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By David W. Brunton

(San Francisco Meeting, October, 1911.) MINE-DRAINAGE and the ever-increasing demand for water on the plains have within the past few years necessitated the driving of a great number of adits and tunnels, including many of considerable size and great length. In most instances, ex isting conditions have called for extreme rapidity of execution; and this necessity, coupled with the high altitudes at which most of the work has been carried on, excessive freight-rates, and difficulty -of access, has involved many complex and interesting problems. One of the most rapidly executed undertakings of this class is the Laramie tunnel, recently completed for the Laramie-Poudre Reservoirs & Irrigation Co. This tunnel is driven through Green ridge, a spur of the Continental Divide, which separates the Laramie river from the Cache-la-Poudre in Laramie county, Colo. Green ridge is extremely persistent, and further northward in Wyoming is known as Sherman hill, the highest point on the Union Pacific railway. At the point where the tunnel is driven, two opposing bends bring these streams within 2.5 miles of each other, with a difference in elevation of 500 ft. The rock exposed on the banks of the two rivers does not differ materially in hardness; and, without a geological study of the conditions involved, it would appear that the difference in the depth of erosion of the two streams is due principally to the greater volume of water at this point in the Cache-la-Poudre, which has a drainage-area above the tunnel-portal of 110 sq. miles, as against 30 sq. miles of natural drainage for the Laramie. To increase the water-supply at the tunnel, however, this latter amount has been augmented by two side collection-canals, which bring the available drainage-area up to 84 square miles. The nearest railroad shipping-point to the eastern portal is

Apr 1, 1912

By John A. Bonucci

AMAX Base Metals R&D, Inc. has developed technology for extracting and recovering platinum and palladium from spent automobile exhaust emission control catalyst. Our most promising route is a chloride-based hydrometallurgical flowsheet in which catalyst pellets or crushed monoliths are leached in HC1 with an oxidant at 95°C without agitation. Alumina co-dissolution can be limited by thermal pre-treatment of the catalyst. The leach solutions are treated by one of several precious metals recovery techniques to produce a high grade PGM concentrate. For the new generation of three-way catalytic converters which contain rhodium, an H2S04 preleach could selectively extract much of the rhodium while leaving the platinum and palladium behind. Capital and operating costs will be discussed.

Jan 1, 1984

By R. N. Hunt

GEOLOGICAL and exploration work of the United States Smelting Refining and Mining Company are handled by the mines geological and the exploration divisions of a geological department under the direction of the chief geologist. The mines division at present includes, in Utah. a geologist in charge, resident at Bingham, assisted by a geologist stationed at each operation, and a small group of geologists resident at the Bayard unit, in New Mexico. The duties of the mines division include the mapping and delineation of the geology of the mines, direction of sampling and diamond drilling, and the periodic calculation of ore reserves. At Bingham an amount of underground drilling within the limestone and porphyry formations which are hosts to the ore bodies supplements and completes development by mine workings. At Bayard, five to seven drills are kept busy underground, and eight to twelve drills operate on the surface. The mines division men live at the mine and work in close co-operation with mine superintendents and foremen. Development work is discussed, initi-

Jan 1, 1948

By Zhu Weishen, Xu Dongjun

In the 1st part of this paper a comparassion of the different methods for determining the modules of elasticity and deformation of hard rock is made. It is found that the plate bearing method has a serious shortcoming. The slit flat-jack method seems to be a mare reasonable technique, which is recommended as a desirable method for in situ testing. In the 2nd part, a new test method to determine the properties of deformation and strength of weak plane in rock mass is recommended. Then the relation of weak plane character to the character of stress-strain curve, the relation of normal stress to the character of shear displacement curve and the yielding criterion of weak plane are discussed.

