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By William L. Boyd, Eugene L. McCarthy, Laurance S. Reid

Proper control of the moisture content of natural gas is essential to reliable operation of gas transmission and distribution facilities serving northern markets. The moisture content of natural gas is usually determined by dew point measurement at the existing pressure. For any gas of constant moistrire content. the dew Point varies with the pressure. A correlation of the data of several investigators is prezented in graphical form by the authors. These data were correlated by the authors and F. M. Townsend, C. C. Tsao. M. I). Rogers. Jr.. and J. A. Porter. graduate students in chemi(.a1 engineering at the University of Oklahoma. Of articular interest are the hitherto unpublished low temperature data observed by Wickliffe Skinner. Jr., which are included in this correlation. PRESENTATION OF DATA The problem of interpreting water dew points, or saturation temperatures. of natural gas in terms of specific moisture con-tent has increased in importance during the past decade bec.arl.;e of extensive development.; in the transmission and petro-chemical phases of the natural gas industry. Virtually all gas transported to northern and eastern markets must be dehydrated to a low water vapor content to prevent hydrate formation in transmission and distribution lines and resultant interruption.; in gas deliveries. Complete dehydration is required in certain phases of tile petro-chemical industry involving low-temperature operations. It is a well-known fact that the water vapor content of pure hydrocarbon vapors and their mixtures at superatmospheric pressures cannot be predicted with accuracy by assuming validity of the ideal gas laws." Earlier interest in the general problem was concentrated on the water vapor content of pure hydrocarhons and hydrocarbon mixtures in the pressure and temperature ranges common to gas and oil producing reservoirs in order to obtain fundamental data for the improvement of production techniques and the furtherance of reservoir studies. Excellent data are published for pressures ranging from atmospheric to 10,000 psig and for temperatures ranging from 100° to 460° F4,9,10,11 and are found to be in close agreement. However, experimental data at high pressures and temperatures below 100°F are comparatively limited in scope. Experimental data in the lower temperature range have been reported by Laulhere and Briscoe.8 Deaton, et al,2,3 Hammerscllmidt,5,6 and wade," In general, the pressures employed in these investigations ranged from atmospheric to 1.000 psig while temperatures ranged from 32° to 120°F; i.e., the usual conditions encountered in gas transmission line operations, Additional data were reported by Russell, et al,12 at pressures as high as 2.000 psig and covering a rather narrow atmospheric temperature range. In 1947, Hammerschmidt published a correlation of all available data,' in which the water vapor content of gases at saturation. under high pressure and low temperature. was predicted by extrapolation. In 1948, Wickliffe Skinner. Jr.. presented data on the moisture content of a low nitrogen content gas at low temperature and at pressures ranging upward to 1.500 psia.1-3 Comparison of Skinner's experimental data with the extrapolated data of Hammerscllmidt revealed an appreciable variation in the lower temperature range. emphasizing the need for a new correlation which would rely on Skinner's data at lower temperatures. Careful scrutiny of available data suggested that presence of an appreciable quantity of nitrogen in a gas mixture may affect its saturated moisture content so that data obtained from gases with more than three per cent nitrogen were not used in this correlation. CORRELATION OF DATA Data employed in this correlation are presented in Table I. The data of Dodson and Standing.4 McKetta and Katz,9 and Olds, Sage and Lacey10 were compared and found to be in close agreement so that the data of Olds. et al, re-plotted in a more convenient form by the Humble Oil and Refining Co.,' were used for temperatures of 100°F and above. Skinner's data were used for temperatures below 40°F. Between these intermediate temperature limits, the data of Hammerschmidt.7 Wade" and extrapolated data of Olds. et al.1 were tabulated

Jan 1, 1950

By T. Sterry Hunt

IT is now five years Since I called the attention of the Institute to the industrial importance of the coal and the iron ores of the Hocking Valley in Southeastern Ohio, and in a pamphlet on the region published Soon after, in 1874, endeavored to resume the principal facts then known respecting it, including the observations of the geological survey of Ohio, made and published up to the time by Professors Andrews and Wormley, together with an estimate of the probable future of the region, and its relations to the coal and iron markets of the country. Since that time the labors of the Geological Survey have included a further Study of the coal by Prof. Edward Orton, the results of which will be awaited with much interest. I may say from my knowledge of them, that while confirming the general conclusions of his predecessors, he has been enabled to add much to our knowledge as regards the correlation of the various members in different parts of the coal-field, and to Show more clearly the positions and the importance of the ore-beds in the Hocking Valley region. The only ore mined in that vicinity previous to 1874, was below what is called the Great Vein or No. VI coal, and to the west of what is known as the Hocking Valley coal-field, and although experiments in a few furnaces in the State had Shown that this coal could be used with advantage in iron-Smelting there was not a single blast furnace within the field. My observations at that time, however, impressed me with the abundance of iron ore, not only below but above this important coal Seam, and I then ventured to express the opinion that this region, from its cheap and easily mined Smelting-coal, its native ores and limestones, and its geographical position and relations to the great markets of the West, and to the supply of rich iron-ores from Lake Superior, was destined at no distant time to become a great metallurgical centre, where iron could be made more cheaply than at any other equally accessible point in the country. The object of the present communication is to report progress, and to State how far my observations made in the region last month have justified the predictions of 1874. The five years which have elapsed have been, as all know, most unfavorable to the iron trade, and especially to new enterprises in untried regions, yet they have not passed without important industrial developments in the Hocking Valley, where not less than thirteen blast furnaces have been erected

