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By S. F. Emmons

IN a report upon the geology of Leadville and vicinity, which is still in the hands of the Public Printer, I have given, at some length, my conclusions as to the genesis of the remarkable silver-lead deposits of that region, and the data, gathered during a long and careful consideration, upon which my views were founded. In the brief abstract of this report, published in 1881, the bare conclusions are given, with but few of the facts upon which they were founded. Since that time, these conclusions have been variously criticised, and it has even been assumed that the views I expressed with regard to these deposits were intended as a theory of ore-deposits in general. Had my final report been printed, no such misconception could have occurred; for, in that I explicitly disclaim any intention of general application of the theories there presented. Even in the abstract I am unable to find any statements which would. justify such a conclusion. Since my Leadville work, however, I have had further opportunities of examining ore-deposits, and have given the general subject much thought and study, and, as a result, I have made in my own mind certain generalizations, which, I am conscious, need the test of a far greater number of practical applications than I have yet been able to make, but which, I think, it may be well to present to the members of the Institute as suggestive, that their own observations may further prove or disprove them. I shall use my Leadville observations and the criticisms which have been made upon them as a sort of text for my remarks. The salient facts, which I thought to have determined with regard to the Leadville deposits, which, as is well known, are silver-lead deposits in a dolomitic limestone, overlain and in

Jan 1, 1913

By R. P. Corbett

Since the beginning of operations at the Kelley mine in 1952, Anaconda has emplaced more than 150,000 cu yd of concrete underground. Concreting practices have changed over the years but the net result is still the same- lower costs along the line and more versatility.

Jan 7, 1961

By Eugene Stebinger

INTRODUCTION. A LARGE number of papers and reports dealing with the coalfields of Montana have been published + during the last 30 years, but the information is much scattered, appearing in many technical and scientific journals and in government reports, in many cases inaccessible to those most interested. In recent years, especially since 1905, ,our knowledge of the geology and coal contents of the important fields of the State has been much increased. Fairly specific and detailed information is. at hand on all of the principal coal-bearing areas. The fields for which data are not at hand are small and inaccessible, and their omission will not materially affect an estimate of the coal resources of the State, viewed as a whole. The paper here presented is a summary of existing information, all sources having been freely utilized in its preparation. The viewpoint adopted is that of the geologist, rather than that of the engineer or colliery operator, because by far the greater portion of the coal areas present have had only the most meager development, making information that, will aid in prospecting and opening the at present little used coal lands of paramount importance to those interested in the coal fields of the State.

Jan 9, 1913

By V. N. Mackiw

IN the process employed by Sherritt Gordon Mines Ltd. for the production of metallic nickel, a sul-fide concentrate is leached with ammonia and air under pressure. Following the removal of iron, copper, and other impurities, there remains a purified solution having the following analysis: 40 to 50 g per liter Ni, 200 to 400 g per liter (NH4)2 SO 4, and 20 to 30 g per liter NH3. Metallic nickel is reduced from this solution by hydrogen under pressure at 300' to 350°F in mechanically agitated autoclaves. A catalyst, ferrous sulfate, is required to initiate the first reduction. After the reduction, the depleted solution is discharged, leaving the metallic nickel in the autoclave. The nickel produced, being in a finely divided form, is used as a catalyst for the reduction of the next batch of solution. Upon repeated use the metallic nickel particles increase in size and become more compact, resulting in the production of a powder with higher apparent density. For this reason, each reduction is termed densification. Finally, when the burden of metal powder in the autoclave becomes too great to obtain effective agitation, both powder and depleted solution are discharged. The autoclave is then filled with fresh solution, ferrous sulfate catalyst added as before, and a new cycle started. The operation is described in earlier publications.1-6 A comprehensive historical review of the reduction of metals from solutions in general was given in a paper by Schaufelberger.7 The experimental data presented in this paper were taken from the work done in the Research Laboratory of Sherritt Gordon Mines Ltd. in Ottawa during the development of the process in 1951 and 1952. The results of the work were tested on a pilot plant scale in Ottawa in the period 1952 to 1953. Following laboratory and the pilot plant studies a commercial process has operated successfully since 1954 in the Nickel Refinery of Sherritt Gordon Mines Ltd. in Fort Saskatchewan, Alberta. General Experimental Technique The experiments were carried out in a stainless steel, 1-gallon, agitated autoclave designed and manufactured by Autoclave Engineers Inc. The inside dimensions of the vessel were 5 in. diam and 12 in. depth. The stirrer consisted of a 1/2 in. diam shaft 11 in. long fitted, with an axial flow type impeller (three blades bent to throw downwards) and a radial flow

