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By C. H. North, L. E. Lynd, W. W. Anderson, H. Sicurdson

D. R. Grantham (Institute of Mining and Metallurgy, London, England)—This paper is a very valuable contribution to our knowledge of ilmenite and its alteration products. Two aspects are not treated in the paper and further information would be valuable. How far are the alteration processes described influenced by the original composition of the ilmenite? The word gangue is used but it is not clear whether this refers to other chemical constituents in the ilmenite, e.g., magnesia, or to other minerals loose or in composite grains. Has the work described been related to specific gravities? Pure ilmenite is stated to have a specific gravity of 4.79. Some varieties range up to over 5.0, while high magnesic varieties have a specific gravity ranging to below 4.2. Alteration to hematite might lower the specific gravity and a porous texture due to the removal of iron and the formation of rutile might also lower it. As specific gravity is a quick method which often gives an approximate indication of composition, data on the above would be valuable. L. E. Lynd (authors' reply)—Because of the way in which beach sand deposits were formed, it is impossible to tell exactly what the original composition of the parent ilmenites might have been. Information on the influence of original composition on the alteration processes must be derived from other sources, perhaps by comparing the alteration products formed from ilmenite in place in a variety of rock deposits, where parent ilmenite and its alteration product can be recognized. No information of this type has yet been brought to our attention. The material referred to as gangue includes all constituents other than oxides of titanium and iron. Nearly all of this was present as separate grains of garnet, augite, hornblende, quartz, feldspar, spinel, or other gangue minerals. Inclusions of gangue minerals within ore grains were rare, and we believe there is little MgO (1 pct or less) or other impurity actually held in the ilmenite structure in any of the concentrates studied. No specific gravity measurements were made on the samples studied. However, the suggestion that alteration involving loss of iron would lower the specific gravity is a very reasonable one, and is in accord with the findings of Creitz and McVay (Ref. 9 of our paper) who reported two magnetic opaque fractions from Trail Ridge, Fla., to have the following specific gravities and pompositions: The specific gravity of this porous, high TiO² alteration product of ilmenite is closer to that of rutile (4.25) than to that of ilmenite. Due to the porosity, it may even be less dense than rutile, although lower in TiO² and higher in iron.

Jan 1, 1955

By K. K. Landes

The north central and northeastern states supply over 50 pct of the chemical and metallurgical limestone produced annually in the United States, and Ontario is the leading source of this material in Canada. About three fourths of the chemical and metallurgical stone produced in this area comes from Michigan, Pennsylvania, Ohio, and Ontario. The specifications, physical and especially chemical, for chemical and metallurgical stone depend upon the end use, but in general the tolerance for impurities is so low as to rule out most limestones and dolomites. Both high calcium limestone and dolomite are used in the metallurgical and chemical industries. The principal metallurgical use is as a flux in iron ore blast furnaces and open hearth steel furnaces. The major chemical uses are in lime burning and soda-ash manufacture. Other important uses include glass manufacture, in making calcium carbide, and in sugar factories. All deposits of high quality carbonate rock are definitely finite. Invariably and inevitably they diminish in either thickness or quality laterally so as to become unworkable as chemical and metallurgical stone. The size of these high quality lenses ranges from a few thousands of tons to hundreds of millions of tons. The best hunting for new supplies is in the geologic formations known to contain premium quality deposits. However, because of high transportation costs, carbonate rocks, to be workable, must be close to market, dollarwise. Definitions: Chemical stone is limestone or dolomite used as a raw material by the chemical industry. The major chemical uses are in lime burning and soda-ash manufacture. Other important uses include glass manufacture, making calcium carbide, and in sugar factories. The specifications for chemical stone depend entirely upon the end product. Some uses require dolomite, some require high calcium limestone; in a few instances, notably in lime burning, either type of carbonate rock can be used as raw material. As a general rule, a fairly pure stone is necessary and for certain particular uses the tolerance for some elements such as sulfur, iron, and phosphorus may be extremely small. Metallurgical stone is used as a flux in furnace operations, especially in the blast furnace where iron ore is converted into pig iron and in the open hearth furnace where pig iron is made into steel. Either limestone or dolomite can be used in the blast furnace, but only high calcium stone is charged in the open hearth (except for rice-size dolomite used as a refractory). There are no rigid chemical specifications for blast furnace stone, but low silica, alumina, sulfur, and phosphorus are desirable. For open hearth use, in addition to low magnesia, a very low sulfur content is also specified by many furnace operators. For furnace use, fluxstone also must be sufficiently shatter resistant that it will remain in lump form during transport and charging into the furnace. Commercial stone is the term applied in the trade for crushed stone used for roadstone and in concrete aggregate. Many of our best chemical and metallurgical limestones are too soft to qualify in the Los Angeles abrasion test for use as commercial stone. However, some limestones, and a higher proportion of dolomites, do qualify for commercial stone and so can be sold to either market. Place Value: Even the highest grade limestone is still a bulk commodity with a relatively low value per ton. As a matter of fact there is very little difference in the average price per ton between high grade chemical and metallurgical stone and crushed limestone used commercially. Most high quality stone is produced in large operations with consequent low cost per ton whereas most commercial stone is produced in relatively small local quarries. As in the case of other bulk commodities most limestone buyers pay more for transporting the raw material than the cost of the stone at its source. For this reason steel furnaces and chemical plants

