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By Guy W. Jordan, David P. Hale

High-iRon cements have a number of advantages over cements carrying little or no iron. The presence of iron in Portland cement aids in the manufacture of the cement and also imparts certain advantageous physical properties to the finished product. In manufacture, the presence of iron lowers the fuel consumption, increases the ease of proper"burning, and lessens the destructive action of the charge on the kiln refractories. In the finished cement the presence of iron reduces the expansion and contraction, adds strength, adds increased resistance to"freezing and thawing, and increases the resistance of the cement to sea "or sulphate waters. [" During the past few years the construction of numerous dams through- "out the Southeast by the Tennessee Valley Authority has stimulated the "production of high-iron cements. At present a great number of specifica- "tions call for an iron cement, and the industry is supplying this demand "with a Portland cement carrying approximately 5 per cent iron oxide. "Several manufacturers are now making practically all of their cement "of this type and a number of others manufacture it as a special cement "over short periods to meet demands from the Tennessee Valley Authority "and other buyers. " The recent increase in the use of iron in Portland cement has created "a market for iron products that previously was nonexistent. The chief "sources of supply for the cement manufacturers at present are iron sand, "iron sinter and slag, and ocher. The Copperhill mining district, Ten- "nessee, supplies both iron sinter and slag for use in cement. The Carters- "ville district supplies iron sand, ocher, and some iron resulting from the "magnetic separation of iron from barite. The advantages of these "products vary according to the chemical properties of the raw materials "and the methods of handling used by the different manufacturers. Where "the iron is to be handled by conveying belts and in hopper cars, the iron"sand and sinter and slag are preferable. Where the silica content must "be raised, the iron sand is doubly advantageous because it supplies both

Jan 1, 1942

By David P. Hale, Guy W. Jordan

High-iRon cements have a number of advantages over cements carrying little or no iron. The presence of iron in Portland cement aids in the manufacture of the cement and also imparts certain advantageous physical properties to the finished product. In manufacture, the presence of iron lowers the fuel consumption, increases the ease of proper"burning, and lessens the destructive action of the charge on the kiln refractories. In the finished cement the presence of iron reduces the expansion and contraction, adds strength, adds increased resistance to"freezing and thawing, and increases the resistance of the cement to sea "or sulphate waters. [" During the past few years the construction of numerous dams through- "out the Southeast by the Tennessee Valley Authority has stimulated the "production of high-iron cements. At present a great number of specifica- "tions call for an iron cement, and the industry is supplying this demand "with a Portland cement carrying approximately 5 per cent iron oxide. "Several manufacturers are now making practically all of their cement "of this type and a number of others manufacture it as a special cement "over short periods to meet demands from the Tennessee Valley Authority "and other buyers. " The recent increase in the use of iron in Portland cement has created "a market for iron products that previously was nonexistent. The chief "sources of supply for the cement manufacturers at present are iron sand, "iron sinter and slag, and ocher. The Copperhill mining district, Ten- "nessee, supplies both iron sinter and slag for use in cement. The Carters- "ville district supplies iron sand, ocher, and some iron resulting from the "magnetic separation of iron from barite. The advantages of these "products vary according to the chemical properties of the raw materials "and the methods of handling used by the different manufacturers. Where "the iron is to be handled by conveying belts and in hopper cars, the iron"sand and sinter and slag are preferable. Where the silica content must "be raised, the iron sand is doubly advantageous because it supplies both

Jan 1, 1942

By J. S. Johnson, W. C. McCulloch

All phases of plant operation must be synchronized so that the A number of interruptions in the flow of material may be reduced to a minimum. In the majority of plants operating under a labor agreement, time lost during the operating shift cannot be made up with overtime. With the work week restricted to 35 hr., the ratio of productive time to total time justifies extra effort in keeping the plant operating at capacity during the productive shift. This does not apply when central plants with adequate storage are operated by multiple shifts. In such installations the problems become similar to those of any factory or mill where added units, parallel circuits, or excess capacity serve to maintain the average production during intervals of maintenance shut- down. These plants, by special agreement, may run continuously, barring mechanical interruptions. The control of plant operation is in those procedures that are practiced to obtain from the run-of-mine product a high recovery of clean coal products to meet adopted trade standards and consumer specifications at the lowest possible cost. Correlation of all factors for continuous operation requires more than mechanical perfection in the plant. The run-of-mine coal must be delivered to the preparation plant without delays and the clean coal and refuse products taken away. Power supply and water requirements must be adequate. Signal systems must be established for emergency stops and to facilitate resumption of coal flow.