Jan 1, 1958

By Arthur Zentner

THE PAST YEAR saw important developments in all the main branches of zinc metallurgy, which can only be douched on briefly here. Vertical Retort Smelting-The New Jersey Zinc Co. reports their operations to be about as last year when the number of vertical retorts at the Palmerton plant was increased from 16 to 28. The first unit of eight vertical retorts at Oker, Germany, to treat the Rammelsburg complex ore was completed early in the year. A second unit has been under construction and is probably ready to start operations about this time. Each unit is rated for 10,000 metric tons of zinc per year. A plant of 40,000 metric tons annual capacity is the goal. A reflux plant was also built to make high-grade zinc. The plant program is being -carried forward with government finan¬cial assistance, as was the case with the electrolytic zinc plant at Magdeburg. Government subsidies cover mining and 'smelting, and allow for depreciation and reasonable return on invested capital, according to U. S. Bureau of Mines reports.

Jan 1, 1938

By GEORGE A. KIERSCH

The awesome destructive power of known and projected weapons of war presages a new need for geologists and engineers, who may be called upon to locate vital industry underground, thereby protecting it from sky-borne destruction. The Corps of Engineers is now conducting special tests to establish design standards covering the general field of underground installations as well as surveys a of construction methods and the operational hazards connected with such plants. National planning must dictate a policy that is either tactical, where surface manufactured parts; are stored underground and during art emergency assembled, or operational with both the manufacturing and assemblage completed in subsurface plants. Both plans of operation require the use of subterranean plants. Relocation of vital plants underground will probably involve only a small percentage of the production capacity of this nation. The cost of rebuilding in new location will obviously limit its adoption

Jan 1, 1949

By E. M. Chance

HERBERT M. WILSON, Pittsburgh, Pa. (written discussion).-Permit me to endorse the author's conclusions and their form of presentation as ,being, in my judgment, the last word 'on the subject of lights for the illumination of coal mines. I also feel that the open-flame oil lamp has outlived its usefulness, and that it should go, in the interests not only of safety but of efficiency. Where an open-flame lamp can be used with safety in non-gaseous mines, the acetylene light adds materially to efficiency by its better illumination, and to safety for the numerous reasons given by Mr. Chance. The latter, however, lays chief stress on the value of the acetylene because of its non-fouling and non-obscuring effect on the atmosphere. Another important advantage over any other form of illumination is the clear, bright light projected at the point where the workman may look for danger. The better illumination materially safeguards the worker against obstacles over which he may stumble when traveling, and against dangers from falls of roof or of coal, weakness in timbering, and similar conditions. The acetylene lamp, where it may be used with safety, has advantages even over the present electric cap lamp, in that it gives a higher luminosity; and when the miner comes to learn its signals, as he will in time, just as he learns those given by the open-flame or the safety lamp, he will find that the acetylene lamp is a fair detector not only of methane but of carbon dioxide, as clearly shown by Mr. Chance. The only, serious objection, raised against the use of carbide lamps. has been recently in Pennsylvania, due to the belief of the State Mine Inspection Department that it endangered miners working on pillar work, or other places where carbon dioxide might accumulate, or where there is lack of sufficient ventilation, and because it was believed that the indications of the carbide lamp would not give the miner sufficient warning. On this point Mr. Chance has clearly shown the fallacies of the objections. I may add that for those unable to detect carbon dioxide with the acetylene lamp, the maximum of protection would be afforded by using an open oil lamp or a flame safety lamp in such places; or, because the miner might not watch his oil light, a better, protection still would be offered by a sufficient number of daily inspections of such working places by a fire boss or other official, with flame safety lamp.