Jan 1, 1982

By E. J. KENNEDY

THE annual dinner-dance was held in the large ball room of the Commodore hotel Wednesday evening. A total of 577 were seated at the dinner, over which President Eavenson presided as chairman and toastmaster. In introducing George C. Stone, the James Douglas Medalist, W. R. Ingalls outlined the former's association with the zinc industry. He said, in part In designing and building Palmerton, Stone erected a metallurgical monument and won the title of chief engineer of the New Jersey Zinc Co., with transferal to its New York office in 1900. There lie held forth in dignity, efficiency, and with appreciation until his retirement from active service in 1929. After a few years lie was diverted from the position of chief engineer for his company to the superior one of chief metallurgist and that gave to Stone his next big chance.... This was the conception of a research department and the ability to persuade his directors to adopt it. I shall not pretend to summarize the great things that afterward developed. I shall mention only the institution of the manufacture of lithopone in this country, the charging of the Wetherill furnace with briquets, the mechanicalization of the Wetherills, the accomplishment of continuous distilling, and most recently the introduction of reflux-refining.

Jan 1, 1935

By J. Gross

G. H. Clevenger, Chairman of the Milling Methods Committee of the Institute, made the following introductory remarks: "Several years ago, a number of us felt that the time was ripe for a fundamental investigation of crushing and grinding. At the outset, it appeared that the first thing we needed was a yardstick whereby grinding efficiency could be measured. "The U. S. Bureau of Mines has been most generous in cooperating with the Milling Methods Committee in getting this work well under way. John Gross, who served the committee for a year as secretary, was placed in charge of the investigation and has been ably assisted by S. R. Zimmerley. "Messrs. Gross and Zimmerley will now present the Progress Report covering their work to date." PROGRESS REPORT J. Gross, Salt Lake City, Utah. -This has not been a simple problem, and when I tell you that we can give you a verbal report of what we have done during three years in five or ten minutes you will realize that we have necessarily done a great deal of work that does not appear in the final results. We have been in a virtually new field. Therefore, we have had to feel our way at each step so as to be fairly sure we were correct. The first thing that was realized in this problem was that unless we had some method of measuring what happened when we crushed an ore, we might as well quit and not go further. We realized that if we tried to measure the results of crushing or grinding by the ordinary sizing test we would not get anywhere. We could sieve down to say 200 mesh fairly accurately; we could even go one sieve size further with a little less accuracy, and then we were absolutely lost, unless we went into microscopic measurement. Even this latter method would not have been satisfactory. The question was: what were we going to measure? If we were going to measure size, we might measure one particular dimension of a particle and be off 200 per cent. or more. If we tried to measure surface, we would have something tangible; the surface of a particle, no matter how irregular, is something definite, far more definite than any linear dimension would be. Moreover, if we could measure surface, we would immediately have a method of checking the Rittinger law as to whether it was or was not correct. So the first thing that we sought was a method whereby we could measure surface on crushed particles or, we will say, on particles; it would not make any difference whether crushed or not. It then became a question of what kind of particles we were going to use in obtaining a method for surface measurement. We realized that it would be rather a com-

Jan 1, 1928

By Roy E. Dickerson, W. M. O Connor

The production of crude petroleum of the Bacuranao field, Cuba, fell off rapidly because no new wells Mere drilled. In December 1938, the total was 15 bbl. per day. The estimated average from this serpentine field for the year is 20 bbl. per day. The Motembo area produced an estimated average of 160 bbl. per day. Production in July was 215,946 gal of gasoline, or 165 bbl. per day. In August production was higher because a new well in the concession, the Luisa Marcela, produced 189 drums the first day and required pit storage. The Atlantic Refining Company of Cuba started a deep test upon a long, narrow, surface-defined anticline 3 km. south of Remedios, a town on the north coastal plain of Santa Clara province, in December 1938. The Atlantic Refining Co. is doing extensive seismograph arid gravity-meter work in Matanzas arid Santa Clara provinces. The Shell company was rigging for a deep test in western Havana province at a location about 2 km. west of the town San Antonio dc los Banos New Petroleum Law More serious attention was given by some of the major oil companies to the development of petroleum in Cuba as a, result of the passage of a Petroleum Law ill that country on May 9, 1938. Under the old mining lam of Cuba, which gave no special treatment to petroleum, the usual provisions giving reasonably satisfartory guarantees to encourage investmerit of foreign capital were either entirely lacking or were 30 ambiguously expressed as to require legislative action. Under the new law, Government royalty is fixed at 10 per cent with the provision that it will be reduced to 9 per cent on crude petroleum that is refined in Cuba. Royalty to the surface owner is 1 per cent. A surface tax on a sliding scale from 10¢ to 406 per hectare per year is applicable to all exploitation concessions granted under the law or adapted to its provisions. So export tax is payable upon petroleum. Stability of taxation

