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By Haibin Wang, Baojun Zhao, Xueyi Guo, Zhixiang Cui, Zhi Wang

In conventional copper production, anode copper is produced from concentrate in three furnaces in a process that entails four oxidation steps and one reduction step. Three types of slags are produced that require further treatment to recover copper. Dongying Fangyuan Nonferrous Metals recently developed a simplified process which requires only two custom-designed furnaces instead of the conventional smelting, converting and re fining furnaces. The first furnace continuously produces high-grade matte (>75 wt% Cu) that contains little iron (<2 wt% Fe). The liquid matte is continuously fed to the second furnace, which produces anode copper. The new process signi ficantly reduces the capital and operating costs and increases productivity and environmental sustainability. This paper presents fundamental concepts that enable the simpli fied process to be developed. The detailed operations in Dongying Fangyuan Nonferrous Metals are also described.

Mar 1, 2018

By Avnulf Muan, P. V. Riboud

The effect of Cr2O3 on melting relations of iron oxide at oxygen pressures slightly above those prevailing in contact with metallic iron has been determined. Liquidus and solidus temperatures of wüstite are raised by the addition of Cr2O3, from 1385°C for pure iron oxide to 1420°C at the peri-ledie point where wüstite, iron chromite, liquid, and gas coexist in equilibrium under the atmospheric conditions used in the present investigation (CO2/H2 = 1). It has been shown in a previous investigation1 that the liquidus and solidus temperatures of iron oxide are drastically increased by the addition of Cr2O3 under the relatively oxidizing conditions prevailing in air. This is to be expected in view of the easy substitution of cr3+ for Fe3+ in crystalline oxide structures which are stable at high oxygen pressures, as demonstrated for instance by the completeness of the solid solution series Fe2O3-Cr2O3 at high temperatures (>1000°C). The stable phase of iron oxide at oxygen pressures approximating those prevailing when metallic iron is present is wüstite. This phase, although commonly represented by the simplified formula FeO for sake of convenience, in reality has a defect structure in which a part of the iron ions are present as Fe3+. It is to be expected that at least a limited amount of cr3 ions will substitute for Fe in this structure when Cr2O3 is added to wüstite. Depending on the ease of this substitution in comparison with that of cr3 substitution for Fe in iron oxide-Cr2O3 liquids under the same atmos- pheric conditions, the liquidus and solidus temperatures of wüstite may increase or decrease upon addition of Cr2O3. The methods of establishing these melting relations and the results obtained are presented in the following. I) EXPERIMENTAL METHOD 1) General Procedure. The quenching technique was used in this study. Oxide mixtures were heated at chosen constant temperatures in an atmosphere consisting of equal parts of CO2 and H2 until equilibrium was established among gas and condensed phases. The samples were then quenched in mercury to room temperature, and the phases present were determined by microscopic and X-ray investigation. 2) Preparation of the Mixtures. Starting mixtures were prepared by weighing and thoroughly mixing Fe2O3 and Cr2O3, or wüstite and Cr2O3. The Fe2O3 and Cr2O3 used were "Baker Analyzed" reagent grades, whereas wüstite of composition was synthesized by reducing Fe203 at 1325°C in an atmosphere consisting of equal parts of CG andHz. In order to avoid contact with crucibles, the equilibration runs were made with small pellets suspended from thin (-0.004-in.) platinum wires. Mixtures made from FOs and Cr203 were readily pelletized at a pressure of 500 atm in a 9.5-mm die, whereas mixtures made from wüstite and Cr203 when treated identically were too weak for handling. In order to obtain a stronger product, these pellets were sintered by heating for 2 min at -1200°C in the same atmosphere as was subsequently used for the equilibration runs (CG/H2 = 1:1). During the sintering, these pellets were wrapped in thin (0.0004-in.) platinum foil, which was stripped off before the equilibration runs. In order to reduce the time needed for equilibrium to be attained, preliminary equilibration of relatively large pellets of each mixture was carried out at -1200°C for 4 to 12 hr. Smaller pellets