Jan 1, 1961

By Ferid Kromer

Geography: The Tagtepe district of the Vilayet of Eskigehir is about 20 miles northeast of the city of Eskigehir (approximately midway between Ankara and Istanbul) in western Anatolia. The area is a mountainous one, the highest peak being Tagtepe Mountain (5200 ft) which is approximately in the center of the district. The mountains drop off to the deep valley of the Sakarya River on the north and to the plain of Eskigehir on the south. FERID KROMER, Junior Member AZME, is a Consulting Mining Engineer and General Manager, Bagtag Turk Maadin Ltd., Istanbul, Turkey. New York Meeting, February 1950. TP 2629 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Dec. 29, 1948. For the most part, the watershed is on the northern side of the mountain barrier, draining into the Sakarya River, which in turn empties into the Black Sea midway between Zonguldak and the mouth of the Bosphorus. The approximate area covered by the Tagtepe district is shown in fig. 1. Transportation to shipping points is available via the Istanbul-Ankara railroad. The station on this line nearest the mining district is Alpikoy station, about 20 miles by road southwest of Tagtepe Mountain. Interior roads within the district are poor. Being of dirt, the winter rains and snows render them almost impassable for trucks from about the middle of December until the end of March, thus presenting a considerable transportation problem. However, the roads from the Bagoren and Tagtepe chromite mines to the railroad shipping point at Alpikoy station have recently been repaired and will be maintained for all-weather truck transportation. Detailed climatic data are not available. However, in general the spring, summer, and early autumn months are dry, and good weather may be expected from May until early November. Then the winter rains commence, and heavy snow is usual during January and February. Geology: The mountainous structure of Tagtepe belongs to basic rocks of serpentine (Variscan Orogeny) which is in contact with Paleozoic schists at west, and an Oligocene outcrop of red clays in Margi-Sepetci region (see fig. 1) at southeast. The northwest and southwest borders of Tagtepe district are, respectively, surrounded by Paleozoic schists and pebbly gray and yellow Neogene clays. More recent formations of alluviums overlay the plain of Eskigehir. Dark basic rocks of trachytes with hornblende are visible on Turkmenbaba Mountain, at the west of Tagtepe. Mineral Occurrences: Chromite: the most important mineral found in any quantity in the Tagtepe district. The alignment of the deposits of chromite is in general along the line Bagoren-Tagtepe (see fig. 1). The first mines in the area were those of Tagtepe and Bagoren, which were developed over 20 years ago with Swedish capital. Other deposits of chromite, more recently discovered and so far of less importance, are being worked at Kurucor, Komurcu, Gelinmezari, and Lacin (see fig. 1). Deposits average generally between 46 and 48 pct chromic oxide, with the exception of the Bagoren mine which averages 44 pct. However, a new lode, very recently plotted, in the Tagtepe mine averages 50 pct Cr,O,, 4.6 pct SOz, and 7 pct FeO. Geological character of the chromite occurrences in the Tagtepe mine may be considered typical of most chromite lodes in this area. The indications are that the formations of ore lenses are developed by the segregation of chromite crystals intruded into the serpentinized rock, and exposed later to tectonic movement within the zone of crystallization. All lenticular masses are more or less regular in shape and follow each other in southeast-northwest direction and dip generally 70" NE. Ore lenses do not seem to persist in depth, average depth of two lenses is 60 ft below surface. Three lodes .have been mined as open-pit. The average dimensions of individual lenses are as follows: pitch length, 100 ft; breadth, 27 ft; and width, 20 ft. The lenses and their enclosing rocks are broken by parallel fractures in approximately east-west direction. These joints are filled, except in one lode, with cementing material, which gives to the ore a

Jan 1, 1951

By Ferid Kromer

Geography: The Tagtepe district of the Vilayet of Eskigehir is about 20 miles northeast of the city of Eskigehir (approximately midway between Ankara and Istanbul) in western Anatolia. The area is a mountainous one, the highest peak being Tagtepe Mountain (5200 ft) which is approximately in the center of the district. The mountains drop off to the deep valley of the Sakarya River on the north and to the plain of Eskigehir on the south. FERID KROMER, Junior Member AZME, is a Consulting Mining Engineer and General Manager, Bagtag Turk Maadin Ltd., Istanbul, Turkey. New York Meeting, February 1950. TP 2629 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Dec. 29, 1948. For the most part, the watershed is on the northern side of the mountain barrier, draining into the Sakarya River, which in turn empties into the Black Sea midway between Zonguldak and the mouth of the Bosphorus. The approximate area covered by the Tagtepe district is shown in fig. 1. Transportation to shipping points is available via the Istanbul-Ankara railroad. The station on this line nearest the mining district is Alpikoy station, about 20 miles by road southwest of Tagtepe Mountain. Interior roads within the district are poor. Being of dirt, the winter rains and snows render them almost impassable for trucks from about the middle of December until the end of March, thus presenting a considerable transportation problem. However, the roads from the Bagoren and Tagtepe chromite mines to the railroad shipping point at Alpikoy station have recently been repaired and will be maintained for all-weather truck transportation. Detailed climatic data are not available. However, in general the spring, summer, and early autumn months are dry, and good weather may be expected from May until early November. Then the winter rains commence, and heavy snow is usual during January and February. Geology: The mountainous structure of Tagtepe belongs to basic rocks of serpentine (Variscan Orogeny) which is in contact with Paleozoic schists at west, and an Oligocene outcrop of red clays in Margi-Sepetci region (see fig. 1) at southeast. The northwest and southwest borders of Tagtepe district are, respectively, surrounded by Paleozoic schists and pebbly gray and yellow Neogene clays. More recent formations of alluviums overlay the plain of Eskigehir. Dark basic rocks of trachytes with hornblende are visible on Turkmenbaba Mountain, at the west of Tagtepe. Mineral Occurrences: Chromite: the most important mineral found in any quantity in the Tagtepe district. The alignment of the deposits of chromite is in general along the line Bagoren-Tagtepe (see fig. 1). The first mines in the area were those of Tagtepe and Bagoren, which were developed over 20 years ago with Swedish capital. Other deposits of chromite, more recently discovered and so far of less importance, are being worked at Kurucor, Komurcu, Gelinmezari, and Lacin (see fig. 1). Deposits average generally between 46 and 48 pct chromic oxide, with the exception of the Bagoren mine which averages 44 pct. However, a new lode, very recently plotted, in the Tagtepe mine averages 50 pct Cr,O,, 4.6 pct SOz, and 7 pct FeO. Geological character of the chromite occurrences in the Tagtepe mine may be considered typical of most chromite lodes in this area. The indications are that the formations of ore lenses are developed by the segregation of chromite crystals intruded into the serpentinized rock, and exposed later to tectonic movement within the zone of crystallization. All lenticular masses are more or less regular in shape and follow each other in southeast-northwest direction and dip generally 70" NE. Ore lenses do not seem to persist in depth, average depth of two lenses is 60 ft below surface. Three lodes .have been mined as open-pit. The average dimensions of individual lenses are as follows: pitch length, 100 ft; breadth, 27 ft; and width, 20 ft. The lenses and their enclosing rocks are broken by parallel fractures in approximately east-west direction. These joints are filled, except in one lode, with cementing material, which gives to the ore a