Jan 1, 1939

By W. M. O Connor, Roy E. Dickerson

The production of crude petroleum of the Bacuranao field, Cuba, fell off rapidly because no new wells Mere drilled. In December 1938, the total was 15 bbl. per day. The estimated average from this serpentine field for the year is 20 bbl. per day. The Motembo area produced an estimated average of 160 bbl. per day. Production in July was 215,946 gal of gasoline, or 165 bbl. per day. In August production was higher because a new well in the concession, the Luisa Marcela, produced 189 drums the first day and required pit storage. The Atlantic Refining Company of Cuba started a deep test upon a long, narrow, surface-defined anticline 3 km. south of Remedios, a town on the north coastal plain of Santa Clara province, in December 1938. The Atlantic Refining Co. is doing extensive seismograph arid gravity-meter work in Matanzas arid Santa Clara provinces. The Shell company was rigging for a deep test in western Havana province at a location about 2 km. west of the town San Antonio dc los Banos New Petroleum Law More serious attention was given by some of the major oil companies to the development of petroleum in Cuba as a, result of the passage of a Petroleum Law ill that country on May 9, 1938. Under the old mining lam of Cuba, which gave no special treatment to petroleum, the usual provisions giving reasonably satisfartory guarantees to encourage investmerit of foreign capital were either entirely lacking or were 30 ambiguously expressed as to require legislative action. Under the new law, Government royalty is fixed at 10 per cent with the provision that it will be reduced to 9 per cent on crude petroleum that is refined in Cuba. Royalty to the surface owner is 1 per cent. A surface tax on a sliding scale from 10¢ to 406 per hectare per year is applicable to all exploitation concessions granted under the law or adapted to its provisions. So export tax is payable upon petroleum. Stability of taxation

Jan 1, 1939

By Charles R. Fettke

The outstanding event of the year 1929 in the Appalachian area was the intensive drilling activity in the Bradford and Richburg pools of northwestern Pennsylvania and southwestern New York State, particularly the former, in connection with the continued extension of the five-spot system of water-flooding. More new development work was undertaken and completed than during any previous year since reclamation methods were first applied. This was due in part to an excellent price for oil and in part to discovery of the fact that more intensive methods (five-spotting) yielded greater profit. While several oil wells of comparatively large initial production were completed, no new oil pools of significance were discovered in the Appalachian area during the year. A number of small gas pools were opened in areas already surrounded by producing wells and at least three others in areas located some distance from any producing pools. Petroleum Development According to statistics of the U. S. Bureau of Mines, 33,7,57,000 bbl. of petroleum were produced in the Appalachian field during 1929 as compared to 31,060,000 bbl. in 1928.' Of the total 1929 production, 23,391,618 bbl. consisted of Pennsylvania grade oil as compared to 21,096,710 bbl. in 1928. The 1929 Pennsylvania grade production represents an increase of 37.4 per cent. over that of 1924. This increase can be attributed largely to the rapid development of water-flooding in the Bradford and Richburg pools. The Bradford field of northwestern Pennsylvania and adjaccnt portions of New York State experienced the busiest year since the boom days of the early eighties. Wells completed during the year totaled 2679.2 In spite of the high prices asked for acreagc, which in some of the choicest territory has been as high as $6000 an acre, a considerable number of properties changed ownership during the year. There is at present a pronounced tendency to consolidate the great number of small individually operated properties into larger units.