Jan 1, 1964

By M. S. Safarzadeh, V. Agarwal

"The solvent extraction of cerium(III) and samarium(III) from mixed solutions of all rare earth elements (REEs) except promethium using PC88A (2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester), an acidic extractant, was investigated. The effects of aqueous equilibrium pH, various acids (sulfuric acid (H2 SO4 ), hydrochloric acid (HCl) and nitric acid (HNO3 )), initial metal ion concentration and extractant concentration on the solvent extraction of Ce(III) and Sm(III) were systematically studied. From the experimental results, HNO3 and HCl were found to be the preferred aqueous media for the solvent extraction of both Sm(III) and Ce(III). The most promising experimental conditions of pH, PC88A concentration and metal ion concentration were identified for the extraction of Ce(III) and Sm(III). Separation results showed that H2 SO4 at pH 2 provided the best separation between Sm(III) and Ce(III). IntroductionIn recent years, demand for rare earth elements (REEs) has increased significantly because of their many commercial applications. REEs have especially important high-tech applications owing to their unique physical and chemical properties, and they are used in a wide range of areas such as catalysts, ceramics, magnets, lasers, glass, neutron absorption and alloys. As REEs have very similar physicochemical properties, their separation and purification from each other is challenging and gaining significant interest. Samarium (Sm) and cerium (Ce) are found in different REE minerals, including bastnäsite ((Ce,La,Nd(CO3)F), xenotime (YPO4) and monazite ((Ce,La,Nd,Th)PO4) at major production sites in the United States and China, as listed in Table 1 (Bleiwas and Gambogi, 2013). The most common acidic organophosphorous extractants used for REEs extraction and separation are DEHPA (di-(2-ethylhexyl)phosphoric acid), PC88A (2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester), Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) and Cyanex 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) (Sarangi, Reddy and Das, 1999; Surampally et al., 2012; Tian, Jia and Liao, 2013). Out of these extractants, PC88A is known for providing higher separation factors (Acharya, Mishra and Misra, 2015). El-Hefny et al. (2010) investigated the kinetics of the solvent extraction of Sm from chloride media using sodium salt of Cyanex 272 and reported the extracted species to be Sm(OH)A2•2HA. Lee et al. (2005) investigated the solvent extraction of Sm(III) with PC88A and saponified PC88A from chloride solutions and found the stoichiometry of the extraction reactions to be 1.5 with PC88A and 3 with saponified PC88A."

Jan 1, 2017

By Evan Jannoulakis, Wilfrid Comeau

Using the Scaled Distance (SD) and the vector sum Peak Particle Velocity (PPVvs) from a single delay, preferably single blasthole, in a shot, a number is derived which has shown itself to be consistently related to blasting efficiency, as experienced by one of the authors of this paper over the last thirty years. The numbers derived by this process range in value over one order of magnitude more or less. This variation, a function of distance, weight of explosive in the delay, blasthole diameter, blast design, powder factor and the geological environment, can be consistently related to two of these factors, powder factor and distance. In actual use the measured "BED" representing good blasting results should not vary by more than + 33 to + 50 percent of the estimated "BED" in non calibrated cases, and + 10 to 20 percent where previous experience is available. Relatively high "BED" values are indicative of poor blasting results while relatively low "BED" values may be precursors of poor blasting results in a shot. There are many variables in the geological environment which can affect the "BED". A case study is presented from a surface coal mining operation in eastern Canada. This case study tries to evaluate the reasons for the variability in "BED" values derived from multi-hole shots. A problem in using "Signature Vibrations" from a single-hole shot to predict blasting vibrations from multiple-hole production shots is identified.

