Information about Lead (metal)
This article is about the metal. For other uses, see Lead (disambiguation).
For "Pb" as an abbreviation, see .
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Notable characteristics
Lead has a dull luster and is a dense, ductile, very soft, highly malleable, bluish-white metal that has poor electrical conductivity. This true metal is highly resistant to corrosion. Because of this property, it is used to contain corrosive liquids (e.g. sulfuric acid). Lead can be toughened by adding a small amount of antimony or other metals to it. Lead is the only metal in which there is zero Thomson effect. Lead is also poisonous. All lead, except 204Pb, is the end product of a complex radioactive decay (see isotopes of lead below).History
Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable and ductile as well as easy to smelt. In the early Bronze Age lead was used with antimony and arsenic. Lead was mentioned in the Book of Exodus (15:10). Alchemists thought that lead was the oldest metal and associated it with the planet Saturn. Lead pipes that bear the insignia of Roman emperors are still in service and many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centres. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; originally it was plumbum nigrum, where plumbum candidum was tin. The English word "plumbing" also derives from this Latin root.Lead is also very toxic, and lead poisoning was recognized even by the ancients. Similarly, in the Twentieth Century, the use of lead in paint pigments was sharply reduced because of the danger of lead poisoning, especially to children.[1][2][3] By the mid-1980s, a significant shift in lead end-use patterns had taken place. Much of this shift was a result of the U.S. lead consumers' compliance with environmental regulations that significantly reduced or eliminated the use of lead in nonbattery products, including gasoline, paints, solders, and water systems. Recently, lead use is being further curtailed by the European Union's RoHS directive. Lead may still be found in harmful quantities in stoneware, vinyl (such as that used for tubing and the insulation of electrical cords), and brass manufactured in China.
Occurrence
Native lead does occur in nature, but it is rare. Currently lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6% lead. Other common varieties are cerussite (PbCO3) and anglesite (PbSO4).Lead mining in Wales
Lead ore (galena) is found commonly in north-east Wales. The North-east Wales Orefield was by far the most important source of lead and zinc in Wales and second in national importance only to the North Pennine Orefield. Lead mining dates back to at least Roman times and continued until well into the 20th century. Galena is present in steeply-dipping fissure veins and in pipes and is in Mississippi Valley-type lead-zinc-fluorite and copper-dolomite associations. The mineralisation occurs in the upper parts of the Loggerheads and Cefn Mawr Formations of the Carboniferous Limestone.[4]Processing of metal from ore
The principal ores of lead are galena (PbS), anglesite (PbSO4), and cerussite (PbCO3). Most ores contain less than 10% lead, and ores containing as little as 3% lead can be economically exploited. Ores are crushed and concentrated by froth flotation typically to 70% or more. Sulfide ores are roasted, producing primarily lead oxide and a mixture of sulfates and silicates of lead and other metals contained in the ore.[5]Lead oxide from the roasting process is reduced in a coke-fired blast furnace.[6] This converts most of the lead to its metallic form. Three additional layers separate in the process and float to the top of the metallic lead. These are slag (silicates containing 1.5% lead), matte (sulfides containing 15% lead), and speiss (arsenides of iron and copper). These wastes contain concentrations of copper, zinc, cadmium, and bismuth that can be recovered economically, as can their content of unreduced lead.<ref name="samans" />
Metallic lead that results from the roasting and blast furnace processes still contains significant contaminants of arsenic, antimony, bismuth, zinc, copper, silver, and gold. The melt is treated in a reverberatory furnace with air, steam, and sulfur, which oxidizes the contaminants except silver, gold, and bismuth. The oxidized contaminants are removed by drossing, where they float to the top and are skimmed off.<ref name="samans" />[7]
Most lead ores contain significant concentrations of silver, resulting in the smelted metal also containing silver as a contaminant. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process.<ref name="pauling" /><ref name="samans" /><ref name="leadorg" />
Desilvered lead is freed of bismuth according to the Betterton-Kroll process by treating it with metallic calcium and magnesium, which forms a bismuth dross that can be skimmed off.<ref name="samans" />[7]
Very pure lead can be obtained by processing smelted lead electolytically by means of the Betts process. The process uses anodes of impure lead and cathodes of pure lead in an electrolyte of silica fluoride.<ref name="samans" /><ref name="leadorg" />
Production and Recycling
Worldwide production and consumption of lead is increasing. Total annual production is about 8 million tonnes; about half is produced from recycled scrap. The main countries are Australia, China and the US, which account for more than half of primary production. The most common lead ore is galena or lead sulphide.[8]- Annual Metal Production (2006): 7918 Thousand tonnes [9]
- Annual Mine Production (2006): 3442 Thousand tonnes (lead content)
Isotopes
Health effects
Lead is a poisonous metal that can damage nervous connections (especially in young children) and cause blood and brain disorders. Long term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. The concern about lead's role in cognitive deficits in children has brought about widespread reduction in its use (lead exposure has been linked to schizophrenia). The majority of cases of adult elevate blood lead levels are workplace-related.[10]Many older houses may still contain substantial amounts of lead paint. White lead paint has been withdrawn from sale in industrialized countries, but the yellow lead chromate is still in use; for example, Holland Colours Holcolan Yellow. It is generally recommended that old paint should not be stripped by sanding, as this generates inhalable dust.