Jan 1, 1930

By E. M. Wise

WHEN man became dissatisfied with the mere utilization of physical force and began to use weapons, he made a definite stride forward. At first he used sticks, animal bones and stones, often rudely shaped to some particularly lethal form. These devices, while crude, were moderately effective. How- ever, some of the brighter men of the tribe found that certain particularly heavy "stones" were somewhat ductile and could be hammered into more effective weapons than those previously known. Later, probably through the misuse of one of these weapons to stir the campfire, it was found that heating softened and perhaps actually melted the material. The process of annealing had been discovered! Smelting the more easily reducible metals was in all probability one of those fortuitous accidents which was followed up by thoughtful researchers who ultimately developed the technique of mixing various ores to produce bronze and even some of the nickel content alloys. The resulting products were at first lumps of more or less ductile material which could be hammered to shape, and were thus incidentally hardened by this process. The hardening of metals by alloying and cold working remained for many centuries the only known methods for improving their properties.

Jan 1, 1931

By Christopher J. Bise

Introduction In August 1977, the federal Surface Mining Control and Reclamation Act was signed into law. It stated that: "The Congress finds and declares that because of the diversity in terrain . . . and other physical conditions in areas subject to mining operations, the primary governmental responsibility for developing. authorizing, issuing, and enforcing regulations for surface mining and reclamation operations subject to the Act should rest with the States." Section 516 of Title V (Control of the Environmental Impacts of Surface Coal Mining) of the Act deals with the surface effects of underground coal mining operations. "Each permit issued under any approved State or Federal program pursuant to this Act and relating to underground coal mining shall require the operator to adopt measures consistent with known technology in order to prevent subsidence. causing material damage, to the extent technologically and economically feasible, maximize mine stability, and maintain the value and reasonable foreseeable use of such surface lands, except in those instances where the mining technology used requires planned subsidence in a predictable and controlled manner: Provided, that nothing in this subsection shall be construed to prohibit the standard method of room and pillar mining." This section raises many questions. Precisely what is the "reasonably foreseeable" future as far as land use is concerned? And what is the "standard method of room and pillar mining"? The first part of the paragraph seems to rule out longwall mining, but isn't longwalling a "predictable" manner of "planned subsidence"? Does the Act take into account variations among mining methods in differing regions or coal seams? With these questions and the need to comply with the Act's provisions in mind, many states may turn to the Pennsylvania Bituminous Mine Subsidence Act of 1966- the only comprehensive subsidence act passed by any state-as a model for their own programs. Thus, it is very important to evaluate Pennsylvania's Act to see whether its basic assumptions can accommodate national application. This paper will note the Subsidence Act's provisions and guidelines, briefly analyze the current state-of-the-art in subsidence damage prevention and control, and list several recommendations for altering the Act's application guidelines for different mining areas.

Jan 1, 1982

By William Campbell

(Cleveland Meeting, October, 1912.) THE structure of iron and steel, though the object of so much study and research for the past 25 years, is by no means thoroughly understood. In the first place, we have three or more distinct iron-carbon thermal diagrams, each with its own supporters, and each representing a theory of the structure and constitution of cast-iron. In the second place, by reason of the fact that austenite, the solid solution of carbon in iron, decomposes in the solid state into ferrite, or pure iron, and cementite (Fe3C), and that quenching from above this transition-range, no matter how rapid, cannot entirely prevent the change and thus preserve the austenite by itself at ordinary temperatures, it happens that under the microscope we find, in addition to the ferrite, Fe3C, and austenite, which the thermal diagram of steel requires, it series of transition-products with distinctive structures, to which have ,been given the names martensite, troostite, sorbite, etc. Now these transition-products, in addition to the solid solution, austenite, have been the source of much controversy, at times very bitter. One side would insist that, say, troostite was an entity, which the other side would deny, pointing out that it must be a transition-mixture, with a particular structure. That austenite was a solid solution of carbon in iron has been denied by one school ; we have been told that Fe24C dissolved both Fe3C and Fe, and thus gave rise to a whole series of quenching-products-all this in spite of the fact that no matter how the thermal diagrams differ in regard to cast-iron, they all agree in regard to the solid solution, austenite, for Fe24C finds no place on the diagram. Thus it happens that while the authorities fight both in regard to the iron-carbon diagram and the structures met with in hard- * Associate Professor of Metallurgy, Columbia University in the City of New York.

