DOCSLIB.ORG

Applied Dental Materials

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Applied Dental Materials Chapter 21 Dental Amalgam 21.1 Introduction compositional limit specifi ed in the earlier version of the ISO Standard represented an attempt to An amalgam consists of a mixture of two or more control properties such as corrosion and setting metals, one of which is mercury. Dental amalgam expansion in the absence of any real understand- consists, essentially, of mercury combined with a ing of the structure of amalgam. Materials having powdered silver–tin alloy. Mercury is a liquid at a composition which is in line with the pre-1986 room temperature and is able to form a ‘work- standard are referred to as ‘conventional’ amalgam able’ mass when mixed with the alloy. This behav- alloys. The change in the compositional limits iour renders the material suitable for use in specifi ed in the current standard (post-1986) dentistry. refl ects a marked improvement in the understand- The reaction between mercury and alloy which ing of structure–property relationships for the follows mixing is termed an amalgamation reac- materials. tion. It results in the formation of a hard restor- The quantities of silver and tin specifi ed ensure ative material of silvery-grey appearance. The a preponderance of the silver/tin intermetallic colour generally limits its use to those cavities compound Ag Sn. This compound, known as the where appearance is not of primary concern (see 3 γ (gamma) phase of the silver–tin system, is formed Fig. 21.1). over only a small composition range and is par- Dental amalgam has been used for many years ticularly advantageous since it readily undergoes with a large measure of success. For many years an amalgamation reaction with mercury. Most it was the most widely used of all fi lling materials. conventional alloys contain around 5% copper, For various reasons, including the development of which has a signifi cant strengthening effect on the viable alternatives based upon resins and ceramics set amalgam. and perceptions of a dubious and frequently ques- The role of zinc is as a scavenger during the tioned level of safety, its popularity has declined. production of the alloy. The alloy is formed by melting all the constituent metals together. At the elevated temperatures required for this purpose 21.2 Composition there is a tendency for oxidation to occur. Oxida- Mercury used in dental amalgam is purifi ed by tion of tin, copper or silver would seriously affect distillation. This ensures the elimination of impu- the properties of the alloy and amalgam. Zinc rities which would adversely affect the setting reacts rapidly and preferentially with the available characteristics and physical properties of the set oxygen, forming a slag of zinc oxide which is amalgam. easily removed. Many alloys contain no zinc. The composition of the alloy powder is con- They are described as zinc-free alloys and oxida- trolled by the ISO Standard for dental amalgam tion during melting is prevented by carrying out alloy (ISO 1559). The compositional limits the procedure in an inert atmosphere. allowed by the standard are given in Table 21.1. The majority of alloy powders contain no It can be seen that the major components of the mercury. Those products containing up to 3% alloy are silver, tin and copper. Small quantities mercury are called pre-amalgamated alloys. They of zinc, mercury and other metals such as indium are said to react more rapidly when mixed with or palladium may be present in some alloys. The mercury. 181 182 Chapter 21 (a) (b) Fig. 21.1 This shows an occlusal amalgam filling which has been contoured and polished. Table 21.1 Compositional limits of dental amalgam alloys specified in ISO 1559. Weight (%) Limits prior to 1986 Metal (‘conventional’ alloys) Current limits Silver 65 (min) 40 (min) Tin 29 (max) 32 (max) Fig. 21.2 Dental amalgam alloys. (a) Lathe-cut alloy Copper 6 (max) 30 (max) particles (×100). (b) Spherical alloy particles (×500). Zinc 2 (max) 2 (max) Mercury 3 (max) 3 (max) The shape and size of the alloy powder particles separation to occur and for a cored grain structure vary from one product to another. Two methods to be formed. The heat treatment involves heating are commonly used to produce the particles. to about 420ºC for several hours. The resulting Firstly, fi lings of alloy may be cut from a pre- alloy contains relatively large grains of γ phase homogenized ingot of alloy. These lathe-cut alloy material. The second heat treatment is carried out powders are irregular in shape (Fig. 21.2a) and after lathe-cutting. This is a lower temperature are graded according to size, being described as treatment typically involving heating the alloy fi ne-grain or coarse-grain. Secondly, particles may