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By J. E. Andersen, J. Halpern, C. S. Samis

In the presence of oxygen, galena is oxidized in an aqueous medium containing sodium hydroxide, in accordance with the following reaction: PbS + 2O2 + 3OH ? HPbO2 + SO4 = + H2O A novel method was devised for following this reaction which takes place in an autoclave under oxygen pressure, by measuring the concentration of HPbO2- in the solution with a cathode ray polarograph employing stationary platinum electrodes. Using this procedure a study was made of the kinetics of the reaction, in which the effect of a number of variables, including temperature, oxygen pressure, NaOH concentration, and agitation, on the rate, were determined. The results of this study are described and discussed, in terms of possible mechanisms for the reaction. IT is known that sulphide minerals can be oxidized in aqueous media in the presence of oxygen under pressure. Reactions of this type can be classified in two categories depending upon whether the products of oxidation are insoluble or soluble in the aqueous medium. An example of the first type of reaction is the oxidation of pyrite in alkaline solutions, giving rise to an insoluble iron oxide. The kinetics of this reaction have been investigated and its mechanism established.' It has been applied in the oxidation of iron sulphides present in refractory gold ores to improve the subsequent recovery of gold by cyanida-tion.' The second type of reaction finds application where it is desired to recover the metal by leaching during oxidation. In this case a medium is selected in which the oxidized mineral is soluble. For example, nickel, copper, and cobalt sulphide ores can be treated by oxidation in the presence of a solution of ammonia dissolving the nickel, copper, and cobalt as the metal ammine sulphate salts.:' A similar treatment has also been reported to apply to zinc sulphide ores.' It is known that lead sulphate is soluble in solutions of sodium hydroxide or ammonium acetate. It should therefore be possible to dissolve the lead from galena ores by aqueous oxidation with oxygen under pressure using either of these solutions. The applicability of the ammonium acetate treatment has been investigated and confirmed in a recent study.' The present paper describes the results of a similar study in which the kinetics of the oxidation of galena in sodium hydroxide solutions have been investigated. The object of this investigation was pri- marily to obtain information of a fundamental nature relating to the kinetics and mechanism of this reaction. The use of pulps of comminuted ore in a study of this type is undesirable because of the difficulty in controlling and measuring the surface area. The measurements were therefore made using galena crystals of measured surface area and in this way absolute reaction rates were obtained. The reaction was found to proceed as follows: PbS + 2O2 + 3OH ? HPbO2 + SO4 + H2O [I] The products are sodium plumbite and sodium sulphate salts which dissolve in the aqueous solution. The reaction studies were carried out in an autoclave in which a desired pressure of oxygen was maintained. The reaction was followed by measuring the concentration of lead in the solution with a cathode ray polarograph. The results obtained in this investigation are presented and discussed in the present paper. Experimental Materials: The crystals of galena were obtained from Violamac Mines, Sandon, B. C. The following impurities were indicated by spectrographic analysis carried out by the Provincial Assay Office, Victoria, B. C.: Sn, 0.02 to 0.2 pct; Sb, 0.07 to 0.7; Zn, 0.01 to 0.1; Si, Fe, Mg, As, less than 0.05 pct; Ag, 126 oz per ton, the latter determined by standard fire-assaying procedure. After cutting a specimen measuring approximately 5x7x12 mm, the crystal surfaces were ground parallel to the 100 axes using No. 2 emery, washed with water, and the dimensions were measured with a micrometer. Oxygen gas was of commercial grade and supplied in cylinders by Canadian Liquid Air. Solutions were made up with chemicals of chemically pure grade and distilled water. Equipment: Autoclave: The autoclave used in these studies was constructed of stainless steel and