Dec 1, 1912

By J. F. K. Brown

ANTHRACITE?S satisfactory showing in 1942 was accomplished in the face of adverse conditions, such as the loss of man power to the active services and to other industries, and the difficulty and delay in obtaining the necessary materials and equipment required in mining operations. Although the in- creased output was stimulated by the war, and thus does not impress one as contributing to continuing improvement in the industry, nevertheless the year witnessed several efforts ant1 consideration of others that have the appearance of permanent progress.

Jan 1, 1943

By Jay A. Carpenter

IN six years the construction of Hoover Dam and the power plants probably will have reached the operating stage and this vast new source of power will then be continuously available for industry. The height of the darn will be 580 ft. and the average annual flow of the Colorado River is calculated at approximately 24,000 cu.ft. per sec. If this full head and average flow can be maintained the year round, about one million horsepower will be generated. The U. S. Reclamation engineers, taking into consideration the probable range in flow and head, have set the figure for power contracts at 660,000 firm horsepower, which can be assured at all times of the year. During the months of heavy run-off of water from the Colorado River Basin the power plants should be able to generate the full 1,000,000 hp. capacity of the power plants, so there will be 340,000 excess or secondary horsepower. The cost of firm power at the switchboard will be close to 2.15 mills per kw.-hr., equal to $14.05 per hp.-yr., and the cost of the secondary or off-peak power will be close to 0.8 mills per kw.-hr., or $5.22 per hp.-yr. In no place in the country can such cheap power be obtained today. The electrochemical industry is in a state of flux because the power costs from its old sources have increased so much (to $30 per hp.-yr. at Niagara) that the industries have had to seek new sources, so they have gone to Canada and Norway and built new plants.

Jan 1, 1932

By H. J. LONGMORE

MORE improvements have probably been made in the diamond-drill field in the past decade than were accomplished in the entire prior period since diamond drilling was discovered in 1864 by a French engineer named Leschot. True, machines were improved, and new accessories were adopted from time to time up to 1929, but no radical changes were made. The basic principle instituted during the early years of the industry were still in use in 1929. At that time, practically the only diamonds used were "black diamonds" or "carbon." These came from Brazil through a rather round- about route, and by the time they got to the drilling trade their cost was excessive-$175 per carat and even higher at the peak. Perhaps because of this. or perhaps because of increased competition, the industry sought ways to reduce expenses even in the face of constantly increased labor costs due to higher wages and reduction in hours worked. The solution seemed to rest in two things-use of a cheaper cutting medium to replace the carbon diamond and the development of new machines to drill faster and thus produce more hole per shift of operation.

Jan 1, 1940

By Fred R. Ingram

FOR the purpose of this discussion, let us consider that the Rocky Mountain region covers the area in the seven Mountain States, Idaho, Montana, Wyoming, Utah, Colorado, New Mexico, and Arizona, and before we discuss the needs of these states, let us define Industrial Hygiene. Industrial Hygiene is that branch of preventive medicine concerned with the protection of health, improvement of efficiency, and prolongation of life of the industrial worker; in short, adult health conservation. It includes in its broad meaning not only the prevention of occupational diseases, such as silicosis, lead poisoning, cadmium poisoning, and many others, but such relative problems as overcrowding, fatigue, and personal and mental hygiene; exposure to abnormal temperatures, pressures, and humidities; ventilation, heating, and lighting. It is a science which requires the combined activity of medical personnel (doctors and nurses), engineers, and chemists to evaluate the exposures and determine the means of eliminating the hazard. The engineer surveys the workplace, takes air samples at the breathing level of the workman, and analyzes the work exposure. The chemist determines in his laboratory the exact amount of toxic material collected in the sample, which represents the exposure of the workman. The doctor must diagnose the occupational disease, recognize its cause, and evaluate the disability. Together, all three must correlate the data obtained and devise efficient methods, medical or engineering or process changes, for controlling or minimizing the dangerous condition and for studying the effectiveness of these measures. The plant doctor, in addition, must aid in the readjustment of the incapacitated worker and provide facilities for prevention. Industrial hygiene, however, is of no avail without the understanding co-operation of management.