Jan 1, 1879

By F. M. Lewis, J. F. Myers

The crushing of ore, as defined by Taggart, is "usually a stage process, utilizing . . . machines especially suitable for the reduction of particular sizes. . . . down to a final stage, employed for the reduction of the finest sizes. ... In contradistinction, comminution to 20-mesh or finer is called grinding. There is a twilight zone in which the product is 6, 10, or 14-mesh limiting size which is either crushing or grinding. ..." Since the data in this paper pertain to a rod-mill operation, comminuting a particular ore size of ¾ in. to a final stage, coarser than 20-mesh, the rod mill is designated as a "fine crusher machine" in this paper. The published literature discloses a wealth of data regarding a rod mill as a fine-grinding machine but relatively little as a fine-crushing operation. Typical of the latter operation is: (I) a description by F. J. Tuck2 in which a fine-crushing rod mill replaced crushing rolls and (2) a description by the present authors3 in which a fine-crushing rod mill was installed instead of a collventional fine-crushing machine. The experience of the authors is that a definite distinction must he made between the rod mill functioning as a fine crusher and as a fine-grinding machine. As a fine crushing machine it prepares relatively large amounts of ore for a subsequent fine grinding operation; as a grinding machine, it grinds relatively small amounts of ore to some predetermined finished product. Pulp Movement and Action in Mill In considering the work performed by a fine-crushing rod mill, it seems important to understand just what takes place within the mill. We were inspired to study this matter by a paper by E. W. Davis,4 which indicated that definite water classification of ore particles took place in a ball mill. However, in thinking of the rod-mill action from this point of view, we were confronted with the fact that our rod-mill discharge product showed no evidence of action by water classification. The Tennessee Copper Co. ore is relatively high in sulphides, and the gangue rock and the sulphides are of about the same hardness. In the presence of any action by classification, the coarser sizes are definitely very lean in sulphide minerals.

Jan 1, 1947

By J. F. Myers, F. M. Lewis

The crushing of ore, as defined by Taggart, is "usually a stage process, utilizing . . . machines especially suitable for the reduction of particular sizes. . . . down to a final stage, employed for the reduction of the finest sizes. ... In contradistinction, comminution to 20-mesh or finer is called grinding. There is a twilight zone in which the product is 6, 10, or 14-mesh limiting size which is either crushing or grinding. ..." Since the data in this paper pertain to a rod-mill operation, comminuting a particular ore size of ¾ in. to a final stage, coarser than 20-mesh, the rod mill is designated as a "fine crusher machine" in this paper. The published literature discloses a wealth of data regarding a rod mill as a fine-grinding machine but relatively little as a fine-crushing operation. Typical of the latter operation is: (I) a description by F. J. Tuck2 in which a fine-crushing rod mill replaced crushing rolls and (2) a description by the present authors3 in which a fine-crushing rod mill was installed instead of a collventional fine-crushing machine. The experience of the authors is that a definite distinction must he made between the rod mill functioning as a fine crusher and as a fine-grinding machine. As a fine crushing machine it prepares relatively large amounts of ore for a subsequent fine grinding operation; as a grinding machine, it grinds relatively small amounts of ore to some predetermined finished product. Pulp Movement and Action in Mill In considering the work performed by a fine-crushing rod mill, it seems important to understand just what takes place within the mill. We were inspired to study this matter by a paper by E. W. Davis,4 which indicated that definite water classification of ore particles took place in a ball mill. However, in thinking of the rod-mill action from this point of view, we were confronted with the fact that our rod-mill discharge product showed no evidence of action by water classification. The Tennessee Copper Co. ore is relatively high in sulphides, and the gangue rock and the sulphides are of about the same hardness. In the presence of any action by classification, the coarser sizes are definitely very lean in sulphide minerals.

Jan 1, 1947

By N. F. Schulz

The purpose of this investigation was to evaluate the effects of variables in equipment and procedure on tube test results. This information was then to be used to formulate specifications, preferably within the practical ranges of existing machines, for test procedures capable of yielding precise and meaningful data concerning the magnetic separation of any magnetite ore, regardless of its origin. A survey of current practice was conducted among laboratories using the Davis tube test. Many tube tests were performed to experimentally evaluate the variables most likely to affect test results. A simple method was then sought for adequately interpreting tube test results. The Davis magnetic tube concentrator is a laboratory machine designed to separate a small sample of pulverized magnetic iron ore into magnetic and non-magnetic fractions. It was developed in 1921 by mechanization of a test previously performed manually No significant changes have been made in the design of the apparatus since that time. The Davis magnetic tube test continues to serve as a practical basis for judging the amenability of an ore to magnetic separation and for controlling magnetic separation plant operations. The apparatus consists of an inclined cylindrical glass tube supported adjacent to closely spaced pointed poles of a powerful C-magnet. (Fig. 1). To conduct a tube test, a sample of suitably prepared ore is poured into the water-filled tube. With wash water flowing through, the tube is oscillated to gradually reject the non-magnetic and weakly magnetic ore particles until the desired degree of separation is attained. Both the magnetic concentrate and the tailings may be recovered for examination. MAGNETIC SEPARATION BY THE DAVIS TUBE Mechanical separation of a specified mineral component from an ore usually requires comminution to fine sizes for sufficient liberation. Some distinguish- ing property of the mineral is then exploited to sort the desired mineral particles from the gangue particles. The magnetic separation of iron ores is based on the fact that magnetite, Fe3O4, is strongly attracted by a magnetic field while the gangue minerals are not. Maghemite, ?-Fe2O3, which may occur in certain chemically processed ores, responds similarly to magnetite. The magnetic process is practical only when the loss of iron in the form of relatively nonmagnetic hematite, Fe2O3, goethite, Fe2O3.nH2O, or other iron mineral can be tolerated. In the Davis magnetic tube concentrator, magnetic attraction holds magnetically susceptible particles in a magnetic field. Forces due to gravity, inertia, and fluid-solid friction tend to remove the less susceptible particles from the field. The probability that a given middling particle will be rejected from the tube in a given period of time is an inverse function of its magnetite content, with some modification due to particle size and mineral specific gravities. The net result is that ore particles tend to be rejected in their order of increasing magnetite content, while the retained portion or magnetic concentrate increases in grade continuously during the process. MAGNETIC SEPARATION CHARACTERISTIC The magnetic separation characteristic or MSC of a magnetite ore is the correlation between concentrate

