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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 James W. Malcomson

The Tigre Mining Co. of Mexico, owned by the Lucky Tiger Combination Gold Mining Co. of Kansas City, decided early in 1910 to enlarge its mill, which consisted of a concentrator milling 3,000 tons of ore per month. The enlarged plant was designed to crush and concentrate 6,000 of ore and to cyanide 7,500 tons per month. The extra tonnage cyanided was to be obtained from tailings which were stored below the old mill. Power was supplied to the old mill from four boilers; a 150-h-p. Corliss engine and two Weber 60-h-p. gas-engines using producer-gas made from charcoal. The total horse-power required, including 60 h-p. used for machine-drills in the mine, was approximately 275. Cord-wood cost $4.32 per cord, 8 by 4 by 3 ft., and charcoal $15 per ton. The fuel supply in the surrounding country was approaching exhaustion; more than 150 mules and 50 men were engaged in cutting and transporting this fuel, and the unsettled political conditions in Sonora were such that it would be practically impossible to keep an organization of this kind together. The price of fuel was steadily rising and at times it became almost impossible to get sufficient fuel to operate. It was estimated that the enlarged plant, together with the mine, would require 750 h-p., as follows: Horse-Power. Old mill, which was left unchanged,..............180 New concentrator,.......................90 Cyanide-plant,........................380 Mine and other requirements,................. 100 Total,........•..................750 In a study of the best manner to obtain power the following alternative propositions were considered:

Jan 1, 1914

By Jack Fox

It is some time since these columns have contained a report to the members on just what is doing in the Society of Mining Engineers. Accordingly, even though it is now a month and a half after the Annual Meeting in Denver, it seems that a report on what transpired at the SME Board Meeting there is in order. First off, I'd like to say that the Members of the Society of Mining Engineers can be justly proud of their representatives on the SME Board of Directors. Of 21 members and officers on the "Old" Board of Directors, 19 were present. President Brower Dellinger chaired the "Old" Board Meeting. Of the 21 members on the "New" Board of Directors, every single one was present. James Boyd, the outgoing AIME President, attended and expressed his appreciation of the support that the Society of Mining Engineers had given him during his year as President of AIME. Members Multiply Robert S. Shoemaker, Chairman of the SME Membership Committee, pointed out that based on figures available, the Society of Mining Engineers had a net gain of 523 members during 1969 while SPE had a 490 net gain and The Metallurgical Society a net loss of 159. This is probably the first time in the last 20 years that anyone has exceeded the SPE net gain in membership. While SME still has a way to go to surpass the Society of Petroleum Engineers in number of members, we did have, on December 1, 1969, 16,369 members. However, 419 were dropped at the end of that month leaving us with a net for the year of 15,950.

Jan 1, 1970

Prior to any detailed discussion, I'd like to say that Dr. Aplan has made direct hits on two important considerations: 1) The most demanding need in Fine Coal research is to develop improved methods of sulfur reduction. 2) The areas of particle (impurity) liberation and froth flotation hold real near-term promise as techniques for improved sulfur removal. Digressing for a moment, I thin kwe can all remember the time when the biggest problem facing coal research was simply defined - "No money!" In the mid 70's we suddenly found ourselves dealing with a product worth five to seven times the value it carried in the mid60's. All of a sudden, we're talking about a high-profile, high- value commodity. The coal industry still hasn't made the complete psychological adjustment - especially in the operating areas (prep plants included). We have a valuable material at hand which is, in' many cases still being processed as though it were a two or three dollar per ton item. Simply put, I think that while the industry has made some major strides during this transition, a stronger commitment of attitude (and finances) needs to be made toward deeper definition of beneficiation work. Back to specifics - Dr. Aplan has really highlighted three areas where strong research efforts are needed. 1) Liberation processes - not limited to mechanical comminution - must be more fully studied.The industry certainly needs a better handle on value returned (improved ability to beneficiate) for dollars spent on improved liberation. 2) Flotation processes probably hold the most promise for near- term improvement in fine coal beneficiation technology. Dr. Aplan’s.