Jan 1, 1945

By G. S. Hume

Three provinces in Canada—New Brunswick, Ontario and Alberta— produce oil and gas in commercial quantities. In addition a small amount of oil is being produced and refined in the Northwest Territories at Norman on the Mackenzie River. The production at Norman is derived from two wells drilled by Northwest (Imperial Oil) Co. in 1920 and 1923. The refined products of the oil are used locally in connection with mineral developments on Great Bear Lake. The production of petroleum by provinces and the consumption of natural gas are shown in Table 3. In addition a small amount of natural gas is produced in the southwestern part of Manitoba from shallow wells for local use. Tables 1 and 2 give detailed information. The greatest drilling activity in 1933 in Canada centered around the southern end of the Turner Valley field, Alberta. In addition to several wells previously commenced in this area, eleven new wells were begun. There were three completions to the Paleozoic producing zone in 1933 in the southern part of Turner Valley and one well was abandoned as a result of being off the favorable structure. Of two wells completed in

Jan 1, 1934

By E. C. Truesdale, R. K. Waring

THE Research Division of The New Jersey Zinc Company (of Pa.) has conducted, over a period of years, numerous tests of the reducibility of various zinc ores and the reactivity of various kinds of coal, using a number of different experimental methods. Most of these tests have involved the reduction of mixtures of ore and coal. In such cases the following simultaneous reactions are believed to be mainly responsible for the production of zinc, as was shown by Bodenstein1 some years ago: ZnO + CO = Zn + CO2[I] C + CO2 = 2CO[2]. Each of these reactions is dependent upon the other for the supply of CO and C02, respectively, and the over-all rate of formation of zinc vapor will be determined by the slower of these two reactions. An analogous pair of reactions sometimes of importance is: ZnO + H2 = Zn + H2O[3] C+ H2O=CO+H2[4] While it is possible to obtain an indication of the relative reducibility of various ores, or of a fine versus a coarse ore, by testing them with a given coal, and while coal reactivities may be measured in a corresponding manner, a more direct determination of relative reaction rates is possible by carrying out the desired reactions, such as I and 2, separately and under reproducible conditions. It is one purpose of this paper to present some of the results that have been obtained by the latter method. C. G. Maier2 discusses the relative rates of reactions I and 2 and concludes that while at relatively low temperatures reaction I is faster than reaction 2, this difference becomes less with increasing temperatures, although at smelting temperatures reaction I is still the faster. He also says (p. 48), "At temperatures . . . between 1100° and 1300°C the zinc oxide reduction reaction is intrinsically more rapid than its physical limitations; that is, it is limited by gas diffusion rates." In the course of numerous reactivity tests involving the separate use of reactions and I and 2, we have obtained data that show by direct experiment, we believe for the first time, the correctness of Maier's statements concerning these reactions. We also include data on the relative rate of reaction 3, involving reduction by hydrogen. Finally, some interesting results obtained by carrying out the reduction of a zinc ore-coal briquet in streaming atmospheres of nitrogen, carbon monoxide and hydrogen, respectively, are presented.*

