View source for Lead

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|{{Elementbox_header | number=82 | symbol=Pb | name=lead | left=[[thallium]] | right=[[bismuth]] | above=[[tin|Sn]] | below=[[ununquadium|Uuq]] | color1=#cccccc | color2=black }}
{{Elementbox_series | [[Post-transition metal]]s or [[poor metal]]s }}
{{Elementbox_groupperiodblock | group=14 | period=6 | block=p }}
{{Elementbox_appearance_img | Lead brick| bluish gray }}
{{Elementbox_atomicmass_gpm | 207.2[[List of elements by atomic mass|(1)]] }}
{{Elementbox_econfig | &#91;[[xenon|Xe]]&#93; 4f<sup>14</sup> 5d<sup>10</sup> 6s² 6p² }}
{{Elementbox_epershell | 2, 8, 18, 32, 18, 4 }}
{{Elementbox_section_physicalprop | color1=#cccccc | color2=black }}
{{Elementbox_phase | [[solid]] }}
{{Elementbox_density_gpcm3nrt | 11.34 }}
{{Elementbox_densityliq_gpcm3mp | 10.66 }}
{{Elementbox_meltingpoint | k=600.61 | c=327.46 | f=621.43 }}
{{Elementbox_boilingpoint | k=2022 | c=1749 | f=3180 }}
{{Elementbox_heatfusion_kjpmol | 4.77 }}
{{Elementbox_heatvaporiz_kjpmol | 179.5 }}
{{Elementbox_heatcapacity_jpmolkat25 | 26.650 }}
{{Elementbox_vaporpressure_katpa | 978 | 1088 | 1229 | 1412 | 1660 | 2027 | comment= }}
{{Elementbox_section_atomicprop | color1=#cccccc | color2=black }}
{{Elementbox_crystalstruct | cubic face centered }}
{{Elementbox_oxistates | 4, '''2'''<br />([[Amphoterism|Amphoteric]] oxide) }}
{{Elementbox_electroneg_pauling | 2.33 }}
{{Elementbox_ionizationenergies4 | 715.6 | 1450.5 | 3081.5 }}
{{Elementbox_atomicradius_pm | 180 }}
{{Elementbox_atomicradiuscalc_pm | 154 }}
{{Elementbox_covalentradius_pm | 147 }}
{{Elementbox_vanderwaalsrad_pm | 202 }}
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{{Elementbox_magnetic | [[diamagnetism|diamagnetic]] }}
{{Elementbox_eresist_ohmmat20 | 208 n}}
{{Elementbox_thermalcond_wpmkat300k | 35.3 }}
{{Elementbox_thermalexpansion_umpmkat25 | 28.9 }}
{{Elementbox_speedofsound_rodmpsatrt | (annealed)<br />1190 }}
{{Elementbox_youngsmodulus_gpa | 16 }}
{{Elementbox_shearmodulus_gpa | 5.6 }}
{{Elementbox_bulkmodulus_gpa | 46 }}
{{Elementbox_poissonratio | 0.44 }}
{{Elementbox_mohshardness | 1.5 }}
{{Elementbox_brinellhardness_mpa | 38.3 }}
{{Elementbox_cas_number | 7439-92-1 }}
{{Elementbox_isotopes_begin | color1=#cccccc | color2=black }}
{{Elementbox_isotopes_decay | mn=204 | sym=Pb
 | na=1.4% | hl=>1.4×10<sup>17</sup> [[year|y]]
 | dm=[[alpha emission|Alpha]] | de=2.186 | pn=200 | ps=[[mercury (element)|Hg]] }}
{{Elementbox_isotopes_decay | mn=205 | sym=Pb
 | na=[[synthetic radioisotope|syn]] | hl=1.53×10<sup>7</sup> [[year|y]]
 | dm=[[Electron capture|Epsilon]] | de=0.051 | pn=205 | ps=[[thallium|Tl]] }}
{{Elementbox_isotopes_stable | mn=206 | sym=Pb | na=24.1% | n=124 }}
{{Elementbox_isotopes_stable | mn=207 | sym=Pb | na=22.1% | n=125 }}
{{Elementbox_isotopes_stable | mn=208 | sym=Pb | na=52.4% | n=126 }}
{{Elementbox_isotopes_decay2 | mn=210 | sym=Pb
 | na=[[Trace radioisotope|trace]] | hl=22.3 [[year|y]]
 | dm1=[[alpha emission|Alpha]] | de1=3.792 | pn1=206 | ps1=[[mercury (element)|Hg]]
 | dm2=[[Beta emission|Beta]] | de2=0.064 | pn2=210 | ps2=[[bismuth|Bi]] }}
{{Elementbox_isotopes_end}}
{{Elementbox_footer | color1=#cccccc | color2=black }}
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|[[Image:Lead pipe Bath.jpg|thumb|150px|Lead pipe in Roman baths]]
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'''Lead''' ({{pronEng|ˈlɛd}}) is a transitional [[element]] with a symbol '''Pb''' ({{lang-la|plumbum}}). Lead has the [[atomic number]] 82. Lead is a soft, [[malleable]] [[poor metal]], also considered to be one of the [[heavy metal (chemistry)|heavy metals]]. Lead has a bluish white color when freshly cut, but tarnishes to a dull grayish color when it is exposed to air and is a shiny chrome silver when melted into a liquid. Lead is used in building construction, [[lead-acid battery|lead-acid batteries]], [[bullet]]s and  [[lead shot|shot]], weights, and is part of [[solder]], [[pewter]], and fusible [[alloy]]s. Lead has the highest [[atomic number]] of all [[stable element]]s, although the next element, [[bismuth]], has a half-life so long (longer than the estimated age of the universe) it can be considered stable. Like [[mercury (element)|mercury]], another heavy metal, lead is a potent [[neurotoxin]] that accumulates in soft tissues and bone over time.

