermes, the messenger of the immortals, and expect an instructive or enlivening flight into the area of current exploitation and popular interest in transportation would, of course, require the performance of a miracle or at least the exhibition of genius to which I can lay no claim. But copper and nickel, headliners in other classifications, are also indis-pensable as components of the important new structural materials of transportation, and together with lead, tin and zinc perform many minor or contributory functions in this field that may indeed be con-sidered well-nigh indispensable. A complete and well planned fabric of classification, explanation and critique of even these secondary functions would take much time, and I cannot hope in the 25 minutes or so alloted for the purpose to offer more than a rambling treatment, in which a thread of continuity will be sought by anchorage to one after another of the following attributes or appurtenances of the moving vehicle: 1. The machinery and accessories. 2. The framework and superstructure, and the line or travelway. 3. Light, heat, power, water, sanitary and housekeeping services. 4. Embellishment, or style.

Jan 1, 1936

By John T. Norton

In spite of the very general errlployment of nitride hardening, there is still considerable doubt as to the real nature of the mechanism involved. Experience has shown that the addition of small amounts of hardening elements to iron or steel results in a wide variety of desirable properties in a nitrided case. Perhaps the foremost of these elements is aluminum and in this investigation an attempt has been made to study the behavior of aluminum during the hardening process. It is believed that the establishment of a complete atomic picture of the metal at various stages of the process will indicate the relationships between the several kinds of atoms and their individual influences on the physical properties in a clear and direct fashion. A consideration of the problem suggests a surprising similarity between the mechanisms of nitride hardening and of age-hardening. It is now generally understood that age-hardening may take place by one of two distinct processes, the first involving the precipitation of a finely dispersed phase and the other being concerned with the modification of an existing phase. Following much the same line of reasoning, two theories of nitride hardening have been suggested. The first explanation, which has been generally discussed, particularly by Fry,' states in brief that the presence of aluminum causes the precipitation of aluminum nitride during nitriding and that this finely dispersed phase is the primary cause of hardening. The second explanation, which has not been published but which has been freely discussed by those interested in the problem, postulates the substitution of aluminum atoms for certain of the iron atoms in the several iron-nitrogen phases in the same manner that the substitutional iron-alurninurn solid solution is formed. The marked increase in hardness, as compared with the aluminum-free system, is attributed to the severe lattice distortion accompanying this replacement.

Jan 1, 1934

By O. A. Knight, Helmut Muller-Stock

The suppression of the austenite-martensite transformation that can be brought about by the addition of certain alloying elements, such as manganese or nickel, to plain carbon steel has been known for a long time, especially since Guillet's investigation at the beginning of this century. The extent to which the critical range is lowered depends upon the percentage and nature of the special element added. First the Arl point is lowered gradually, then at a certain percentage a sudden lowering to about 300" C. occurs. The addition of still larger percentages of the alloy may result in lowering the Ar, point to room temperature or below, in which case the steel remains austenitic at room temperature, especially after rapid cooling. The effect of alloying elements of this general type on the lowering of the transformation temperature is well illustrated by Sauveur(lJ$ in his Fig. 281a, reproduced here as Fig. 1. This type of curve is characteristic of both manganese and nickel though it requires about 21/2 times as much nickel as of manganese to produce the same result. The influence of nickel in retarding the transformation of austenite into the lower transition constituents is due to its lowering of the critical range of the steel, which is also well illustrated by Sauveur'l) (after Osmond) in his Fig. 284, reproduced here as Fig. 2. Scott('" presents a diagram illustrating the effect of manganese on the Ac3 and Ara points which is strikingly similar to the diagram above referred to in Fig. 2 concerning the effect of nickel. Lowering the critical range has the effect of increasing the viscosity, or, rigidity, of the alloy at the time when it is undergoing its transformation, which greatly slows down the transformation reaction velocity, and this, in turn, makes it easier to suppress, wholly or in part, the transformational changes. Reaction rates are normally much slower at low

Jan 1, 1934

By Reamy Joyce

Conditions in underground mining are so variable that in approaching the problem of the economies effected by the use of pressure-treated mine ties and mine timbers, it is necessary to secure specific data for each mine. Facts must first be dug out to show the service life of untreated timber and the reason for its failure. Generally speaking, decay is the usual cause of failure, but in some mines mechanical destruction is an important factor. Occasionally the two causes combine to produce fail-urrs, and it is difficult to determine positively which factor is responsible. In making comparisons, it is always necessary to start with the cost in place and for this reason there must be accurate information covering the labor cost of installation and the labor cost of renewals. When treated timber is used, it is necessary to know the specifications for the treating process, whether the timber was painted, dipped, treated open tank, or impregnated under pressure according to standard specifications. It is also necessary to know the preservative used and the amount of the preservative that was retained by the timber after treatment. It is also well to know whether the timber was thoroughly air-seasoned before treatment or was green at the time it was treated. The kind of timber available, both untreated and treated, must be known and all of the factors listed above must be taken into consideration in the study of any problem. Variable Conditions A study was made recently of the untreated mine ties used by a bituminous coal company in two of its mines, which are about 20 miles apart. The mine ties were secured from the same sources for both mines. A careful check was made over a 10-yr. period on the life of untreated main-haulage ties, and it was found that in the mine where the haulage roads were on intake air the average life was approximately 5 yr., while in the other mine, where the haulage roads were on return air, the average life was 2 yr. A similar variability in untreated timber