Jan 1, 1941

By R. K. Waring, E. C. Truesdale

The Research Division of The New Jersey Zinc Company (of Pa.) has conducted, over a period of years, numerous tests of the reducibility of various zinc ores and the reactivity of various kinds of coal, using a number of different experimental methods. Most of these tests have involved the reduction of mixtures of ore and coal. In such cases the following simultaneous reactions are believed to be mainly responsible for the production of zinc, as was shown by Bodenstein1 some years ago: ZnO+ CO = Zn + CO2 [1] C + CO2 = 2 CO [2] Each of these reactions is dependent upon the other for the supply of CO and CO2 , respectively, and the over-all rate of formation of zinc vapor will be determined by the slower of these two reactions. An analogous pair of reactions sometimes of importance is: ZnO + H2 = Zn + H2 O [31 C + H2O = CO + Ha [4] While it is possible to obtain an indication of the relative reducibility of various ores, or of a fine versus a coarse ore, by testing them with a given coal, and while coal reactivities may be measured in a corresponding manner, a more direct determination of relative reaction rates is possible by carrying out the desired reactions, such as I and 2, separately and under reproducible conditions. It is one purpose of this paper to present some of the results that have been obtained by the latter method. C. G. Maier2 discusses the relative rates of reactions I and 2 and concludes that while at relatively low temperatures reaction I is faster than reaction 2, this difference becomes less with increasing temperatures, although at smelting temperatures reaction I is still the faster. He also says (p. 48), "At temperatures . . . between IIOO° and I3oo°C., . . . the zinc oxide reduction reaction is intrinsically more rapid than its physical limitations; that is, it is limited by gas diffusion rates." In the course of numerous reactivity tests involving the separate use of reactions and I and 2, we have obtained data that show by direct experiment, we believe for the first time, the correctness of Maier's statements concerning these reactions. We also include data on the relative rate of reaction 3, involving reduction by hydrogen. Finally, some interesting results obtained by carrying out the reduction of a zinc ore-coal briquet in streaming atmospheres of nitrogen, carbon monoxide and hydrogen, respectively, are presented. *

Jan 1, 1943

By E. C. Truesdale, R. K. Waring

The Research Division of The New Jersey Zinc Company (of Pa.) has conducted, over a period of years, numerous tests of the reducibility of various zinc ores and the reactivity of various kinds of coal, using a number of different experimental methods. Most of these tests have involved the reduction of mixtures of ore and coal. In such cases the following simultaneous reactions are believed to be mainly responsible for the production of zinc, as was shown by Bodenstein1 some years ago: ZnO+ CO = Zn + CO2 [1] C + CO2 = 2 CO [2] Each of these reactions is dependent upon the other for the supply of CO and CO2 , respectively, and the over-all rate of formation of zinc vapor will be determined by the slower of these two reactions. An analogous pair of reactions sometimes of importance is: ZnO + H2 = Zn + H2 O [31 C + H2O = CO + Ha [4] While it is possible to obtain an indication of the relative reducibility of various ores, or of a fine versus a coarse ore, by testing them with a given coal, and while coal reactivities may be measured in a corresponding manner, a more direct determination of relative reaction rates is possible by carrying out the desired reactions, such as I and 2, separately and under reproducible conditions. It is one purpose of this paper to present some of the results that have been obtained by the latter method. C. G. Maier2 discusses the relative rates of reactions I and 2 and concludes that while at relatively low temperatures reaction I is faster than reaction 2, this difference becomes less with increasing temperatures, although at smelting temperatures reaction I is still the faster. He also says (p. 48), "At temperatures . . . between IIOO° and I3oo°C., . . . the zinc oxide reduction reaction is intrinsically more rapid than its physical limitations; that is, it is limited by gas diffusion rates." In the course of numerous reactivity tests involving the separate use of reactions and I and 2, we have obtained data that show by direct experiment, we believe for the first time, the correctness of Maier's statements concerning these reactions. We also include data on the relative rate of reaction 3, involving reduction by hydrogen. Finally, some interesting results obtained by carrying out the reduction of a zinc ore-coal briquet in streaming atmospheres of nitrogen, carbon monoxide and hydrogen, respectively, are presented. *

Jan 1, 1943