Jan 1, 1951

By Clifford Frondel

THE aluminum oxide known as corundum has several varieties that have been used as gem materials since ancient times. These include the red variety called ruby, the blue variety sapphire, and the asteriated types of ruby and sapphire. Asteriated sapphire was known to the ancients under the name of astrios, and descriptions of this gem were given by Pliny and other early writers. The relation of these gem materials to each other as varieties of a single species, corundum, was first clearly established by Haüy in 1805 and J. M. Güthe' in 1809. Natural gem corundum is obtained principally in Ceylon, Siam, Burma, India, and Australia. Star sapphires and rubies always have been highly prized and in recent years have become particu- larly popular in the United States. Natural star rubies of large size and fine quality are extremely rare and rank with large and fine emeralds and diamonds as the most valuable of gem stones. Interest thus attaches to the recent success in commercially synthesizing star sapphires and rubies of a size and perfection unmatched by nature. Corundum was first synthesized as crystals in 1837 by A. Gaudin, who fused alum and aluminum oxide with potassium sulphate. Numerous other syntheses have been reported in more recent years. Summaries of this work are given in Doelter's Hand-buch der Mineralchemie, Mellor's Compreheizsive Treatise of Inorganic Chemistry, and other reference works. The methods employed include the reaction in the gaseous state at high temperatures of halogen compounds of aluminum with water vapor or boric oxide; the crystallization of aluminum oxide from fusion in potassium molybdate, potassium dichrom-ate or borax; and crystallization from highly aluminous silicate melts. Red, blue, or green colored varieties can be obtained by the addition of small

Jan 1, 1955

By Herbert A. Stein, John B. Murdock

AN analysis of perlite expansion furnaces must be based upon one consistent theory which explains how and why perlite does expand when heated. There is more than one such theory, so to establish a basis for the rest of this paper, the authors will outline one theory and the data that support it before going into the construction details of different furnaces. JOHN B. MURDOCK, Associate Member AIME, is President, and HERBERT A. STEIN is Secretary, of the Perlite Corp., Phoenix, Arizona. San Francisco Meeting, February 1949. TP 2736 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 3, 1949. Why Perlite Expands: Perlite is known to contain some dissolved or combined fluid, probably water, which is lost when the material is heated to fusion. It is generally agreed that when particles of this volcanic glass are heated to fusion in such a way that vaporization of this water into steam takes place at the same time as the glass becomes soft, the steam puffs up each particle into a mass of glass foam. It is a simple matter to expand perlite under a blow torch for demonstration purposes, but in commercial installations, the problem is made more complicated by the necessity of making efficient use of both raw material and fuel, and producing an expanded aggregate conforming to close specifications for size distribution and density, using many different types of perlite rock. The ability of a given operation to fulfill these requirements depends upon the proper handling of four variables. They are: (1) the nature of the perlite rock used, (2) the heating time taken to get the perlite particle up to its highest temperature, (3) the size of the particle, and (4) the maximum temperature the particle reaches. Types of Perlite Rock: Perlite may be classified in many ways, but the characteristics most easily correlated with its behavior in furnaces are its softening temperature, its effective water content, and its "liveliness." Actually there is a close correlation among these three characteristics so it is possible to describe a perlite using any one of them. Lively perlites always have low softening temperatures and high effective water contents, whereas the deader perlites have higher softening temperatures and lower effective water contents. These softening temperatures run from 1400°F to above 2000°F and the effective water contents run from over 2 pct down to 0.2 pct. Included in the category of lively glasses are the green pitchstone from the Edgar claim in Superior, Ariz., the red pitchstone on the Animas highway south of Lordsburg, N. Mex., and a gray glass from Beatty, Nevada. Examples of intermediate perlites (in order of decreasing liveliness) are the Guzman-Lobb perlite with obsidian

Jan 1, 1951

By Herbert A. Stein, John B. Murdock

AN analysis of perlite expansion furnaces must be based upon one consistent theory which explains how and why perlite does expand when heated. There is more than one such theory, so to establish a basis for the rest of this paper, the authors will outline one theory and the data that support it before going into the construction details of different furnaces. JOHN B. MURDOCK, Associate Member AIME, is President, and HERBERT A. STEIN is Secretary, of the Perlite Corp., Phoenix, Arizona. San Francisco Meeting, February 1949. TP 2736 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 3, 1949. Why Perlite Expands: Perlite is known to contain some dissolved or combined fluid, probably water, which is lost when the material is heated to fusion. It is generally agreed that when particles of this volcanic glass are heated to fusion in such a way that vaporization of this water into steam takes place at the same time as the glass becomes soft, the steam puffs up each particle into a mass of glass foam. It is a simple matter to expand perlite under a blow torch for demonstration purposes, but in commercial installations, the problem is made more complicated by the necessity of making efficient use of both raw material and fuel, and producing an expanded aggregate conforming to close specifications for size distribution and density, using many different types of perlite rock. The ability of a given operation to fulfill these requirements depends upon the proper handling of four variables. They are: (1) the nature of the perlite rock used, (2) the heating time taken to get the perlite particle up to its highest temperature, (3) the size of the particle, and (4) the maximum temperature the particle reaches. Types of Perlite Rock: Perlite may be classified in many ways, but the characteristics most easily correlated with its behavior in furnaces are its softening temperature, its effective water content, and its "liveliness." Actually there is a close correlation among these three characteristics so it is possible to describe a perlite using any one of them. Lively perlites always have low softening temperatures and high effective water contents, whereas the deader perlites have higher softening temperatures and lower effective water contents. These softening temperatures run from 1400°F to above 2000°F and the effective water contents run from over 2 pct down to 0.2 pct. Included in the category of lively glasses are the green pitchstone from the Edgar claim in Superior, Ariz., the red pitchstone on the Animas highway south of Lordsburg, N. Mex., and a gray glass from Beatty, Nevada. Examples of intermediate perlites (in order of decreasing liveliness) are the Guzman-Lobb perlite with obsidian