Jan 1, 1979

By D. W. Rudd, D. W. Vose, J. B. Vetrano

In an earlier paper the permeability character of Mo-0.5 pct Ti to hydrogen was described.' It was shown that this alloy is a more effective barrier to the passage of hydrogen than previously studied systems, i.e., copper,2 nickel,3 and several stainless steels.4 The permeability of Hastelloy B to hydrogen was investigated as a material having promising high-temperature structural properties which might have a low permeability to hydrogen. The general theory of permeation has been previously discussed,' and here only a summary of the more important results are given. It is found that except for very thin membranes, at low temperature, permeation of a gas through a metal barrier is determined by the rate of diffusion of the gas through the crystal lattice of the specimen, and that for hydrogen and the common diatomic gases, this passage involves dissociated particles as the diffusing species. The rate of permeation for hydrogen is therefore proportional to the square root of the pressure. It has also been found that the rate of permeation is inversely proportional to the thickness of the barrier. The apparatus used in this investigation was fundamentally the same as that employed in previous studies,' except that several simplifications result in the case of Hastelloy, since oxidation at the temperatures investigated is no longer a problem and welding of the specimen is relatively easy. A cross section of the membrane assembly is shown in Fig. 1. When finished, the assembly is about 5 in. long. The wall thickness is about 6 times the membrane thickness. The membrane (A) can be maintained at

Jan 1, 1963

The co-operation of the members of the Institute is earnestly sought by the Committee on Nominations, recently appointed by the Board of . Directors, in its work of formulating a ticket for officers and places falling vacant in the Board of Directors in February, 1916. The Committee must present the official ticket of nominations to the Board of Directors at its October meeting. Members are, therefore, urged to send promptly their nominations for officers and Directors in order that the Committee may have an opportunity to give them full consideration. The officers to be elected at the annual meeting in February, 1916, are: One officer, known as Director and President. Two officers, known as Director and Vice-President. Five officers, known as Director; The attention of members is called to Articles V and VII of the Constitution, and to By-Law XIII, which reads as follows: "The geographical districts to be considered by the Committee on Nominations shall he as follows, until otherwise ordered by the Board. District No. 1. New England, New York, and New Jersey, excepting New York City and district., which is provided for in the Constitution. (N. B.-New York City and district is designated District 0.) District No. 2. Pennsylvania. District No. 3. Ohio, Indiana, Illinois, Iowa, and Missouri. District No. 4. Minnesota, Wisconsin, and Michigan. District No. 5. Montana, North and South Dakota, Wyoming, Nebraska, Kansas, Washington, Oregon, Idaho, and Alaska. District No. 6. California and Nevada. District No. 7. Utah, Colorado, Arizona, and New Mexico. District No. 8. Louisiana and Texas. District No. 9. Other Southern States and District of Columbia. District No. 10. Mexico. District No. 11. Canada."

Jan 7, 1915

By H. D. Hoskold

This instrument, shown in Fig. 1, is not generally known, though it has been used in England, and found very practical, handy and useful in work not requiring a transit or theodolite. It is not only a good miner's dial, but a circumferentor as well; that is, it can measure horizontal angles like a theodolite. The magnetic bearings are conveniently read on the inward-beveled upper divided circle; while another circle, graduated on the base-plate, is used for reading the horizontal angles with a vernier. Two leveling spirit-bubbles are sunk in the same base-plate. The vertical divided semicircle is attached to the compact-box by two short axes, which permit the semicircle, with its plain sights, to be turned down to a horizontal position, and rest upon a pin, which relieves the axes from strain. This adjustment gives a clear view of the needle and vernier, and protects the instrument from injury, when carried through low mine-workings. A groove in the semicircle receives a sliding-bridge which carries the plain sights, and a vernier for reading vertical angles. A ball-and-socket-headed tripod is used; but sometimes the instrument is mounted on parallel-plates and level-ing-screws; and sometimes a telescope is attached, instead of the plain sights. The instrument is admirable for all such Mexican surveys as Mr. E. A. H. Tays describes ;l and saves so much time and labor as to be vastly superior to the less accurate hanging-compass called by him a " bully " instrument. If the hanging-compass was ever used in England, it has long since given way to more modern and superior instruments.

