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By J. Campbell

The hydrostatic tensions in pure metals and long freezing range alloys are evaluated theoretically considering the viscous flow of residual liquid and the general plastic collapse of the casting. The former mechanism operates until the radii of the remaining liquid channels are of the order of 10-3 cm radius, after which the second process limits the attainable negative pressures which range from —1500 to -4200 atm for nickel, aluminum, copper, and iron. In previous reports1'2 the maximum possible hydrostatic tensions developed during solidification have been evaluated employing spherical symmetry. This inevitably involves the concept of totally confined liquid regions, the reality of which has recently been brought into serious doubt3 following observations of the freezing of various transparent materials. Regions of interdendritic liquid which are apparently about to be isolated by the growth of dendrite arms are observed not to be cut off because the advance of the dendrite tips is arrested until the region has completely solidified. Although this may be the result of the very low melting point liquid available at this late stage in freezing, or the result of a higher rate of heat transfer to the dendrite tips because of the acceleration in liquid flow rate near the completion of solidification, this point need not concern us. In this paper an attempt is made to approximate more closely to real conditions; thus the assumption of confined liquid regions is abandoned and cylindrical symmetry adopted. It has also been necessary, therefore, to consider the viscous flow of residual liquid through the remaining channels in the pasty zone. Furthermore, the rather special conditions of spherically symmetric solidification led to extremely high solidification rates and hence unusually high tensile stresses as solidification neared completion; the cylindrical Symmetry appears to yield solidification rates and stresses which are more typical of real castings. The rate of solidification is first considered since this critically affects both the flow of the liquid and the creep of the solid.

Jan 1, 1969

By Robert C. Linares

Cubic zinc sulfide has been grown from molten salt solutions substantially below the hexagonal-cubic phase transition of 1020°C. Crystals free of birefringence have been grown from molten lead chloride at temperatures from 500° to 800°C. Factors affecting the optical transmission and the birefringence are discussed. CUBIC zinc sulfide is of interest for electrooptic devices and as an optical coating material. However, it cannot readily be produced as large crystals which are free of birefringence. The birefringence arises from the fact that the cubic ZnS is usually grown as the high-temperature hexagonal phase and is transformed to the lower cubic phase by annealing.' This results in stacking faults, stress, and birefringence. A requirement for the growth of cubic ZnS is that it be grown below the phase transition of 1020°C.2 Crystals of cubic ZnS have been grown below 1020°C by the hydrothermal,3 flux,4 and vapor transport5 techniques. However, these all appear to have limitations in size or quality of material produced. It was felt that a new flux method might have a good chance of overcoming some of the previous problems. Mita6 reported the growth of hexagonal ZnS from molten NaCl and wilke7 reported the growth of iron sulfides from molten lead chloride solution, indicating that molten chlorides make good solvents for sulfides. An investigation of a number of possible molten chlorides as solvents showed that molten PbCl2 has an appreciable solubility for zinc sulfide and that crystals can be grown at temperatures from 500° to 800°C. EXPERIMENTAL Crystal growth was performed in open or sealed Vycor or fused silica tubes, in an argon atmosphere or vacuum. There were no deleterious effects due to using vacuum; however, a sealed essentially isothermal system must be used to prevent vapor transport mechanisms from dominating. This will be discussed later in detail. Noble metal containers were not usable as they were severely attacked by these melts. The materials used were: reagent-grade PbC12, reagent-grade ZnS, optical-coating-grade ZnS, and Irtran 2 (ZnS). Crystal growth was accomplished by both slow cooling techniques and gradient growth techniques. In the slow cooling techniques, 15 g of ZnS and 100 g of PbCl2 were used. The components were placed in the silica tube, heated at 800°C for 2 hr, and then slowly cooled (l° to 10° C per hr) to 500°C. The furnace was constructed so that the tube could be inverted, thus allowing the liquid to drain off the crystals at the end of the run. The gradient runs were made by placing the above mixtures in a silica tube at 550° to 600°c, Fig. 1. A temperature gradient was maintained such that the floating mass of undissolved sulfide was 10° to 50°C warmer than the bottom of the tube. Growth occurred on spontaneously nucleated sites at the cooler bottom. RESULTS When using high cooling rates (5° to 10°C per hr), crystals form in thin sheets perpendicular to the {111} face. Crystals 5 by 5 by 1.2 mm, Fig. 2, have been ob-

Jan 1, 1969

The mineralogy and textures of a portion oC ore from the 25 level northern orebody, North mine, Broken Hill are described. This ore, in places, contains up to 70 per cent cubanite (CuFe2S3 ) which has crystallized directly with other sulphides and associated gangue minerals.Several breakdown reactions involving the cubanite are also considered.