Jan 1, 1951

By C. H. Curtis

HE valuable mineral content of the current feed -*- to the Miami concentrator is as follows: copper, 0.7 pct total; molybdenum, 0.01. Flotation of this ore yields a sulphide concentrate containing: chalco- cite, 44 pct; molybdenite, 0.5; pyrite, 50.0; insol, 5.5. A combination of potassium ethyl xanthate and pentasol amyl xanthate as collectors, and pine oil as frother, are used in this flotation. Rejection of pyrite is encouraged by holding the amount of collectors used to the minimum consistent with copper recovery and by operating at high alkalinity (equivalent to 0.35-0.40 lb CaO per ton solution of pH 11.0). The molybdenum recovery in the sulphide concentrates under the above flotation conditions is approximately 50 pct of that originally present in the ore. Taking into account the acid soluble molybdenum, indicated molybdenite recovery is 75 to 80 pct. The attempt to separate the molybdenite into an acceptable molybdenum product begins with the bulk sulphide flotation concentrate just described. This concentrate is composed of chalcocite, whose floatability has been promoted to the fullest extent possible for the sake of its recovery from the ore, together with the pyrite which has been activated along with the copper mineral. The problem is to deaden the copper and iron minerals, and to float the molybdenite. Obviously in the accomplishment of this end, conditioning and preparation of the pulp, prior to flotation, plays an all important role. The first step is thickening to 50 to 60 pct solids, with milk of lime added to the thickener feed to maintain an alkalinity of the pulp equivalent to a pH of 8.5 to 8.8 during its residence in the thickener. The purpose of the thickening is primarily to reduce the volume of pulp for subsequent treatment. However, the relatively prolonged retention of the pulp in the thickener at the desired alkalinity is known to have a favorable depressing effect upon pyrite. There is a limit for this alkalinity above which a depressing effect upon molybdenite occurs. The thickened pulp (alkalinity: 0.015 lb CaO per ton, pH 8.8), discharges into an agitator, retention time approximately 2 hr, to which additional lime is added to raise the alkalinity to 0.35 to 0.40 lb CaO per ton solution, pH 11.6. This additional lime is required for pyrite depression and can be tolerated without loss of molybdenite because of the limited time of contact in the conditioner tank. The pulp leaving the lime conditioner passes through two successive steaming tanks, which are mechanically agitated, and into which live steam is admitted directly into the pulp near the bottom of the tanks. The temperature of the pulp is maintained as near boiling as possible. The steaming time is approximately 4 hr. The pulp leaving the last steamer has an alkalinity of about 0.04 lb Cao per ton solution, pH 8.7. It is believed that oxidation of the copper and iron sulphides occurs during steaming, the resulting sulphates reacting the calcium hydroxide to calcium sulphate and thus reducing the alkalinity. Since the steamer-feed solution is already saturated with calcium sulphate, the calcium sulphate produced during steaming is precipitated. It is believed that this calcium sulphate is precipitated preferentially on copper and iron mineral surfaces thus decreasing their floatability. Aside from the "lime chemistry" during steaming, pine oil is displaced from the pulp and xanthate decomposed, which has a major effect upon the deadening of the copper and iron sulphides. Following steaming, the hot pulp is admitted to another conditioning tank wherein it is aerated, primarily for cooling, but incidentally for additional oxidation of the copper and iron sulphides. The resulting "deadened" pulp is then diluted to 20 pct solids, a specific collector for molybdenite, ordinary stove oil, is added and the separation of the molybdenite by flotation is undertaken at a pH of 8.5 to 8.8 in standard Miami air-flotation ma-chines. B-22 frother is used when necessary. A re-grind of the thickened rougher concentrates is made prior to the first cleaning operation chiefly for rejection of insoluble in subsequent flotation. The cleaner concentrate is then stepped up to 90 pct MoS, in an 8-cell Denver flotation machine No. 18. Sodium silicate is added to the cleaner circuit. Its effect is to flocculate molybdenite and stabilize the froth. In summary, it may be stated: 1. Separation of molybdenite into an acceptable product from sulphide copper concentrates by flotation involves preliminary preparation and conditioning of the pulp, which is of major importance. 2. This preparation and conditioning consists of several successive steps: (A) Thickening to 50 to 60 pct solids at controlled alkalinity to reduce volume of pulp and to contribute to depression of pyrite. (B) Agitation at high-pulp density for limited time with additional lime to provide for depression of pyrite. (C) Steaming at high-pulp density for decomposition of xanthate and xanthate surface films, evolution of pine oil, and oxidation of sulphide minerals other than molybdenite. The latter involves sulphating of lime with probable precipitation of calcium sulphate preferentially on copper and iron minerals. (D) Aeration at high-pulp density for cooling, and for further oxidation of copper and iron sulphide minerals. (E) Dilution of pulp to 20 pct solids and addition of specific collector for molybdenite, common stove oil. It is hardly necessary to point out that this rather drastic procedure for depression of previously activated copper and iron sulphide minerals, without at the same time depressing molybdenite, is possible due to the inherently high floatability and refractory nature of molybdenite. However, molybdenite is susceptible to depression by excessive lime which must therefore be limited to the amount consistent with satisfactory molybdenite recovery. The steaming procedure is being carried on at Miami Copper Co. under license agreement with Janney, Nokes, and Johnson, holders of letters patent on the process.