Jan 1, 1954

By A. U. Seybolt, D. H. Haman

The rate of oxidation of the lowest nitride of chromium, Cr2N, was measured to be equal to the rate of oxidation of chromium metal. It was found that, while the presence of Cr2N in chromium does not affect the oxidation mechanism, a long exposure at high temperature affects the morphology of Cr2N in chromium, causing a massive internal nitriding along chromium pain boundaries. Marker expen' -ments showed that the rate of oxidation of Cr2N layers on chromium is determined by the rate of chromium diffusion through Cr,03. The rate of formation of Cr2N is determined by diffusion rate of nitrogen through Cr2N. This rate at 1000°C is around thirty times faster than the rate of oxiahtion. Evidence is presented which suggests that nitrogen from the air reaches the chromium through the Cr2O9 by migration through pores or cracks rather than by a diffusive process. IT has long been recognized that, when chromium or alloys containing substantial amounts of chromium are oxidized in air, some chromium nitride (Cr2N) is formed under the oxide scale. Although the presence of this nitride layer has often been described, there appears to have been no systematic study of the role played by the nitride during the oxidation process. Indeed, there have been conflicting re-ports'92 on the kinetics of oxidation of chromium and chromium alloys in air and in oxygen. However, it is now well-established'-5 that the rate-controlling process during the parabolic oxidation of chromium to Cr2O3 is chromium-ion diffusion through Cr2O3. Because of the importance of chromium-containing alloys as oxidation-resistant materials, it seemed desirable to investigate the behavior of chromium during oxidation with and without the presence of chromium nitride. Since a semicontinuous Cr2N layer forms relatively early during the oxidation of chromium in the air, chromium atoms must either pass out of or through the Cr2N layer to become incorporated in the growing Cr2O3 scale. Therefore, it seemed desirable to examine the oxidation behavior of the pure nitride. MATERIALS AND EXPERIMENTAL PROCEDURE The chromium used in this investigation consisted of slices of an ingot made from "five-nine" iodide chromium which had been argon-atmosphere melted in a Y2O 3-stabilized ZrO2 crucible in an induction furnace. The only impurity of any significance was 625 ppm of 0, which was usually reduced to a microscopically invisible amount by hydrogen annealing at 1400°C. However, one sample of chromium was used with the as-cast oxygen level as explained below. The samples were used after abrading through 600 Sic paper and then washing in toluene and alcohol. Both nitriding and oxidation experiments were performed in a vertical tube furnace connected to a glass vacuum system. 'This system was equipped with pressure measuring instruments for the range of 10 p to 1 atm, and a cartesian-diver pressure-control device was used in conjunction with a needle valve to allow control of pressure in the range of about 10 to 760 mm. The nitrogen or hydrogen gas was purified by passing through hot copper chips at 600°C, anhydrous calcium sulfate (Drierite), and liquid nitrogen. Oxygen gas was dried through the Drierite column and a dry-ice trap (-78°C). Changes in specimen weight were followed by a Pyrex helix used in conjunction with a cathetometer which could reproducibly be read to +0.001 cm, yielding an accuracy of about +0.2 mg. The spring was maintained in the cool upper part of the furnace tube where the temperature did not rise above about 35°C. The nitride in equilibrium with metallic chro-

Jan 1, 1964

Conservatively, there are a half million square miles in Australia just like it, this spot near the western border of New South Wales. Space and distance are the elements. Mulga tree and salt bush, silvery under the sun, hug the ground too close to make welcome shade. To the east a wrinkle on the empty plain marks the line of lode, the Broken Hill bonanza. Strangely, the outback stops at a cyclone fence close by the ridge. Beyond, the peculiar island continent vegetation flourishes with the same frosty patina of the mulga and the salt bush. A city of 30,000 people is hidden behind the screen of vegetation. Once, the city was ugly and the people miserable from marching, flying sand. Now with a protective screen of vegetation, it is an oasis in the outback. The secret of the oasis is the fence. All regeneration plans failed until it was built to keep kangaroo, rabbit, sheep and man from destroying the plantations.

