Image of a racing car with lead room

Without lead room

With lead room

In photography, filmography and other visual arts, lead room, or sometimes nose room, is the space in front, and in the direction, of moving or stationary subjects.^[1][2] Well-composed shots leave space in the direction the subject is facing or moving.^[1] When the human eye scans a photograph for the first time it will expect to see a bit in front of the subject.^[3]

For example, moving objects such as cars require lead room.^[4] If extra space is allowed in front of a moving car, the viewer can see that it has someplace to go; without this visual padding, the car's forward progress will seem impeded.^[4]

See also[link]

Photography portal

• Headroom (photographic framing)
• Rule of thirds

References[link]

This photography-related article is a stub. You can help Wikipedia by expanding it. v t e

thallium ← lead → bismuth Sn ↑ Pb ↓ Fl 82Pb Periodic table
Appearance
Metallic gray
General properties
Name, symbol, number	lead, Pb, 82
Pronunciation	/ˈlɛd/ LED
Element category	post-transition metal
Group, period, block	14, 6, p
Standard atomic weight	207.2
Electron configuration	[Xe] 4f14 5d10 6s2 6p2
Electrons per shell	2, 8, 18, 32, 18, 4 (Image)
Physical properties
Phase	solid
Density (near r.t.)	11.34 g·cm−3
Liquid density at m.p.	10.66 g·cm−3
Melting point	600.61 K, 327.46 °C, 621.43 °F
Boiling point	2022 K, 1749 °C, 3180 °F
Heat of fusion	4.77 kJ·mol−1
Heat of vaporization	179.5 kJ·mol−1
Molar heat capacity	26.650 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 978 1088 1229 1412 1660 2027
Atomic properties
Oxidation states	4, 2 (Amphoteric oxide)
Electronegativity	2.33 (Pauling scale)
Ionization energies	1st: 715.6 kJ·mol−1
	2nd: 1450.5 kJ·mol−1
	3rd: 3081.5 kJ·mol−1
Atomic radius	175 pm
Covalent radius	146±5 pm
Van der Waals radius	202 pm
Miscellanea
Crystal structure	face-centered cubic
Magnetic ordering	diamagnetic
Electrical resistivity	(20 °C) 208 nΩ·m
Thermal conductivity	35.3 W·m−1·K−1
Thermal expansion	(25 °C) 28.9 µm·m−1·K−1
Young's modulus	16 GPa
Shear modulus	5.6 GPa
Bulk modulus	46 GPa
Poisson ratio	0.44
Mohs hardness	1.5
Brinell hardness	38.3 MPa
CAS registry number	7439-92-1
Most stable isotopes
Main article: Isotopes of lead
iso NA half-life DM DE (MeV) DP 204Pb 1.4% >1.4×1017 y α 2.186 200Hg 205Pb syn 1.53×107 y ε 0.051 205Tl 206Pb 24.1% 206Pb is stable with 124 neutrons 207Pb 22.1% 207Pb is stable with 125 neutrons 208Pb 52.4% 208Pb is stable with 126 neutrons 210Pb trace 22.3 y α 3.792 206Hg β 0.064 210Bi
v t e · r

Lead ( /ˈlɛd/) is a main-group element in the carbon group with the symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shots, weights, as part of solders, pewters, fusible alloys and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei.

Lead, at certain exposure levels, is a poisonous substance to animals as well as for human beings. It damages the nervous system^[1] and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

Characteristics[link]

A sample of recently solidified lead (from a molten state)

Lead is a bright and silvery (with a very slight shade of blue^[2]) metal in a dry atmosphere; upon contact with air, it begins to tarnish. It has a few characteristic properties: high density, softness, ductility and malleability, poor electrical conductivity (compared to other metals), high resistance to corrosion, and ability to react with organic chemicals.^[2]

Various traces of other metals change its properties significantly: addition of small amounts of antimony or copper increases hardness and improves the corrosion reflection from sulfuric acid for lead.^[2] A few other metals also improve only hardness and fight the metal fatigue, such as cadmium, tin, or tellurium; metals like sodium or calcium also have this ability, but they weaken the chemical stability.^[2] Finally, zinc and bismuth simply impair the corrosion resistance (0.1% bismuth content prevent lead from the industrial usage).^[2] In return, lead impurities mostly worsen the quality of industrial materials, although there are exceptions: for example, small amounts of lead improve the ductility of steel.^[2]