Jan 1, 1969

Jan 1, 1969

By Thomas R. Bur

This method of performing general transformations by use of Eulerian angles greatly reduces the time required for the determination of values for the elastic compliance constants (sij), elastic stiffness constants (cij ), Young's modulus, shear modulus, or Poisson's ratio for any orientation the cartesian coordinate system in an anisotropic material.

Jan 1, 1969

By V. A. Danielson

The Bureau of Mines studied waste disposal methods a1 a coal mine in Kentucky and another in Alabama to develop cost estimates, to provide better knowledge of current practices, and to guide consideration of alternate disposal methods. Costs of the existing waste disposal systems at each mine were estimated using present-day costs of equipment and labor. Costs of waste disposal systems using alternate equipment were also estimated. Although total disposal costs were essentially the same for both operations, reclamation costs will differ because of different reclamation practices.

Jan 1, 1969

By James S. Browning

Mica mining in the United States is confined largely to pegmatites and schists in a few well-defined areas. The largest region extends from central Virginia southward through western North and South Carolina, northern Georgia, and east-central Alabama. 1, 2, 3 Whereas in western North Carolina these pegmatite dikes are weathered to only a shallow depth, they are deeply weathered in the Carolina Piedmont and in Georgia and Alabama. Particularly in Georgia and Alabama, mica is found in the decomposed slates and schists adjacent to the pegmatites, and in deeply weathered granites. Most flake mica is obtained as the major marketable product by crushing and milling pegmatites.4 To a lesser extent, mica is produced as a byproduct of feldspars and spodumene.6 Past research by the Bureau of Mines has developed two methods for mica flotation. One method utilizes acid-cationic flotation for recovery of mica." This method requires thorough desliming of the ore with consequent fine mica losses. The other method utilizes an alkaline-anionic-cationic process for recovering fine size mica from pegmatite ores after desliming sufficiently to remove clay materials but not so drastically as to remove the fine mica. 8, 9, 10, 11, 12, 13 The latter process has also been successfully applied to a micaceous schist ore from California.14 This report summarizes the results of these research studies. Both of the flotation processes developed by the Bureau of Mines have been adopted by the mica industry and are being commercially utilized separately and in combination for flotation of mica from weathered pegmatite ores.

Jan 1, 1969

The mineralogy of the rocks now observed in the Nairne pyrite deposit developed under conditions of internally-controlled sulphur activity during amphibolite facies metamorphism. In the sulphide-deficient metasediments the activity of sulphur was low, and pyrrhotite developed with iron-bearing silicate minerals. At higher sulphur activity, in the sulphide-rich meta-sediments, pyrite formed in addition to pyrrhotite, and the associated silicate minerals are iron-deficient.

Jan 1, 1969

Reliable and discriminating small, laboratory scale methods of study have been developed and used successfully in the critical evaluation and interpretation of the carbonization characteristics of a wide range of raw and prepared materials, the variable factors in the coking process, and' the mechanical properties of the carbonized products. The simple and highly economic technologies have been successfully and effectively integrated with detailed surface and subsurface geological exploration programmes (particularly in the coalfields of the .Central Bowen Basin of Queensland) as well as with quality and utilization studies of a nUII!ber of representative Australian and Japanese coals. Previously, only the results of comparatively large, laboratory scale studies have provided information reasonably indicative of those to be anticipated hi industrial practice, but these suffer serious disadvantages in terms of economy of material, time and resources; they have been difficult or even impossible to use as an essential part of any normal or comprehensive exploration programme. On the other hand, although previously developed smaller scale laboratory methods derive considerable advantage from their flexibility, amenity to critical control and inherent potential for speed and economy, they have hitherto permitted no effective or direct comparison with the results of industrial practice or full scale assessment. Comprehensive study results achieved through technologies developed recently at the University 'of Sydney demonstrate that carefully controlled small laboratory scale methods of evaluation quite suitable for use in exploration and, other programmes may be used to predict with considerable accuracy and reliability (in some cases exceedingthat of pilot scale study) the principal strength index of one of the established and internationally recognized full sc:ale tests-the Japanese Industrial-Standard Drum Test. It is probable that further study may establish satisfactory correlations with the results of other standard industrial procedures.