Lead salts used in pottery glazes have on occasion caused poisoning, when acid drinks, such as fruit juices, have leached lead ions out of the glaze. It has been suggested that what was known as "Devon colic" arose from the use of lead-lined presses to extract apple juice in the manufacture of cider. Lead is considered to be particularly harmful for women's ability to reproduce. For that reason many universities do not hand out lead-containing samples to women for instructional laboratory analyses. Lead acetate (also known as sugar of lead) was used by the Roman Empire as a sweetener for wine, and some consider this to be the cause of the dementia which affected many of the Roman Emperors. [11]
Lead as a soil contaminant is a widespread issue, since lead may enter soil through (leaded) gasoline leaks from underground storage tanks or through a wastestream of lead paint or lead grindings from certain industrial operations.
Biochemistry of lead poisoning
In medicine, lead inhibits α-aminolevulinate (ALA) dehydratase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, the final step in heme synthesis. Inhibition of both of these steps results in ineffective heme synthesis and subsequent microcytic (hemoglobin-poor) anemia.Leaching of lead from metal surfaces
In a Pourbaix diagram the acidity is plotted on the x axis using the pH scale, while how oxidising/reducing nature of the system is plotted on the y axis in terms of volts relative to the standard hydrogen electrode. The diagram shows the form of the element which is most chemically stable at each point, it only comments on thermodynamics and it says nothing about the rate of change (kinetics).
Descriptive chemistry
Various oxidized forms of lead are easily reduced to the metal. An example is heating PbO with mild organic reducing agents such as glucose. A mixture of the oxide and the sulfide heated together without any reducing agent will also form the metal.[12]- :2PbO + PbS → 3 Pb + SO2
Metallic lead is attacked only superficially by air, forming a thin layer of oxide that protects it from further oxidation. The metal is not attacked by sulfuric or hydrochloric acids. It does, however, dissolve in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO3)2.
- :3 Pb + 8 H+ + 8 NO3– → 3 Pb2+ + 6 NO3– + 2 NO + 4H2O
When heated with nitrates of alkali metals, metallic lead oxidizes to form PbO (also known as litharge), leaving the corresponding alkali nitrite. PbO is representative of lead's II oxidation state. It is soluble in nitric and acetic acids, from which solutions it is possible to precipitate halide, sulfate, chromate, carbonate (PbCO3), and basic carbonate (Pb3(OH)2(CO3)2) salts of lead. The sulfide can also be precipitated from acetate solutions. These salts are all poorly soluble in water. Among the halides, the iodide is less soluble than the bromide, which, in turn, is less soluble than the chloride.[13]
The II oxide is also soluble in alkali hydroxide solutions to form the corresponding plumbite salt.<ref name="pauling" />
- :PbO + 2OH– + H2O → Pb(OH)42–
Chlorination of plumbite solutions causes the formation of lead's IV oxidation state.
- :Pb(OH)42– + Cl2 → PbO2 + 2 Cl– + 2 H2O
Lead dioxide is representative of the IV state, and is a powerful oxidizing agent. The chloride of this oxidation state is formed only with difficulty and decomposes readily into the II chloride and chlorine gas. The bromide and iodide of IV lead are not known to exist.<ref name="brady_holum" /> Lead dioxide dissolves in alkali hydroxide solutions to form the corresponding plumbates.<ref name="pauling" />
- :PbO2 + 2 OH– + 2 H2O → Pb(OH)62–
Lead also has an oxide that is a hybrid between the II and IV oxidation states. Red lead (also called minium) is Pb3O4.