Jan 1, 1951

By C. H. Curtis

HE valuable mineral content of the current feed -*- to the Miami concentrator is as follows: copper, 0.7 pct total; molybdenum, 0.01. Flotation of this ore yields a sulphide concentrate containing: chalco- cite, 44 pct; molybdenite, 0.5; pyrite, 50.0; insol, 5.5. A combination of potassium ethyl xanthate and pentasol amyl xanthate as collectors, and pine oil as frother, are used in this flotation. Rejection of pyrite is encouraged by holding the amount of collectors used to the minimum consistent with copper recovery and by operating at high alkalinity (equivalent to 0.35-0.40 lb CaO per ton solution of pH 11.0). The molybdenum recovery in the sulphide concentrates under the above flotation conditions is approximately 50 pct of that originally present in the ore. Taking into account the acid soluble molybdenum, indicated molybdenite recovery is 75 to 80 pct. The attempt to separate the molybdenite into an acceptable molybdenum product begins with the bulk sulphide flotation concentrate just described. This concentrate is composed of chalcocite, whose floatability has been promoted to the fullest extent possible for the sake of its recovery from the ore, together with the pyrite which has been activated along with the copper mineral. The problem is to deaden the copper and iron minerals, and to float the molybdenite. Obviously in the accomplishment of this end, conditioning and preparation of the pulp, prior to flotation, plays an all important role. The first step is thickening to 50 to 60 pct solids, with milk of lime added to the thickener feed to maintain an alkalinity of the pulp equivalent to a pH of 8.5 to 8.8 during its residence in the thickener. The purpose of the thickening is primarily to reduce the volume of pulp for subsequent treatment. However, the relatively prolonged retention of the pulp in the thickener at the desired alkalinity is known to have a favorable depressing effect upon pyrite. There is a limit for this alkalinity above which a depressing effect upon molybdenite occurs. The thickened pulp (alkalinity: 0.015 lb CaO per ton, pH 8.8), discharges into an agitator, retention time approximately 2 hr, to which additional lime is added to raise the alkalinity to 0.35 to 0.40 lb CaO per ton solution, pH 11.6. This additional lime is required for pyrite depression and can be tolerated without loss of molybdenite because of the limited time of contact in the conditioner tank. The pulp leaving the lime conditioner passes through two successive steaming tanks, which are mechanically agitated, and into which live steam is admitted directly into the pulp near the bottom of the tanks. The temperature of the pulp is maintained as near boiling as possible. The steaming time is approximately 4 hr. The pulp leaving the last steamer has an alkalinity of about 0.04 lb Cao per ton solution, pH 8.7. It is believed that oxidation of the copper and iron sulphides occurs during steaming, the resulting sulphates reacting the calcium hydroxide to calcium sulphate and thus reducing the alkalinity. Since the steamer-feed solution is already saturated with calcium sulphate, the calcium sulphate produced during steaming is precipitated. It is believed that this calcium sulphate is precipitated preferentially on copper and iron mineral surfaces thus decreasing their floatability. Aside from the "lime chemistry" during steaming, pine oil is displaced from the pulp and xanthate decomposed, which has a major effect upon the deadening of the copper and iron sulphides. Following steaming, the hot pulp is admitted to another conditioning tank wherein it is aerated, primarily for cooling, but incidentally for additional oxidation of the copper and iron sulphides. The resulting "deadened" pulp is then diluted to 20 pct solids, a specific collector for molybdenite, ordinary stove oil, is added and the separation of the molybdenite by flotation is undertaken at a pH of 8.5 to 8.8 in standard Miami air-flotation ma-chines. B-22 frother is used when necessary. A re-grind of the thickened rougher concentrates is made prior to the first cleaning operation chiefly for rejection of insoluble in subsequent flotation. The cleaner concentrate is then stepped up to 90 pct MoS, in an 8-cell Denver flotation machine No. 18. Sodium silicate is added to the cleaner circuit. Its effect is to flocculate molybdenite and stabilize the froth. In summary, it may be stated: 1. Separation of molybdenite into an acceptable product from sulphide copper concentrates by flotation involves preliminary preparation and conditioning of the pulp, which is of major importance. 2. This preparation and conditioning consists of several successive steps: (A) Thickening to 50 to 60 pct solids at controlled alkalinity to reduce volume of pulp and to contribute to depression of pyrite. (B) Agitation at high-pulp density for limited time with additional lime to provide for depression of pyrite. (C) Steaming at high-pulp density for decomposition of xanthate and xanthate surface films, evolution of pine oil, and oxidation of sulphide minerals other than molybdenite. The latter involves sulphating of lime with probable precipitation of calcium sulphate preferentially on copper and iron minerals. (D) Aeration at high-pulp density for cooling, and for further oxidation of copper and iron sulphide minerals. (E) Dilution of pulp to 20 pct solids and addition of specific collector for molybdenite, common stove oil. It is hardly necessary to point out that this rather drastic procedure for depression of previously activated copper and iron sulphide minerals, without at the same time depressing molybdenite, is possible due to the inherently high floatability and refractory nature of molybdenite. However, molybdenite is susceptible to depression by excessive lime which must therefore be limited to the amount consistent with satisfactory molybdenite recovery. The steaming procedure is being carried on at Miami Copper Co. under license agreement with Janney, Nokes, and Johnson, holders of letters patent on the process.

Jan 1, 1951

By E. A. G. Colls

IN all branches of the chemical industry, corrosion plays a very costly part unless it is suitably com-batted, and as a result it is probably correct that chemical and design engineers are more corrosion conscious in the field of chemical industry than in others. Most metals occur in nature in combination with other elements. The refined or reduced state to which man converts them for his use, by removing the combining elements, leaves them in an unstable condition. Therefore in most of the media to which the metals are exposed they are constantly combining with the constituents of their environment, or in other words they are continually being corroded. Similarly, nonmetallic materials are corroded by undergoing chemical change. The rate at which corrosion takes place varies widely from metal to metal and medium to medium. In practically all cases the corrosion of metals in solutions (electrolytes) is electrolytic in nature and the rate of corrosion is dependent on many factors such as temperature, pressure, internal stresses, galvanic action, metal-ion concentration, and so on. In the chemical industry substances must be handled which are particularly corrosive to materials of construction. At the chemical plants of The Consolidated Mining and Smelting Co. of Canada, Ltd. (otherwise known as Cominco), situated at Trail, B. C., Canada, the following are some of the materials that have to be handled: Gases. Sulphur dioxide, sulphur trioxide, carbon dioxide, carbon monoxide, oxygen, hydrogen fluoride, ammonia, hydrogen sulphide, and oxides of nitrogen. Liquids. Solutions of ammonium sulphate, ammonium sulphite, ammonium nitrate, caustic soda and potash, sulphuric acid, nitric acid, hydrofluo-silicic acid, hydrofluoric acid, phosphoric acid, aqua ammonia, and formic acid. Solids. Gypsum (containing phosphoric acid), ammonium sulphate, ammonium nitrate, phosphate rock, caustic soda, potash, and phosphate fertilizers.

Jan 1, 1951

By E. A. G. Colls

IN all branches of the chemical industry, corrosion plays a very costly part unless it is suitably com-batted, and as a result it is probably correct that chemical and design engineers are more corrosion conscious in the field of chemical industry than in others. Most metals occur in nature in combination with other elements. The refined or reduced state to which man converts them for his use, by removing the combining elements, leaves them in an unstable condition. Therefore in most of the media to which the metals are exposed they are constantly combining with the constituents of their environment, or in other words they are continually being corroded. Similarly, nonmetallic materials are corroded by undergoing chemical change. The rate at which corrosion takes place varies widely from metal to metal and medium to medium. In practically all cases the corrosion of metals in solutions (electrolytes) is electrolytic in nature and the rate of corrosion is dependent on many factors such as temperature, pressure, internal stresses, galvanic action, metal-ion concentration, and so on. In the chemical industry substances must be handled which are particularly corrosive to materials of construction. At the chemical plants of The Consolidated Mining and Smelting Co. of Canada, Ltd. (otherwise known as Cominco), situated at Trail, B. C., Canada, the following are some of the materials that have to be handled: Gases. Sulphur dioxide, sulphur trioxide, carbon dioxide, carbon monoxide, oxygen, hydrogen fluoride, ammonia, hydrogen sulphide, and oxides of nitrogen. Liquids. Solutions of ammonium sulphate, ammonium sulphite, ammonium nitrate, caustic soda and potash, sulphuric acid, nitric acid, hydrofluo-silicic acid, hydrofluoric acid, phosphoric acid, aqua ammonia, and formic acid. Solids. Gypsum (containing phosphoric acid), ammonium sulphate, ammonium nitrate, phosphate rock, caustic soda, potash, and phosphate fertilizers.