powder to approximately 100ºC for about 1 hour. be produced by atomization. Here, molten alloy This treatment is referred to as alloy ageing; it is is sprayed into a column fi lled with inert gas. The thought to remove residual stresses introduced droplets of alloy solidify as they fall down the during cutting and ensures that the alloy remains column. Particles produced in this way are either stable during future storage. spherical or spheroidal in nature (Fig. 21.2b). For spherical alloys the method of manufacture Lathe-cut alloys are normally subjected to two dictates that each small sphere is like an individual heat treating procedures. The fi rst of these is a ingot. Thus homogenization is normally carried homogenization heat treatment (see Section 6.5) out for the reasons outlined above. normally carried out on the alloy ingot before Many alloy powders are formulated by mixing lathe-cutting and designed to produce homoge- particles of varying size or even shape in order to neous grains in which the Ag3Sn intermetallic increase the packing effi ciency of the alloy and compound predominates. During the formation of reduce the amount of mercury required to produce the ingot of alloy there is a tendency for phase a workable mix. Dental Amalgam 183 After the discovery in the 1960s that some of the properties of ‘conventional’ amalgam materi- als could be improved by the inclusion of great quantities of copper (in place of silver) a new class of materials was developed and became available for use by the dentist. The ISO Standard fi nally recognized this change in composition when the 1986 version of ISO 1559 was published. As shown in Table 21.1, these newer alloy powders have the same basic ingredients as the conven- tional products but they contain much greater concentrations of copper, typically 10–30% compared with less than 6% in the conventional materials. These newer alloys are referred to as Fig. 21.3 Dispersion-modified alloy powder. Lathe-cut copper-enriched alloys. In addition to the increased particles of conventional alloy and spherical particles of copper levels some alloys also contain small quan- silver-copper eutectic alloy (×500). tities of other metals such as palladium. Higher copper levels in alloy powders may be produced by the manufacturer in one of several ways. Lathe- cores of alloy particles remain embedded in a cut, spherical or spheroidal powders can be pro- matrix of reaction products. duced in which the manufacturer alters the ratio In simplifi ed terms, the reaction for conven- of metals at the melting stage. Hence the resulting tional amalgam alloys may be given by the follow- alloy particles are similar in shape and size to ing unbalanced equation: conventional alloys but simply contain a higher Ag Sn + Hg → Ag Hg + Sn Hg + Ag Sn copper content. These are single-composition, 3 2 3 x 3 or γ + Hg → γ + γ + γ copper-enriched alloys. An alternative approach is 1 2 to blend particles of conventional alloy with those The primary reaction products are a silver– of, for example, a silver–copper alloy in order to mercury phase (the γ1 phase) and a tin–mercury achieve a higher overall copper content. Such phase (the γ2 phase). The γ2 phase has a rather blends are called dispersion-modifi ed, copper- imprecise structure and the value of x in the enriched alloys and one widely used product con- formula SnxHg may vary from seven to eight. The tains two parts by weight of a lathe-cut alloy of equation emphasizes the fact that considerable conventional composition (less than 6% copper) quantities of unreacted alloy (γ phase) remain and one part by weight of spherical silver–copper unconsumed. eutectic particles (Fig. 21.3). The latter particles For copper-enriched alloys the reaction may be contain 72 parts silver and 28 parts copper and represented by: the overall copper content in the blended alloy Ag Sn + Cu + Hg → Ag Hg + Cu Sn + Ag Sn is 12%. 3 2 3 6 5 3 or γ + Cu + Hg → γ1 + Cu6Sn5 + γ The essential difference between this and the 21.3 Setting reactions reaction for conventional alloys is the replacement The reaction which takes place when alloy powder of the tin–mercury, γ2 phase in the reaction product and mercury are mixed is complex. Mercury dif- with a copper–tin phase. The copper–tin phase fuses into the alloy particles; very small particles may exist in the form of Cu6 Sn5 (η phase) or Cu3 may become totally dissolved in mercury. The Sn (ε phase) depending on the precise formulation alloy structure of the surface layers is broken of the alloy. In either case, the elimination of the down and the constituent metals undergo amalga- γ2 phase has a profound effect on the properties mation with mercury. The reaction products crys- of the set material. tallize to give new phases in the set amalgam.