Jan 1, 1905

By N. W. Shed

The specifications for bridge-steel are usually not severe. The main difficulty is to secure a material which will roll easily, without showing signs of cracking on the corners of the blooms or on the flanges of the beams. In many mills sulphur has been deemed the most harmful constituent in this respect. It has been thought hazardous.to roll steel containing over 0.07 per cent. of sulphur. Yet, in making steel for the Phoenix Iron Company, I have produced from stock running as high as 0.13 per cent. of sulphur a material which rolled very satisfactorily. It is reasonable to infer that the injurious effect of sulphur can be neutralized, to a great extent, by proper treatment in the open-hearth furnace; and the following notes from my usual practice here may be of interest to those obliged to use high-sulphur stock. The steel made at Phoenixville in the 20-ton furnaces has about the following composition : Per cent. Carbon,...0.15 to 0.20 Manganese,.........0.50 to 0.60 Sulphur,..........0.11 to 0.13 Phosphorus,.: .0.04 to 0.06 Silicon,.......... 0.01 to 0.02 The best running heats were made with a small amount of pigiron. In using large proportions of pig the quantity of ore is also increased. This not only cuts the bottom, but also lengthens the time required to bring the charge down. Up to 50 per cent. of pig may be used, but 25 per cent. is much better. A 40,000-pound charge, containing 10,000 pounds of pig and 30,000 pounds of Bessemer butts or beam-scrap, works very well.

Jan 1, 1890

Discussion of the paper of C. W. Goodale and J. H. Klepinger, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 50, August, 1913, pp. 1935 to 2010. PROF. JOSEPH W. RICHARDS, South Bethlehem, Pa.:-Mr. Chairman, I would like to call attention to one valuable feature of the paper which may interest some: I have worked a good deal with the Pitot tube, and have always had difficulty with what is called the static end of that apparatus, so much so that I became almost hopeless of securing good results with it. I find here, however, what is stated to be a perfectly satisfactory static end for the Pitot tube, satis factory under probably all conditions. I congratulate Mr. Klepinger on the design of that tube and the consequent improvement he has made in the technical measurement of the volumes of gases. I would also like to ask if the total volume coming out of the chimney per day could not be computed by chemical analyses of the SO and SO2 in the gases, and calculation on the basis of the known weight of.. sulphur going out in a day; so that the Pitot tube measurements . could be checked by a method independent of measurements in the flues. J. H. KLEPINGER :-I think the volume of gases could be determined in that way. Those of a chemical turn of mind would go. about it so, but I am not enough of a chemist to follow that method, and consequently I always look at the mechanical way to obtain the results.

Jan 11, 1913

By E. J. Schmitz

This section was obtained last year during an examination of the iron-ore resources of the Rich Patch Mountain region and along Craig's creek valley. The geological members below the Oriskany and Lower Helderberg are exposed along the gap in a beautiful arch, while the higher formations appear in a more or less disturbed state on both sides of this arch, and are partly covered by dèbris. I have thought it of interest to the Institute to reproduce the drawing of this section at the gap which I made in my note-book at the time of my examination; those parts of the section, which lie at both sides of the arch, are only approximated. I give also a number of notes and measurements, referring to the Clinton formation and especially to the characteristics of the fossiliferous ore-seam opened in the various tunnels along the arch (see section). I. In Tunnel C: For the first 110 to 120 feet to second shute, we find the ore only here and there in small deposits, and interchanging with, or changing into, either a very siliceous limestone or a sandstone. About 10 feet beyond shute we have : Sandstone roof. Clay-slate, 211/2 inches Brown lean ore, 1 inch. Sandy clay, 3 to 31/4 inches. 1. Dark .brown ore, 3 inches. 2. Fossil-ore, changing into sandstone or very siliceous limestone, 2 inches. 3. Brown lean ore, 6 inches. Clay and slate below, 1 foot. 194 feet from entrance : Sandstone roof. Clay-slate, 4 inches. Clay 15 inches. Fossil-ore, 63 to 7 inches. Clay and ore, If inches. Lean brown ore, 2 inchea. Clay to bottom, 2 feet.