Jan 1, 1969

By Sidney Katell

This report, covering the period January 1968 through December 1968, is a continuation of a series that began with the publication of Information Circular 7516 in October 1949. It is the tenth in a series of reports prepared in cooperation with the American Association of Cost Engineers. The abstracted articles are concerned with all phases of cost of engineering in the field of chemical and petroleum plants and related subjects. They are from the following sources: 1. American Association of Cost Engineers Bulletin. 2. Bureau of Lines Information Circulars. 3. Bureau of Mines Reports of Investigations. 4. Chemical Engineering. 5. Chemical Engineering Progress s 6. Chemical Week. 7. Coal Age. 8. Coal Mining and Processing. 9. Cost Engineering. 10. European Chemical News. 3 11. Hydrocarbon Processing. 12. Industrial and Engineering Chemistry 13. Oil and Gas Journal. 14. Petroleum Engineer. 15. World Oil.

Jan 1, 1969

By John D. Spencer

Surveys to establish the quantity and quality of coals available for metallurgical, industrial, and energy use, investigations to develop better mining methods, and studies aimed at improving the health and safety of those who mine the coal highlighted Bureau of Mines research and technologic work on coal in 1968. Also being developed are more efficient methods of coal preparation, transportation, storage, and utilization. Supplementing this effort are projects designed to assure minimum disturbance of land, water, and air resources. Research centers and laboratories of the Bureau of Mines are listed in appendix A. Publications released during 1968 are cited with the various projects and in appendix C. Organizations that cooperated in the work in various ways are cited in appendix B.

Jan 1, 1969

By T. D. Parris

At the Frood Mine of International Nickel, tests were begun in March 1966 to evaluate the use of low profile diesel Load- Haul-Dump equipment in cut-and-fill operations. In December 1966, this test was extended to drawpoint loading of caved ore at the Creighton Mine. The results of these tests conclusively demonstrated the effectiveness of this equipment in the operations at International Nickel. This paper describes the equipment used, the operation of the equipment, production data and operating details. Also discussed in the paper are other trackless equipment which works with the Load-Haul-Dump carrier. Production and Safety comparisons are made with the slusher method in bulk mining, giving the reasons for replacing the slushers at the mines of International Nickel Company of Canada, Limited, Ontario Division.

Jan 1, 1969

By H. S. Price, J. C. Cavendish, R. S. Varga

A numerical formulation of bigh-order accuracy, based on variational methods, is proposed for the solution of multidimensional diffusion-convection-type equations. Accurate solutions are obtained without the difficulties that standard finite difference approximations present. In addition, tests show that accurate solutions of a one-dimensional problem can be obtained in the neighborhood of a sharp front without the need for a large number of calculations for the entire region of interest. Results using these variational methods are compared with several standard finite difference approximations and with a technique based on the method of characteristics. The variational methods are shown to yield higher accuracies in less computer time. Finally, it is indicated how one can use these attractive features of the variational methods for solving miscible displacement problems in two dimensions. INTRODUCTION The problem of finding suitable numerical approximations for equations describing the transport of heat or mass by diffusion and convection simultaneously has been of interest for some time. Equations of this type, which will be called diffusionconvection equations, arise in describing many diverse physical processes. Of particular interest here is the equation describing the process by which one miscible liquid displaces another liquid in a one-dimensional porous medium. The behavior of such a system is described by the following parabolic partial differential equation:

Jan 1, 1969

By Joseph Moses Botbol

Two methods are developed whereby; (1) mineralogic data can be arranged in order of typicality, and (2) mineralogic data external to a model can be compared with the model and the degrees of association computed. Thirty arbitrarily selected base metal mining districts in the conterminous United States were classified as copper, lead, or zinc districts on the basis of tonnage of the major base metal produced. For each of the copper, lead, and zinc districts binary-occurrence distributions were compiled for primary (unoxidized) and secondary (oxidized) minerals. Primary and secondary minerals were then arranged in order of decreasing typicality. Model copper districts are most typified by primary chalcopyrite, pyrite, and secondary malachite. Model lead districts are most typified by primary galena, quartz, pyrite, sphalerite, and secondary anglesite and cerargyrite. Model zinc districts are most typified by primary sphalerite, galena, pyrite, quartz, and secondary smithsonite and cerus-site. The Park City district was removed from the model and its primary and secondary mineralogy was compared with the model copper, lead, and zinc districts. The primary mineralogy of the Park City district is about equally associated with the model copper and lead districts, but the secondary mineralogy is much more akin to the model copper districts. Thus, with respect to the model data, the geochemical target presented by the Park City district resembles a copper district more closely than a lead district.

Jan 1, 1969

This study was done to evaluate the economic and technical considerations of using pozzolanic materials in order to guide cement manufacturers, pozzolan producers, contractors, Government organizations, and others interested in concrete construction work. Five hundred and thirty-eight samples of pozzolanic raw materials were taken from 27 central and western States. These samples were evaluated by petrographic procedures, and about 200 of the most promising ones were given a complete series of physical tests (American Society for Testing and Materials) to evaluate further their suitability as a pozzolan. This investigation showed that deposits of natural pozzolan materials were widely dispersed in the central and western parts of the United States but that exploiting these deposits would depend on whether they could compete economically with an increasingly abundant industrial waste product--fly ash.