Lead has only one common allotrope, which is face-centered cubic, with the lead–lead distance being 349 pm.^[3] At 327.5 °C (621.5 °F),^[4] lead melts; the melting point is above that of tin (232 °C, 449.5 °F),^[4] but significantly below that of germanium (938 °C, 1721 °F).^[5] The boiling point of lead is 1749 °C (3180 °F),^[6] which is below than those of both tin (2602 °C, 4716 °F)^[4] and germanium (2833 °C, 5131 °F).^[5] Densities get simply bigger down the group: the Ge and Sn values (5.23^[7] and 7.29 g·cm⁻³,^[8] respectively) are significantly below that of lead: 11.32 g·cm⁻³.^[7]

A lead atom has 82 electrons, having an electronic configuration of [Xe]4f¹⁴5d¹⁰6s²6p². In its compounds, lead (unlike the other group 14 elements) most commonly loses its two and not four outermost electrons, becoming lead(II) ions, Pb²⁺. Such unusual behavior is rationalized by considering the inert pair effect, which occurs because of the stabilization of 6s-orbital due to relativistic effects, which are stronger closer to the bottom of the periodic table.^[9] Tin shows a weaker such effect: tin(II) is still a reducer.^[9]

The figures for electrode potential show that lead is only slightly easier to oxidize than hydrogen. Lead thus can dissolve in acids, but this is often impossible due to specific problems (such as insoluble salts formation).^[10] Powdered lead burns with a bluish-white flame. As with many metals, finely divided powdered lead exhibits pyrophoricity.^[11] Toxic fumes are released when lead is burned.

Isotopes[link]

Lead occurs naturally on Earth exclusively in the form of four isotopes: lead-204, -206, -207, and -208.^[12] All four can be radioactive as the hypothetical alpha decay of any would release energy, but the lower half-life limit has been put only for lead-204: over 1.4×10¹⁷ years.^[13] This effect is, however, so weak that natural lead makes no radiation hazard. Three of them are also found in three of the four major decay chains: lead-206, -207 and -208 are final decay products of uranium-238, uranium-235, and thorium-232, respectively. Since the amounts of them in nature depend also on other elements' presence, the isotopic composition of natural lead varies by sample: in particular, the relative amount of lead-206 varies between 20.84% and 27.78%.^[12]

Aside from the stable ones, thirty-four radioisotopes have been synthesized: they have the mass numbers of 178–215.^[13] Lead-205 is the most stable radioisotope of lead, with a half-life of over 10⁷ years. 47 nuclear isomers (long-lived excited nuclear states), corresponding to 24 lead isotopes, have been characterized. The most long-lived isomer is lead-204m2 (half-life of about 1.1 hours).^[13]

Chemical reactivity[link]

Lead is classified as a post-transition metal, being a member of the group 14 of the periodic table. Lead only form a protective oxide layer although finely powdered highly purified lead could ignite in the air. Melted lead oxidises in air to lead monoxide. At 430 °C (810 °F). All chalcogens oxidize lead upon heating.^[14]

Fluorine does not oxidize cold lead. Hot lead can be oxidized, but the formation on a protective halide layer lowers the intensity of the reaction above 100 °C (210 °F). The reaction with chlorine is similar: thanks to the chloride layer, lead persistence against chlorine surpasses those of copper or steel up to 300 °C (570 °F).^[14]

Water in presence of oxygen attacks lead to start an accelerating reaction. Presence of carbonates or sulfates lead to formation of insoluble lead salts, which prevent the metal from corrosion. So does carbon dioxide, as the insoluble lead carbonate is formed; however, excess of the gas leads to the formation of the soluble bicarbonate; this dangers the usage of lead pipes.^[10] Lead dissolves in organic acids (in presence of oxygen) and concentrated (≥80%) sulfuric acid thanks to complexation; however, it is only weakly affected by hydrochloric acid and is stable against hydrofluoric acid, as the corresponding halides are weakly soluble. Lead also dissolves in quite concentrated alkalis (≥10%) thanks to the amphoteric character and solubility of plumbites.^[10]