Jan 1, 1896

By A. A. Beard

ABOUT three years ago, I. L. Dunn, of Marietta, Ohio, found that wells could be cleaned by blowing with compressed air; this method has been used with great success on many wells in the Marietta, Ohio, district, where compressed air is being used to increase production, by forcing oil through the depleted sands. About a year ago, the process was successfully used to clean out wells in the Lenapah pool in Oklahoma, where an air plant had been installed, under the supervision of I. L. Dunn. Wells from 900 to 1000 ft. deep, with 40 ft. of sand and cavings in them, were cleaned out in from two to three days. The use of this process had, so far, been limited to properties using the Smith-Dunn process, where compressed air, under suitable pressure and volume, was available. For other properties, a portable compressor seemed essential; this was built and successfully demonstrated by Mr. Dunn, for the Tidal Oil Co. in September, 1924. The process of cleaning out with air has been described.1 It consists of lowering the tubing into the well, with a shoe or nipple of heavy pipe substituted for the perforated anchor on the bottom. Into the tubing, compressed air is introduced through a rotary swivel hose at the top, or by means of swing connections. The tubing is lowered to the top of the cave to be cleaned out, several barrels of water are put into the hole, and the compressed air is turned on. This blows out the material between the casing and the tubing, the tubing being lowered as the material is removed.

Jan 9, 1925

By John V. Beall

With some difficulty we framed the picture of the village on the mountain getting in the railroad bridge and tunnel at the base. It was a charming scene of red-tile roofs on a green mountain in the golden autumn sunshine with the black hole of the railroad tunnel looking like something out of the movie, "The Train." We clicked the shutter, advanced the film and started back to our rented Audi. At which point there was a hail from the other side of the railroad bridge. A man in uniform was brandishing an object in the air which looked suspiciously like a rifle. We peered around. We were the only other persons in view. He must be yelling at us. He was now closing the distance at a brisk, determined gait but was still 100 yards away. The car was handy but the road was straight, paralleling the railroad tracks for some distance. We dismissed the idea of running for it. Who knows, he might shoot. When he came up we didn't have much of a conversation because it had taken us a week to learn three words of Yugoslavian-zhiveli, long life, huhvalla, thank you, and schlivavitza, the national drink (plum brandy). None of these seemed appropriate. We got the Idea that photographs of railroad tunnels and bridges were prohibited. The guard, for such he seemed to be, took the Audi plate number, administered a last scowling reprimand and stalked off. This incident was the only one in a 15-day visit to Yugoslavia which we would have associated with "Iron Curtain restrictions."

Jan 1, 1970

By K. G. Black, B. P. Faulkner

Laboratory batch flotation rests are used for comparison of the floatability of ores and for comparison of the effect of various treatments on ore floatability. Although it is difficult to predict exact recoveries for continuous flotation on the basis of batch tests, considerable quantitative information can be obtained through their use. A simple method is presented which provides a convenient means of quantitatively evaluating results from laboratory batch tests. The information obtained is in the form of a discrete flotation rate distribution, which, if desired, can be used directly in a simulation of continuous flotation. Equation of Batch Flotation The validity for batch flotation of the first-order kinetic equation is accepted: [ ] where k is flotation rate of a class of articles and W (t) is weight of particles of the class in cell at time t. Thus, at time t, the fraction of the original amount of the class of particles still remaining in the cell is [ ] where W (0) is weight of class of particles in cell at time zero. If there are several classes of particles in the cell, each with its own flotation rate, k4, the fraction of the particles remaining is [ ] where W (t) is now the total weight of n classes, a, being the original fraction of W (0) belonging to the ith class. Accordingly, [ ] [Fig. 1] shows the result of a typical batch test. Such result can be characterized by a set of particle classes, each set described by a flotation rate, [ki,] and a corresponding fractional magnitude, [ai.] [ ] Multiple Regression Equation Eqs. 3 and 4 may be combined to give

Jan 1, 1973

By Carl E. Reistle

ENGINEERS as a group are often criticized because they have been responsible for the development of many technical improvements only to allow the administration of them to pass into the hands of others who may have little understanding of how they operate and little competence in their use. These criticisms are not always justified. There are many engineers who have shown themselves to be great administrators in addition to being great creators or builders, and more and more one sees the engineer demonstrating unusual administrative ability as he moves into the executive ranks. The last five or ten years have seen a new movement developing in this country-a movement brought about through the recognition by business statesmen that successful business administrators and executives just cannot be expected to develop like Topsy, that the management of a company must deliberately take steps to cultivate the proper climate or environment for growth if it wishes to provide an adequate and capable succession of executives in the future. This movement has taken on a number of names-Management Development, Executive Development, Personnel Development-but are these not actually misnomers? Can we develop anybody? In the strictest sense of the word, the author doubts that anyone can change any other person, at least, not much. The change must come from within. Perhaps this movement should be looked at not as a program of developing people but as one of giving people an opportunity to develop themselves. In the Humble Oil & Refining Co. there is an Executive Development Program; maybe it might better be called a Program of Development for Executives.