Jan 1, 1943

CHARLES E. WILSON'S second quarterly report "Meeting Defense Goals" was encouraging on the outlook for the mining industry, as prolonged demand for minerals seems assured; but for the individual engineer things are not so rosy. Ten percent of the gross national product is going for defense but the gross national product has been increased by 9 pct since the national emergency was declared apparently a commendable rate of progress. The increased production does not seem to have had the stabilizing effect on prices it should and housewives have been revising domestic budgets upward on a quarterly basis. Government economists have reached the conclusion that more taxes and wage and salary freezing are necessary to counteract inflation.

Jan 8, 1951

For the year ending February, 1923 PRESIDENT ARTHUR S. DWIGHT, District 0 NEW YORK, N. Y. PAST PRESIDENTS HERBERT HOOVER, District 4 WASHINGTON, D. C. EDWIN LUDLOW, District 0 NEW YORK, N. Y. FIRST VICE-PRESIDENT J. V. W. REYNDERS NEW YORK, N. Y. TREASURER CHARLES F. RAND NEW YORK, N. Y. SECRETARY FREDERICK F. SHARPLESS,. . . . . NEW YORK, N. Y. ASSISTANT SECRETARY PERCY E. BARBOUR NEW YORK, N. Y.

Jan 7, 1922

By John Suman

DURING the past few years the taking of cores in drilling with rotary equipment has been perfected to a remarkable degree in the Gulf Coast fields of Texas and Louisiana. Taking of cores is becoming quite a common thing, especially in the newer fields, and drillers are becoming expert in this work. The writer has seen cores 5 to 8 ft. long taken with great ease in wells as deep as 4500 ft. Coring is doing much to remove the prejudice which so many petroleum engineers seem to have against .the use of rotary drilling equipment for exploratory work. Some operators .are now claiming that when used with a reasonable amount of coring the rotary system is even more satis-factory than cable tools for exploring in certain territory. A case has recently been pointed out in the South Electra field of North Texas, where producing oil sands, passed over by cable-tool drillers, are being brought in with rotary equipment. It seems that in this particular territory the sands are rather thin. Cable-tool drilling was carried on for the most part in a wet hole and the red mud encountered in drilling caved into the hole very badly, so that the cuttings showed mostly red mud and the driller, thinking that the sand did not amount to anything, carried his water string through the sand. The later .operators, drilling into the sand with rotary equipment and coring it, found that it was well worth testing.

Jan 10, 1922

By E. T. Dumble

PROF. EDWARD ORTON, in his Report on the Occurrence of Petroleum, Natural Gas and Asphalt Rock in Western Kentucky, thus clearly states his ideas of the universal dissemination and rare accumulations of the bitumens:1 " We need to bear in mind that the various members of the bituminous series are abundantly and almost universally distributed among the unaltered sedimentary rocks of the earth's crust. The valuable accumulations of these substances are rare, it is true, but one can scarcely go amiss of petroleum, asphalt or gas, at least in small quantities, among the stratified rocks that retain their original structure." Speaking of the Ohio valley, he adds: "A fifth of one per cent. of petroleum, if distributed through a, thousand feet of rock, would make a total to the acre, or square mile far , beyond any production that has ever been realized from the richest oil field, and percentages of this amount are not only not rare to find, but are even hard to miss." Dr. F. W. Clarke in his Data of Geochemistry (Bulletin No. 491, U. S. Geological Survey, 1911), discussing these views of Orton with similar views of T. Sterry Hunt and Szajnocha, says that they "lead to the conviction that the formation of bitumens is a general process and by no means exceptional. Wherever sediments are laid down, inclosing either animal or vegetable matter, there bitumens may be produced."2 The organic origin of the bitumens, including petroleum, has long been an accepted fact with nearly all geologists, but the method, place, and time of the transformation into petroleum or other bitumen is still under discussion.