Compounds[link]

Lead compounds exist mainly in two main oxidation states, +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.^[9]

Oxides and sulfide[link]

Three oxides are known: PbO, Pb₃O₄ (sometimes called "minium"), and PbO₂. The monoxide exists as two allotropes: α-PbO and β-PbO, both with layer structure and tetracoordinated lead. The alpha polymorph is red-colored and has the Pb–O distance of 230 pm; the beta polymorph is yellow-colored and has the Pb–O distance of 221 and 249 pm (due to asymmetry).^[15] Both polymorphs can exist under standard conditions (beta with small (10⁻⁵ relative) impurities, such as Si, Ge, Mo, etc.). PbO reacts with acids to form salts, and with alkalies to give plumbites, [Pb(OH)₃]^- or [Pb(OH)₄]^2-.^[16] The monoxide oxidizes in air to trilead tetroxide, which at 550 °C (1020 °F) degrades back into PbO.

The dioxide may be prepared by, for example, halogenization of lead(II) salts. Regardless the polymorph, it has a black-brown color. The alpha allotrope is rhombohedral, and the beta allotrope is tetragonal.^[16] Both allotropes are black-brown in color and always contain some water, which cannot be removed, as heating also causes decomposition (to PbO and Pb₃O₄). The dioxide is a powerful oxidizer: it can oxidize hydrochloric and sulfuric acids. It does not reacts with alkaline solution, but reacts with solid alkalies to give hydroxyplumbates, or with basic oxides to give plumbates.^[16]

Reaction of lead salts with hydrogen sulfide yields lead sulfide. The solid has the NaCl-like striucture (simple cubic), which it keeps up to the melting point, 1114 °C (2037 °F). When heated in air, it oxidised to the sulfate and then the monoxide.^[17] The compounds is almost insoluble in water, weak acids, and (NH₄)₂S/(NH₄)₂S₂ solution is the key for separation of lead from analythical groups I to III elements, tin, arsenic, and antimony. The compounds, however, dissolves in nitric and hydrochloric acids, to give elemental sulfur and hydrogen sulfide, respectively.^[17] Heating a mixture of the monoxide and the sulfide heated together forms the metal.^[18]

2 PbO + PbS → 3 Pb + SO₂

Halides and other salts[link]

Heating lead carbonate with hydrogen fluoride yields the hydrofluoride, which decomposes to the difluoride when melts. This white crystalline powder is more soluble than the diiodide, but less than the dibromide and the dichloride.^[19] The tetrafluoride, a yellow crystalline powder, is unstable.

Other dihalides are obtained upon heating lead(II) salts with the halides of other metals; lead dihalides precipitate to give white orthorhombic crystals (diiodide forms yellow hexagonal crystals). They can also be obtained by direct elements reaction at temperature exceeding melting points of dihalides. Their solubility increases with temperature; adding more halides first decreases the solubility, but then increases due to complexation, with the maximum coordination number being 6. The complexation depends on halide ion numbers, atomic number of the alkali metal, the halide of which is added, temperature and solution ionic strength.^[20] The tetrachloride is obtained upon dissolving the dioxide in hydrochloric acid; to prevent the exothermic decomposition, it is kept under concentrated sulfuric acid. The tetrabromide may not, and the tetraiodide definitely does not exist.^[21] The diastatide has also been prepared.^[22]

The metal is not attacked by sulfuric or hydrochloric acids. It dissolves in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO₃)₂.^[19] It is a well-soluble solid in water; it is thus a key to receive the precipitates of halides, sulfate, chromate, carbonate, and basic carbonate Pb₃(OH)₂(CO₃)₂ salts of lead.^[23]

Organolead[link]

The best-known compounds are the two simplest plumbane deratives: tetramethyllead (TML) and tetraethyllead (TEL). The homologs of these, as well as hexaethyldilead (HEDL), are of lesser stability. The tetralkyl deratives contain lead(IV); the Pb–C bonds are covalent. They thus resemble typical organic compounds.^[24]