Jan 1, 1969

By James D. Cooper

Long range projections of demand for nonmetallic minerals are presented, together with data on the domestic resources which are available or which can be made available to meet the requirements through the balance of the century. Past successes in solving nonmetallic mineral requirement problems are briefly reviewed to illustrate the capability for solving present and future problems of a similar nature. Major problems threatening the future supply of specific industrial minerals are described together with possible methods for assuring the necessary raw materials for future needs. The growing importance of environ- mental degradation, land use conflicts, and other important factors which affect several or all of the nonmetallic mineral industries is covered, and the necessity of planning for efficient and orderly extraction and rehabilitation of mineral deposits is stressed. The present Bureau of Mines methods and tools for long range planning are briefly discussed.

Jan 1, 1969

By H. L. Retcofsky

Carbon-13 nuclear magnetic resonance (18CNMR) spectra of nine 2-substituted pyridines, seven 3 -substituted pyridines, and nine 4-substituted pyridines have been obtained and analyzed. Substituents included both electron-releasing groups and electron-with hawing groups. Substituent effects on the magnetic shieldings of the ring carbons, except for those in the 2-positions of 2-substituted pyridines, were found to be quite similar to the effects reported for the monosubstituted benzenes, Thus, at least to a first approximation, the two classes of compounds have similar shielding mechanisms. Shieldings of the carbon atoms in the 5-positions of 2-substituted pyridines and those in the 6-positions of 3-substituted pyridines were found to reflect electron release or withdrawal by substituent groups, The pyridinium cation and the compounds 2,2'-dipyridyl and benzonitrile were also investigated.

Jan 1, 1969

Applications of helium in aerostatics, cryogenics, space, and undersea work are described in papers from the Helium Applications Symposium. Specific subjects include investigations of X-ray sources by means of balloon-borne instruments, meteorological soundings by balloons, powered lighter-than-air flight, tethered balloons, refrigeration techniques, large superconductive magnets, electronic devices, superconducting transmission lines, high-precision thermal conductivity analysis, He3-He4 dilution refrigerators, uses of helium in the atomic energy program, helium-cooled nuclear reactors, power- plant applications for high-temperature gas-cooled reactors, helium welding of stainless steel tubing and pipe, development of helium-shielded arc welding, helium as a diluent in spacecraft atmospheres, helium utilization in the Saturn-Apollo program, and helium utilization in diving environments. Papers from the Helium Centennial Symposium at the national meeting of the American Chemical Society cover the history of the discovery of helium, the history of its development by the Bureau of Mines from a laboratory curiosity to an important item of commerce, the source of helium in natural gases, the world of liquid helium, and liquid helium-3.

Jan 1, 1969

By Paul W. Johnson

A computer program for calculating capital and operating costs from material and energy requirements and equipment costs for use in preparing cost estimates for metallurgical process evaluations has been written by the Bureau of Mines' College Park process evaluation group. The program permits rapid recalculation of processing costs when changes of data or equipment are desired, and produces tables of capital and operating costs suitable for publication. Equipment cost summary tables for each process section end supplemental information for input-data checking is included in the computer printout. The program is written in Fortran IV except for several subroutines which are written in machine assembly language for the IBM 7094.3 With a few modifications, the program can be used on other computers.

Jan 1, 1969

By Haskiel R. Shell

While the original purpose of the Bureau of Mines work on fluorine micas was to synthesize large single crystals or film suitable to replace natural muscovite or phlogopite, the objective was broadened to include development of the many possible fluorine micas as a class of new, unique materials. Several methods were developed for the synthesis of the fluorine micas at atmospheric pressure: Solid state reaction, melting in crucibles, internal resistance electric melting, and arc resistance electric melting. The latter two methods are now med commercially. A variety of fluoromicas were synthesized by isomorphic substitution including disilicic, trisilicic, and tetrasilicic. Fluorophlogopite, KMg3AlSi3O10F2, is the fluoromica most widely used. While most of the fluoromicas are completely stable to water, many water-swelling fluoromicas and fluoromontmorrilonoids were synthesized. Single crystals or film of the fluorine micas were grown to 2 inches or more by a number of methods, but none has as yet proved economical. In the report, detailed data and descriptions are given on compositions, syntheses, products, and uses, and on the properties including physical, dielectric, chemical, X-ray, optical, and structural.

Jan 1, 1969