Jan 1, 1998

By Matthew D. Marks

"The Sacramento Area Flood Control Agency initiated the Natomas Levee Improvement Program in 2006 which would bring the entire 42 mile Natomas Basin perimeter levee system into compliance with applicable Federal and State standards for levee protecting urban areas. The soil-bentonite slurry cutoff has been utilized as the primary construction method for addressing the under seepage deficiencies. To date, a combined total of over 4,500,000 square feet of slurry cutoff wall have been constructed utilizing excavation methods to a maximum depth of 75 feet and deep soil mixing methods to a depth of 90 feet. The construction of these cutoff walls has required the use of newly designed and custom built long boom and stick attachments for large hydraulic excavators and additional resource will be required to complete future phases. Key components of the NLIP program have included advancements in the development of soil-bentonite backfill mix designs, specified ranges on the soil backfill gradation to address concerns of long term consolidation of the backfill material, evaluation of the trench slurry filtrate loss with regard to cutoff wall acceptance, maintenance high slurry densities to provide greater trench stability, and continued development of backfill mixing procedures.IntroductionThe Natomas Levee Improvement Program (NLIP) was initiated by the Sacramento Flood Control Agency (SAFCA) in 2006. The long term objective of the NLIP is to provide 200-year level flood protection to the basin. To date, approximately 21 of the 42 mile Natomas Basin perimeter levee system has been completed, totaling over $100,000,000 in construction contracts, of which slurry cutoff walls make up approximately $25,000,000. Other construction elements include excavation and removal of unsuitable levee materials, raising or widening existing levees, construction of landside seepage berms, drainage canals, and miscellaneous structures.Although each construction phase of the NLIP includes various construction elements of levee restoration program, the slurry cutoff wall is the primary construction element for addressing the under seepage deficiencies. To date, approximately 4,500,000 square feet of slurry cutoff walls have been installed using excavation and deep soil mixing (DSM) methods. This includes approximately 2,000,000 square feet of slurry cutoff wall along 5 miles of the NCC South Levee and 2,500,000 square feet of slurry cutoff wall along 16 miles of the Sacramento River East Levee (SREL). The work has been completed under 8 separate contracts, through SAFCA, and performed between September 2007 and December 2012. A summary of the contract phases and associated cutoff wall square footage is provided in Table 1. Most of the work has been performed within the seasonal dry weather period in the Sacramento valley, which occurs between April and October. This has required much of the work to be performed on an aggressive construction schedule, year after year."

Jan 1, 2017

By Karl-Heinz Frohne

This report presents the findings of a study of a portion of the Clover-Rush Run oilfield located in Roane County, W. Va. The study was made to investigate the possibilities of secondary oil recovery in the Big Injun sandstone underlying the William Kaufman lease. Reservoir properties, original reserves, and primary oil recovery are also presented. The investigation is based on a core analysis and related laboratory tests, well records, field production data, and subsurface information from the Kaufman property. A theoretical primary oil recovery of 9.7 percent of original oil in place is predicted for the reservoir. A waterflood performance prediction of a hypothetical pilot area was made by use of a computer. The prediction showed that, based on laboratory oil water relative permeability curves, the water-injection time needed to initiate oil production is excessive and that the stabilized water-injection and corresponding oil-production rates are very low. This precludes waterflooding the reservoir on an economic basis. A prediction for secondary oil recovery by gas injection was attempted but could not be completed because essential reservoir data were not available. In July 1965, the lease operator initiated, and is currently conducting, a gas-injection program, but there had been no increase in oil production up to November 1966.

Jan 1, 1967

By Edwin E. Maust

In response to the ever- increasing demand for high temperature materials, the Bureau of Mines instituted a program for the study and development of superrefractories, One of the major tools obtained for use in this research was an image furnace of the double-paraboloidal mirror type. Although extensive theoretical analyses of solar furnace performance may be found in the literature, comparable detailed information on the double-paraboloidal-mirror image furnace has been nonexistent. This report presents an analysis based on an investigation undertaken to ascertain the limitations and characteristics of the furnace so that it can be used most effectively. The quantitative determination of the energy available at the image, the control of this energy by mans of a 60-inch iris diaphragm, and its variation with position and time relative to the heat source used have all been dealt with in detail. The quantitative results were obtained using a specially designed waterflow calorimeter and these measurements, in conjunction with the theoretical analysis, are used to present a fairly complete description of the furnace and its capabilities.

Jan 1, 1962

By V. A. Scovazzo

The analytical pillar design procedure employing the Wilson equation is based on the site-specific material strength of the floor, pillar, and roof rock. Stable pillars so designed will sometimes be larger than those designed using empirical methods thus providing more stability or at other times smaller than empirically designed pillars thus conserving natural resources. Presented here is a detailed procedure for the analytical design of soft rock pillars using the Wilson Equation. An example of this procedure is presented that uses data from a mine in the Owl Seam in Southern Appalachia. These Owl Seam pillars are now in use and are performing as expected. Also addressed is an assessment of the Dr. Scovazzo?s analytically designed pillars based on pillar performance data gathered by Dr. Mark in the Southern Appalachian Coal Field.