Jan 3, 1914

By David E. Jones, Dean K. Hunt, C. Y. Chen

INTRODUCTION Of all the numerous geological hazards that threaten the well-being of urban areas in the United States, probably none is so widespread, persistent, and diversified as surface subsidence (HRB-Singer, Inc., 1977). Simply defined, subsidence is the vertical displacement or sinking of the ground surface caused by either natural phenomena or man's activities. The downward movement, however, can be accompanied by horizontal movement, strain, tilt and even by a locally upward movement. Damage to structures and the environment can result from any of these movements. Extracting subsurface materials, fluids and solids, accounts for most man-induced subsidence in the United States. Among all the mining-related subsidences, the collapse of voids created by underground coal mining has been the major cause in inflicting surface damage (Comptroller General of the United States, 1979). Subsidence from coal mining may occur within a few weeks or be delayed for years, depending upon the mineral layer's depth below the surface, the overlying rock strata's characteristics, the extent and methods of mining that were employed, and the time deterioration of pillar and mine structure. Unless underground resources are not mined or control measures are implemented to prevent or minimize damage, some degree of surface subsidence and its accompanied deleterious effects are often inevitable. The ways to control the subsidence and minimize surface damage may include: 1. Precautionary measures built into new structures or surface features. 2. Preventive works applied to existing structures or surface features. 3. Mine design incorporating special underground layouts. 4. Any combination of the above measures. Upon the enactment of Public Law 95-87, the Secretary of the Interior, through the recently created Office of Surface Mining (OSM), was authorized to promulgate rules to regulate mining reclamation including subsidence control. Proposed on September 18, 1978, these rules were finalized, following public comment and hearings, on March 13, 1979, as part of the permanent regulatory program for the regulation of surface mining and reclamation operations which include the surface effects of underground mining. On January 28, 1981, Secretary Watt of the Department of the Interior issued an order to re- quire all agencies to identify with recommendations all regulations which are believed to be excessive, burdensome or counterproductive. Also on February 17, 1981. President Reagan issued Executive Order No. 12291 requiring all Federal agencies to conduct a regulatory review to make a determination that each promulgation of a regulation is clearly within the authority delegated by law and consistent with Congressional intent (Federal Register, 1981). As a result, OSM initiated the regulatory reform to revise the permanent regulatory program. Following a brief discussion of the technical aspects and the effects of subsidence on man and his environment, this paper presents a historical overview of how rules and regulations are used to govern the subsidence related problems. The development of the regulation of subsidence under Public Law 95-87, the Surface Mining Control and Reclamation Act of 1977 (SMCRA or the Act) are also discussed, including the new regulations being developed under the regulatory reform program. SOME TECHNICAL ASPECTS Am EFFECTS OF FINE SUBSIDENCE An extensive historical review of mining subsidence is given by Zwartendyk (1971) and Shadbolt (1978). Comprehensive technical presentations have been given by Henry (1956), King and Whetton (1957), Hall and Orchard (1963). Muller, et al. (1968). Grard (1969), Voight and Pariseau (1970). Kapp and Williams (1972), Cummins and Given (1973), Brauner (1973) , and NCB (1975). A theory of surface subsidence due to underground mining was perhaps first fundamentally stated by a French engineer, Toillez, in 1838, and formulated by a Belgian engineer, Gonot, in 1839 (Goldreich, 1913, cited by Zwartendyk, 1971). Since that time,

Jan 1, 1982

By J. D. Miller, A. Cortez, J. Hupka

The separation efficiency of the hot water digestion-flotation technique used for bitumen recovery from various domestic tar sands was evaluated. Bitumen viscosity was found to be the most important tar sand property in determining the success of the bitumen separation. Bitumen viscosity of the tar sand war controlled by changes in digestion temperature and/or changes in diluent (kerosene) addition. Complete and uniform dilution of the bitumen phase was achieved by providing a sufficient presoaking, or penetration time, for a given tar sand type. For all the tar sand samples tested, an excellent correlation was obtained between the coefficient of separation and the bitumen viscosity. To achieve a satisfactory coefficient of separation, it was found that the bitumen viscosity must be reduced below 1.5 Pa.s (16 P) at the temperature of digestion. This was the case regardless of the tar sand type, grade, or origin.