Load more

Recommended publications
  • Evaluation of Scale-Up Model for Flotation with Kristineberg Ore
    Evaluation of Scale-up Model for Flotation with Kristineberg Ore Adam Isaksson Chemical Engineering, master's level 2018 Luleå University of Technology Department of Civil, Environmental and Natural Resources Engineering Evaluation of Scale-up Model for Flotation with Kristineberg Ore Adam Isaksson 2018 For degree of MASTER OF SCIENCE Luleå University of Technology Department of Civil, Environmental and Natural Resources Engineering Division of Minerals and Metallurgical Engineering Printed by Luleå University of Technology, Graphic Production 2018 Luleå 2018 www.ltu.se Preface As you may have figured out by now, this thesis is all about mineral processing and the extraction of metals. It was written as part of my studies at Luleå University of Technology, for a master’s degree in Chemical Engineering with specialisation Mineral and Metal Winning. There are many people I would like to thank for helping me out during all these years. First of all, my thanks go to supervisors Bertil Pålsson and Lisa Malm for the guidance in this project. Iris Wunderlich had a paramount role during sampling and has kindly delivered me data to this report, which would not have been finished without her support. I would also like to thank Boliden Mineral AB as a company. Partly for giving me the chance to write this thesis in the first place, but also for supporting us students during our years at LTU. Speaking of which, thanks to Olle Bertilsson for reading the report and giving me feedback. The people at the TMP laboratory deserves another mention. I am also very grateful for the financial support and generous scholarships from Jernkontoret these five years.
    [Show full text]
  • Mercury and Mercury Compounds
    United States Office of Air Quality EPA-454/R-97-012 Environmental Protection Planning And Standards Agency Research Triangle Park, NC 27711 December 1997 AIR EPA LOCATING AND ESTIMATING AIR EMISSIONS FROM SOURCES OF MERCURY AND MERCURY COMPOUNDS L & E EPA-454/R-97-012 Locating And Estimating Air Emissions From Sources of Mercury and Mercury Compounds Office of Air Quality Planning and Standards Office of Air and Radiation U.S. Environmental Protection Agency Research Triangle Park, NC 27711 December 1997 This report has been reviewed by the Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, and has been approved for publication. Mention of trade names and commercial products does not constitute endorsement or recommendation for use. EPA-454/R-97-012 TABLE OF CONTENTS Section Page EXECUTIVE SUMMARY ................................................ xi 1.0 PURPOSE OF DOCUMENT .............................................. 1-1 2.0 OVERVIEW OF DOCUMENT CONTENTS ................................. 2-1 3.0 BACKGROUND ........................................................ 3-1 3.1 NATURE OF THE POLLUTANT ..................................... 3-1 3.2 OVERVIEW OF PRODUCTION, USE, AND EMISSIONS ................. 3-1 3.2.1 Production .................................................. 3-1 3.2.2 End-Use .................................................... 3-3 3.2.3 Emissions ................................................... 3-6 4.0 EMISSIONS FROM MERCURY PRODUCTION ............................. 4-1 4.1 PRIMARY MERCURY
    [Show full text]
  • Corrosion and Mercury Release from Dental Amalgam
    Corrosion and Mercury Release from Dental Amalgam 1 Jaro Pleva, Ph.D. Abstract been presented, amalgam is still by far the most Corrosion attacks on twenty-two dental extensively used material for dental restorations.2 amalgam restorations after in vivo service have Since the investigations and warnings of the been studied by Scanning Electron Microscopy outstanding German chemist Alfred Stock, 1920- together with the Energy Dispersive X-Ray 19453 4 5 little epidemiological studies of mercury Technique, and by optical microscopy. From the release and its effects have been made. One of the measured depth and type of corrosion attack, possible reasons may be the very interdisciplinary estimates of released mercury amounts are made. character of the problem. For correct answer, The amalgam fillings have been obtained from specialist competence in the following fields is members of a group of 250 individuals, who required: materials science, suspected their health troubles potentially to be corrosion/electrochemistry, toxicology, chronic mercury poisoning from amalgam and medicine/diagnostics, physical biology, analytical were to have all amalgam fillings removed. Three chemistry. typical patient cases are presented. The common type of dental amalgam is an Model calculations of released mercury, based alloy containing typically in weight-%; 50 Hg, 35 on previously published measurements of Ag, 10 Sn, Cu, Zn. corrosion currents with and without abrasion are Reported types of amalgam degradation are also given. crevice corrosion,2 6 7 8 selective corrosion,9 The investigations show, that the long-term galvanic corrosion in contact with dissimilar release of mercury from a few amalgam fillings alloys10 11 and mechanical wear.12 33 Besides will often reach or exceed the recommended selective attack, stress corrosion has been limits for daily intake of mercury.