== Notable characteristics == 
Lead has a dull luster and is a [[density|dense]], [[ductile]], very soft, highly malleable, bluish-white metal that has poor [[electrical conductivity]]. This true metal is highly resistant to [[corrosion]], and because of this property, it is used to contain corrosive liquids (e.g. [[sulfuric acid]]). Because lead is very malleable and resistant to corrosion it is extensively used in building construction e.g. external coverings of roofing joints.  Lead can be toughened by adding a small amount of [[antimony]] or other metals to it.  It is a common misconception that lead has a zero [[Thermoelectric effect#Thomson effect|Thomson effect]].  All lead, except <sup>204</sup>Pb, is the end product of a complex radioactive decay (see isotopes of lead below).  Lead is also [[lead poisoning|poisonous]].

== 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 [[smelting|smelt]]. In the early [[Bronze Age]], lead was used with [[antimony]] and [[arsenic]].  Lead was mentioned in the [[Exodus|Book of Exodus]] (15:10). [[Image:Hook-and-cross black.svg|thumb|left|130px|A stylistic variation of the [[Alchemical symbol]] for lead, also used for the [[Blue Öyster Cult]] logo]] In [[alchemy]], lead was thought to be the oldest metal and was associated 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. The Romans also used lead in molten form to secure iron pins that held together large [[limestone]] blocks in certain monumental buildings.  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 words "plumbing" and "[[plumb-bob]]" also derive from this Latin root.

Lead also refers collectively to the organic and inorganic compounds of lead, which are toxic. [[Lead poisoning]] was documented in ancient Rome, Greece, and China. In the 20th century, the use of lead in paint [[pigment]]s was sharply reduced because of the danger of lead poisoning, especially to children.<ref>{{cite web|url=http://www.health.nsw.gov.au/health-public-affairs/mhcs/publications/4465.html|title=NSW Multicultural Health Communication Service|accessdaymonth=7 April|accessyear=2007|publisher=NSW Health}}</ref><ref>{{cite web|url=http://www.epa.qld.gov.au/publications?id=1528|title=Download: Lead paint: Cautionary note|accessdaymonth=7 April|accessyear=2007|publisher=Queensland Government}}</ref><ref>{{cite web|url=http://www.qld.mpa.org.au/index.php/content/33/|title=Lead Paint Information|accessdaymonth=7 April|accessyear=2007|publisher=Master Painters, Australia}}</ref> 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 non-battery products, including [[gasoline]], paints, solders, and water systems.  Lead use is being further curtailed by the European Union's [[Restriction of Hazardous Substances Directive|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. Between 2006 and 2007 many children's toys made in China were recalled, primarily due to lead in paint used to color the product.