Jan 1, 1984

By W. C. PAGE

HARVEY S. MUDD has the unusual distinction of having virtually inherited a Directorship in the -A.I.M.E., for he was appointed to the Board to fill the unexpired term of his father in 1926. Since then he has served as a Director continuously until 1936, and now he is a candidate for Vice-President. One of the first words that young Harvey tried to say was "ore," for he was born in Leadville, Colorado, in the heyday of that camp, where Seeley W. Mudd for years ran the Small Hopes mine. Stanford and Columbia gave him his mining education, and the Shattuck-Arizona, at Bisbee, his first job. Afterwards he examined many

Jan 1, 1937

By C. M. Loeb, A. M. Gaudin, J. H. Brown

R. E. Carter (General Research Laboratory, Schenec-tady, N. Y.)—Brown, Gaudin, and Loeb in their study of intergranular comminution by heating attempt to find one explanation for all types of rock in terms of the properties of the phases present. The only necessary condition for intergranular cracking by heating is the setting up of high stresses at the grain boundaries. Such stresses may be set up in multiphase isotropic mixtures if the thermal expansions of the phases are different, in non-cubic single phases because of the anisotropy of thermal expansion in the various crys-tallographic directions, and in materials containing quartz because of the a-p' transformation at 575°C. In addition, for intergranular comminution by heating, the cooling and not the heating is most important.

Jan 1, 1960

By R. E. Hurst, D. E. Ramsey, J. M. Moore

The "frac" method of well stimulation has been applied successfully to all producing formations in the Permian Basin area. During the five years since its development, many changes and improvements have been made in treating materials. procedures, and equipie11t. A number of fluid carrying agents, having different physica1 and chemical properties, have been developed to meet variorus well requirements. The current trend is toward larger gallonage treatments, employing higher injection rates. The use of "down-the-casing" techniques has greatly reduced high surface working pressures, attributable to friction losses resulting from injection throrugh tubing. Petrographic studies of various Permian Basin formations, coordinated with laboratory and well log data, have been found a valuable guide in planning frac treat111o1t.s. A knowledge of the extent (and orientation of naturally occurring fractures and planes of weakness in the formation, aid in predicting the ultimate drainage pattern resulting from the frac treatment. INTRODUCTION The South Permian Basin covers an area in Wcst Texas and New Mexico about onc-half the size of the state of Texas, This vast region has been called the "Permian Basin" for so long that the term will he used here. It includes an area south of the Matador Arch. approximately 250 miles wide and 300 miles long. Structural features of importance within the basin are the Northwest Shelf, Eastern Platform, Midland Basin, Central Basin Platform, and Delaware Basin. The principal producing formations include sand, limestone and dolo-mite, with lesser amounts of shale, anhydrite. chert. and various silicates. All of the producing formations in the Permian Basin have responded to some type of frac treatment. Essentially, a frac treatment may be defined as the injection, into a formation. of a fluid carrying agent containing a particulated solid (usually sand), for the purpose of increasing production. The application of this method of well stimulation to many differing Permian Basin reservoirs has necessitated numerous changes and improvements in carrying agents, solids, service equipment. well equipment. and treating techniques. CARRYING AGENTS A number of different types of fluid carrying agents have been developed since the introduction of the frac method of well stimulation. These agents have different physical and chemical properties, and in many cases the extent of production increase derived from the frac treatment depends on the choice of fluid carrier. Unfortunately, due to many different systems of nomenclature used in the oil field, these differences are not always recognized by the oil Operator. In general, carving agents may he divided into the following broad classi-

Jan 1, 1956

By A. B. Johnson, J. S. Browning

The USBM has developed new and improved physical beneficiation techniques for economically recovering potash minerals from high-clay and low-grade ore from the Permian Basin of New Mexico. With the depletion of the high-grade ores a need for changes in industry's standard methods of recovery is a must. Technology may be improved in the beneficiation of the ore prior to mineral flotation and in brine clarification from the desliming phase to effect a reduction of losses of fine potash and brine in the disposal of the clay slimes. This report summarizes the results of these tests and demonstrates the feasibility of producing products that meet the requirements of the agriculture market, namely, 95% KCl equivalent to 60% K2O with recoveries ranging between 80 and 90%.

Jan 1, 1973

By J. M. Cabal, M. Chica Olmo, J. P. Laille

One of the main goals of a simulation of a coal deposit mining is to predict a series of parameters considered by the miner to be useful, e.g. ash content, sulphur content, seam thickness etc). The idea is to simulate different ways of mining a multi-seam brown coal deposit (the Mine Puentes de Garcia Rodriguez deposit, ENDESA, Spain ), which is exploited by several bucket-wheel-excavators (BWE) . Two mining models are used: a geostatistical model which provides a numerical way of re- presenting the three-dimensional ore-body, then a deterministic model, consisting of simulating the technical aspects of the mining. The main purpose of this simulation is to show how the mining operations can be reproduced using these two techniques.