Lead readily forms an equimolar alloy with sodium metal that reacts with alkyl halides to form organometallic compounds of lead such as tetraethyl lead.[14]
Chloride complexes
Lead(II) forms a series of complexes with chloride, the formation of which alters the corrosion chemistry of the lead. This will tend to limit the solubility of lead in saline media.Equilibrium constants for aqueous lead chloride complexes at 25°C[16] Pb2+ + Cl– → PbCl+ K1 = 12.59 PbCl+ + Cl− → PbCl20 K2 = 14.45 PbCl20 + Cl− → PbCl3− K3 = 3.98 ×10−1 PbCl3− + Cl− → PbCl42− K4 = 8.92 × 10−2
Phase diagrams of solubilities
Lead(II) sulphate is poorly soluble, as can be seen in the following diagram showing addition of SO42− to a solution containing 0.1M of Pb2+. The pH of the solution is 4.5, as above that, Pb2+ concentration can never reach 0.1M due to the formation of Pb(OH)2. Observe that Pb2+ solubility drops 10,000 fold as SO42− reaches 0.1M
Here it can be seen that the addition of chloride can lower the solubility of lead, however in very chloride rich media (such as aqua regia) the lead can become soluble again as anionic chlorocomplexes.
The Pourbaix diagram on the right is for a moderate concentration (0.1 M) of chloride.
Applications
- Lead is a major constituent of the lead-acid battery used extensively in car batteries.
- Lead is used as a coloring element in ceramic glazes, notably in the colors red and yellow.
- Lead is used as projectiles for firearms and fishing sinkers because of its density, low cost compared to alternative products and ease of use due to relatively low melting point.[17]
- Lead is used in some candles to treat the wick to ensure a longer, more even burn. Because of the dangers, European and North American manufacturers use more expensive alternatives such as zinc.[18]
- Lead is used as shielding from radiation.
- Molten lead is used as a coolant, eg. for lead cooled fast reactors.
- Lead glass is composed of 12-28% lead oxide. It changes the optical characteristics of the glass and reduces the transmission of radiation.
- Lead is the traditional base metal of organ pipes, mixed with varying amounts of tin to control the tone of the pipe.
- Lead is used as electrodes in the process of electrolysis.
- Lead is used in solder for electronics, although this usage is being phased out by some countries to reduce the amount of environmentally unfriendly waste.
- Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulation.
- Lead is used for the ballast keel of sailboats. Its high weight-to-volume ratio allows it to counterbalance the heeling effect of wind on the sails while at the same time occupying a small volume and thus offering the least underwater resistance.
- Lead is added to brass to reduce machine tool wear.
- Lead sheets are used as roofing material.
- Lead is frequently used in scuba diving weight belts to counteract the diver's natural buoyancy and that of his equipment.
- Lead is often used to balance the wheels of a car; this use is being phased out in favor of other materials for environmental reasons.
- Lead is still widely used today in statues and sculptures.
Former applications
- Lead was used as a pigment in lead paint for white as well as yellow and red colors. It was discontinued because of the dangers of lead poisoning. However, lead chromate is still in use.
- Lead was used for plumbing in Ancient Rome
- Lead was used as a preservative for food and drink in Ancient Rome.
- Lead was used for joining cast iron water pipes and used as a material for small diameter water pipes until the early 1970s.
- Tetraethyl lead was used in leaded fuels to reduce engine knocking; however, this is no longer common practice in the Western world due to health concerns.[19]
- Lead was used to make bullets for slings.
- Lead was formerly used as a component of toys, though due to many toy safety regulations, this has been stopped.
- Lead was used in car body filler, which was used in many custom cars in the 1940s-60's. Hence the term Leadsled.
- Lead is a superconductor at 7.2 K and IBM tried to make a Josephson Effect Computer out of lead-alloy.[20]
Phrases
A "lead pipe cinch" is something that is absolutely certain. In the 19th century a horse saddle was safe when it was well "cinched". The "lead pipe" qualifier is an obscure "intensifier"[22].See also
Literature
- Keisch, B., Feller, R. L., Levine, A. S., and Edwards, R. R.: Dating and Authenticating Works of Art by Measurement of Natural Alpha Emitters. In: Science, 155, No. 3767, p. 1238-1242, 1967.
- Keisch, B: Dating Works of Art Through their Natural Radioactivity: Improvements and Applications. In: Science, 160, p. 413-415, 1968.
- Keisch, B: Discriminating Radioactivity Measurements of Lead: New Tool for Authentication. In: Curator, 11, No. 1., p. 41-52, 1968.