Jan 1, 1964

By M. W. Legatski, D. L. Katz

The best currently available description of the longitudinal mixing properties of a porous medium is an equation of the form which relates the effective longitudinal dispersion coefficient Dp to the molecular diffusion coefficient Do, the electrical resistivity factor F, the porosity <f> and a Peclet number. If the parameters dpa and m are determined for a porous medium of known porosity and electrical resistivity factor, then a dispersion coefficient may be estimated for a given flow rate and a given gas pair. A new method, featuring on-line gas analysis by thermal conductivity and on-line data reduction by analog computation, was developed and used to determine these mixing parameters for eight naturally occurring sandstones and two dolomite samples. The exponent m of the above equation was found to vary between 1.0 and 1.5. The characteristic length dpa in the above equation was found to vary between 0.25 and 1.9 cm, with an average value of 0.4 cm for sandstones. Measurements were made on two cores in which paraffin wax had been deposited by evaporation from a pentane solution. They indicated that the presence of an immobile phase such as connate water could increase the dispersion coefficients significantly. INTRODUCTION While the petroleum and chemical industries have studied the mixing of miscible liquids flowing in consolidated porous media and of miscible gases flowing in unconsolidated porous media, relatively little data have been presented to describe the mixing of gases flowing through consolidated porous media. Such data are of particular interest to the gas storage industry. For instance, the U. S. Bureau of Mines is storing large quantities of a rich helium-nitrogen gas in contact with a natural gas in a dolomite reservoir. Since the rich gas occupies only 15 percent of the total reservoir volume, it is essential that the extent of rich gas-natural gas mixing be predicted and understood as a function of rock properties, pressure and rate of movement. This investigation was concerned only with the determination of longitudinal dispersion coefficients. It is understood that a transverse dispersion coefficient, which characterizes mixing perpendicular to the direction of flow, may be an order of magnitude less than the coefficient characterizing mixing in the direction of bulk flow.5719 It should also be recognized that the use of any dispersion coefficient is in itself a simplification. It is necessary to assume that mixing in a porous medium may be characterized by the equation for flow in a single direction. A number of authors1 l8,19 have pursued the mixing problem, not in terms of the so-called "dispersion model" described by Eq. 1, but in terms of a "mixing cell model". This model supposes that a porous medium is constructed of a large number of small mixing chambers and that the concentration of the diffusing component within each mixing chamber is uniform. Fick&apos;s law (Eq. 1) assumes that there is no gross by-passing of one fluid by another, and that there are not stagnant pockets of gas in the system under consideration as discussed by Coats and Smith.8 These assumptions are not always valid for flow through porous media and it is important to recognize the limitations upon Eq. 1. The most serious limitation upon the assumption of Fick&apos;s law mixing in a porous medium is

By Charles McElroy White

IT is indeed an honor to have been asked to participate in the program which celebrates the seventy-fifth birthday of the American Institute of Mining and Metallurgical Engineers. This great organization has occupied an important place in the professional and industrial life of this country-of the world. Its members have explored the far reaches of our globe and have played a great part in the discovery, extraction and utilization of the mineral resources upon which our civilization so largely depends. These engineers, together with the restless prospectors, on the one hand, and the scientists, on the other, have literally been the advance scouts of our modern way of life. As such, we owe them a deep and lasting debt of gratitude. May I, therefore, wish many happy returns to the American Institute of Mining and Metallurgical Engineers and express the hope that it may long continue to be of great service, as it has been in the past. The subject assigned to me-Iron Ore and the Steel Industry-is, indeed, important, as one considers the future of our world. I shall give as few figures as possible. Pertinent statistical data are included in the tables in this chapter, which, I think, will prove interesting. Many studies of iron-ore reserves have been -published and are available; hence I shall limit myself mainly to an interpretation of these figures. The statistics data are from standard sources, including the Lake Superior Iron Ore Association, the American Iron and Steel Institute, the United States Bureau of Mines, the United States Geological Survey, the United

Jan 1, 1947

By E. D. Cockrell, E. P. Hayes

The figures herein presented show that during the year 1938 drilling in the Texas Gulf Coast continued at a slightly lower rate than during 1937. In 1938 there were 21 new oil fields added to the Texas Gulf Coast; also numerous extensions and new sands in old fields. This report for 1938 cannot be compared with the report for 1937 in Volume 127 of the Transactions, because the area covered by this report is less than that covered last year. The cross-hatched area on Fig. 1 shows the limits of this report. Of the new fields, Cordele, in Jackson County, Eureka Heights and Fairbanks, in Harris County, Francitas, in Jackson County, LaRosa, in Refugio County, and League City, in Galveston County, have the greatest promise of prolific production. The 1938 production for the Gulf Coast area was 92,530,467 bbl. as compared to 94,019,355 bbl. for the same area in 1937. This shows a decrease of 1,488,888 bbl. during 1938, regardless of the increase due to the 21 new oil fields. This decrease was caused mainly by the Saturday and Sunday shutdowns (68 days during 1938) and by cut in allowables. The 68 shut-down days amount to approximately 18.6 per cent of the 365 days possible for production. The decrease in the 1938 production amounted to approximately 1.58 per cent. Therefore there was actually a potential increase in the year&apos;s production. During the past year, 1637 wells were completed as oil wells, 68 as gas wells and approximately 461 dry holes, as compared to 1672 oil wells, 83 gas wells and 448 dry holes in 1937 on the Texas Gulf Coast. Total wells drilled were 2166 in 1938 and 2203 in 1937. Condensate. sands in old fields and new fields are continuing to increase in importance from the standpoint of retrograde condensation and pressure maintenance. The following fields had major extensions during the year 1938 from the standpoint of increased areas of old sands and new deeper sands:

Jan 1, 1939

By E. D. Cockrell, E. P. Hayes

The figures herein presented show that during the year 1938 drilling in the Texas Gulf Coast continued at a slightly lower rate than during 1937. In 1938 there were 21 new oil fields added to the Texas Gulf Coast; also numerous extensions and new sands in old fields. This report for 1938 cannot be compared with the report for 1937 in Volume 127 of the Transactions, because the area covered by this report is less than that covered last year. The cross-hatched area on Fig. 1 shows the limits of this report. Of the new fields, Cordele, in Jackson County, Eureka Heights and Fairbanks, in Harris County, Francitas, in Jackson County, LaRosa, in Refugio County, and League City, in Galveston County, have the greatest promise of prolific production. The 1938 production for the Gulf Coast area was 92,530,467 bbl. as compared to 94,019,355 bbl. for the same area in 1937. This shows a decrease of 1,488,888 bbl. during 1938, regardless of the increase due to the 21 new oil fields. This decrease was caused mainly by the Saturday and Sunday shutdowns (68 days during 1938) and by cut in allowables. The 68 shut-down days amount to approximately 18.6 per cent of the 365 days possible for production. The decrease in the 1938 production amounted to approximately 1.58 per cent. Therefore there was actually a potential increase in the year&apos;s production. During the past year, 1637 wells were completed as oil wells, 68 as gas wells and approximately 461 dry holes, as compared to 1672 oil wells, 83 gas wells and 448 dry holes in 1937 on the Texas Gulf Coast. Total wells drilled were 2166 in 1938 and 2203 in 1937. Condensate. sands in old fields and new fields are continuing to increase in importance from the standpoint of retrograde condensation and pressure maintenance. The following fields had major extensions during the year 1938 from the standpoint of increased areas of old sands and new deeper sands:

Jan 1, 1939

By D. F. Hewett

[In an increasing degree in recent years, especially since the war, men in many parts of the world are turning their attention to the problems of the future, attempting to appraise the basis and extent of man&apos;s progress and interpret the problem that he faces in the near future. The war made clear to ma persons the degree to which modern industry depends upon t continuous flow of enormous quantities of raw materials, a especially of the minerals. In many circles throughout t world, the question of adequate supplies of the mine especially the fuels and metals, for near as well as more remo needs is receiving serious consideration. As a result, persons representing the state as well as industry are looking to geologists and engineers for all the data that throw light on the distribution, extent and availability of the minerals that must serve coming generations.] Obviously, in a brief research I have been able to consider only a few sources of the metals in Europe, perhaps fifty out of a total of many hundreds. In order that the conclusions may have value, however, I have chosen districts which have been important sources during some epoch of the last three hundred years or more.

Jan 1, 1932

By E. E. White

In August, 1911, I read a paper before the Lake Superior Mining Institute1 on surveying and sampling diamond-drill holes. The present paper gives a more thorough descriptiou of these methods, together with a few changes and notes suggested by further experience. Since August, 1911, the methods, used constantly by the Cleveland-Cliffs Iron Co., have been developed to a higher degree of efficiency, and have given great satisfaction. Until a few years ago but little attention was paid to the determination of the actual course of drill-holes, to the accurate sampling&apos; and analysis of the material, or to the scientific location of the drill-holes. It has now been common practice for several years in many districts to test the inclination of drillholes by etching glass tubes with hydrofluoric acid, but the direction of deviation from the vertical has not often been determined. Methods of determining the direction by means of a compass were first developed in connection with drilling in Victoria. The latest method used on the Rand in South Africa has been recently described by John I. Hoffman.2 In the same paper Mr. Hoffman describes an ingenious method of wedging-off a drill-hole so as to start new holes at several successive points. By this means a hole can be deflected in any desired direction, and the curvature can be controlled to a considerable extent, provided the rock is soft enough to permit the hole to be wedged off. Unfortunately, in the Lake Superior district, the jasper iron-formation is so hard that it is very difficult, if not impossible, to do this. I tried to deflect one hole so as to avoid drill-rods stuck in the hole, by using a