Jan 8, 1954

By M. G. F. Söhnlein

In a Bolivian tin concentrator an appliance was needed to furnish a suitable product for fine jigging from a pulp of the following composition: Mesh Per Cent. + 20 8.0 40 36.5 + 60 9.0 + 80 10.5 + loo 5.5 4-150 1 4.5 -150 25.0 99.0 Loss 1.0 In the jigging process, particles of cassiterite as small as 0.1 mm. can be recovered, provided they are not present in excess, that is if the material treated on the jigs contains sufficient coarser sands to keep the interstices between the grains open. Removing the fine material from the pulp by screening, to prepare the jig feed, is impractical, because that means the use of an 80-mesh screen or finer, and is not as effective as hydraulic classification. A screen would eliminate mineral grains from the feed which can be recovered by jigging, and in addition would throw more gangue and low-grade middling on to the jig. Formerly a one-spigot Richards vortex classifier had been used to accomplish this separation, but the tangential openings through which the hydraulic water enters became clogged by fine vegetal matter with which the water was contaminated, and which it was impossible to remove from the water. Consequently the work of the classifier was imperfect and a good deal of slime was sent to the jig. When designing the plant referred to in this paper it was decided to use a hydraulic classifier as shown in Fig. 1. The essential features had been copied from the Anaconda classifier.' This remodeled classifier consists of a truncated pyramidal wooden hopper A with an attachment of cast iron

Jan 1, 1917

Problems discussed and research opportunities identified during the workshop in the major areas of 1) flocculation, 2) flotation, 3) leaching and magnetic separation are summarized below. I. FLOCCULATION Problems Practical problems caused by unintentional flocculation or dispersion were described in the papers that dealt with iron ore processing, selective flocculation, fine coal processing, phosphate processing and potash processing. Ideas generated during the discussions ranged from the very practical suggestion that a conscious effort be made to transfer knowhow from the experienced clay industry to the metals and fuels-from-slimes industry. . . , to the familiar appeals for omnipotent theoretical developments. There was surprising recurrence of some questions in many contexts. Recurring questions are emphasized here rather than commodity-specific problems because their answers would serve a wider clientele usage. There is indeed no objection and some advantage to commodity-specific research, however, provided the proposed project is planned with full cognizance of transferable knowledge in other commodities, and of the possible usefulness of these results in other areas. Research Needs Most of the questions or research opportunities can be classified into three groups: a) water chemistry, b) dewatering, and c) flocculation theory. Other classifications are possible and probably useful. In each group there is a clear need for outwardly esoteric theoretical research a clear application of that work to current practical problems. Higher priority should be given to proposals for theoretical research which explicitly show the expected ultimate usefulness of the result. Likewise, proposals for applied research should demonstrate cognizance of applicable theory. Both of these types of projects could profit from collaboration among industrial, university and government personnel.

Jan 1, 1979

By Reginald S. Dean

THE commercial availability of electrolytic manganese has greatly changed the position of manganese as a nonferrous alloying metal. Manganese metal commercially available up to about ten years ago was reduced with either silicon or aluminum and contained substantial amounts of the oxides of these metals and other impurities. Manganese was accordingly not available as an alloy base and its addition to copper-base and nickel-base alloys was generally limited to a manganese content of a few per cent. Several special alloys like manganin contained up to 12 pct of manganese. A method for the production of electrolytic manganese was developed by the Bureau of Mines in 1936 and commercial production was begun in 1938. At the present time (June 1951), production is about 12 tons per day but appears likely to be substantially increased. Electrolytic manganese is deposited from an aqueous electrolyte containing manganese and ammonium sulphates and is marketed as cathode fragments about 1/8 in. thick. The impurities in its composition are as follows: iron, 0.0015 pct; copper, 0.001; arsenic, 0.0005; cobalt, 0.0025; lead, 0.0025; molybdenum, 0.001; sulfide sulfur, 0.017; sulfate sulfur, 0.014; insoluble, 0.002; carbon, 0.002; hydrogen, 0.015. These figures are from Bulletin 463, U. S. Bureau of Mines. From an alloying standpoint, the most important impurity is hydrogen. This can be removed by heating; 95 pct of the hydrogen can be removed in this way without introducing significant amounts of oxygen or nitrogen. Much of the commercial electrolytic manganese used in alloys is dehydrogenited by the producer, since the amount