References
1. ^ NSW Multicultural Health Communication Service. NSW Health. Retrieved on 7 April 2007.
2. ^ Download: Lead paint: Cautionary note. Queensland Government. Retrieved on 7 April 2007.
3. ^ Lead Paint Information. Master Painters, Australia. Retrieved on 7 April 2007.
4. ^ Davies, J.R., Wilson, D. & Williamson, I.T. (2004). The geology of the country around Flint. Memoir of the British Geological Survey, Sheet 108. (England and Wales). British Geological Survey, Keyworth.
5. ^ Samans, Carl H. Engineering Metals and their Alloys MacMillan 1949
6. ^ Primary Extraction of Lead Technical Notes. LDA International. Retrieved on 7 April 2007.
7. ^ Primary Lead Refining Technical Notes. LDA International. Retrieved on 7 April 2007.
8. ^ Lead Information. LDA International. Retrieved on 2007-09-05.
9. ^ Lead Statistics. International Lead and Zinc Study Group. Retrieved on 2007-09-05.
10. ^ NIOSH ABLES. United States National Institute for Occupational Safety and Health. Retrieved on 2007-10-04.
11. ^ The Pernicious Allure of Lead. New York Times.
12. ^ Pauling, Linus General Chemistry, W.H. Freeman 1947 ed.
13. ^ Brady, James E. and Holum, John R. Descriptive Chemistry of the Elements John Wiley and Sons
14. ^ Merck Index of Chemicals and Drugs, 9th ed., monograph 8393
15. ^ Ignasi Puigdomenech, Hydra/Medusa Chemical Equilibrium Database and Plotting Software (2004) KTH Royal Institute of Technology, freely downloadable software at [1]
16. ^ Ward, C.H.; Hlousek, Douglas A.; Phillips, Thomas A.; Lowe, Donald F. (2000). Remediation of Firing Range Impact Berms. CRC Press. ISBN 1566704626.
17. ^ Dr. Rooney, Corinne. Contamination at Shooting Ranges. The Lead Group, incorporated. Retrieved on 7 April 2007.
18. ^ Randerson, James (June 2002). "Candle pollution". NewScientist.com (2348). Retrieved on 2007-04-07.
19. ^ Countries where Leaded Petrol is Possibly Still Sold for Road Use, as of 22nd February 2007. The Lead Group, incorporated. Retrieved on 7 April 2007.
20. ^ Henkels, W. H.; Geppert, L. M.; Kadlec, J.; Epperlein, P. W.; Beha, H. (September 1985). Josephson 4 K-bit cache memory design for a prototype signal processor.. Harvard University. Retrieved on 7 April 2007.
21. ^ A history of pencils. www.pencils.com. Retrieved on 7 April 2007.
22. ^ Quinion, Michael. lead pipe chich. World Wide Words. Retrieved on 2007-02-19.
External links
- Case Studies in Environmental Medicine - Lead Toxicity
- ToxFAQs™: Lead
- National Pollutant Inventory - Lead and compounds fact sheet
- WebElements.com - Lead
- The Lead Education and Abatement Design Group (Australia)
- International Lead & Zinc Study Group
- International Lead Management Center
- Lead Development Association International
- Do lead fishing sinkers threaten the environment? (from The Straight Dope)
- A Small Dose of Toxicology:Lead. A Small Dose Of.... Retrieved on 7 April 2007.
- Lead. Los Alamos National Laboratory. Retrieved on 7 April 2007.
- NIST's X-Ray Mass Attenuation Coefficients - Lead. NIST. Retrieved on 7 April 2007.
- Jennifer B. McKim, Keith Sharon and William Heisel. "Scandal involving lead-laced Mexican candy being eaten by children in California", Orange Counter Register, 25-04-2004. Retrieved on 2007-04-07.
- Darshak Sanghavi, "Getting the Lead Out: If only it was as easy as recalling the Mattel toys", Slate magazine, August 21, 2007
- National Institute for Occupational Safety and Health - ABLES Page
Lead can have several meanings and pronunciations, usually related to either the chemical element lead or the verb to lead.Meanings associated with the chemical element
All of these meanings are pronounced
..... Click the link for more information.1
(mildly basic oxide)
Electronegativity 1.62 (scale Pauling)
Ionization energies 1st: 589.4 kJ/mol
2nd: 1971 kJ/mol
3rd: 2878 kJ/mol
Atomic radius 190 pm
Atomic radius (calc.