Jan 1, 1913

By J. W. Paul, J. N. Geyer

The measures overlying some coal beds are under stress as the result of geological movements after the measures have been deposited. The removal of the coal in the process of mining induces additional stress in the roof measures. Certain types of deposits have sufficient inherent strength to be self-supporting over definite width of excavations and the stress is adjusted without appreciable movement of the material, to the extent that no part of the material will become detached and fall. The uplifting of the measures in geological time often results in the establishing of cleat planes or planes of weakness in the measures overlying the coal, and these planes generally have a uniform direction. Measures that have not been subject to uplifts are less liable to have noncompensable stresses, although any method of underground mining results in the creation of stress in the roof measures over the excavations and over the coal pillars. The immediate roof measures extending upwards of 10 to 15 ft. above the coal give the greatest concern in maintaining the roof in the advance work in the solid coal. Immediate measures which are inherently weak often may be scaled and supported for indefinite periods by a system of timbering. As an excavation is made, the pillars adjoining must take on the weight previously supported by the coal removed. The roof over the excavations takes on the function of a beam and if too weak to be self-supporting it will fail either through shearing or bending, and the roof cavity may enlarge until a self-supporting arch is formed. As support is removed by taking the coal away, there is a tendency for the roof members to move toward the excavation in an effort to compensate the stress; particularly is this true where there is an overlying bed of clay, which may act as a lubricant on which adjoining members may slide. Unstabilized stresses, plus the force of gravity, plus the inherent strength of the material, govern the tendency of mine roof to fall when not supported by timber. In general, most mine roof depresses when the coal is removed. This depression may be in the nature of a sag as the result of bending, or the edges of the pillar may break away or the floor may come up or heave.

Jan 1, 1934

By Samuel Storchheim

IT was noted that variations existed in the magnetic properties, namely, coercive force, He, and rema-nence, Br, of 18/8 stainless steel wires of the same analysis when these wires were given the same percentage of reductiori of area at different rates of reduction. In order to determine the extent of these variations, a program was initiated whereby commercial 302 and 304 stainless steels were drawn with a wide variation of speeds. Ultimate tensile strengths and specific resistances, as well as the Hc-BT measurements, were determined. If variations of considerable magnitude were found, it was thought that the knowledge accrued from the investigation could probably aid in determining the particular drawing speed required to obtain desired properties for a given specification for a particular analysis of wire. Drawing Procedure Two specimens (set I, No. 302 and No. 304), the chemical analyses of which are given in Table I, were drawn at different speeds, namely, 45 to 3900 ft per min, directly from 0.016 in. diam wire to 0.004 in. diam wire, a 93.7 pct reduction of area. To obtain this high percentage of reduction, the wire at 0.016 in. was softened by annealing at 1150°C. It was then strung in a No. 16CF variable speed Vaughn drawing unit and passed through 13 B.&S. gage dies of successively smaller diameter, as shown in the accompanying table. Following this step, several hundred feet of the wire was drawn, at a particular speed, through the dies and wound upon a spool. Once the sample of wire was drawn at the desired speed, the spool with the finished sample was removed, tagged for later identification, and an empty spool was placed in the machine. Another wire sample was drawn at a different speed, after making the necessary adjustments upon the Vaughn unit. At the greater speeds, several thousand feet of sample were drawn to insure that the wire to be used for testing would be uniform. This was done because the desired speed was not reached instantly; the wire taking a short while to attain the required drawing rate. All speed measurements were made by placing a tachometer against one of the machine&apos;s pulleys during the actual drawing of the specimens. 84.4 pct reduction of area. The 0.072 in. diameter wire was also annealed at 1150°C. The process of obtaining samples was the same as described above. The only difference between the two was that the rates involved were not as extensive, set II covering a range of 625 to 1150 ft per min. Tensile tests were carried out for the 0.004 in. diam wires on a horizontal Scott Tensile Tester, while tensile tests for the 0.028 in. diam wires were made on a vertical Scott Tensile Tester. Each value listed in the tables represented the average of five samples with a maximum deviation of approximately 3 pct among the samples. Resistance per foot of the wires was determined by use of standard bridges accurate to the nearest hundreth of an ohm for the 0.004 in. wire, and to the nearest thousandth of an ohm for the 0.028 in. wire. The resistances per foot were then converted to resistivities by use of the following equation: P = RxCM where R is the resistance per ft in ohms per ft; CM, the area in circular mils; and P, the resistivity in ohms—CM. The values listed in the tables likewise