Jan 1, 1953

By John Dilworth

IN considering the valuation of industrial properties in general, and of developed coal properties in par-ticular, it is assumed as fundamental that they have but one true value regardless of the object for which they are appraised. As regards developed coal lands, this value is only very approximately indicated by the recent sale price of neighboring lands, for the reason that it is rarely possible to find a sale of a coal property sufficiently similar in essential mining conditions to the one under consideration to serve as a measure of its value; and if such a one is found there are frequently incidental conditions peculiar to this particular transaction which invalidate the use of the sale price as a measure of general values. The true measure of the value of a coal mining opera-tion is the amount and rate of earnings it will afford with intelligent and experienced management. Prac-tically all of the features of a property which are gen-erally recognized as affecting its value relate either to the cost of producing the coal, or to the price it will bring, and so are intimately associated with earnings. In practice it is customary to appraise those portions of a developed coal property which are produced -by the industry of man-mine plant, equipment, development, town, etc.-at their cost of replacement at prevailing prices of materials, machinery, and labor, with such deductions for age, condition, obsolescence, and lack of usefulness as conditions warrant. Surface is appraised at the estimated cost of similar land in the district. Coal value is the difference between the worth of the entire property; considered as an industrial unit and

Jan 9, 1927

By M. G. F. Sohnlein

IN a Bolivian tin concentrator an appliance was needed to furnish a suitable product for fine jigging from a pulp of the following composition: Mesh Per Cent. +20 8.0 +40 36.5 +60 9.0 +80 10.5 +100 5.5 +150 4.51 -150 25.0 99.0 Loss 1.0 IN the jigging process, particles of cassiterite as small as 0.1 mm. can be recovered, provided they are not present in excess, that is if the material treated on the jigs contains sufficient coarser sands to keep the interstices between the grains open. Removing the fine material from the pulp by screening, to prepare the jig feed, is impractical, because that means the use of an 80-mesh screen or finer, and is not as effective as hydraulic classification. A screen would eliminate mineral grains from the feed which can be recovered by jigging, and in addition would throw more gangue and low-grade middling on to the jig. Formerly a one-spigot Richards vortex classifier had been used to accomplish this separation, but the tangential openings through which the hydraulic water enters became clogged by fine vegetal matter with which the water was contaminated, and which it was impossible to remove from the water. Consequently the work of the classifier was imperfect and a good deal of slime was sent to the jig. When designing the plant referred to in this paper it was decided to use a hydraulic classifier as shown in Fig. 1. The essential features had been copied from the Anaconda classifier.1 This remodeled classifier consists of a truncated pyramidal wooden hooper A with an attachment of cast iron

Jan 4, 1916

By J. L. Leland Myer

Some of the early experiments on the oxidation temperature of coal1 were undertaken in England in connection with a study of self-heating, or spontaneous combustion. It was then suspected that coals with low oxidation temperature were most likely to ignite by self-heating, but further experiments showed that many additional factors were involved. The oxidation temperature has importance as a physical property or characteristic of the coal. While only a few of the physical properties have been studied, they appear to have basic significance2 in the ultimate classification of all coals. When reliable data become available on the oxidation temperatures, as determined by standard and adequate methods, it should provide an additional basis for classification and comparative evaluation. Oxidation Temperature Defined For such a heterogeneous substance as coal is known to be, no simple definition of oxidation temperature can be established on a theoretical basis. If coals were homogeneous and of simpler structure, the accepted definition of "ignition temperature " as applied to simple gaseous mixtures might be adopted; that is, the temperature at which self-heating of the mixture sets in. But most coals self-heat slightly even at storage temperature, as evidenced by spontaneous combustion, and the definition for gases cannot be applied to coals with any exactness. By subjecting coals to suitable experimental conditions various oxidation characteristics can be obtained and examined for critical or significant stages of the oxidation process. Oxidation temperature itself must then be defined on the basis of such experimental results. Experimental Methods Attempts to determine critical points in the temperature functions of coal undergoing oxidation have resulted in the following experimental methods:

Jan 1, 1932