Jan 1, 1951

By W. S. Gillam

A need for new supplies of fresh water exists today and in many specific areas that need is urgent. One solution lies in saline water conversion, a problem complicated by cost factors. The principles involved in saline water conversion, the status of development, and the estimated costs (present and future) of several processes are presented. Among the methods discussed are distillation, electrodialysis, and freezing. In general, the costs presented are based on a standardized procedure for estimating conversion costs, permitting a valid comparison among the various processes. The need for new supplies of fresh water and the potential benefits to be derived from an abundant supply of converted water are recognized by practically everyone concerned with water problems. The water supply problem exists today; it is urgent in many specific areas in this country and also in the world, and it will become more acute in the future. One answer to the growing problem of adequate water supplies is the development of new sources. Very significant quantities of brackish underground and surface waters exist in certain areas and an inexhaustible supply of ocean water is available. Thus in many areas water resources can be extended through saline water conversion. Congress recognized the need for new sources of fresh water in 1952 and passed the Saline Water Act, Public Law 448, amended it in 1955, and in September 1958, enacted Public Law 85-883, calling for the construction of at least five demonstration plants. The program is administered by the Dept. of Interior through the Office of Saline Water, and its primary objective is to reduce the cost of converted water produced, whether it be by development of new processes or improvement of known processes. This is a most difficult problem and one that will require several years of prodigious effort. It is difficult—not because of any intricate or new chemistry, engineering, or physics involved—but because of the difficulty in converting water at low cost. Whatever the sources of the saline water, the salts which are held tenaciously in solution must be removed before the water becomes suitable for industrial or domestic uses. Saline water is a relatively simple system of salts dissolved in water. It has certain chemical and physical properties that determine the various methods by which the salts may be separated from the water. The system, although not complex, in most instances, has had countless years in which to reach equilibrium and is, therefore, comparatively stable. Because of its stability, separation of saline solutions requires relatively large quantities of energy. The unique properties of water depend on the fact that its molecules are chemically active. The chemical and physical properties of water are associated with the type of bonding involved in the water molecule. Chemical changes such as hydrolysis, or rusting of iron, involve the breaking of chemical bonds between the hydrogen and oxygen atoms. Physical changes, such as evaporation in a boiler, the melting of ice, or the viscous resistance to flow in a pipe, involve breaking of the hydrogen bonds. (The hydrogen nucleus is so small that it can attract two negative atoms.) Thus water molecules not only combine with molecules of other compounds but even with one another; e.g., each molecule may be bounded to four other molecules. Water molecules cling to the ions of dissolved salt to form water-encumbered hydrated ions and they cling to one another to form entangling networks through which hydrated ions can be propelled only by tearing the networks apart. That is one reason why considerable energy still needs to be expended in our simplest procedures for purifying water. If water molecules did not have this habit of clinging so tenaciously to other molecules, and to one another, it would be easy to push salt ions past the water molecule and get a separation. But the water would not then dissolve salt, so the problem would not exist.' Water when heated evaporates very slowly, relative to other liquids having simple molecules. Vaporization involves the separation of molecules from the liquid, and this means overcoming the attraction between molecules which is due to the hydrogen bonding. The heat of vaporization for water is high; consequently, the boiling point of water is also high. Water boils at 100" C; hydrogen sulfide (H2S) at -60" C; oxygen (02) at -183" C; nitrogen (N2) at -196" C; and methane (CH4) at-161°C, even though the latter has about the same molecular weight as water. Because of these peculiar properties of water, it exists as a liquid on earth instead of a gas such as hydrogen sulfide or nitrogen and oxygen.

Jan 1, 1961

By Katherine Mather

This paper is an attempt to put together petrographic, physical, and chemical data about the large and varied group of rocks generally called limestones. Results of the properties of these rocks on their performance as concrete aggregates are discussed. CRUSHED stone classified as limestone comprises about 70 pct of the crushed concrete aggregate and roadstone produced in this country, and the product has amounted in the recent past to about 97 million tons per year, valued at more than $123,-000,000.' Therefore an evaluation of the properties of rocks classified in these statistics as limestones and an ability to predict their behavior as aggregate in portland cement concrete are matters of considerable economic consequence to producers and consumers of aggregate. This paper is an attempt to put together petrographic, physical, and chemical data about the large and varied group of rocks generally called limestones. It also points out certain results of the properties of these rocks on their performance as concrete aggregates. The problems encountered in efforts to explain the behavior of limestones, dolomites, and related rocks as concrete aggregate lie on the frontiers between the ignorance of the geologists and the ignorance of the engineers. The mineral composition and textures of the rocks have not been adequately explored and described, and the effects of mineral composition and texture on the performance of aggregates have been worked out in only a few cases. There are instances of unsatisfactory performance and some generalizations of those experiences. There are many more examples of satisfactory performance than of unsatisfactory, but there is practically no published information as to why a particular aggregate was satisfactory in a specific use. There are all too few investigations of undeteriorated concrete; more is known about the pathology of concrete than about its normal structure and aspect. As part of the investigation of aggregates, the classification of rocks is not an end in itself, but is a step toward recognition of properties expected to influence the behavior of aggregates in their intended use. Rock of any type may perform well or poorly as concrete aggregate, depending on the physical condition of the rock, its physical and chemical properties as compared to those of the matrix in which it is placed, and the circumstances under which the concrete is exposed. Some classification and descrip- tion of the limestones is necessary to distinguish subgroups whose members will probably behave in similar ways and to evaluate the group as a whole. The group name, limestone, includes and tends to conceal the identity of rocks that have a very great range in chemical and mineralogical composition, structure and texture, conditions of deposition, subsequent history, and suitability for use as concrete aggregate. All the rocks classified as limestones include one or both of the most abundant rock-form-ing carbonate minerals, calcite and dolomite, as major constituents. Carbonate rocks is a more descriptive and more accurate group name than limestone, which has generally been used to include dol-omitic or magnesian limestones and dolomites as well as calcitic limestones. Classification and Description of the Carbonate Rocks The question of names to be applied to the carbonate rocks may appear academic, but it is of practical importance as long as there are specifications for aggregate that result in acceptance or rejection of rocks by name and as long as failure to make distinctions among the carbonate rocks leads to misunderstandings of their properties and of what may be expected of them in performance. Materials included in production statistics as limestone and tested for concrete aggregate as limestone range in fact from calcareous shale and calcareous or dolomitic sandstone and argillaceous limestone and dolomite to calcitic limestone and pure dolomite and to rocks close to calcitic and dolomitic marble. To take a simple example: consider two manufactured coarse aggregates, both dense and unweathered, one composed principally of crystalline calcite and the other of crystalline dolomite, but both known as limestone. If each is used as coarse aggregate in a standardized concrete mixture with the same fine aggregate used in both cases, made into concrete specimens, and tested in accelerated freezing-and-thaw-ing, the test results will probably be quite different, because of the differences in internal bond and thermal properties between the two aggregates. As long as both aggregates are called limestone, the test results cannot be explained, or used except in a very limited way; if the aggregates are distinguished as limestone and dolomite and the consequent differences in texture and thermal properties are recognized, the results are reasonable. Classification of the carbonate rocks used as aggregate should be based on structure and on composi-