Jan 1, 2010

By Leandro de Jesus Jorge

O presente trabalho apresenta um comparativo da utilização de diferentes condições de tratamento térmico para soldagem do aço 80-HSLA. Neste experimento realizou-se soldagens multipasse utilizando o processo de eletrodo revestido, em diferentes condições de tratamento térmico adicionando ou retirando o pré ou pós-aquecimento de soldagem, a fim de se obter o comparativo dos efeitos nas propriedades mecânicas e metalúrgicas, encontradas em cada condição. Após a soldagem foram realizados ensaios não destrutivos para identificação de descontinuidades e ensaios mecânicos caracterizadores. Os resultados dos ensaios mecânicos e metalográficos foram conclusivos para afirmar que quaisquer tratamentos térmicos podem ser dispensados para a soldagem desse aço e, principalmente, o tratamento de pós-aquecimento de soldagem, e que a aplicação ou não desses tratamentos não alteraram significativamente a microestrutura do material e nem as suas características mecânicas.

Oct 30, 2017

By Edward D. Thimons

The Bureau of Mines conducted a state-of-the-art study of techniques currently employed to close large openings in underground mines. A large opening was considered to be any opening over 10 feet high and having a cross section of at least 200 square feet. Five salt mines and one limestone mine were visited to observe various methods of sealing large openings. Because of the variations in conditions from mine to mine, no definite conclusions could be drawn as to which is the best method. In mines where waste material is available, stoppings built by piling waste material are efficient and economical. Where waste material is not available properly constructed brattice cloth stoppings are superior to those built from wood, concrete block, or urethane foams.

Jan 1, 1975

By Roger L. Keller, John Dean Smith

The Amax Coal Company's Ayrshire Mine in Southern Indiana is faced with one of the toughest blasting applications concerning vibration in the nation. As a means of maintaining regulatory compliance the operation elected to exercise the option of frequency analysis. A site-specific computer processing program which suggests ideal delay interval ranges for the lowest vibration was utilized.

Jan 1, 1987

By Ralph H. Phelps

WHAT information do you have on precision investment casting? Please send me all available information on the removal of paraffin from oil wells and pipe lines. How can I find out how to remove magnesium oxide from lime? I want a good book on the pickling of steel. Can liquid oxygen be used as an explosive in a mine? Where can I get a bibliography on the plasticity of metals? These questions, selected from the scores of questions asked the Engineering Societies Library staff every day, indicate some of the diversity of the requests received. The samples chosen relate to interests of AIME members but the questions that come to the Library by mail, telephone, telegraph, and in person cover all fields of engineering, science, and technology. Some questions can be answered quickly; others require extensive searching. Those that can be answered in a few minutes or ten, twenty, or even thirty minutes are usually done without charge. For the more difficult questions a charge is made. In this way those requiring considerable service pay for it and the Library finds it possible to serve more persons.

Jan 1, 1948

By Howard N. Eavenson

WASTE of coal, or perhaps more properly the percentage of its recovery in mining, has keenly interested me during an experience of over a half century in coal mining. In the early part of that time and until a few ears after World War I the use of better mining plans and supervision resulted in an increased recovery. Since then, and particularly since controlled prices have been effective and mechanized mining has been extensively practiced, the tendency has all been toward lesser recovery in mining. The purpose of this paper is not to criticize the methods being used, which after all are the result of economic forces, nor to point to any particular mining method or to any locality where the best recovery is obtained. but to call attention to the tremendous waste of our national coal resources that is constantly continuing. A possible method of reducing this loss will be suggested. but without any illusions that it will be followed or that much attention will be paid to it.

Jan 1, 1946

By Carlton E. Brown

This report contains information on the relation between and precision or reproducibility of counts (light-and dark-field) of the dust in liquid from simultaneous impinger, midget-impinger, electric-precipitator, and filter-paper samples. The impinger was the main sampler used from about 1922 to 1939 by industrial hygienists in the United States for collecting samples of unhygienic dust from the atmospheric environment of workers. The midget-impinger, a small modification of the preceding impinger described in 1937, has been the sampler used most since about 1939. Electric precipitators5/6/ have been used to a limited extent, mainly by the Bureau of Mines in the laboratory, for obtaining results comparable to impinger results. A filter-paper sampler for obtaining results comparable to impinger results has been described by Brown. All these samplers have a high collecting efficiency for particles larger than 1 micron in diameter revealed by the usual light-field counting procedure. However, their collecting efficiencies are quite variable for the smaller particles revealed by the dark-field counting procedure used in this study. Published information on the relation between the results of these samplers is limited and scattered. Summaries of some of this information are given in this report along with some previously unpublished information.