..... Click the link for more information.3, 5
(mildly acidic oxide)
Electronegativity 2.02 (scale Pauling)
Ionization energies
(more) 1st: 703 kJmol−1
2nd: 1610 kJmol−1
3rd: 2466 kJmol−1
..... Click the link for more information.TIN may refer to:- Tax identification number
- Triangulated irregular network, a data structure used in a geographic information systems
See also
- Tin
This article is about the metallic chemical element.
..... Click the link for more information.Ununquadium (IPA: /ˌjuːˌnʌnˈkwɒdiəm/), or eka-lead, is the temporary name of a radioactive chemical element in the periodic table that has the temporary symbol Uuq and has the atomic
..... Click the link for more information.
..... Click the link for more information.<onlyinclude> This is a list of chemical elements, sorted by name and color coded according to type of element.
Given is each element's element symbol, atomic number, atomic mass or most stable isotope, and group and period numbers on the periodic table.
..... Click the link for more information.<onlyinclude> This is a list of chemical elements by symbol, including the current signification used to identify the chemical elements as recognized by the International Union of Pure and Applied Chemistry, as well as proposed and historical signs.
..... Click the link for more information.A table of chemical elements ordered by atomic number and color coded according to type of element. Given is each element's name, element symbol, group and period, Chemical series, and atomic mass (or most stable isotope).
..... Click the link for more information.A group, also known as a family, is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table.
The modern explanation of the pattern of the periodic table is that the elements in a group have similar
..... Click the link for more information.The trivial name poor metals (or post-transition metals) is sometimes applied to the metallic elements in the p-block of the periodic table. Their melting and boiling points are generally lower than those of the transition metals and their electronegativity higher, and they
..... Click the link for more information.The trivial name poor metals (or post-transition metals) is sometimes applied to the metallic elements in the p-block of the periodic table. Their melting and boiling points are generally lower than those of the transition metals and their electronegativity higher, and they
..... Click the link for more information.A group, also known as a family, is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table.
The modern explanation of the pattern of the periodic table is that the elements in a group have similar
..... Click the link for more information.Periods:]] 1 2 3 4 5 6 7 8
Series Alkalis Alkaline earths Lanthanides Actinides Transition metals Poor metals Metalloids Nonmetals Halogens Noble gases
..... Click the link for more information.A block of the periodic table of elements is a set of adjacent groups. The respective highest-energy electrons in each element in a block belong to the same atomic orbital type.
..... Click the link for more information.The carbon group is group 14 (IUPAC style) in the periodic table. Once also known as the tetrels (from Latin tetra, four), stemming from the earlier naming convention of this group as Group IVB.
..... Click the link for more information.A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the elements, including the lanthanides.
These are: Chemical elements in the sixth period
Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
#
..... Click the link for more information.The p-block of the periodic table of the elements consists of the last six groups minus helium (which is located in the s-block). In the elemental form of the p-block elements, the highest energy electron occupies a p-orbital.
..... Click the link for more information.Color or colour[1] (see spelling differences) is the visual perceptual property corresponding in humans to the categories called red, yellow, blue, black, etc.
..... Click the link for more information.atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units.[1] The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom (when the atom is motionless).
..... Click the link for more information.To help compare different orders of magnitude, the following list describes various mass levels between 10−36 kg and 1053 kg.
Factor (kg) Value Item
10−36 1.
..... Click the link for more information.This is a list of chemical elements, sorted by relative atomic mass, or more precisely the standard atomic weights, (most stable isotope for artificial elements) and color coded according to type of element.
..... Click the link for more information.electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (e.g., a crystal). Like other elementary particles, the electron is subject to the laws of quantum mechanics, and exhibits both particle-like and wave-like nature.
..... Click the link for more information.Xenon (IPA: /ˈzɛnɒn, ˈziːnɒn/) is a chemical element that has the symbol Xe and atomic number 54.
..... Click the link for more information.Electron
Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
..... Click the link for more information.An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n. Electron shells are made up of one or more electron subshells, or sublevels
..... Click the link for more information.In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
..... Click the link for more information.A solid object is in the states of matter characterized by resistance to deformation and changes of volume. At the microscopic scale, a solid has these properties :- The atoms or molecules that comprise the solid are packed closely together.
..... Click the link for more information.In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
..... Click the link for more information.Room temperature (also referred to as ambient temperature) is a common term to denote a certain temperature within enclosed space at which human beings are accustomed.
..... Click the link for more information.
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