Lead readily forms an equimolar alloy with sodium metal that reacts with alkyl halides to form organometallic compounds of lead such as tetraethyllead.^[25] The Pb–C bond energies in TML and TEL are only 167 and 145 kJ/mol; the compounds thus decompose upon heating, with first signs of TEL composition seen at 100 °C (210 °F). The pyrolisis yields of elemental lead and alkyl radicals; their interreaction causes the synthesis of HEDL.^[24] TML and TEL also decompose upon sunlight or UV light.^[26] In presence of chlorine, the alkyls begin to be replaced with chlorides; the R₂PbCl₂ in the presence of HCl (a by-product of the previous reaction) leads to the complete mineralization to give PbCl₂. Reaction with bromine follows the same principle.^[26]

History[link]

World lead production peaking in the Roman period and the rising Industrial Revolution^[27]

Lead ingots from Roman Britain on display at the Wells and Mendip Museum

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. Metallic lead beads dating back to 6400 BCE have been found in Çatalhöyük in modern-day Turkey.^[28] In the early Bronze Age, lead was used with antimony and arsenic.

The largest preindustrial producer of lead was the Roman economy, with an estimated output per annum of 80,000 t, which was typically won as a by-product of extensive silver smelting.^[27][29][30] Roman mining activities occurred in Central Europe, Roman Britain, the Balkans, Greece, Asia Minor; Hispania alone accounted for 40% of world production.^[27]

Roman lead pipes often bore the insignia of Roman emperors (see Roman lead pipe inscriptions). Lead plumbing in the Latin West may have been continued beyond the age of Theoderic the Great into the medieval period.^[31] Many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centers. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings. In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists accordingly used Saturn's symbol (the scythe, ♄) to refer to lead.

Up to the 17th century, tin was often not differed from lead: lead was called plumbum nigrum (literally, "black plumbum"), while tin was called plumbum candidum (literally, "bright plumbum").^[32] Their inherence through history can be seen in other languages: the word "olovo" stands for lead in Czech, but in Russian it ("олово") stands for tin. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; the English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.

Occurrence[link]

Lead and zinc bearing carbonate and clastic deposits. Source: USGS

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 by weight. Other common varieties are cerussite (PbCO₃) and anglesite (PbSO₄).

Ore processing[link]

Galena, lead ore

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.^[33]

Lead oxide from the roasting process is reduced in a coke-fired blast furnace to the metal.^[34] 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.^[33]

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.^[33][35]

Since lead ores contain significant concentrations of silver, the smelted metal also is commonly contaminated with silver. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process.^[18][33][35]

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.^[33][35]

Very pure lead can be obtained by processing smelted lead electrolytically by means of the Betts process. The process uses anodes of impure lead and cathodes of pure lead in an electrolyte of silica fluoride.^[33][35]

Production and recycling[link]

Production and consumption of lead is increasing worldwide. Total annual production is about 8 million tonnes; about half is produced from recycled scrap. The top lead producing countries, as of 2008, are Australia, China, USA, Peru, Canada, Mexico, Sweden, Morocco, South Africa and North Korea.^[36] Australia, China and the United States account for more than half of primary production.^[37]

In 2010^[update], 9.6 million tonnes of lead were produced, of which 4.1 million tonnes came from mining.^[38]

At current use rates, the supply of lead is estimated to run out in 42 years.^[39] Environmental analyst Lester Brown has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.^[40] This may need to be reviewed to take account of renewed interest in recycling, and rapid progress in fuel cell technology. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of lead in use in society is 8 kg. Much of this is in more-developed countries (20–150 kg per capita) rather than less-developed countries (1–4 kg per capita).

Applications[link]

Elemental form[link]

Lead bricks are commonly used as radiation shielding.

Because of its high density and resistance from corrosion, lead is used for the ballast keel of sailboats. Its high density 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. For the same reason it is used in scuba diving weight belts to counteract the diver's natural buoyancy and that of his equipment. It does not have the weight-to-volume ratio of many heavy metals, but its low cost increases its use in these and other applications.

Roman lead water pipes with taps

Lead pipe in Roman baths

Multicolor lead-glazing in a sancai ceramic cup, Tang dynasty, China, 8th century CE.