Jan 4, 1917

By G. R. Fitterer

By means of the C-Sic thermocouple1, liquid metal temperatures have been found to vary much more than was previously supposed, and fortunately these variations can be directly associated with some of our former knowledge which combined to form the "art" of liquid-metal manipulation. Commercial Development of This Device Several types of installations are operating in different plants. There are so many variables in steel plants in regard to operation, procedure, arrangement of pouring platforms, ladles, etc., that most of the installations now in service in this country are "tailor-made"; nevertheless, it is felt that satisfactory gains have been made, inasmuch as each installation has indicated some effect of temperature upon the metallurgical operation, and has pointed the way toward technical and financial benefits. In most cases, it has been necessary to accumulate the temperature data until sufficient metallurgical information is available for the drawing of conclusions. When mechanical difficulties have been eliminated, a distinct correlation of these factors has been obtained. The installations now in service are used for the determination of temperatures in the basic open-hearth furnace prior to tapping and in ladles from both acid and basic furnaces prior to pouring. Some of the installations are in shops making the higher priced steels; others are in "tonnage shops." The errors of human element, smoke screens and emissivity corrections connected with the use of the optical pyrometer do not affect the C-SiC thermocouple readings. The accuracy of the C-Sic thermocouple and the temperatures measured are discussed later in this paper. Temperature Variations or Liquid Pig Iron One well-known discussion between the blast-furnace and open-hearth (or Bessemer) departments has occurred intermittently for more

Jan 1, 1936

By J. W. Bolton

PRODUCTION of sound bronze castings is a matter of great practical interest to users and manufacturers of high-grade non-ferrous engineering specialties. Although there has been much excellent research in this field, there still remains some confusion regarding the fundamental principles underlying production of really sound bronze. The literature of the past 20 years on this subject indicates that the prevailing opinion of metallurgists and foundrymen has been that unsoundness in bronze is due generally to oxidation. The following references are typical.

Jan 1, 1929

By H. I. Smith

THE recently developed potash industry in southeastern New Mexico, though based on a relatively new discovery, marks the latest and perhaps culminating phase of the effort to obtain a domestic source of potash that began with the leaching of wood ashes more than 300 years ago. In the search for mineral potash in America, the Geological Survey has played a conspicuous part and has paved the way for much of the private activity that now bids fair to free the nation of foreign domina¬tion in supplying the nation's potash requirements. HISTORICAL REVIEW A pamphlet published by Thomas Stephen in 1758 pictures the industry in its early struggling condition.1 Just before the Civil War, a deposit of mineral potash had been found in Germany and its value as a fertilizer had been discovered. On this account and because the supply of wood ashes had decreased, the Ameri-can potash industry gradually lost its importance. During the next 50 years, with European potash available with little effort and with satisfactory substitutes on the market for the manufacture of soap, the interest of the American people in American potash declined. In 1910 this interest was suddenly revived by the abrogation of American potash contracts in Europe. Congress passed an act, approved by President Taft March 4, 1911, providing for "researches with a view to determining geological conditions favorable to the presence of deposits of potash salts." Appropriations were made to the Geological Survey and the Bureau of Soils to carry out the provisions of this act. The work of the Survey was directed toward the finding of commercial bodies of natural soluble potash salts; the Bureau of Soils was more concerned with the processes of extracting potash from industrial wastes and organic sources. Private agencies also became interested in the program. The Geological Survey has continued its search throughout the ensuing period of more than 20 years and has studied many types of deposits in many parts of the country.