Jan 1, 1983

By E. O. Wagner, V. F. Parry

This paper summarizes investigations during 1949 on three pilot plants for drying low-rank fine coal by entrainment in hot gases. Detailed operating results on processing seven coals having moisture ranging from 24 to 62 pct, formulas and data for calculating performance of large units, and general conclusions on the problem of drying fine coal are presented.

Jan 9, 1950

By M. P. Boss

Of the two methods of mechanical reduction—that of percussion and that of abrasion—it is not easy to say which was first employed by primeval man. The stone hammer and the flat or hollowed stone used for grinding are found together in the remains of prehistoric periods. But the use of the maray, or bucking-stone, developed from the hammer, was probably introduced later than that of crude millstones. Diodorus Siculus, the Roman historian of the first century B. c., mentions such millstones as used in the mines of Egypt to pulverize material which had been previously broken in a mortar. The invention of the arrastra for fine grinding is declared by some authorities to have been made by Bartolomeo de Medina, at Pachuca, Mexico, about A. D. 1557—which is quite probable. Being the first to amalgamate silver on anything like a business scale, he must have felt the necessity for oregrinding apparatus of greater capacity than the old primitive millstones; and the arrastra was thus the natural successor of the millstone. It is very unfortunate that the archives of Pachuca, which has made so much history in ore-treatment, were destroyed in some one of the many insurrections for which, also, the place is renowned. The first application of the stamp to the crushing of rock is asserted by some writers to have been the invention of a Saxon nobleman named Von Maltitz, about the year 1505. Better authenticated reference, however, is made to one Paul Gronstetter, a native of Schwarz, and called an ingenious worker, who, in the year 1519, established at Joachimsthal a process of wet stamping and sifting. Two years later, a larger plant was established at the came place. It is said that he had previously introduced the same device at Schneeberg. How much of the invention was due to Gronstetter is not certain;

Jan 1, 1902

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period Feb. 10, 1916 to Mar. 10, 1916: D. A. S. Bell, Ottawa, Can. E. B. Latham, Santa Maria, Cal.. John Cooper, Exeter, Devonshire, Eng. H. N. Lawrie, Portland, Ore. I. Dally, Seattle, `Wash. L. A. Levensaler, Tacoma, Wash. George W. Evans, Seattle, Wash. George J. Lyon, Schenectady N. Y. Alexander Fyfe, London, Eng. Fred MacCoy, Antofagasta, Chile. F. C. Greene, Seattle, «rash. J. Mitchell-Roberts, London, Eng. I. Ishikawa, Tokio, Japan. Chas. W. A. Sultan, Yonkers, N. Y. William Kelly, Vulcan, Mich. R. B. Tinsley, Big Stone Gap, Va. Paul S. King, Wilmington, Del. Walter E. Trent, Reno Nev. Oscar Lachmund, Greenwood, B. C. Alfred W. G. Wilson, Ottawa, Can. J. S. Lane, New York City. Nelson Dickerman has resigned as general Manager of the Pato Mines (Colombia), Ltd., and The Nechi Mines (Colombia), Ltd., and will return from Colombia to San Francisco, Cal., the latter part of April. W. A. Prichard has been appointed as his successor.