Jan 1, 1954

By H. G. Papacharalambous, S. C. Sun

Experimental results indicate that wet cyclones could be effectively used for the preliminary classification of the tested synthetic abrasive materials, thus supplementing the currently used sedimentation method. An empirical formula is also proposed on the basis of the test data to calculate the particle size of separation. One of the basic operations in the abrasive industry is the classification of the crushed and ground materials into different sized products. The relatively coarse grains, plus 325 mesh, are commonly sized by dry screening with satisfactory results. On the other hand, however, the currently used grading tank, for classifying grains finer than 325 mesh, is intermittent. Consequently, it is difficult to operate efficiently and keep pace with erratic market requirements. Little success was made in an attempt to substitute air settling and continuous hydraulic settling for the grading tank, because size specifications1 for abrasive powders are very stringent and difficult to meet. Finally, a wet cyclone was chosen for experimentation. Even though wet cyclones have not been extensively used in the classification of abrasives; however, their performance as a classifier has been verified by Driessen2,4 on coal, McCarrel5 with manganese, and Herkenhoff6,7 on iron ore. Experimental work on silicon carbide, boron carbide, and fused alumina has shown that the cyclone

Jan 1, 1963

By S. M. Brisbane

THE life of refractory linings in rotary cement kilns can be shortened by uneven or inadequate support of the kiln and its shell and by variations in the conditions of operation. Alteration of these factors may, according to their nature, bring about mechanical deterioration of the lining or promote chemical attack. Chemical attack has been described elsewhere.1-4 The distortion of cement kilns has been discussed in a general manner by Rochow,6 ho indicates the amount of distortion which may occur in an unlined shell, and by Rosenblad: who states that the deformations of the shell are greatest above the trunnions. The present article indicates the extent of the distortion of a kiln to an oval shape in certain selected positions and the deviation from a straight line of the kiln along its length between two supports. The cement kiln is a long, hollow, rotating cylinder consisting of steel plates which may be either welded or riveted together. This shell is supported on tires, frequently 60 ft apart, which roll on trunnions. The large mass of the kiln causes distortion of its cross-section; it becomes slightly oval, i.e., diameters lengthen as they become horizontal and shorten as they become vertical. There is also a tendency for the shell to bow between supporting tires; this bowing may be upwards or downwards depending on the position of the weight forces and the supports. The extent of the deviations from the ideal kiln shape was investigated. Observations described in this paper were made on the shell of the clinkering zone between the first and second tires of two of the kilns at the Geelong works of Australian Portland Cement Pty. Ltd. The kilns were both 400 ft long and 10 ft diam with a welded enlarged burning zone 11 ft 6 in. diam. The shell was fabricated from mild steel and in this section its thickness was 1 in. It was lined with 41/2 in. of chemically bonded magnesite-chrome bricks which were jointed with mild steel plates. The kilns operate on a 4 pct slope and the speed may be varied between 0.75 and 1.68 rpm. The wet process is used; kilns are coal fired and are fitted with integral coolers. Temperatures within the kiln are difficult to determine with any accuracy because of the absence of black body conditions, but surface temperatures are probably in the range 1420° to 1470°C. Average shell .temperatures at the two positions at which the deformation studies were made were 370°C and 355"C respectively. Methods: In determining the ellipticity it was necessary to measure the lengths of the vertical and horizontal diameters while the kiln was in operation; data obtained from a stationary kiln would not have the same practical significance. For this purpose the four points V, W, X, and Y at the ends of two mutually perpendicular diameters were marked on one kiln. The point X is shown in Fig. 1. For the measurement of the length of the vertical diameter a vertical column, to which a horizontally aligned telescope was attached, was placed 10 ft from the kiln. The telescope could be racked up and down in a vertical plane. Two sets of readings were taken, one set when each of the points V, W, X, and Y was at its maximum height above the

Jan 1, 1957

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By Louis Moyd

The Concrete Research Division, U.S. Corps of Engineers, has developed a simple procedure for determining the coefficients of linear thermal expansion of rocks by means of resistance wire (SR-4) strain gauges. Gauges are cemented to the surfaces of specimens, which are then brought alternately to temperatures of 35OF and 1350F. Results are accurate to the seventh decimal place. IN the course of investigations of the thermal properties of various rocks proposed for use as aggregates in concrete structures, a relatively rapid method of determining coefficients of linear thermal expansion was required. A method which proved to be satisfactory for this purpose was developed in the petrographic laboratory of the Concrete Research Division, U.S. Corps of Engineers, at Clinton, Miss. The method is based on the fact that strain effects in a specimen can be determined by measuring variations in the resistance of an electrical conductor firmly cemented to the surface of the specimen. Equipment for the determination of strain, electrically, has been developed by the Baldwin-South-wark Division of the Baldwin Locomotive Works in Philadelphia. This equipment includes small strain gauges made of coils of resistance wire bonded between thin sheets of paper (SR-4 gauges), and a portable "Strain Indicator" which records variations in the length of the gauges in microinches per inch. Gauges of this type are now in general use for determinations of various mechanically-induced strains, but their use for the determination of coefficients of thermal expansion appears to be a new application. The advantages of the method are that the test specimens may be relatively small and require only a minor amount of preparation, that a large number of tests can be run at the same time, and that the installation and operation of the equipment is relatively simple. The method and equipment described are now in regular use for determining the coefficients of linear thermal expansion of rock samples submitted to this laboratory. Rocks which have been tested include granites, syenites, gabbros, and other igneous rocks, limestones and dolomitic limestones, sandstones, and quartzites. Specimen Preparation: To standardize the conditions of the tests, the rock specimens are sliced by diamond saw into slabs about 11/2x11/4 in. In the case of bedded or foliated rocks, three oriented slabs are cut from the same specimen, and represent, respectively, a direction in a plane of the bedding or foliation of the rock; a direction along the bedding or foliation and at a right angle to the first; and a direction across the planes of bedding or foliation. One of the large surfaces of each slab is lapped for a few minutes with No. 100 abrasive powder to remove saw scars and irregularities. The slabs are soaked in petroleum ether and then dried in an oven to remove all traces of oil picked up in the sawing