== Occurrence ==
Metallic lead does occur in nature, but it is rare.  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]] (PbCO<sub>3</sub>) and [[anglesite]] (PbSO<sub>4</sub>). 

===Sources of Lead===

Top lead producing countries (2008) are Australia, China, USA, Peru, Canada, Mexico, Sweden, Morocco,  South Africa and North Korea.<ref name="leadorg">{{cite web|url=http://www.infomine.com/commodities/lead.asp|title=Global InfoMine - Lead Mining|publisher=GlobalInfoMine|accessdaymonth=17 April|accessyear=2008}}</ref>

===Lead mining in Wales===
Lead ore (galena) is found commonly in northeast Wales. The Northeast 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 [[Carbonate hosted lead zinc ore deposits|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.<ref name="davies">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.</ref>

===Processing of metal from ore===
[[Image:LeadOreUSGOV.jpg|thumb|left|Lead ore]]
The principal ores of lead are [[galena]] (PbS), [[anglesite]] ({{chem|Pb||S||O|4|}}) and [[cerussite]] (PbCO<sub>3</sub>). 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 [[Roasting (metallurgy)|roasted]], producing primarily lead oxide and a mixture of [[sulfates]] and [[silicates]] of lead and other metals contained in the ore.<ref name="samans">Samans, Carl H. ''Engineering Metals and their Alloys'' MacMillan 1949</ref>

Lead oxide from the roasting process is reduced in a coke-fired blast furnace.<ref name="leadorg1">{{cite web|url=http://www.ldaint.org/technotes1.htm|title=Primary Extraction of Lead Technical Notes|publisher=LDA International|accessdaymonth=7 April|accessyear=2007}}</ref> 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 (metallurgy)|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 [[dross]]ing, where they float to the top and are skimmed off.<ref name="samans" /><ref name="leadorg">{{cite web|url=http://www.ldaint.org/technotes2.htm|title=Primary Lead Refining Technical Notes|publisher=LDA International|accessdaymonth=7 April|accessyear=2007}}</ref>

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" /><ref name="leadorg"/>

Very pure lead can be obtained by processing smelted lead electolytically by means of the [[Betts electrolytic process|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 sulfide.<ref name="ldaint">{{cite web|url=http://www.ldaint.org/information.htm|title=Lead Information|publisher=LDA International|accessdate=2007-09-05}}</ref>
* Annual Metal Production (2006): 7918 Thousand tonnes<ref name="ilzsg">{{cite web|url=http://www.ilzsg.org/statistics.asp?pg=lead|title=Lead Statistics|publisher=International Lead and Zinc Study Group|accessdate=2007-09-05}}</ref>
* Annual Mine Production (2006): 3442 Thousand tonnes (lead content)

At current use rates, the supply of lead is estimated to run out in 42 years.<ref>{{cite journal | date=[[May 26]], [[2007]] | journal = New Scientist  | volume = 194 | issue = 2605  | pages = 38&ndash;39  | issn = 0262 4079 | title = How Long Will it Last? }}</ref> Environmental analyst, [[Lester Brown]], however, has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.<ref name="Brown">{{cite book|author=Brown, Lester|title=Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble|publisher=New York: W.W. Norton|date=2006|page=109|isbn=0393328317}}</ref> This may need to be reviewed to take account of renewed interest in [[recycling]], and rapid progress in [[fuel cell]] technology.

==Isotopes==
{{main|Isotopes of lead}}
[[Lead]] has seven [[isotopes]] in total (3 stable, 3 unstable 1 radiogenic). The 3 stable isotopes are <sup>206</sup>Pb, <sup>207</sup>Pb, & <sup>208</sup>Pb, and the 3 unstable isotopes are  <sup>204</sup>Pb, <sup>205</sup>Pb, & <sup>210</sup>Pb, along with one common [[radiogenic isotope]] <sup>202</sup>Pb with a [[half-life]] of ~53,000 years.