Jan 4, 1916

By Fred D. Gustafson

With the postwar emergency for new housing and for new industrial buildings, much research has been done on lightweight aggregates for use in concrete and plaster. The trend toward lighter weight aggregates to relieve the dead load on the higher, steel framework buildings started toward the end of the last century. Progressively the requirements became more stringent, crushed bank slag, weighing 80 lb per cu ft as compared to 100 lb for crushed rock, was supplemented in some sections by foamed slags and expanded shales weighing from 40 to 60 lb per cu ft. In other sections cinders were used weighing from 40 to 50 lb, including sand. Sections favored with more recent vulcanism turned to pumice weighing from 30 to 60 lb, whereas other localities made use of diatomite, from 28 to 40 lb. Exfoliated vermiculite weighing from only 6 to 10 lb per cu ft came into use. As the search for lighter weights in aggregates continued so did the search for other desirable properties such as nailability, ease of cutting or channeling, and good insulation to both sound and heat. This search eventually led to a widespread interest in the expansion of perlite, or similar volcanic glasses, with the result that in 1946, the Office of the Housing Expediter' listed eleven firms reporting the operation of processing plants either on pilot or commercial scale producing aggregates weighing from 2 to 16 lb per cu ft. Geology Perlite is one of the large family of rocks originating from a granitic or acidic magma and generally has a "rhyolitic composition with a marked perlitic structure."² The name "perlite" is a derivation from "perlstein" originally given "to certain glassy rocks (hyaloliparites, hyalo-rhyolites) with numerous concentric cracks, from the fancied resemblance of broken out fragments to pearls."3 The cause of the perlitic texture is somewhat controversial. Johannsen attributes the texture to strain set up in the glass by cooling and describes the finding of peculiar, glassy balls, called marekanite, more or less rounded and showing concave indentations, which may be left when perlite is broken. Frank Rutley, on the other hand, in 1881, while working on vitreous rocks from Montana, observed that there was incipient or partially started crystallization with segregation of water toward the un-crystallized portion in all specimens of perlite examined. Further he observed evidence of strain around focii of crystallization to which he ascribed the development of the spherical cracking which gives the rock its perlitic texture.4 Widespread over the western and southwestern United States where Tertiary vulcanism is exposed, perlite commonly is associated with andesitic, basaltic, and rhyolitic lavas with inter-bedded tuffs and ash of Eocene age although some deposits are associated with rocks assigned to the Pliocene age.5, 6 n nearly all cases the perlite overlies water laid tuff beds or agglomerates or breccias of explosive nature, an outstanding exception being the occurrence of perlite as the chilled selvage of andesite intrusions.7'8 Available chemical analyses of per-lites from the western and southwestern United States indicate that they are varieties of leucorhyolites rather than of normal rhyolites, leucorhyolites having less than 5 pct of dark minerals, normal rhyolites having more than 5 pct. This conforms with Johannsen's observation that leucorhyolites are the prevailing kind in North America.9 Tables 1 and 2 give

Jan 1, 1950

Allan Gibb, Mount Perry, Queensland, Australia (communication to the Secretary):—In drawing conclusions from his observations, Mr. Van Liew has apparently overlooked the reduction in weight that takes place in the content of the converter. The percentage-compositions of the matte, etc., are not directly comparable for determining the rate of elimination of the impurities; and, in the absence of exact weights (which in such an operation could not be obtained), it is necessary to determine the relation between the impurities and the copper with which they are combined at various stages, in order to get data that are comparable. Owing to a portion of the copper being removed in the slag, etc., the weight of copper in the converter is not a fixed quantity, but.it is sufficiently approximate to permit very reasonable comparison. The analytical data given by Mr. Van Liew, reduced to this basis (a ratio between the impurities and the copper with which they are combined), are shown in the table on page 958. From this table it will be evident that Mr. Van Liea's conclusions as to the source of heat at digerent stages are not quite correct. During the first 10 minutes, no iron is scorified, the heat being derived from the oxidation of the sulphur, of which 7 per cent. of the total is removed in this time. Prom

Jan 1, 1904

By E. Stansfield

IT. has long been known that coal is unstable and oxidizes in air, even at ordinary atmospheric temperatures; also, that such oxidation affects the analysis of coal. Nevertheless little or no precaution is taken to prevent oxidation in the ordinary methods of analysis, and the possibility of error due to oxidation is sometimes ignored even in researches on coal. Although the general nature of coal oxidation is well known, and many workers have made careful studies of the rate of oxidation of different types of coal exposed to oxygen at different temperatures, yet the amount of oxidation coals undergo in the ordinary process of analysis, and its influence on the determined analysis, is not well known, and the published data are widely scattered through the literature. This paper is a collec-tion, from this laboratory, of data that bear on the subject, together with a brief summary of three methods employed here to evaluate the oxidizabil-ity of coal. The post-Carboniferous coals of Alberta range all the way from anthracite down to lignite. As some of them are notably susceptible to oxidation, the necessity for care was early forced upon our attention, and oxidation has been reduced either by the removal of air with a vacuum pump or by the displacement of air with natural gas (methane). The two routine analytical operations most liable to involve oxidation are the preliminary, partial drying of the crushed coal (called air-drying) and the determination of moisture. The first is a prolonged operation on coarse coal at ordinary temperatures, and the second a short treatment on powdered coal at higher temperatures. Oxidation also occurs in coal samples stored in ordinary sample bottles. In order to gain information for this study, determinations were recently carried out on the same samples in air, in natural gas, and in vacuo. Sixteen coals were tested; three would be classed in the United States as coking bituminous coals, two as noncoking, nonslacking, bituminous coals, and the rest as subbituminous. Table 1 gives typical analyses of these coals as mined.

Jan 1, 1934