Jan 1, 1952

By Jei Y. Choi, P. G. Shewmon

The surfrrce-diffusion coefficients (DJ for Aulg8 on (100) and (111) surfaces of copper have been determined between 1050" and 780°C using a new avuzlysis imd experimental procedure. The results are: D, has also been determined fm cua4 at 870°C, and the values found are 4.5 times larger than those measured by the grain boundary grooving technique for the same surface orientations. This difference is felt to result from the approximate nature of the mathematical solution used in the present work. Attempts to measure D, for silver on copper and silver surfaces indicated a means of matter transport different from surface diffision was dominant in moving tracer from the source out over the surface. Cnlculations and experiment both indicate that this is the flow of silver through the vapor phase which completely masks the much smaller flow due to surface diffusion. The previous self-difhsion studies of D, for silver and copper are discussed in terms of our own analysis and found to yield values of D, factors of lo5 or more greater than those found by the grain boundary grooving tech -nique. UNTIL about 5 years ago it was widely believed that the activation energy for surface diffusion, AH, , was less than that for grain boundary diffusion, AHb,, which in turn was less than that for diffusion through the lattice, AHz.&apos; This was concluded from various evidence that D,> Db>Dl, and one tracer study of D, for silver on silver from which AH, was inferred.2 In 1959 Mullins and Shewmon demonstrated that D, could be determined from the kinetics of the growth of grain-boundary grooves.3 Using this procedure, Gjostein measured D, on copper between 800" and 1050°C and found that the activation energy was roughly equal to AHl .4 Subsequent work on copper,5" silver,&apos;,&apos; and goldg between the melting temperature T, and 0.87 T, confirmed that AH, as determined using the grain boundary grooving or scratch-relaxation technique was equal to or greater than AHz. During the same period, Drew and Pye again determined AH, for silver on silver using a tracer techniquelo and a mathematical solution similar to that of Nicker son and arker.&apos; Though the values of D, Drew and Pye measured at any given temperature were about 200 times smaller than those reported by Nickerson and Parker, they again found a low activation energy of about 10 kcal, or about one fifth that found at the higher temperatures with the mass transport technique. A distinguishing characteristic of these two previous tracer studies is that they have worked at low temperatures (-1/2 T,) where they felt volume diffusion was negligible and then analyzed these data as if all tracer atoms leaving the source flowed out into and remained in a homogeneous high-diffusivity surface layer of undefined thickness. This is totally different from the model used in the mass-transport studies or the studies of grain boundary diffusion, which assume the high-diffusivity surface layer to be only a few angstroms thick. If this latter model is applied to the earlier tracer studies, it is shown that the tracer has really pe!etrated into the lattice a mean distance of 1000A. Thus the tracer distribution observed after an anneal is thought to be due to the combined effects of surface and volume diffusion. Independent of the relative validity of the two models, it seems evident to us that any comparison of the values of D, as determined in these two ways is meaningless and misleading, since the values of D, and AH, obtained in these two ways would be totally different for the same physical distributions of tracer. Once the fundamental difference in the approaches of the two techniques is established, we are faced with the question of which model better approximates physical reality. Here all the evidence seems to be on the side of the &apos;&apos;thin surface layer" analysis. In fact, the authors of Refs. 2 and 9 do not argue for the "thick-layer model" we have described; they simply invoke it through the equation they use to calculate D, . The primary evidence for the thin-film approach is: a) grain boundary grooves and scratches widen in proportion to tU4 and Mullins&apos; rigorous analysis shows that this is only valid for a surface layer which is quite thin relative to the width of the groove;11 b) all accepted or seriously discussed models of solid-vapor interfaces and high-angle grain boundaries assume that the disturbed region of the interface is at most a few a0 thick. With the above in mind, it was desirable to determine D, using a radioactive tracer and a "thin-

Jan 1, 1964

By J. J. Oberly

WHILE examining lineage boundaries in germanium single crystals as described by Vogel et al.,&apos; patterns of conical etch pits were noted which reveal interesting properties of dislocations. The crystals were grown by pulling in the <100> direction, and (100) surfaces perpendicular to the growth direction were etched 4 min in a mixture of 6 cu cm HF, 10 cu cm HNO3, 6 cu cm acetic acid, 3 drops Br,. Lineage boundaries extended in any direction, but favored the <110> direction. The patterns which were noted first were composed of two or three etch pits arranged symmetrically about the lineage boundary, so that the doublets were spaced equally on either side of the boundary line and the triplets had their center pit on the boundary line. The triplets occurred less often than did the doublets; occasionally combinations were found. Two such combination patterns are shown in Figs. 1 and 2. The orientation of the patterns was determined approximately by subsequently etching the same surfaces in a mixture of 5 cu cm HF, 5 cu cm super-0x01, and 20 cu cm distilled water which produced nearby random square etch pits having edges in the <110> direction. In all cases, the axis of symmetry was <110>, being parallel to the etch-pit edges. Several successive lapping and etching operations showed that the patterns tended to continue through the crystal in the <100> direction, but eventually changed or vanished. It can be seen in both photographs that the pits in the patterns are much further apart than the pits in the adjacent section of the lineage boundary. In Fig. 1, the 10 pits of the pat-

Jan 1, 1955

By A. A. Brant

In this presentation, concepts of the formation and evolution of the universe, the earth, and the cyclic civilizations of man are broadly outlined. The 5 billion or more years of the universe and the 4% billion years of the earth are contrasted to the 5000 years of modern society and the 100 years of objective scientific breakthrough. THE UNIVERSE Let us start back as far as possible, to the beginnings of this universe, some 5 billion or more years ago. This is a time interval that can be crudely underestimated by the moon-earth tidal friction effects that have increased the length of the day by about 1/1000 second per century — from a 5 to 7 hour day to its present 24 — and have moved the moon away at 5 inches per year to its present 240,000 miles. The oldest stony meteorites from interplanetary space give an age dating of some 4.6 billion years, approximating the time of formation of our earth. Further, certain stars pulsate, the period of pulsation being related to their absolute brightness. Measuring apparent brightness and comparing, gives the distance away. Thus Hubble and Shapley of Harvard, from 1925 on, were able to show that the universe reached as far as our telescopes could scan. The Doppler shift of the hydrogen red lines could only mean that the nebulae, or galaxies, were moving away away at velocities increasing with their distances, by 180 km/sec velocity increase for every million light year&apos;s distance. In short, the universe is expanding like an exploded bomb. Comparing the velocity increase per million light year&apos;s distance again indicates a zero time of some 5 billion years&apos; Thus it appears that this universe had a finite beginning. Physical measurements and present theories permit some picture of our universe&apos;s birth. We know since Einstein that many forms of energy are equivalent, e.g., mass, and electromagnetic radiation, aspects of which are heat and light. Now with expansion, radiation density or equivalent mass decreases as a length factor to the 4th power, while mass as matter decreases at a length factor cubed. The temperature in outer space is now perhaps 100° absolute and the radiation mass equivalent is but 1/1000 the rarefied interstellar gas densities. Decompressing the universe to a starting point, however, raises temperature more rapidly than mass density, and results in a high radiation mass energy fraction, which since it is proportional to temperature to the 4th power suggests a zero point temperature of several billion degrees, brighter than any sun. "Let there be light and there was light," according to Genesis 1-3. Now what further initial conditions must there be to explain the relative abundance of the elements in the universe, which by spectral analyses of the earth&apos;s crust, stony meteorites, and the sun and stars is surprisingly uniform throughout. Some 55% of all cosmic matter is hydrogen, some 44% is helium and only 1% is made up of all the heavier elements in much the same proportions as on earth. These latter decrease logarithmically in abundance up to atomic weight 100, then level out. This consistent abundance distribution of elements in the universe may be generally explained by taking at Time Zero a hot neutron gas of density about 10-3 grams per cc, at a temperature of several billion degrees Centigrade, with a high radiation energy fraction. Generally neutrons break down into positrons and electrons within about ten minutes, but at the initial high temperature and radiation pressure would recom-bine. However, with rapid expansion and decrease of temperature and pressure, the neutron disintegration would run uncompensated and aggregation would result from neutrons and protons uniting in different degrees of complexity. The total calculated element aggregation time would be about one hour while the temperature still remained above one billion degrees. The element abundances formed would depend on density of the nuclear gas, simplicity of the atom formed, and the neutron capture cross section. Thus a higher density