    [Show full text]
  • NATURE MAY 6, 1944, Vol
    562 NATURE MAY 6, 1944, VoL. 153 If the number of young people leaving school and nineteenth century led to the emancipation of the college is much larger in recent years than at the lower classes and of women, and to increasing de­ beginning of the century, it would seem that this is mands for improved social status and better educa­ less marked in Switzerland than in certain other tion. Dr. Erb considers that, in Switzerland, the countries. For example, it is pointed out that, in exaggerated importance imputed to academic learn­ 1930-31, per 100,000 of population, Germany had 63 ing of the more showy or superficial type was par­ Abiturienten (holders of school-leaving certificates or ticularly marked, and was closely associated with equivalent) whereas Switzerland had only 34. Japan the growing soci»l prejudice for black-coated respect­ and Rumania in 1934 had more than six times as ability. Those who had not themselves attained many with academic training as in 1913. In the to this status were anxious and determined that their same period those of Holland increased by 146 per children should do so; and this delusion, says Dr. cent, of France 112 per cent, of Great Britain 83 per Erb, will continue until it is more generally realized cent, and of Switzerland 59 per cent. According to that the harder one studies the more certainly will Dr. Erb, the most disturbing aspect of this increase he miss the road to wealth. This may be often true, in quantity is the serious decline in quality : he but scarcely attains the dignity of a general thinks the standard, however measured, is definitely proposition ; and in any event strikes a slightly dis­ lower.
    [Show full text]
  • Silver City Santa Rita Hurley
    SCENIC TRIPS to the GEOLOGIC PAST SILVER CITY SANTA RITA HURLEY NEW MEXICO Scenic Trips to the Geologic Past Series: No. I - Santa Fe, New Mexico No. 2 - Taos-Red River - Eagle Nest, New Mexico, Circle Drive No. 3 - Roswell- Capitan - Ruidoso and Bottomless Lakes Park, New Mexico No. 4 - Southern Zuni Mountains, New Mexico No. 5 - Silver City-Santa Rita-Hurley, New Mexico Additional copies of these guidebooks are available, for 25 cents, from the New Mexico Bureau of Mines and Mineral Resources, Campus Station, Socorro, New Mexico. HO: FOR THE GOLD AND SILVER MINES OF NEW MEXICO Fortune hunters, capitalists, poor men, Sickly folks, all whose hearts are bowed down; And Ye who would live long, be rich, healthy, and Happy; Come to our sunny clime and see For Yourselves. Handbill -- 1883 Santa Rita Open Pit, 1959. Scenic Trips to the Geologic Past No. 5 SILVER CITY - SANTA RITA - HURLEY, NEW MEXICO by JOHN H. SCHILLING 1959 STATE BUREAU OF MINES AND MINERAL RESOURCES a division of NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY Socorro - New Mexico NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS Members Ex Officio The Honorable John Burroughs ...............Governor of New Mexico Tom Wiley ……….…… ...........Superintendent of Public Instruction Appointed Members Holm 0. Bursum, Jr. ........................................................ Socorro Thomas M. Cramer.......................................................... Carlsbad Frank C. DiLuzio ...................................................... Albuquerque John N. Mathews, Jr. ....................................................... Socorro Richard A. Matuszeski .............................................. Albuquerque PREFACE Much of the work undertaken at the New Mexico Bureau of Mines and Mineral Resources is done to help the mineral industries -- the prospector, miner, geologist, oil man.