Jan 1, 1933

By Willard H. Mutchler, Henry S. Rawdon

As part of the study of the scratch-hardness method for metals and alloys in coöperation with one of the technical committees of the American Society for Testing Materials, the authors devoted considerable time to the study of the changes in hardness of metals when cold rolled. Various seemingly contradictory statements in the technical literature concerning the applicability of the serateh-hardness method to such cold-rolled materials were among the principal reasons for the investigation, the results of which are in part presented here. The effect of cold deformation, at least in moderate degrees, on the hardness as measured by the Brinell aid other common methods is so well known that further reference is unnecessary. Concerning the scratch hardness of cold-worked metals, Martens and Heyn state1 that hardness, whether measured by the ball-pressure rnethod (Kugeldruck) or by the scratch method (Ritzverfahren), will be increased by cold deformation. Jeffries and Archer give a seemingly diametrically opposite view. They state,2 that "the sclerometer (indicating scratch hardness) shows little difference between cold-worked and annealed metals." Portevin3 has shown that the rate at which the Brinell hardness of cold-worked copper and brass increases is very high for relatively slight deformation after which it drops to zero, while Merica and Walten-berg4 have observed that monel metal shows evidence of softening on

Jan 1, 1924

By G. R. Fitterer

By means of the C-Sic thermocouple1, liquid metal temperatures have been found to vary much more than was previously supposed, and fortunately these variations can be directly associated with some of our former knowledge which combined to form the "art" of liquid-metal manipulation. Commercial Development of This Device Several types of installations are operating in different plants. There are so many variables in steel plants in regard to operation, procedure, arrangement of pouring platforms, ladles, etc., that most of the installations now in service in this country are "tailor-made"; nevertheless, it is felt that satisfactory gains have been made, inasmuch as each installation has indicated some effect of temperature upon the metallurgical operation, and has pointed the way toward technical and financial benefits. In most cases, it has been necessary to accumulate the temperature data until sufficient metallurgical information is available for the drawing of conclusions. When mechanical difficulties have been eliminated, a distinct correlation of these factors has been obtained. The installations now in service are used for the determination of temperatures in the basic open-hearth furnace prior to tapping and in ladles from both acid and basic furnaces prior to pouring. Some of the installations are in shops making the higher priced steels; others are in "tonnage shops." The errors of human element, smoke screens and emissivity corrections connected with the use of the optical pyrometer do not affect the C-SiC thermocouple readings. The accuracy of the C-Sic thermocouple and the temperatures measured are discussed later in this paper. Temperature Variations or Liquid Pig Iron One well-known discussion between the blast-furnace and open-hearth (or Bessemer) departments has occurred intermittently for more

Jan 1, 1936

By Frank C. Roberts

Progress in the facilities for handling mining products has been largely superinduced by the necessities of commercial economy ren dered requisite in order to meet the demand of competition. So rapid has been the depreciation in the value of mineral products, primarily due to the disproportionate increase of output over con sumption, that it may be justly claimed that mining, when considered as a commercial success, depends largely upon the ease and cheap ness by which the products are brought to the surface of the ground. In all methods of performing this operation, wire rope enters as an important factor; and the object of the present sketch will be to explain, as fully as is consistent with the space allotted, the various • adaptations of wire rope employed in placing coal and ores within the reach of our overground systems of transportation. These adaptations will be considered in the following order: I. Hoists. II. Inclined planes. a. Engine planes. b. Gravity planes. c. Aerial planes. III. Haulage. a. Tail-rope system. b. Counter-rope system. c. Endless-rope system. IV. Hoists. The term " hoist" is applied to the system whereby the mine product is elevated from the mine-level to the surface through ver-