Jan 10, 1964

By G. S. Hume

Activity in geological exploration and drilling continued in Canada in 1945 at about the same rate as in the previous year, but with disappointing results as far as new production is .concerned. Both in the foothills and on the Plains of Alberta, however, there are wildcat wells that have either given encouraging shows or some production, which are very important in relation to future developments. The normal decline of Turner Valley, the largest producing field in Canada, has continued, and this decrease has not been offset by new discoveries. In addition, the closing of the Canol pipe line on March 31, 1945, isolated the Norman Wells field in the Mackenzie River valley, and the outlet at present. is confined to supplying the relatively small local requirements. This

Jan 1, 1946

Jan 1, 1936

By B. E. Morgan, C. K. Dumbauld

The need for a low-strength cementing composition for use in well cementing is reviewed and results are presented of laboratory and experimental field tests of a modified cement having a controlled ultimate tensile strength of approximately 200 psi. The modified cementing composition may he prepared from either high early strength or normal portland cements by the addition of bentonite clay and a suitable agent for dispersing and controlling the set of the slurry. Substitution of the modified cement for conventional slow-set cements may give better completion results in many wells because the modified cementing composition has lower set strength, lower slurry density, and greater slurry stability than conventional cement slurrieh. The lower ultimate strength allows greater penetration with less shattering of the set cement when perforating casing and cement. The lower elurry density allows the placement of longer columns of cement slurry, and the greater slurry stability reduces the possibility of having an uncemented section caused by the settling of cement particles before the cement set.. INTRODUCTION High strength lias always been one of the accepted criteria of a good cement. During the early use of portland cement in well cementing. emphasis was placed upon securing cements with higher strengths. In 1931, Barkis' reported that, "Normal oil well cements have been improved to develop greater strengths and uniformity of product, which has aided in producing successful jobs in cementing the deeper strings." As long as most wells were completed by the open-hole method. the use of cements having high strengths seemed desirable, and there was no objection raised against high-strength cementing compositions. For a number of years. how-ever, the industry has been completing a large numher of wells by setting and cementing casing through productive horizons and then obtaining production by gun-perforating the section of casing opposite the desired interval. Although this method has been generally successful, difficulties have been experienced in some cases in completing or recompleting wells because of apparent lack of adequate penetration by the bullets through the casing and surrounding sheath of cement and into producing formation. In addition to the penetration trouble: there have been indications that fracturing and shattering of the set cement by perforating might he a contributing factor in causing the failure of some jobs to exclude water or gas from oil producing zones. The possibility that cements having high set strengths were contributing to til difficully ill obtaining satihfartory perforating results has re. ceived attention during recent years. Gun perforating tests conducted in 1944 showed that the depth of bullet penetration into set cement varied with the hardness of the cement, the greater the strength of the cement the less being the penetration. In 1946, Farris2 pointed out that high strength cements were not needed in well cementing, and in 1947, data published by Oliphant and Farris3 showed that set cement was perforated without shattering at approximately 150 psi tensile strength. whereas at approximately 300 psi tensile strength severe cracking and shattering occurred. Oliphant and Farris suggested that wells be perforated at the proper time interval after placement of the cement so that the set cement would have the desired strength. Several difficulties may he encountered in trying to perforate a cement job at the correct time to catch the tensile strength near 150 psi. The rate of strength development of different cements varies considerably. This fact is illustrated by results of tensile strength measurements presented in Fig. 1. These data show that at 175°F the tensile strengths of three conventional slow-set cements varied from 75 to 235 psi at the end of 12 hours. After 24 hours, the tensile strengths varied from 200 to 455 psi. The rate of strength development is affected. also. by the temperature of the forniation, and this adds to the uncertainty of perforating at the rorrect time, since accurate well cementing temperatures may not he known in many cases. Furthermore, in the recomple-tion of wells it is sometimes necessary to perforate cement which has set for a long period and has developed maximum or final strength. In view of the apparent need for a cementing composition having a controlled ultimate strength, an investigation was