    [Show full text]
  • Chemistry As a Tool for Historical Research: Identifying Paths of Historical Mercury Pollution in the Hispanic New World
    Bull. Hist. Chem., VOLUME 37, Number 2 (2012) 61 CHEMISTRY AS A TOOL FOR HISTORICAL RESEARCH: IDENTIFYING PATHS OF HISTORICAL MERCURY POLLUTION IN THE HISPANIC NEW WORLD Saúl Guerrero, History Department, McGill University, Montreal, QC H3A 2T7, Canada, [email protected] Introduction silver ores to identify and quantify the different mercury loss vectors that resulted from the amalgamation process This article is the first of a series that explore the as practiced in the Hispanic New World. potential of chemistry as an efficient tool for historical research. Basic chemical principles such as the The Scale of Anthropogenic Emissions of stoichiometry of chemical reactions provide the historian Mercury in the New World with a powerful tool to judge the reliability of archival records and interpret better the historiography of events From 1521 to 1810 Spain produced nearly 69% of that relate directly to processes of production based the total world output of silver from its mines in New on chemical reactions. Chemical mass balances have Spain (present day Mexico) and in the Vice-Royalty of determined both revenue streams and environmental Peru (present day Peru and Bolivia). During this period consequences in the past. there was no other non-Hispanic major silver produc- A very appropriate case study to apply this ap- tion in the New World (2). The global economic impact proach is the first industrial scale chemical process to of these exports of silver to Europe and China during have caused a global economic impact. The application the Early Modern Era has received wide coverage in of mercury amalgamation to extract silver from the ores the historiography of this period (3).
    [Show full text]
  • Pdf 631.92 Kb
    Separating Platinum from Gold During the Early Eighteenth Century THE METHODS USED IN SPANISH SOUTH AMERICA By Professor L. F. Capithn-Vallvey Department of Analytical Chemistry, University of Granada, Spain Following the discovery of platinum in the Viceroyalty of New Granada at the beginning of the 18th Century, its use to degrade gold forced the colonial authorities to improve their existing methods of separating and analysing the precious metals. Using information from the Royal Mint of Santa F6 de Bogota, the various ways of separating these metals are now considered, including the little-knuwn method of inquartation. Even before the discovery of the Americas by European explorers, elementary platinum metallurgy was apparently known to some of the indigenous population of the central region of New Granada; an area, shown alongside on a rare 18th century map, which was never fully integrated into the Inca world, and which now constitutes the southern part of Colombia and the northern part of Equador. Following the conquest of the New World by European in- vaders, however, this information appears to have been lost. The somewhat late discovery of platina in the Reproduced by courtesy of the Bibliotecn Nacional, Madrid Chocd area of the New Granada viceroyalty, during the 18th century, was due to several fac- ed. Its presence in the gold obtained from tors. This area had remained relatively isolated alluvial deposits would have been noted by the from Spanish penetration because of the moun- miners, by employees of the Novita and CitarA tainous terrain, high temperatures, heavy rain- foundries, and by officials of the Royal Mints at fall, numerous rivers and, above all, warlike the administrative centres of Popayan, Mari- inhabitants.