Jan 1, 1949

By Cathy Aimone-Martin, Robert Brentar, Brent Meins, James Lauer

Vibration measurements of multi-story structures in an urban environment began 3 years ago in New York City during close-in blasting to adopt correct measurement procedures and recommend revised ground vibration limits that best characterize cracking potential in mid- to high-rise structures. Two broad categories of structures included non-engineered 4- to 6-story multi-family unreinforced brick masonry buildings, built from the late 1800s to around 1930, and post-WWII, high-rise structures of reinforced concrete and steel rising 12 to 40 stories. In-ground vibration limits similar to those recommended by the U.S. Bureau of Mines safe criteria, developed for 1- and 2-story residential structures, are imposed by the New York City Fire Code. However, these limits are often lowered by project engineers or New York Department of Buildings when blasting is planned near buildings designated Landmark or historic and classified as fragile or vibration-sensitive. Seismograph measurements to determine compliance with in-ground velocity limits currently employ geophones mounted to basement walls and on concrete slabs overlying rock. These measurements cannot be correlated with upper structure cracking potential and are often exceeded, resulting in excessive and costly downtime to allow post-blast damage investigations.

Jan 1, 2014

Between two and three years ago, in response to an unmistakable and insistent demand, the four Founder Societies appointed Committees on "Aims and Organization," or on "Development," charged with reporting on the internal organization and the external (non-professional) ac-tivities of the engineers societies and to advise as to coöperations and coordination. Each of these committees formulated a report, recognizing that effi-ciency in external activities could only be attained by intimate coopera-tion between the four Societies. As a consequence, each of the Founder Societies was requested to appoint members of a Joint Conference Committee, charged with discussing the situation and evolving if possible a plan of cooperation in external activities which would coordinate not only the efforts of the four Founder Societies but also other national technical and scientific societies, as well as local engineering and profes-sional associations, groups or clubs. The Joint Conference Committee entered on its task with enthusiasm, and after great labor evolved the outline and many of the details of plan for engineering cooperation in public and inter-society activities. This report has now been submitted to the Boards of the Four Founder Societies, and has been ordered printed by our Board for the information of our members.

Jan 12, 1919

By D Piason

Newstan Mine commenced mining operations in 1887 and has since undertaken extensive mining within the Young Wallsend, Great Northern, Fassifern, Borehole and West Borehole coal seams using a range of mining methods including board and pillar mining and longwall mining.Newstan Mine is planning to extend the existing mine workings using longwall and miniwall mining methods to produce up to 4.5 Mt/a of run-of-mine (ROM) coal for at least 25 years. The planned extension in the Main East and South West sections will involve developing new longwall panels and related mains headings. The new area contains higher specific gas emissions (SGE) than previously experienced at Newstan Mine. To achieve the optimum ventilation requirements for the longwall operation in this new area, a new ventilation shaft was designed to be constructed using the blind boring method in the South West Headings section.This paper presents the shaft design parameters and selection criteria for the construction of the new ventilation shaft, including the construction phase and the holing process to connect the shaft to the underground workings. The paper also discusses future ventilation requirements for Newstan Mine.CITATION:Piason, D, 2015. South-west ventilation shaft project at Newstan Mine, in Proceedings The Australian Mine Ventilation Conference, pp 229–238 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Eduard Stefanescu, James M. Mwase, Egon Sehner, Stoyan Gaydardzhiev