Jan 1, 1964

By H. W. Knott, M. H. Mueller

The crystal structures of Ti2Cu, Ti2Ni, Ti4Ni2O, and Ti4Cu20 have been determined using powder specimens examined by X-ray and neutron diffraction. Lattice constants have been determined for all four phases using X-ray powder diffraction films. Atom positional parameters of all four phases have been determined from observed neutron intensities. X-ray diffraction calculated intensity data have been presented also for the phase Ti2Cu to point out the particular suitability of neutron diffraction in this case. Interatomic distances have been determined using the positional parameters obtained from neutron diffraction. ALTHOUGH some investigations of the crystal structures have been made of these four compounds previously,&apos;-13 it was the purpose of the present investigation to expand the previous work in order to locate the various atoms, determine their coordinates, and to confirm or to correct some of the previous work. It was convenient to group these four compounds together since they are related chemicallv and/or structurally. The compound Ti2Cu is tetragonil; and Ti2Ni, Ti4Ni2O, and Ti4CU2O are all large fees of the same space group. Ti2Cu has been previously reported as a fee phase by Laves and Wallbaum;1 and Rostoker2 which was possibly the oxide phase, Ti4Cu20. Joukainen, Grant, and Floe;3 and Trzebiatowski, Berak, and Ramotow-ski4 have also reported a phase of this composition. karlsson5 has reported a small fct phase of the composition Ti3Cu which may be the presently discussed Ti2Cu phase. More recently Ence and Margolin6 have reported a small fct phase for Ti2Cu and the present authors7 together with Nevitt8 have briefly reported it to be a bet related to the fct with a co three times the length of the co of the fct and have also reported that this phase has a very limited composition. Further refinements will be reported which have varied some of the parameters of this bct structure slightly. Ti2Ni has been reported as a fee phase by Laves and wallbaum;1 Duwez and taylor;9 Rostoker;2 Poole and Hume-Rothery;10 and Yurko, Barton, and parr.11 In a later paper Yurko, Barton, and parr12 have given the complete structure of this phase based on an X-ray diffraction study which was independently confirmed with neutron diffraction by Mueller and knott.7 Additional crystal structure information will be given. Ti4Ti2O, Ti4Cu2O, and a number of other compounds including Ti4Fe2O have been reported as fcc phases by Rostoker,2 and more recently Nevitt13 has confirmed the Ti4Ti2O phase. Rostoker,2 however has reported diffraction lines for Ti4Fe2O which do not have all odd or all even indices. These lines, therefore, cannot be observed if this compound has a fee structure. This same error has crept into the diffraction results reported for TiNi2O and Ti4Cu20 in the ASTM powder data which has been credited from Rostoker&apos;s data. Complete crystal structures of these two phases will be presented. Although all four of these structures have large unit cells and hence do not lend themselves for completely resolved neutron powder patterns, a sufficient number of individual reflections was observed for solving the structure. They also serve as good examples of some of the advantages to be gained by using both neutron and X-ray diffraction techniques. EXPERIMENTAL PROCEDURE All of the alloys were prepared by arc melting. The starting metals had the following purity: Cu 99.999 pct, Ni 99.83 pct, and Ti 99.92 pct. Oxygen was introduced into the two oxide phases as chemically pure TiO2, with the remainder of the titanium coming from the above mentioned metal. All of the sample buttons were annealed in evacuated Vycor tubes, the two binary phases for 5 days at 700°C and the two oxide phases for 3 days at 900°C. Oxygen analyses were performed on all four phases by two independent laboratories with the following amounts of oxygen present in atomic percent; Ti2Cu-0.06, Ti2Ni-1.03, Ti4Ni2O-13.95, and Ti4Cu20-13.87. The stoichiometric amount for the oxide phases is 14.29 at. pct. Since all of the samples were very brittle they were easily reduced to a powder for diffraction measurements. The lattice constants given in Table I were determined for the four compounds from X-ray diffraction patterns of powder samples exposed to filtered copper radiation using a 114.59 mm diam Debye-Scherrer type camera using the Straumanis loading. None of the patterns showed a detectable amount of a second phase. The lattice constants were obtained from an IBM 704 computer program employing a least squares treatment with systematic correction terms as previously reported.14