Jan 1, 1888

By C. H. Samans, G. F. Tisinai

HARDENING and embrittlement of the ferritic chromium stainless steels at temperatures near 885 °F have been known for a long time.' However, no satisfactory explanation has been given. Both ordering and precipitation hardening have been suggested. Fisher, Dulis, and Carroll2 discovered a chromium-rich body-centered-cubic precipitate in embrittled alloys. Subsequently, Williams' and Wright4 also have found evidence of this body-centered-cubic constituent. William's hardness, electrical resistance, and magnetic studies led to his proposal of a new constitutional diagram for the Fe-Cr alloys. The new feature of this diagram is the eutec-toidal decomposition, below about 970°F, of the s phase into two stable body-centered-cubic solid solutions, one rich in iron and the other rich in chromium. An observation of Heger5 that the amount of s phase has increased and the amount of chromium-rich body-centered-cubic phase decreased in the interval 5000 to 32,600 hr at 900°F, even though the alloy increased in hardness, casts some doubt on this diagram. If precipitation hardening causes the embrittlement, the precipitate probably is always coherent with the matrix, since no evidence of overaging has been reported. It cannot be stated positively, however, that Fisher's body-centered-cubic constituent is the embrittling phase. According to Preston's data,6 such a chromium-rich phase should have a parameter less than about 0.5 pct larger than that of the iron-rich matrix lattice. Moreover, the constitutional relationships whereby Fisher's constituent forms, and whether it is stable, metastable, or a transition phase, are not yet completely clear. The recent studies of Wright4 and of Lommel,7 as well as the earlier studies of Becket8 and of Hochmann,9 have shown that 885°F hardening occurs in relatively pure Fe-Cr alloys. No evidence of its occurrence or absence in chromium itself has been reported. The rate of hardening in high purity alloys seems appreciably slower than that in alloys containing larger amounts of impurities (chiefly carbon and nitrogen). This may be due merely to the absence of hardening and straining effects from precipitated carbides and/or nitrides. These observations on high purity alloys make it seem unlikely that 885 °F hardening is caused by a constituent containing other than iron and chromium atoms, e.g., carbides and/or nitrides. Wright,4 Lommel,7 and Lena and Hawkes10 emonstrated the accelerating effects of a finely dispersed precipitate of (probably) chromium nitride on the hardening reaction. This appears to be evidence that lattice straining increases the rate of nucleation of the hardening constituent. Some new observations on 885°F hardening are reported here. They show an effect of preheat treatment that should contribute to a better understanding of the 885°F hardening phenomenon. They also clarify a discrepancy which exists in the literature. Some investigators have reported most rapid hardening at 885", whereas others have reported it at 930°F. The present work also shows that 885°F hardening does not occur in electrolytic chromium, and that any long range ordering type of reaction affecting any sizeable part of the volume is unlikely. Materials Studied Table I shows the currlposition of the alloys used in this investigation. In these alloys carbon and nitrogen are present in roughly similar amounts. Presumably both elements precipitate, as carbides and/or nitrides, during the heat treatments given.

Jan 1, 1958

DISCUSSION, G. Derge and D. J. Girardi presiding N. A. Gokcen (Michigan College of Mining and Technology, Houghton, Mich.)—While the authors present very interesting results on the effect of sulphur upon the solubility of oxygen, they have not established convincingly the lines of two-fold saturation (the valleys in Fig. 2) and the ternary eutectic point. Their contention that sample S-7, upon melting at