    [Show full text]
  • Treating Gold Ores
    Vol. VI, No.3 April I, 1935 Jlnintfsttp af Ari8nna iulltttn ARIZONA BUREAU OF MINES G. M. BUTLER, Director TREATING GOLD ORES (Second Edition) By T. G. CHAPMAN ARIZONA BUREAU OF MINES, METALLURGICAL SERIES NO. 4 BULLETIN No. 138 ptTBI.JSJID BY •••••lIIftIttv Iff ArtII1aa TUCSON,AlUZONA VoL VI, No.3 April 1, 1935 HOMERLERoy SHANTZ,PH.D., SC.D President of the University PUBLICATIONS COMMITTEE C. Z. LEsHER, Chairman; G. M. BUTLER;P. S. BURGESS;R. J. LEONARD; M. P. VOSSKUBLER;R. H. GJELSNESS;H. A. PRAEGER ARIZONA BUREAU OF MINES STAFF G. M. BUTLER,Director E. P. MATHEWSON,Metalll1l"gist T. G. CHAPMAN,Metallurgist ELDREDD. WILSON,Geologist M.uut Em.E, Mining Engineer R. E. S. lIJ:mEMAN, Mineralogist G. R. FANSE'rr, Mining Engineer STATEMENTOF MAn:.mGPRIvn.EGE The University of Arizona Bulletin is issued semi-quarterly. Entered as second-class matter June 18, 1921, at the post office at Tucson, Arizona, under the Act of August 24, 1912. Acceptance for mailing at special rate of postage provided for in Section 1103, Act of October 3, 1917, authorized June 29, 1921. Vol. VI, No.3 April 1, 1935 llnturrsitp of ~rt~ouu 1Bul1rtin ARIZONA BUREAU OF MINES G. M. BUTLER, Director TREATING GOLD ORES (Second Edition) By T. G. CHAf'MAN ARIZONA BUREAU OF MINES, METALLURGICAL SERIES NO.4 BULLETIN No. 138 PUBLISHED BY "niuusity of Arizona TUCSON, ARIZONA PREFACE As is stated by the author of this bulletin, it was prepared not to enable the owners of relatively small gold mines to decide what process should be used in extracting the gold from their ores, but rather, to acquaint them with the various processes available and the advantages and disadvantages of each of them.
    [Show full text]
  • Flotation of Sulphide Ores - HZL Experience
    FROTH FLOTATION : RECENT TRENDS @IIME, JAMSHEDPUR, 1998; pp. 18-41 Flotation of Sulphide Ores - HZL Experience V.P. KOHAD Hindustan Zinc Ltd., Zawar Mines, Udaipur - 313 901 ABSTRACT Flotation process, patented in the year 1906, was originally developed for mineral industry to recover values from high grade tailings of gravity separation plants. This technology has acclaimed importance as a versatile process for the beneficiation of vast variety of sulphide minerals. Due to flexibility of the process and remarkable development taken place in flotation technology and its ancillary systems, it has now become possible to recover fine grained sulphide minerals from complex ore deposits, whose processing was earlier considered un- economical. Today, about 400 million tonnes of sulphide ore is treated annually by flotation process worldwide. M/s Hindustan Zinc Ltd. (HZL), a leading lead-zinc mining and smelting company in India has experienced a spectacular growth from the time of its inception. Starting from a single 500 MT per day lead-zinc mine at Zawar, HZL has expanded its mining capacity to about 13,000 MT per day with matching ore beneficiation plants, all adopting froth flotation technology. The phenomenal progress is a result of HZL's emphasis on research and development with an objective to improve the efficiency and to optimize performance, and to seek innovative modern technology and control systems in their flotation plant and processes. This has not only solved metallurgical problems but improved overall plant economics. High grade concentrates produced with reduced deleterious impurities have further enhanced smelting efficiency. The paper covers general principles and aspects of industrial sulphide ore flotation practices in brief and processes adopted in HZL's plants.
    [Show full text]
  • Unit4metallurgy.Pdf
    TYBSc CHEMISTRY C303 UNIT IV THE PRINCIPLES OF METALLURGY AND CHEMISTRY OF Fe, Cu, Ni, U, Ag & Pb Minerals: Metals occur in nature, sometimes free but mostly in combined state. Those found in free or in native state are Cu, Hg, Ag, Au and Pb. The metals are found in the combined state with other elements and are obtained by mining from the earth are known as minerals i.e. Cu minerals are oxide ores – Cu2O, CuCO3.Cu(OH)2, Sulphide minerals are Cu2S , CuFeS2 etc. Ore: when a mineral contains sufficient quantity of a metal combined with other element from which it can be readily separated so as to render the extraction of metal of good quality probable. It is said to be an ore of metal. All ores are minerals but all minerals are not ores. i.e. Fe – Fe2O3.3H2O Haematite Al – Al2O3.3H2O Bauxite U – U3O8 Pitchblende Gangue or Matrix: The ores usually contains a large number of impurities like earth matters, rock stones, sand, lime stones, mica and other silicates. These impurities are known as gangue or matrix. The ores are divided into four groups. Native ores or Free State: The less reactive metals like Cu, Ag, Au, Pt, Hg and Pb occur in Free State. These metals are known as native ores. Oxides ores: These ores are classified as: Oxides and Hydroxides: The metals like Cu, Zn, Pb, Al, Sn, Cr, Mn, V, Fe,Ti, Mg, Be, Bi, etc occur as oxide and hydroxides. i.e. Fe2O3.3H2O – Haematite CuCO3.Cu(OH)2 —Malachite Carbonate : The metals like Fe, Cu, Zn, Pb, Mn, Ca, Sr, Ba, Mg etc occur as Carbonate ore.