Jan 1, 1951

By C. K. Dumbauld, B. E. Morgan

The need for a low-strength cementing composition for use in well cementing is reviewed and results are presented of laboratory and experimental field tests of a modified cement having a controlled ultimate tensile strength of approximately 200 psi. The modified cementing composition may he prepared from either high early strength or normal portland cements by the addition of bentonite clay and a suitable agent for dispersing and controlling the set of the slurry. Substitution of the modified cement for conventional slow-set cements may give better completion results in many wells because the modified cementing composition has lower set strength, lower slurry density, and greater slurry stability than conventional cement slurrieh. The lower ultimate strength allows greater penetration with less shattering of the set cement when perforating casing and cement. The lower elurry density allows the placement of longer columns of cement slurry, and the greater slurry stability reduces the possibility of having an uncemented section caused by the settling of cement particles before the cement set.. INTRODUCTION High strength lias always been one of the accepted criteria of a good cement. During the early use of portland cement in well cementing. emphasis was placed upon securing cements with higher strengths. In 1931, Barkis' reported that, "Normal oil well cements have been improved to develop greater strengths and uniformity of product, which has aided in producing successful jobs in cementing the deeper strings." As long as most wells were completed by the open-hole method. the use of cements having high strengths seemed desirable, and there was no objection raised against high-strength cementing compositions. For a number of years. how-ever, the industry has been completing a large numher of wells by setting and cementing casing through productive horizons and then obtaining production by gun-perforating the section of casing opposite the desired interval. Although this method has been generally successful, difficulties have been experienced in some cases in completing or recompleting wells because of apparent lack of adequate penetration by the bullets through the casing and surrounding sheath of cement and into producing formation. In addition to the penetration trouble: there have been indications that fracturing and shattering of the set cement by perforating might he a contributing factor in causing the failure of some jobs to exclude water or gas from oil producing zones. The possibility that cements having high set strengths were contributing to til difficully ill obtaining satihfartory perforating results has re. ceived attention during recent years. Gun perforating tests conducted in 1944 showed that the depth of bullet penetration into set cement varied with the hardness of the cement, the greater the strength of the cement the less being the penetration. In 1946, Farris2 pointed out that high strength cements were not needed in well cementing, and in 1947, data published by Oliphant and Farris3 showed that set cement was perforated without shattering at approximately 150 psi tensile strength. whereas at approximately 300 psi tensile strength severe cracking and shattering occurred. Oliphant and Farris suggested that wells be perforated at the proper time interval after placement of the cement so that the set cement would have the desired strength. Several difficulties may he encountered in trying to perforate a cement job at the correct time to catch the tensile strength near 150 psi. The rate of strength development of different cements varies considerably. This fact is illustrated by results of tensile strength measurements presented in Fig. 1. These data show that at 175°F the tensile strengths of three conventional slow-set cements varied from 75 to 235 psi at the end of 12 hours. After 24 hours, the tensile strengths varied from 200 to 455 psi. The rate of strength development is affected. also. by the temperature of the forniation, and this adds to the uncertainty of perforating at the rorrect time, since accurate well cementing temperatures may not he known in many cases. Furthermore, in the recomple-tion of wells it is sometimes necessary to perforate cement which has set for a long period and has developed maximum or final strength. In view of the apparent need for a cementing composition having a controlled ultimate strength, an investigation was

Jan 1, 1951

By R. C. Earlougher

Based on laboratory tests conducted with the use of fresh core samples as well as a considerable amount of field data obtained from numerous water floods in northeastern Oklahoma, it appears that for any given oil saturation there is a critical maximum velocity above which the oil-recovery efficiency falls off very rapidly. In effect, when a water flood is operated above this critical velocity, the injected water-oil ratio rises extremely fast, thus shortening the economic life of the flood and reducing the ultimate oil recovery. This critical velocity apparently varies considerably with the percentage of oil saturation of the sand, so that in effect the higher the oil saturation at the beginning of a flood the higher the velocity that can be used successfully. In reviewing several of the earlier floods in the Mid-Continent area, it is concluded that most of the failures were due to two things: (I) too low an oil saturation, such as 30 per cent, and (2) too high water-injection rates, Although considerably more field data are necessary to establish definite limits, it would seem that the proper field injection rate for a 330 by 330 or 440 by 440-ft. spacing varies from approximately I bbl. per foot of sand per day where the oil saturation is as low as 30 per cent up to 5 bbl per foot of sand per day when the oil saturation is as high as 45 to 50 per cent, Introduction With secondary recovery by water-flooding receiving more and more attention throughout the industry, a greater working knowledge of multiphase flow under field conditions becomes more and more necessary A great deal of research has been carried on in highly idealized laboratory conditions, from which certain trends have been indicated, but with few exceptions no direct application to field use has been reported. widely varying conclusions have been drawn from the mass of idealized laboratory experiments and often this divergence apparently was due to the neglect of connate or interstitial water. Since interstitial water is such an important factor in water-flooding operations, it then follows that any laboratory flooding experiment must necessarily take it into account; and since it is difficult to set up laboratory models to allow for interstitial water, the next best procedure is to use fresh core samples for such tests. Even this procedure has its difficulties, inasmuch as it is possible to run only one flooding test on each sample, as each sample differs somewhat in character from all other samples. However, this disadvantage can be overcome to a large degree by the use of an extremely large number of samples. The next question that arises is: "IS it possible to get uncontaminated core samples having a true oil and water saturation like that existing in the reservoir?" If the sand under consideration is still in the primary stage of production, with a normal or relatively high amount of gas still in solution in the oil, probably it is not possible to get a nonflushed core. On the other