==Health effects==
{{Mainarticle|Lead poisoning}}

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 PbO<sub>2</sub>) 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]]). Most cases of adult elevated blood lead levels are workplace-related.<ref>{{cite web|url= http://www.cdc.gov/niosh/topics/ABLES/ables-description.html |title=NIOSH ABLES|accessdate=2007-10-04|publisher=United States National Institute for Occupational Safety and Health}}</ref> High blood levels are associated with delayed puberty in girls.<ref>[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1742-7843.2007.00180.x Endocrine Disruptors and Abnormalities of Pubertal Development], Schoeters G, ''et al''. Basic & Clinical Pharmacology & Toxicology, 102, 168–175, 2008</ref>

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. Old paint should not be stripped by sanding, as this produces 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]] that affected many of the Roman Emperors.<ref>{{cite web|url=http://www.nytimes.com/2007/08/21/science/21angi.html?_r=1&oref=slogin|title=The Pernicious Allure of Lead|publisher=New York Times}} </ref>

Lead as a [[soil contaminant]] is a widespread issue, since lead is present in natural deposits and may also enter soil through (leaded) gasoline leaks from [[underground storage tank]]s or through a wastestream of lead paint or lead grindings from certain industrial operations.

===Biochemistry of lead poisoning===
In the human body, 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.  This causes ineffective heme synthesis and subsequent [[microcytic anemia]].

===Leaching of lead from metal surfaces===
{| align="right"
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[[Image:Pb in water Pourbiax diagram.png|thumb|right|240px|The [[Pourbaix diagram]] for lead in a non-complexing aqueous medium (eg [[perchloric acid]] / sodium hydroxide)<ref name="medusa"/>]]
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[[Image:Pb in citrate media pourbiax diagram.png|thumb|right|240px|The [[Pourbaix diagram]] for lead in citric acid/citrate<ref name="medusa"/>]]
|}
It is clear from the [[Pourbaix diagram]] below that lead is more likely to corrode in a citrate medium than it is in a non-complexing medium. The central part of the diagram shows that lead metal is more easy to oxidise in the citrate medium than it is in normal water.

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]]).<br clear="all">

==Descriptive chemistry==
{{seealso|Category:Lead compounds}}
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.<ref name="pauling">Pauling, Linus ''General Chemistry'', W.H. Freeman 1947 ed.</ref>

::2PbO + PbS &nbsp; → &nbsp; 3 Pb + SO<sub>2</sub>

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 acid|sulfuric]] or [[hydrochloric acid|hydrochloric]] acids. It does, however, dissolve in [[nitric acid]] with the evolution of [[nitric oxide]] gas to form dissolved [[lead(II) nitrate|Pb(NO<sub>3</sub>)<sub>2</sub>]].

::3 Pb + 8 H<sup>+</sup> + 8 NO<sub>3</sub><sup>–</sup> &nbsp; → &nbsp; 3 Pb<sup>2+</sup> + 6 NO<sub>3</sub><sup>–</sup> + 2 NO + 4H<sub>2</sub>O

When heated with [[nitrate]]s of alkali metals, metallic lead oxidizes to form [[lead(II) oxide|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 acid|acetic]] acids, from which solutions it is possible to precipitate [[halide]], [[lead sulfate|sulfate]], [[lead chromate|chromate]], [[lead carbonate|carbonate]] (PbCO<sub>3</sub>), and basic carbonate ({{chem|Pb|3|(OH)|2|(CO|3|)|2|)}} salts of lead. The [[lead sulfide|sulfide]] can also be precipitated from [[lead acetate|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.<ref name="brady_holum">Brady, James E. and Holum, John R. ''Descriptive Chemistry of the Elements'' John Wiley and Sons</ref>

The II oxide is also soluble in [[alkali metal|alkali]] [[hydroxide]] solutions to form the corresponding [[plumbite]] salt.<ref name="pauling" />

::PbO + 2OH<sup>–</sup> + H<sub>2</sub>O &nbsp; → &nbsp; Pb(OH)<sub>4</sub><sup>2–</sup>

[[Chlorination]] of plumbite solutions causes the formation of lead's IV oxidation state.