Jan 1, 1963

By E. Keller

Some years ago the writer&apos;s attention was called to the fact that rolling-mill scales from auriferous copper do not have the gold content proportional to the gold contained in the copper from which they are derived.&apos; So, later, he made a few simple experiments, which are described herewith. In order to test the gold movement on the changing surface of a copper plate under the influence of oxidation, plates 6 in. by 8 in. by 1 in. (15.2 cm. by 20.3 cm. by 2.5 cm.) of converter copper, refined, of 99.29 per cent. purity, and leaded copper with a content of 95.65 per cent, copper, were obtained. Ten cuts were made through the thickness of the plates along the longitudinal center and the silver and gold content ascertained in each of the 10 samples in both plates, as shown in the accompanying illustration. The assay results, recorded in Tables 1 and 2, show that the gold distribution is relatively uniform in both plates, while silver has greater variations, especially in the leaded plate. The plates subjected to oxidation were placed in a red-hot muffle for about 2 hr., two small scarifiers being used as supports. Arranged alongside each other, they nearly filled the width of the muffle, and so were practically under equal conditions of heat and draft. The accurate observance of the time was not possible, however, because of other work, but the time of the exposure of each plate in a pair was identical. At the end of each period, each plate was plunged into water and completely freed of scale, which was carefully collected, dried, weighed, and analyzed. Samples of the plates had also been taken of the molten metal and duly analyzed. Table 3 contains the analytical data for the two plates and their several sheets, or layers, of oxide scales. These figures show that in the oxidations of the converter copper the silver is fairly uniform, while the gold is highly irregular and especially low in the first layer. In the oxidations of the leaded copper plate, the silver and gold contents are variable; however, this irregularity is due to two different causes. The

Jan 1, 1919

By J. T. Ryan

SiR Humphry Davy&apos;s epoch-making treatise delivered on Nov. 9, 1815, before the Philosophical Society of London, first announced and demonstrated a flame safety lamp for detecting methane in mine air. Coal mining was known in England as early as 1180, more than 600 years before the advent of a safe lighting and gas-detecting appliance. Mining, no doubt, took place first in outcrop coal, and danger from gas did not become apparent until the workings became deeper and more extensive. Davy&apos;s lamp did much to increase the safety of miners, and a modified Davy lamp is still widely used for detecting the presence and approximate amount of combustible gas in mine air. No factor in coal mining has improved more rapidly during the past 15 years than safety measures. This progress came about not only as a result of the workmen&apos;s compensation laws now in force in most of the states of the Union, but because the research work of the U. S. Bureau of Mines had demonstrated some dangers incident to coal mining which were not considered to be serious matters prior to that time. Electric power and explosives are necessary but potential hazards in American coal mines. A general mechanization program is now under way, while the mines are growing deeper and more extensive. Consequently ventilation problems are more complex and a demand has been created for positive detecting devices for carbon monoxide as well as methane. Scientists and manufacturers, working hand in hand during the past 10 years, have invented and developed appliances which make systematic and effective examination of mine air possible. The object of this paper is to describe briefly the approved testing devices in use today, with the hope that they may lead to the saving of life. Two Groups of Dangerous Coal Mine Gases Dangerous coal mine gases may be placed in two groups: (I) those that are dangerous because of their explosive properties, and (2) those that are dangerous because of their toxic properties. Methane (CH4) is the important gas of the first group, and in so-called gaseous mines constantly exudes from the coal and rock; it may accumulate and form an explosive mixture. The explosive range of methane-air mixtures is well defined. The low limit is 5 per cent., the high limit 15 per cent., and the most explosive

Jan 1, 1927

By G. G. Gunther, C. L. Boeke

(Any discussion resulting from presentation at the Los Angeles Extractive Metallurgy Division Meeting will appear in the November 1953 issue.) I. M. Symonds (Cia Minera de Penoles, Monterrey, N. L., Mexico)—This is a most interesting paper describing zinc deleading operations. Mr. Gunther was kind enough to show me his operation last fall. Outside of the excellent results, I was most impressed by the ease of control. I had expected a difficult operation requiring careful control and supervision, but found one requiring little attention. The only disappointing fact of the separation is the poor copper recovery in the concentrate of the deleading float. The final zinc concentrate still has about 3 pct chalcopyrite (assuming the copper is chalcopy-rite) which adversely affects the zinc grade. If the copper mineral is free, the poor recovery is probably due to the high cyanide concentration. Fortunately, about 75 pct of the copper is recovered before the pulp goes to the zinc circuit. Mr. Gunther&apos;s remarks about proper cyanide to zinc sulphate ratios cannot be overemphasized. Although our experience has been mostly confined to the conventional Pb-Zn separation, we have found these ratios most important, and more important in the mill than in the laboratory. The laboratory appears to give optimum results over a wider range of reagent control than the mill, especially in regard to the effect of cyanide. In the mill in handling relatively high grade ores, we usually find that ratios of cyanide to zinc sulphate of 1 to 10 or 20 or higher work best. Where there is a substantial amount of chalcopyrite present, it has been noted that cyanide in the range of 0.02 to 0.10 lb per ton of ore is often beneficial in zinc rejection and possibly in copper recovery in the lead concentrate, while larger amounts, say 0.20 to 0.25 lb per ton, will float more zinc and cause a serious rejection of chalcopyrite. On an ore with 15 to 20 pct Zn content, we have had to use 0.8 to 1.2 lb of zinc sulphate per ton of ore with the above cyanide to obtain optimum results. Sometime ago we made a laboratory study following Parral and Santa Barbara practice on an ore which never had a very satisfactory rejection of zinc in the lead concentrate. The results were not encouraging and a mill test was not run. Since then the study has been reopened using fresh zinc concentrate from the mill in the laboratory instead of one made in the laboratory. A reasonably clean lead float from the zinc concentrate was obtained. It has been checked several times and each time the zinc concentrate made in the mill responds and the one made in the laboratory does not. Although undoubtedly some reasonable explanations can be given, it is presented here only

Jan 1, 1953