Jan 1, 1943

By R. C. Earlougher

Based on laboratory tests conducted with the use of fresh core samples as well as a considerable amount of field data obtained from numerous water floods in northeastern Oklahoma, it appears that for any given oil saturation there is a critical maximum velocity above which the oil-recovery efficiency falls off very rapidly. In effect, when a water flood is operated above this critical velocity, the injected water-oil ratio rises extremely fast, thus shortening the economic life of the flood and reducing the ultimate oil recovery. This critical velocity apparently varies considerably with the percentage of oil saturation of the sand, so that in effect the higher the oil saturation at the beginning of a flood the higher the velocity that can be used successfully. In reviewing several of the earlier floods in the Mid-Continent area, it is concluded that most of the failures were due to two things: (I) too low an oil saturation, such as 30 per cent, and (2) too high water-injection rates, Although considerably more field data are necessary to establish definite limits, it would seem that the proper field injection rate for a 330 by 330 or 440 by 440-ft. spacing varies from approximately I bbl. per foot of sand per day where the oil saturation is as low as 30 per cent up to 5 bbl per foot of sand per day when the oil saturation is as high as 45 to 50 per cent, Introduction With secondary recovery by water-flooding receiving more and more attention throughout the industry, a greater working knowledge of multiphase flow under field conditions becomes more and more necessary A great deal of research has been carried on in highly idealized laboratory conditions, from which certain trends have been indicated, but with few exceptions no direct application to field use has been reported. widely varying conclusions have been drawn from the mass of idealized laboratory experiments and often this divergence apparently was due to the neglect of connate or interstitial water. Since interstitial water is such an important factor in water-flooding operations, it then follows that any laboratory flooding experiment must necessarily take it into account; and since it is difficult to set up laboratory models to allow for interstitial water, the next best procedure is to use fresh core samples for such tests. Even this procedure has its difficulties, inasmuch as it is possible to run only one flooding test on each sample, as each sample differs somewhat in character from all other samples. However, this disadvantage can be overcome to a large degree by the use of an extremely large number of samples. The next question that arises is: "IS it possible to get uncontaminated core samples having a true oil and water saturation like that existing in the reservoir?" If the sand under consideration is still in the primary stage of production, with a normal or relatively high amount of gas still in solution in the oil, probably it is not possible to get a nonflushed core. On the other