Jan 1, 1954

By E. S. Davenport

IT is indeed an honor and a responsibility to have been selected to present the thirty-fourth in this series of Henry Marion Howe lectures, established to perpetuate the memory of a great teacher and one of America's outstanding scientists. Previous Howe lecturers have established high standards for this annual AIME event. It has been my good fortune to have enjoyed close association with five of these former lecturers; namely, Bain, Grossmann, Johnston, Sosman, and Vilella, all of whom have been prominently identified with the research activities of the organization with which I am connected. Some years ago I had an opportunity to examine a letter written by Professor Howe in 1904. This document was particularly interesting to me since I never had the privilege of personal acquaintance with Professor Howe and do not recall even having seen him during his long and active career. In view of the fact that the letter dealt, to some extent, with matters related to the subject of today's lecture, I would like to quote briefly from it. The letter is datelined, "Bad Kissingen, June 11, 1904." The salutation reads, "Dear Bradley," which suggests that it was probably addressed to Bradley Stoughton, who, I believe, was working with Howe at Columbia University at that time. The letter reads, in part, as follows: "Austenite and Martensite. I have not examined what Osmond says in his new book. His former remarks about austenite I found very confusing, indeed unintelligible. I think we can reconcile matters well enough for the present by assuming that martensite is a transition step between austenite at one end and ferrite and cementite at the other. Above critical range for steel of 0 to 1.80 carbon, austenite is normal state; below Ar1, ferrite and cementite are normal." The letter then continues with a discussion of Osmond's ideas on metallographic nomenclature, particularly his use of the terms martensite, troostite, and sorbite, including the following pointed comment: "For common purposes it seems to me unwise to drag them in, and much simpler to confine ourselves to the end stages Austenite Ferrite plus Cementite Osmond does not really know his own mind— or does not clarify his ideas to others—as to nomenclature." Thus we see that, as far back as 1904, the transformation of austenite, and the products of that

Jan 1, 1958

By H. J. R. Way

The work to be described was undertaken at various periods from 1937 to 1939 on the Busia gold field, in the eastern province of Uganda. It was decided to examine the possibility of reef prospection by the resistivity method, for it was not known how far the usually disintegrated nature of most reefs in the ubiquitous laterite near the surface would obscure indications obtained by resistivity traverses. The work at the commencement was therefore largely experimental, but the results obtained thereby were satisfactory, and a survey was started at the Government closed area at Amonikakine. With the limited time and resources at the writer's disposal, it was not possible to complete the survey to his satisfaction or to follow up exhaustively all the geophysical indications, but some of the results of the experimental work and the survey were of sufficient interest to be worth recording; in particular the relation between the width of reef, electrode separation and shape of the curve, and the interference effect of constant separation curves over zones of float are significant and useful. Three new veins were located, but only one contained sufficient gold to warrant detailed prospection. This was called the Geophysical reef, and was uncovered over a strike distance of 1140 ft., and there are indications that it extends over a distance of 1990 ft. These results and the recom- mendations consequent therefrom were embodied in a special report to the Uganda Geological Survey. History OF the Field The Busia field is in the southeastern corner of Uganda near the Kenya-Uganda border, and is about 17 miles north of the northeastern corner of Lake Victoria. Gold was first discovered in the area in the stream beds by Davies1,2 in 1932. Subsequently numerous small alluvial claims were worked by prospectors and the area was prospected for reef by a company for periods varying from three to nine months, but was finally abandoned, as the results were considered unfavorable. Further prospecting by the Geological Survey in 1935-1936 under Davies8 and later under the writer4 uncovered three reefs with sufficient gold values to be of economic interest. These were finally taken over by a company known as Borderland Syndicate, which still owns the area, and from September 1937 to the end of 1941 about 13,000 oz. of gold was extracted from reefs of the area proved by the Geological Survey. Opencast mining operations are still proceeding (February 1943). The Amonikakine area lies to the immediate north of that of Borderland Syndicate. A certain amount of prospecting had been done when the writer started work there. As a result of his report, this area was taken over by another syndicate, but little further work was accomplished before it ceased operating because of difficulties of wartime working.