::Pb(OH)<sub>4</sub><sup>2–</sup> + Cl<sub>2</sub> &nbsp; → &nbsp; PbO<sub>2</sub> + 2 Cl<sup>–</sup> + 2 H<sub>2</sub>O

[[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 [[plumbate]]s.<ref name="pauling" />

::PbO<sub>2</sub> + 2 OH<sup>–</sup> + 2 H<sub>2</sub>O &nbsp; → &nbsp; Pb(OH)<sub>6</sub><sup>2–</sup>

Lead also has an oxide that is a hybrid between the II and IV oxidation states. [[Red lead]] (also called minium) is Pb<sub>3</sub>O<sub>4</sub>.

Lead readily forms an equimolar alloy with [[sodium]] metal that reacts with [[alkyl halide]]s to form [[organometallic]] compounds of lead such as [[tetraethyl lead]].<ref>''Merck Index of Chemicals and Drugs'', 9th ed., monograph 8393</ref>

===Chloride complexes===
[[Image:Lead complexes in chloride media.png|thumb|right|240px|Diagram showing the forms of lead in chloride media<ref name="medusa">Ignasi Puigdomenech, ''Hydra/Medusa Chemical Equilibrium Database and Plotting Software'' (2004) KTH Royal Institute of Technology, freely downloadable software at [http://www.kemi.kth.se/medusa/]</ref>]]
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.

:{|
|- bgcolor="#D0D0F0"
|colspan="3"| Equilibrium constants for aqueous lead chloride complexes at 25 °C<ref name="ward">{{cite book|title=Remediation of Firing Range Impact Berms|author=Ward, C.H.; Hlousek, Douglas A.; Phillips, Thomas A.; Lowe, Donald F.|isbn=1566704626|date=2000|publisher=CRC Press}}</ref>
|-
|Pb<sup>2+</sub> + Cl<sup>–</sup> → PbCl<sup>+</sup>||&nbsp;&nbsp;&nbsp;&nbsp;||''K<sub>1</sub>'' = 12.59
|-
|PbCl<sup>+</sup> + Cl<sup>−</sup> → PbCl<sub>2</sub><sup>0</sup>|| ||''K<sub>2</sub>'' = 14.45
|-
|PbCl<sub>2</sub><sup>0</sup> + Cl<sup>−</sup> → PbCl<sub>3</sub><sup>−</sup>|| ||''K<sub>3</sub>'' = 3.98 ×10<sup>−1</sup>
|-
|PbCl<sub>3</sub><sup>−</sup> + Cl<sup>−</sup> → PbCl<sub>4</sub><sup>2−</sup>|| ||''K<sub>4</sub>'' = 8.92 × 10<sup>−2</sup>
|-
|}
<br clear="all">

===[[Phase diagrams]] of solubilities===
{| align="right"
|-
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[[Image:PbSO4 solubility graph.png|thumb|right|240px|Plot showing aqueous concentration of dissolved Pb<sup>2+</sub> as a function of SO<sub>4</sub><sup>2−</sup><ref name="medusa"/>]]
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[[Image:Lead sulphate pourdaix diagram.png|thumb|right|240px|Diagram for lead in sulfate media<ref name="medusa"/>]]
|}

Lead(II) sulfate is poorly soluble, as can be seen in the following diagram showing addition of SO<sub>4</sub><sup>2−</sup> to a solution containing 0.1M of Pb<sup>2+</sub>. The pH of the solution is 4.5, as above that, Pb<sup>2+</sup> concentration can never reach 0.1M due to the formation of Pb(OH)<sub>2</sub>. Observe that Pb<sup>2+</sup> solubility drops 10,000 fold as SO<sub>4</sub><sup>2−</sup> reaches 0.1M<br clear="all">

{| align="right"
|-
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[[Image:PbCl2 solubility graph.png|thumb|right|240px|Diagram showing the solubility of lead in chloride media. The lead concentrations are plotted as a function of the total chloride present.<ref name="medusa"/>]]
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[[Image:Lead chloride pourdiax diagram.png|thumb|right|240px|[[Pourbaix diagram]] for lead in chloride (0.1 M) media<ref name="medusa"/>]]
|}

Here it can be seen that the addition of chloride can lower the solubility of lead, however in 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.<br clear="all">