Jan 1, 1943

By W. C. Leslie, R. M. Fisher, K. G. Carroll

A nitride, believed to be Si3N, has been separated from three nitrided silicon steels. Germanium nitride, Ge3N4, has been prepared from pure germanium. Comparison of the diffraction patterns indicates that the two nitrides are isomorphous; on orthorhombic structure is suggested in place of the rhombohedral structure previously reported for Ge3N4. THE possibility that a nitride of silicon may, under appropriate conditions, precipitate in silicon steels or in steels killed with silicon makes it desirable to have some positive means of identifying such a compound. One such means is the X-ray or electron diffraction pattern of the nitride. A review of the meager data in the literature indicates that the nitride most likely to form is Si3N4, a conclusion supported by the results of a study of nitrided silicon steels to be published shortly by L. S. Darken and R. P. Smith, of this Laboratory. Unfortunately, there is available no diffraction pattern for this nitride. Data have been reported, however, for Ge3N4 which, judging from the similarity between germanium and silicon, might be expected to be isomorphous with Si3N4. An effort was made, therefore, to form such a silicon nitride, to determine its composition and diffraction pattern and, if possible, its structure. To this end a series of three silicon steels was nitrided under controlled conditions with the resultant formation of nitride particles which yielded an electron diffraction pattern in situ. The particles were then extracted from the steel and an attempt was made to determine their chemical composition. X-ray and electron diffraction patterns were also obtained from the extracted particles, which indicate that the nitride is isomorphous with Ge3N4, although a complete determination of the structure has not been possible. These results show that a silicon nitride with a well-defined diffraction pattern can form in silicon steels, and they suggest that this nitride is Si3N4. Materials and Procedures The sillicon steels investigated were In the form of thin sheet or strip and had the composition shown in Table I. The 0.58 and 1.21 pct Si steels were nitrided by holding them at 1110°F in an H2-NH3 atmosphere containing 3 pct ammonia for 48 hr. The nitride particle size was increased by subsequent heating at 1500°F for 13 1/2 hr in helium. The resulting microstructure is shown in Fig. 1. The steel containing 3.20 pct Si was nitrided at 1200°F for 16 1/2 hr after which it was held in helium at 1500°F for 4 hr. Its structure as seen under the electron microscope is illustrated by Fig. 2. As would be expected from the higher silicon content and the shorter holding time at 1500 °F, the nitride particles are smaller and more numerous than those in the 1.21 pct Si steel. The ammonia-hydrogen treatment reduced the carbon content of the steels to a very low level, so no interference was encountered from carbon or carbides. In the case of the 3.2 pct Si steel, the carbon was reduced to 0.003 pct before nitriding by heating in dry hydrogen. Attempts to obtain an X-ray diffraction pattern from polished and etched surfaces of the 1.21 and the 3.20 pct Si steels were unsuccessful. However, an electron diffraction pattern was obtained from the surface of the steels. The interplanar spacings obtained from these patterns arc shown in Table 11, col. 5. The nitride particles were then extracted from all three steels by dissolving the ferrite matrix in bromine-methyl acetate, the solution used in the Beeghly method for the extraction of aluminum nitride from steel. X-ray diffraction patterns of these residues, obtained by means of a spectrometer and by a 57 mm Debye-Scherrer powder camera using filtered cobalt or chromium radiation, are given in Table II along with the pattern obtained by

Jan 1, 1953

Jan 1, 1914

By F. C. Langenberg

DURING the course of some magnetic investigations which the authors have under way, six bars of 0.43-carbon steel were tested, a permeameter designed after the Hopkinson yoke type being used. The results obtained were of some interest and although far from complete serve at least to show the necessity for a careful investigation of the previous history of the samples under study as well as the chemical composition. A steel of given chemical composition may assume a great variety of structures, depending on its treatment. Professor Sauveur has devised a very clear and effective means of illustrating this point: The accompanying microphotographs show some of the possible structures assumed by a 0.30 carbon steel (Fig. 1). It is now a well-established fact that a structural change is accompanied by changes in the tensile strength, elastic limit, hardness, etc., and it seems reasonable to assume also, a change in the magnetic properties. Six bars of a 0.43-carbon steel were used, all the bars being taken from the same rod and treated as follows: Bar 1. Heated to 1,100° and cooled in the furnace. Bar 2. Heated to 1,000° and cooled in the furnace. Bar 3. Heated to 900° and cooled in the furnace. Bar 4. Heated to 1,000° and cooled in air. Bar 5. Heated to 900° and cooled in air. Bar 6. Untreated. The bars were then turned to 13 mm. diameter and tested by the Hopkinson yoke method. After testing, three specimens were taken from each bar, one from each end and one from the middle. The homogeneity of the. bars was tested in this manner and in no instance could any difference in structure be detected between the three specimens.1