"The study is focused on investigating the production of synthetic rutile of 95% purity or higher from a Norwegian ilmenite ore concentrate. This was to be achieved using a sequential process involving oxidative-reductive roasting at 975°C, followed by magnetic separation to further concentrate the sample and finally leaching with 20% HCl to remove mostly Fe-based impurities leaving behind synthetic rutile. The key process parameters considered were roasting time (1 and 2 hrs), leaching temperature (100, 125 and 145°C), pulp density (15 and 25wt%) and leaching time (3 and 6 hrs). The option of directly leaching the concentrate without pre-treatment was also evaluated. Test work was conducted using samples screened to a size fraction of 105-212 µm. Samples were leached in a 1 L glass autoclave. The reactor was hermetically sealed and thus the resulting pressure was not controlled but was dependent on the process temperature. The product from leaching was calcined and analysed via XRD and SEM to determine the purity of the product. The magnetic separation step was found to be ineffective and discontinued early in the study. Thus far a product with 97% synthetic rutile purity as analysed by SEM has been produced by directly leaching the concentrate at a temperature of 145°C, pulp density of 25wt% and leaching time of 6 hrs.INTRODUCTION The study investigates the use of a process route comprising oxidative-reductive roasting, followed by magnetic separation and then hydrochloric acid leaching and calcination to produce synthetic rutile from ilmenite concentrate. The grade of synthetic rutile produced should be suitable for chlorination to produce pigment grade TiO2. Hence the proposed process should produce a product consisting of no less than 95% synthetic rutile. Additionally, the product should have no more than 1.5wt% combined content of CaO and MgO (Zhang et al., 2011) as they tend to form high-boiling-point chloride leading to the malfunctioning of fluidized bed chlorinator (Cardarelli, 2008). Finally the product should have no more than 2.1wt% of Fe2O3."

Jan 1, 2018

By T. A. Klinefelter, R. G. O’Meara, Glenn C. Truesdell, Richard W. Smith

THE investigation of domestic tales was undertaken by the Bureau of Mines, Department of the Interior, in cooperation with the University of Alabama, at the request of the U. S. Army, on Dec. I, 1941: "Considerable concern has been expressed by the Supply Arms and Service over maintaining continued availability of supplies of the necessary raw materials. These ceramic products are used by the Signal Corps in all army radio equipment, and to a greater degree in the new ultra-high-frequency equipment. The Air Corps has become a user of large amounts of radio-grade ceramics for aircraft spark-plug covers required for high-altitude operations. In addition, the use of this material is essential to the proper functioning of the radio air-navigation aids of the Civil Aeronautics Board." HISTORY The use of steatite and talc in ceramic bodies goes back a great many years. If pure, tales shrink little under heat-treatment and are very resistant to heat shock. The massive form, commonly called "steatite" by the trade, cuts and works easily, and this was naturally the first method used in obtaining articles of talc. When gas was in general use for illuminating purposes, a large business was carried on in the manufacture of tips for gas burners.1 With the development of uses for electricity, low-tension insulators were made in a similar manner; and, in fact, the forming of shapes from massive talc continues. However, as the business increased, cuttings and waste became more and more of a problem. In the twenties, one of the larger producing firms had a cooperative agreement with the Bureau of Mines at its Columbus station to work out a body using the finely powdered material. Somewhat earlier, manufacturers of spark plugs used the finely ground talc as part of the body and to some extent in wall-tile bodies. Somewhat later it came into use for kiln furniture and similar products and still more recently it has been used in some dinnerwares. With the development of the radio and the high-frequency fields generated, it was found that a dense steatite porcelain was far better than even high-tension electrical porcelain, which is a clay-flint-feldspathic type of body. Until the war increased the demand, the several pioneer steatite-porcelain manufacturers were able to furnish adequate supplies. When war began in Europe and Asia, three important foreign sources of raw material were cut off; i.e., the French, Italian, and Manchurian tales. Domestic producers of high-grade porcelain are few, and the trade

Jan 1, 1943

By N. Menad

The formation of the dioxins can be dependent on the quantities of carbon, hydrogen, chlorine and oxygen present in a given system, as well as on parameters such as temperature and pressure. Inadequate supply of combustion air ( incomplete oxidation ), low combustion temperatures ( incomplete combustion ), and insufficient turbulence in the combustion are factors which can favour their formation. Dioxins were produced also calatytically from chlorinated phenol precursors, non-chlorinated compounds that were chemically, and reaction of phenol with inorganic chloride. In this paper different precursors such as combination of C, H, 0, Cl, rapid formation/combustion intermediates and routes to PCDFs are reviewed, and the influence of PVC amount on the formation of these isomers is discussed.

Jan 1, 2000