    [Show full text]
  • Cqmcogw MOQIQE
    Sept. 29, 1970 H. FURKERT 3,531,240 PROCESS FOR THE PRODUCTION OF SODIUM BICARBONATE AND SODA ASH Filed Feb. 13, 1968 wow NIO MOQIQEcQmcmogW 5.93%@812| EouBEqloz //////V///// mvmrron m: BERT run mu m! Z é, - {a _ ATTORNEY 3,531,240 United States Patent O ' C6 Patented Sept. 29, 1970 1 2 equivalent to the sodium hydroxide solution. This proc 3,531,240 ess is restricted to a combination with an ammonia soda PROCESS FOR THE PRODUCTION OF SODIUM ash process because the considerable amount of sodium BICARBONATE AND SODA ASH Herbert Furkert, Starenweg, Germany, assignor to Che bicarbonate required is generally available only in a soda miebau Dr. A. Zieren GmbH '& Co., KG, Cologne, ash plant. Braunsteld, Germany Filed Feb. 13, 1968, Ser. No. 705,192 SUMMARY OF THE INVENTION Claims priority, application Germany, Feb. 24, 1967, It is therefore an object of the present invention to C 41,606 avoid the above-mentioned disadvantages of the direct Int. Cl. C01d 7/00, 7/12 10 soda precipitation by producing soda ash from sodium US. Cl. 23-63 10 Claims amalgam, carbon dioxide and Water. The production of chlorine by electrolysis in a mer ABSTRACT OF THE DISCLOSURE cury cathode type of alkali chlorine cell has achieved increased economic importance without any correspond A process for the preparation of sodium carbonate ing increase in utility of the sodium hydroxide made comprising: (a) reacting sodium amalgam produced by available thereby. It has therefore become a practice to mercury cathode cells of the chlorine process with an convert the sodium hydroxide solution into soda ash, aqueous sodium bicarbonate solution to form a solution which is more readily sold than the sodium hydroxide containing sodium carbonate and sodium hydroxide; (b) solution.
    [Show full text]
  • Lead Poisoning in the Smelting and Refining of Lead
    U. S. DEPARTMENT OF LABOR BUREAU OF LABOR STATISTICS ROYAL MEEKER, Commissioner BULLETIN OF THE UNITED STATES ) (WHOLE 1 A 1 BUREAU OF LABOR STATISTICS) ' * * (NUMBER lTL 1 INDUSTRIAL ACCIDENTS AND HYGIENE SERIES: No. 4 LEAD POISONING IN THE SMELTING AND REFINING OF LEAD f FEBRUARY 17, 1914 WASHINGTON GOVERNMENT PRINTING OFFICE 1914 Digitized for FRASER http://fraser.stlouisfed.org/ Federal Reserve Bank of St. Louis Digitized for FRASER http://fraser.stlouisfed.org/ Federal Reserve Bank of St. Louis CONTENTS. Lead poisoning in the smelting and refining of lead: Page. Introduction............................................................................................................... 5-17 Dangerous processes in the smelting and refining of lead....... ............... 6-8 Dust and fumes.................................................................................................. 9-11 Sanitary equipment.......................................................................................... 11 Medical care....................................................................................................... 11 Disadvantages of a shifting force................................................................. 11,12 Prevalence of lead poisoning in the industry............................................. 12-14 Prevention of lead poisoning in the smelting industry............................ 14-17 Construction............................................................................................... 15 Sanitary equipment.................................................................................
    [Show full text]