Jan 2, 1915

By F. A. Schaufelberger

METAL can be recovered from a leach solution either indirectly by precipitation as a compound that is later reduced or directly by electrolysis, cementation, or chemical reduction, for example, with hydrogen. The widely used electrowinning processes suffer from the inefficiency of converting fuel to low voltage dc and from low current efficiency when complete recovery is attempted. With the batch hydrogen reduction methods outlined here, a unit of fuel converted to hydrogen in modern gas reform plants will make two to three times as much metal as can be obtained with electrolysis. With continuous hydrogen reduction, four to six times as much metal is obtained. Precipitation by reducing a metal salt solution with H, has been known for almost 100 years.' Commercial use of the process, however, awaited the research and development program initiated by Chemical Construction Corp. Within the last few years this program has brought about construction of commercial plants, listed on page 545. Ideal hydrogen reduction will precipitate a pure metal from a solution obtained by commercial leaching methods at a rapid rate without excessive temperatures and pressures. The metal precipitate will be of desired size and density, less than a percent left in the vessel being deposited on the wetted parts. The present discussion will outline Chemical Construction Corp.'s early development program and will discuss the chemistry and mechanics of reducing copper, nickel, cobalt, and cadmium from solution by H2. Work on selective reduction of nickel from cobalt has been described earlier.' The article is not concerned with precipitation of copper by disproportionation of cuprous solutions where yield is limited3 to 50 pet.* It does not discuss use of gaseous reducing agents other than hydrogen, such as SO2,4 which may lead to contamination with sulfur, or C0,5 which is considerably more expensive than hydrogen and produces a gaseous reaction product, CO2.† The article does not include use of other nongaseous reducing agents,7 which are far more expensive than CO. Also, notes on the history, engineering design, and performance of commercial plants have been given elsewhere.' It will be shown that a pure metal can be precipitated by reduction with hydrogen from solutions obtained by commercial leaching methods when the solution composition is controlled and proper acidity, proper metal ion concentration through controlled complex formation and hydrolysis, and adequate agitation for suspension of metal and for transfer of reducing gas are maintained. Reasonable temperatures and pressures are used which are less excessive than those used by previous workers, although they are maintained at above equilibrium values because of process kinetics.' It has also been found necessary to induce nuclea-tion and to control growth and agglomeration in order to get a powder product of suitable physical properties. Review of the Literature Muller, Schlecht, and Schubardt of I. G. Farben10 claimed a successive reduction of silver, copper, nickel, cobalt, and zinc from ammoniacal solution by applying progressively higher temperatures and hydrogen pressures. Metals produced by this technique were not pure, since no attempt was made to adjust the solution composition between the different reductions. It is doubtful that the zinc product contained any metallic zinc. The major contribution to the literature" was made by the Ipatiews,12 who prepared platinum, iridium, copper, nickel, cobalt, lead, tin, arsenic, antimony, and bismuth at often extreme conditions, up to the critical temperature of water (373ºC), at 1500 to 7500 psi, for as long as several days. Even cadmium and zinc were claimed to have been observed in trace quantities precipitated together with basic salts. In the early experiments solutions were not stirred. Extensive formation of oxides and basic salts occurred, probably long before sufficient hydrogen could be supplied in the unstirred liquid to decrease the metal concentration in solution by reduction. The importance of hydrogen pressure was

Jan 1, 1957

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth's crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth's crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth's crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth's crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By A. M. Rahm

PROBABLY the majority of red brass sand castings are judged merely on the basis of outside appearance and the quality of machined surfaces. Many castings, however, must individually withstand a hydraulic or air-pressure test before being accepted as parts of more complicated machin-ery. Finally, there remains a comparatively small group of castings intended for uses of considerable responsibility where only the highest possible characteristics of the metal are acceptable, and for these specially cast test bars are required. The shape of the cast piece from which the test bar must be detached varies greatly from one country to another. The test bar as specified in the American Society for Testing Materials Specification B62-36 is widely used by the American foundry industry. The actual test piece is at the bottom of the cast block and has a riser about six times its mass. It is obvious that this test bar has an advantage over the actual casting. The latter rarely possesses a riser of as much as 30 per cent of its own weight and that riser cannot generally be located in so convenient a manner. Therefore, the characteristics of the test bar cannot possibly correspond to those of the casting itself. It must be taken into consideration that red brass if melted and cast in the best possible manner may show a tensile strength of 40,000 lb. per sq. in. with 35 per cent elongation in 2 in. Such a test bar would indicate that the metal was nearly perfect from the viewpoint of its gas and inclusion content. Barring some accidental defect, a casting cor-responding to such a test bar could be accepted as being quite sound. However, actual specifications do not demand such high characteristics; indeed, few specifications require over 30,000 lb. per sq. in. and 20 per cent elongation, while one Federal specification demands merely 27,000 lb. per sq. in. strength and 15 per cent elongation. It is obvious that