Jan 1, 1951

By Louis Moyd

The Concrete Research Division, U.S. Corps of Engineers, has developed a simple procedure for determining the coefficients of linear thermal expansion of rocks by means of resistance wire (SR-4) strain gauges. Gauges are cemented to the surfaces of specimens, which are then brought alternately to temperatures of 35OF and 1350F. Results are accurate to the seventh decimal place. IN the course of investigations of the thermal properties of various rocks proposed for use as aggregates in concrete structures, a relatively rapid method of determining coefficients of linear thermal expansion was required. A method which proved to be satisfactory for this purpose was developed in the petrographic laboratory of the Concrete Research Division, U.S. Corps of Engineers, at Clinton, Miss. The method is based on the fact that strain effects in a specimen can be determined by measuring variations in the resistance of an electrical conductor firmly cemented to the surface of the specimen. Equipment for the determination of strain, electrically, has been developed by the Baldwin-South-wark Division of the Baldwin Locomotive Works in Philadelphia. This equipment includes small strain gauges made of coils of resistance wire bonded between thin sheets of paper (SR-4 gauges), and a portable "Strain Indicator" which records variations in the length of the gauges in microinches per inch. Gauges of this type are now in general use for determinations of various mechanically-induced strains, but their use for the determination of coefficients of thermal expansion appears to be a new application. The advantages of the method are that the test specimens may be relatively small and require only a minor amount of preparation, that a large number of tests can be run at the same time, and that the installation and operation of the equipment is relatively simple. The method and equipment described are now in regular use for determining the coefficients of linear thermal expansion of rock samples submitted to this laboratory. Rocks which have been tested include granites, syenites, gabbros, and other igneous rocks, limestones and dolomitic limestones, sandstones, and quartzites. Specimen Preparation: To standardize the conditions of the tests, the rock specimens are sliced by diamond saw into slabs about 11/2x11/4 in. In the case of bedded or foliated rocks, three oriented slabs are cut from the same specimen, and represent, respectively, a direction in a plane of the bedding or foliation of the rock; a direction along the bedding or foliation and at a right angle to the first; and a direction across the planes of bedding or foliation. One of the large surfaces of each slab is lapped for a few minutes with No. 100 abrasive powder to remove saw scars and irregularities. The slabs are soaked in petroleum ether and then dried in an oven to remove all traces of oil picked up in the sawing

Jan 1, 1951

By C. O. Lee, R. H. Feierabend, Z. W. Bartlett

DESPITE the fact that American brimstone production has increased 2 times since the prewar period 1935-1939, the demand for sulphur exceeds the supply. To alleviate this situation efforts are being made to increase the production of sulphur and bring the shortage to an end. The most important developments are being undertaken on the Gulf Coast. One new brimstone mine has been put into operation and three others are being developed. These projects are expected to account for a large part of the additional sulphur production now anticipated for the free world.'.' Except for a small amount of byproduct sulphur from sour natural gas and refinery gases, American brimstone is produced by the same process devised by Frasch 60 years ago, consisting essentially of the injection of superheated water at about 325°F into sulphur-bearing formations through wells which are drilled from the surface by standard oilfield methods. Sulphur deposits vary in depth from a few hundred feet to 2500 ft from the surface; in a typical deposit the sulphur occurs as crystalline aggregates in porous limestone and gypsum in concentrations varying from 5 to 40 pct, the thickness of the formation ranging from a few feet to several hundred.3 The deposits are usually surrounded by formations impermeable to the flow of hot water, the top and sides being enclosed by impermeable sediments and the bottom by dense impermeable anhydrite. As the hot water leaves the well bore, it percolates through the formation and transmits its heat to the rock and sulphur. When the sulphur reaches 240°F it melts, separates from the rock, and flows through the hot channels downward to the bottom of the well. Here it is freed from incoming water and from formation water, which saturates the porous rock, by gravity separation, liquid sulphur being 1.8 times as heavy as water. It then is pumped to the surface in a relatively pure state, 99.5 pct or better. Chief contaminants are organic impurities, such as petroleum residues, which are soluble in sulphur and tend to discolor it.' Sixteen deposits of commercial magnitude have been discovered in the Gulf Coast area. Five of these deposits have been depleted and abandoned with production totalling more than 26,886,000 tons. Eight properties are operating and have produced 65,875,-000 tons to Jan. 1, 1952, for a total Frasch-type production of 92,761,000 tons. Three new deposits are under development. Aforementioned deposits are listed in Table I. Each of these deposits has been found in the cap-rock overlying shallow intrusive salt plugs or domes and buried in several hundred to as much as 2500 ft of sediments. All salt domes do .not contain sulphur; only 16 sulphur deposits have been found in a total of 231 salt domes which are known to exist in the Gulf Coastal states of Texas, Louisiana, Mississippi, and Alabama. Ten of the salt domes lie in the Gulf of Mexico offshore from the Texas and Louisiana coasts. Additional offshore domes may be found, but their value as a sulphur potential is questionable owing to the great hazard and high cost that can be visualized at these exposed locations where depths of water reach 50 ft. Marsh operations of Freeport Sulphur Co. are in the southeast section of Louisiana. In general, the country is low, flat, relatively uninhabited marshland broken by many shallow lakes and bayous which extend for irregular distances inland. Geologically, the coastal area is of sedimentary origin, having been built up gradually under the sea by deposition of material carried down by large streams to their deltas. Offshore bars were formed enclosing

Jan 1, 1953