Jan 1, 1946

By L. W. Kempf, R. S. Archer

The binary aluminum-silicon alloys have certain characteristic advantages which are now well known, and these alloys have come into considerable use during the past several years.' Their field of application has been limited to a certain extent, however, by their low yield point and hardness, low endurance limit, and relatively poor machining characteristics. These properties are improved by the addition of copper, and the ternary aluminum-silicon-copper alloys constitute an important class. The addition of copper decreases the corrosion resistance of the aluminum-silicon alloys and increases specific gravity. Magnesium is a hardening addition which seems to have relatively little effect on corrosion resistance, and which, of course, reduces specific gravity. The object of the work described in this paper was the development of alloys and heat treatments for the production of sand castings and permanent-mold castings having substantially all the advantages of the binary aluminum-silicon alloys together with mechanical properties improved to a degree permitting wider application. Constitution of Alloys Magnesium and silicon combine in aluminum alloys as the compound Mg2Si, which forms a binary system with aluminum. In alloys containing an excess of silicon over that required to form the compound, solidification ends with the freezing at 1022' F. (550' C.) of a ternary eutectic of aluminum, Mg²Si, and silicon. Judging from the horizontal projection of the liquidus surface as given by Hanson and Gayler,² this ternary eut,ectic contains about 13 per cent. silicon and 6 per cent. magnesium. All of the alloys discussed here contain excess silicon, so it

Jan 1, 1931

By Arthur J. Boynton

In the preparation of this paper the writer has been influenced by the fact that descriptions of various means of cleaning blast-furnace gas have been published and that further descriptive treatment of the subject will probably be less interesting than a statement of conclusions with regard to preferable methods which have been reached by him as a result of experience and observation in this country and also as a result of somewhat detailed investigation of the subject made toward the end of the year 1927 on the Continent of Europe and particularly in Germany. Owing to various circumstances, including a cost of fuel that is extremely high in relation to the wages of labor, the German iron and steel industry has accumulated experience in gas washing which is as yet in part lacking in the United States of America. The paper begins with a statement regarding the economics of the use of blast-furnace gas, then considers the principles and practices employed in its purification. Uses of Blast-furnace Gas For many reasons having to do with the utilization of coke-oven and blast-furnace gases in steel manufacture and with the use of hot metal, the blast furnace is now usually a part of a steel-producing unit, which also includes coke plant and rolling mill. Therefore both blast-furnace and coke-oven gas are usually applicable to any of the iron and steel-making processes, including the generation of power, and their allocation in any given works should be considered as a single problem. The uses to which blast-furnace gas, either alone or mixed with coke-oven gas may be put, include the following: Regenerative Heating of Ail. for the Blast Furnace.—This is the oldest and metallurgically the rnost important of all uses. It is universally performed with unmixed blast-furnace gas and under proper conditions should require not over 23.5 per cent. of the total gas generated for a blast temperature of 1350" F. For Steam-raising Purposes.—This is almost universally done with unmixed blast-furnace gas. From the standpoint of quantity used, it is at the present time the most important application in American steelworks practice.

By R. W. Borio, T. S. Spicer

Inflammability and crossing point apparatus were used to study the influence of increasing amounts oi such inerts as ash, fly-ash, pyrite, limestone and Portland cement with several pulverized bituminous coals. The results indicate that it requires large proportions of inerts to substantially suppress the ease of ignition. The ignition phase of the combustion of solid fuels has been under study periodically since 1900. With the advent of pulverized coal firing some 60 years ago, a technique now dominating the coal utilization field, the ignitibility characteristics have become increasingly important. Much of the early work was directed toward the prevention of coal dust explosions and improved mine safety rather than combustion. Many factors affecting ignitibility have been studied and numerous methods devised in an effort to measure the ignition temperature and these have been reviewed by other authors. A recent survey was made by Finney and Spicerl in 1959, so a discussion of previous work will be omitted. Despite these efforts, the initial stage of combustion, termed ignitibility, is still a little understood phenomenon. In fact, no ASTM method has been adopted for the calibration of this illusive property. However, a D-5 Subcommittee XVI on Ignitibility of Coal and Coke of ASTM (now inactive) defined ignitibility:' "The ignitibility of a fuel is that char-

Jan 1, 1963