Jan 1, 1939

By James Tucker MacKeni~ie

BORN in Florida, educated in Ten¬nessee, employed all his life in the iron industry of Alabama, J. T. MacKenzie is truly of the South. In courtesy, hospitality, as well as in accent of speech, he is true to the tradition of the South. His alma neater, the University of the South, has given him the honorary degree of Doctor of Science for his achievements in metallurgy. He has been active in many technical societies; has received the Whiting Medal of the American Foundrymen's Association for his work in the advancement of gray iron metallurgy, and is chairman of the gray iron division of the A.F.A.; was instrumental in initiating the Alloys of Iron Research of the Engineering Foundation and has served as a member of its Alloys of Iron Committee since the Committee's organization.

Jan 1, 1938

By D. W. Philips

THE problem of strata control has of necessity been prominent in mining, and accounts of individual experience and research abound in the literature of most mining countries. Organized research began in Britain by the formation of a committee, upon the recommendation of the Safety in Mines Research Board in 1923, to investigate methods of reducing accidents from falls of roof in coal mines. This committee examined current practice in supporting underground workings in the principal coal fields, and its findings have been published in the Board's publications. Toward the end of these investigations it was suggested by the Chief Inspector of Mines that committees of the several mining institutes be formed to examine the problem in their respective districts. The formation of these committees marked a new phase in research on strata control. The work, though being done in the separate coal fields, followed a scheme outlined by the Chief Mining Engineer of the Research Board, and was coordi¬nated by his office. FACTORS INVOLVED The subject is being considered in Britain from two aspects: I. To provide, by supports, means to prevent falls of fractured ground. 2. To develop methods whereby the strata can be maintained in the least broken condition and thus make falls less likely. The first aspect is the one that will most likely lead to immediate results from the accident standpoint. It depends largely upon the assimilation of already acquired knowledge regarding the proper¬ties of supports and their correct applica¬tion. The second aspect is perhaps more fundamental, and involves also the proper¬ties of the strata and their behavior under the influence of the forces induced by mining. The problem involves many natural factors that cannot be controlled, such as depth, inclination and thickness of seam and nature of the rocks. Other factors, which may be considered to a certain extent controllable, cannot be varied readily and with sufficient fre¬quency to facilitate easy investigation; some of these are: rate of advance of the working face, length of face, direction of the face with regard to cleat and inclination, system and arrangements of rock packing behind longwall faces. In any given case the very many factors present have a mutual influence upon the effects produced in the mine. For example, a study of the effects of rate of advance cannot be done without considering the effects of other factors such as nature of strata, direction of face and quality and arrangement of supports. Conversely, the length and direction of a working face

Jan 1, 1946

1. List of Manuscripts Seen in America 2. List of Manuscripts Seen in England 3. List of Maps Examined 4. List of Newspapers Examined 5. General Bibliography - Numbered Reference List

Jan 1, 1942

NEW MEMBERS The following list comprises the names of those persons who became members during the month of December, 1913: Members ADAMS, CHARLES W., JR., Smelting, American Smelting & Refining Co., Murray, Utah. ARMSTRONG, FRANK H., Mechanical Engineer Vulcan, Mich. ARNOLD, JOHN B., Attorney-at-Law Room 840,200 5th Ave., New York, N. Y. BOYS, HARRY R., Mining Paso Robles, Cal. CAVANAGH, JOHN L., Min. Engr., Nova Scotia Steel & Coal Co.; Wabana, Newfoundland. CHOW, KAI CHI, Student 1120 Amsterdam Ave., New York, N. Y. CLARK, ARTHUR B., Mining Engineer 72 Harbour Bldg., Butte, Mont. CURLEY, JOHN R., State Mine Inspector P. 0. Box 633, Leadville, Colo. DAVIS, ANGUS W., Mining Engineer, Consolidated Mining & Smelting Company of Canada, Trail, B. C., Canada.

Jan 1, 1914