== 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 glaze]]s, notably in the colors red and yellow.
*Lead is used to form glazing bars for [[stained glass]] or other multi-lit windows. The practice has become less common, not for danger but for stylistic reasons.
*Lead is used as [[projectile]]s for [[firearm]]s and fishing [[sinker (fishing)|sinker]]s because of its density, low cost compared to alternative products and ease of use due to relatively low melting point.<ref>{{cite web|url=http://www.lead.org.au/fs/shootingranges.pdf|format=PDF| title=Contamination at Shooting Ranges|first=Corinne|last=Dr. Rooney|publisher=The Lead Group, incorporated|accessdaymonth=7 April|accessyear=2007}}</ref>
*Lead or "sheet-lead" is used as a sound deadening layer in such areas as wall, floor and ceiling design in sound studios where levels of airborne and mechanically produced sound are targeted for reduction or virtual elimination. 
*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.<ref>{{cite journal|url=http://www.newscientist.com/article/mg17423481.900-candle-pollution.html|journal=NewScientist.com|title=Candle pollution|first=James|last=Randerson|month=June|year=2002|accessdate=2007-04-07|issue=2348}}</ref>
*Lead is used as [[lead shielding| shielding]] from [[Ionizing radiation|radiation]], e.g. in [[x-ray]] rooms.
*Molten lead is used as a [[coolant]], eg. for [[lead cooled fast reactor]]s.
*[[Lead glass]] is composed of 12-28% [[Lead(II) oxide|lead oxide]]. It changes the optical characteristics of the glass and reduces the transmission of radiation.
*Lead is the traditional base metal of [[organ pipe]]s, 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 [[Sailing ballast|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 has many uses in the construction industry, e.g. lead sheets are used as roofing material, cladding, flashings, gutters and gutter joints, and on roof parapets. Detailed lead mouldings are used as decorative motifs used to fix lead sheet.
*Lead is frequently used in [[scuba diving]] [[diving weighting system|weight belts]] to counteract the diver's natural buoyancy and that of his equipment.
*Lead is often used to [[Tire balance|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 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 the hot metal used in [[hot metal typesetting]].
* Lead was used for [[plumbing]] in [[Ancient Rome]].
* Lead was used as a [[Food preservation|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 [[Gasoline#Lead|leaded fuel]]s to reduce [[engine knocking]]; however, this is no longer common practice in the [[Western world]] due to health concerns.<ref>{{cite web|url=http://www.lead.org.au/fs/fst27.html|publisher=The Lead Group, incorporated|accessdaymonth=7 April|accessyear=2007|title=Countries where Leaded Petrol is Possibly Still Sold for Road Use, as of 22nd February 2007}}</ref>
* Lead has been used to make "clubs" or bats more lethal by melting it into a hole drilled into the top
* Lead was used to make bullets for [[sling (weapon)|slings]].
* Lead was used as a component of toys.  Due to toy safety regulations, this use has been stopped in the United States.
* Lead was used in car body filler, which was used in many [[custom car]]s in the 1940s–60s. 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.<ref>{{cite web|url=http://adsabs.harvard.edu/abs/1985JAP....58.2371H|title=Josephson 4 K-bit cache memory design for a prototype signal processor.|author=Henkels, W. H.; Geppert, L. M.; Kadlec, J.; Epperlein, P. W.; Beha, H.|accessdaymonth=7 April|accessyear=2007|month=September|year=1985|publisher=Harvard University}}</ref>

Contrary to popular belief, pencil "leads" have never been made from lead. The term comes from the [[Ancient Rome|Roman]] stylus, called the ''penicillus'', which was made of lead.<ref>{{cite web|url=http://www.pencils.com/history.html|title=A history of pencils|accessdaymonth=7 April|accessyear=2007|publisher=www.pencils.com}}</ref> When the pencil originated as a wrapped graphite writing tool, the particular type of [[graphite]] being used was named ''plumbago'' (lit. "act for lead"; "leadmocku").

==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".<ref>{{cite web | last = Quinion | first = Michael | title = lead pipe cinch | | publisher = World Wide Words  |  url = http://www.worldwidewords.org/qa/qa-lea2.htm| accessdate = 2007-02-19 }}</ref>

A "lead pencil" is a leftover term from when the original [[pencil]]s were made from the only known deposit of [[graphite]] ever to be found in a pure, solid state, [[Grey Knotts]] in 16th century England.  The new material was assumed to be a form of lead.  Modern pencils use a marking core made of powdered, refined graphite mixed with clay, as has been the practice for centuries.