Jan 1, 1940

By J. Earl Frazier, Howard A. Meyerhoff

IT is not known when silica sand was first noticed along the north coast of Puerto Rico, but the first mention of its occurrence was made in 1922, by N. L. Britton,1 who described its presence in isolated patches extending from Loiza westward beyond Manati. Further observations were made in 1925 and 1926 by Meyerhoff,2 who extended the known occurrences still farther westward to the low hill belt in the Quebradillas limestone immediately south of Hatillo. The extraordinary purity of the sands, which in most localities exhibit no contamination from the nonsiliceous materials surrounding them, was quickly appreciated, and the feasibility of utilizing them for the manufacture of glass was investigated, initially by the Committee on Mineral Resources3 and later (1936) by the Puerto Rico Reconstruction Administration and by H. C. Ray, mining engineer of the Insular Bureau of Mines. In 1934 samples submitted to the Hazel Atlas Glass Co., of Washington, Pennsylvania, were reported to have the composition as shown in the table on column two. Appreciation of the quality of the sand prompted geological and quantitative studies of the deposits, as well as commercial investigations to determine the feasibility of utilizing it locally or on the mainland for the manufacture of glass containers. [ ] DISTRIBUTION OF THE SANDS The quartz sands consistently lie within the outcrop area of the Quebradillas limestone, the youngest of the Miocene formations in the Tertiary coastal plain that fringes the northern coast of the Island. Many of the deposits are closely associated with limestone outcrops, but some appear to be embedded in lagoonal sediments at some distance from rock exposures, and at least one deposit, near Dorado, has been reworked by waves and littoral currents. With this single known exception, the deposits consist of irregular, patternless patches of white sand, which have sharply defined contacts with the surrounding material. Although patches of sand are present in a 90-km. belt that is not more than 5 km. wide, extending from Loiza to Hatillo, they attain maximum size, purity and number in the north central coastal area between Dorado and Barceloneta. Fifty separate deposits have been mapped in

Jan 1, 1945

By R. H. Doremus

From measurements of carbide precipitation rates in a iron it was concluded that the carbides nucleated on dislocations in both strained and unstrained samples, except for the latter at lower temperatures and higher carbon concentrations, where there were more muclei than could form on the dislocations. The equation of Cottrell and Bilby for the segregation of atoms to dislocations was found to be inapplicable to this system. No satisfactory theory for the growth process is available. A study of the rate at which a second phase separates from solid solution can frequently reveal much about the mechanism of separation. There are still many features of the precipitation of carbon from a iron that are not understood, although this system has been examined extensively. To provide more insight into the mechanism of carbide precipitation in a iron, rates of this process were measured at different temperatures, carbon concentrations, and densities of dislocations in the iron. The concentra- tion of carbon in solution was followed from the height of the internal-friction peak; this height is directly proportional to the amount of carbon in solution and is not affected by the growing carbide particles. In this paper these rates are compared with those found by earlier investigators, and the mechanism of precipitation is discussed in light of these results as well as two earlier studies1, 2 and the electron microscopic work reported in the preceding paper. EXPERIMENTAL The amount of carbon in solution was followed by

Jan 1, 1961

E. L. BLOSSOM, New. York, N. Y.-That this paper deals with a real problem is illustrated by a statement made to the speaker a few months ago by the manager of a silver-lead property: "Our ore contains 60 per cent. silica on which the smelters are penalizing us heavily, and they are not able to take all our stuff even then. We have simply got to find some method other than smelting for getting the silver and lead out of our ores. We have had experts down here and have investigated flotation, leaching and volatilization, of which processes the latter is by far the most promising. We are continuing investigation." I was somewhat concerned in certain chloride volatilization experiments which we carried on in Denver in 1903, working on a carload of ore from Butte. Now being connected with the Cottrell process, by which method the fumes will undoubtedly he recovered if they solve the volatilization problem, I have looked into the matter again, and believe it can be developed into a commercial process. On a laboratory scale, working With silver-lead ores, experimenters have obtained a volatilization of over 90 per cent. of the total values in 30 to 60 min, on quantities of 1 to 5 lb., using a roasting dish and a muffle. That looks very good, and would be entirely commercial. On attempting to duplicate these results in a reverberatory furnace, they found that it is more likely to take 8 hr. firing to yield 75 per cent. extraction, which is not commercial at all, as it requires too much time, labor, and fuel, and the whole process is too slow. Of course it can be done, because we have done it in the laboratory.

Jan 1, 1918