It is said that if one made a lead balloon, it would not fly. As lead is a very heavy element, it is presumed it will not fly. However, if one achieves the right size-to-weight ratio and uses [[helium]] instead of [[oxygen]] or [[air]], a lead balloon could fly. This was tested by the [[MythBusters]].

==Trivia==
The band [[Led Zeppelin]] was originally called '''''lead''' zeppelin''. Keith Moon and John Entwistle suggested that a possible supergroup containing themselves, Jimmy Page, and Jeff Beck would go down like a ''lead zeppelin'', a term Entwistle used to describe a bad gig.<ref name="Led Zeppelin A Story of a Band and their Music 1968-1980">{{cite book | title=Led Zeppelin The Story of a Band and their Music 1968-1980| year=2005| author=Keith Shadwick| pages=36, ISBN 100879308710}}</ref> The group deliberately dropped the 'a' in ''Lead'' at the suggestion of their manager, [[Peter Grant (music manager)|Peter Grant]], to prevent "thick Americans"<ref name="Hammer of the Gods"> {{cite book | title=Hammer of the Gods (LPC) | year=1995 | author=Stephen Davis | pages= 32, 44, 64, 190, 225, 277 ISBN 0330438591}}</ref> from pronouncing it as "''leed''".<ref name="Jimmy Page Online">[http://www.jimmypageonline.com/11318/42826.html Jimmy Page Online]</ref>

==See also==
* [[Adult Blood Lead Epidemiology and Surveillance]]
* [[Medical geology]]
* [[Plumbosolvency]]

== References ==
{{reflist}}

== Further reading ==
* 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.

== External links ==
* [http://www.atsdr.cdc.gov/csem/lead/ Case Studies in Environmental Medicine - Lead Toxicity]
* [http://www.atsdr.cdc.gov/tfacts13.html ToxFAQs: Lead]
* [http://www.npi.gov.au/database/substance-info/profiles/50.html National Pollutant Inventory - Lead and compounds fact sheet]
* [http://www.webelements.com/webelements/elements/text/Pb/index.html WebElements.com - Lead]
* [http://www.lead.org.au/ The Lead Education and Abatement Design Group (Australia)]
* [http://www.ilzsg.org/ilzsgframe.htm International Lead & Zinc Study Group]
* [http://www.ilmc.org/about.html International Lead Management Center]
* [http://www.ldaint.org/default.htm Lead Development Association International]
* [http://www.straightdope.com/mailbag/mfishsinkers.html Do lead fishing sinkers threaten the environment?] (from [[The Straight Dope]])
*{{cite web|url=http://www.asmalldoseof.org/toxicology/lead.php/|title=A Small Dose of Toxicology:Lead|publisher=A Small Dose Of...|accessdaymonth=7 April|accessyear=2007}}
*{{cite web|url=http://periodic.lanl.gov/elements/82.html|publisher=Los Alamos National Laboratory|title=Lead|accessdaymonth=7 April|accessyear=2007}}
*{{cite web|url=http://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html|title=NIST's X-Ray Mass Attenuation Coefficients - Lead|publisher=NIST|accessdaymonth=7 April|accessyear=2007}}
*{{cite news|url=http://www.ocregister.com/investigations/2004/lead/part1_printable.html|title=Scandal involving lead-laced Mexican candy being eaten by children in California|date=[[25-04]]-2004|author=Jennifer B. McKim, Keith Sharon and William Heisel|publisher=Orange Counter Register|accessdate=2007-04-07}}
*Darshak Sanghavi, [http://www.slate.com/id/2172544/pagenum/2/ "Getting the Lead Out: If only it was as easy as recalling the Mattel toys"], ''Slate'' magazine, August 21, 2007
* [http://www.cdc.gov/niosh/topics/ABLES/ables.html National Institute for Occupational Safety and Health - ABLES Page]
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[[Category:Chemical elements]]
[[Category:Soil contamination]]
[[Category:toxicology]]
[[Category:Coolants]]
[[Category:Lead]]
[[Category:Occupational safety and health]]
[[Category:Recyclable materials]]

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