Lead is used in applications where its low melting point, ductility and high density is an advantage. The low melting point makes casting of lead easy, and therefore small arms ammunition and shotgun pellets can be cast with minimal technical equipment. It is also inexpensive and denser than other common metals.^[41] The hot metal typesetting uses a lead based alloy to produce the types for printing directly before printing.

Its corrosion resistance makes it suitable for outdoor applications when in contact with water.

More than half of the worldwide lead production (at least 1.15 million metric tons) is used for automobiles, mostly as electrodes in the lead–acid battery, used extensively as a car battery.^[42]

Cathode (reduction)

PbO₂ + 4 H⁺ + SO₄^2– + 2e^– → PbSO₄ + 2 H₂O

Anode (oxidation)

Pb + SO₄^2– → PbSO₄ + 2e^–[43][44]

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 hazardous waste. Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulation.

Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases.

Lead is used as shielding from radiation (e.g., in X-ray rooms).^[45] Molten lead is used as a coolant (e.g., for lead cooled fast reactors).^[46]

Lead is added to brass to reduce machine tool wear. Lead, in the form of strips, or tape, is used for the customization of tennis rackets. Tennis rackets of the past sometimes had lead added to them by the manufacturer to increase weight.^[47]

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, or sheet-lead, is used as a sound deadening layer in some areas in wall, floor and ceiling design in sound studios where levels of airborne and mechanically produced sound are targeted for reduction or virtual elimination.^[48][49]

Lead is the traditional base metal of organ pipes, mixed with varying amounts of tin to control the tone of the pipe.^[50][51]

Lead has many uses in the construction industry (e.g., lead sheets are used as architectural metals in roofing material, cladding, flashing, gutters and gutter joints, and on roof parapets). Detailed lead moldings are used as decorative motifs used to fix lead sheet. Lead is still widely used in statues and sculptures. 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.

Due to its half-life of 22.2 years, the radioactive isotope ²¹⁰Pb is used for dating material from marine sediment cores by radiometric methods.^{[citation needed]}

Compounds[link]

Lead compounds are used as a coloring element in ceramic glazes, notably in the colors red and yellow.^[52] Lead is frequently used in polyvinyl chloride (PVC) plastic, which coats electrical cords.^[53][54]

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.^[55][56] Lead glass is composed of 12–28% lead oxide. It changes the optical characteristics of the glass and reduces the transmission of radiation.^[57]

Some artists using oil-based paints continue to use lead carbonate white, citing its properties in comparison with the alternatives. Tetra-ethyl lead is used as an anti-knock additive for aviation fuel in piston-driven aircraft. Lead-based semiconductors, such as lead telluride, lead selenide and lead antimonide are finding applications in photovoltaic (solar energy) cells and infrared detectors.^[58]

Former applications[link]

Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Beginning April 22, 2010, US federal law requires that contractors performing renovation, repair, and painting projects that disturb more than six square feet of paint in homes, child care facilities, and schools built before 1978 must be certified and trained to follow specific work practices to prevent lead contamination. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigments. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.^[59][60][61]

Lead is the hot metal that was used in hot metal typesetting. It was used for plumbing (hence the name) as well as a preservative for food and drink in Ancient Rome. Until the early 1970s, lead was used for joining cast iron water pipes and used as a material for small diameter water pipes.^[62]

Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.^{[63][64][65][66]}

Lead was used to make bullets for slings. Lead was used for shotgun pellets in the US until about 1992 when it was outlawed (for waterfowl hunting only) and replaced by non-toxic shot, primarily steel pellets. In the Netherlands, the use of lead shot for hunting and sport shooting was banned in 1993, which caused a large drop in lead emission, from 230 ton in 1990 to 47.5 ton in 1995, two years after the ban.^[67]

Lead was a component of the paint used on children's toys – now restricted in the United States and across Europe (ROHS Directive). Lead was used in car body filler, which was used in many custom cars 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.^[68]

Lead was also used in pesticides before the 1950s, when fruit orchards were treated (ATSDR). A lead cylinder attached to a long line was used by sailors for the vital navigational task of determining water depth by heaving the lead at regular internals. A soft tallow insert at its base allowed the nature of the sea bed to be determined, further aiding position finding. Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. The term comes from the Roman stylus, called the penicillus, which was made of lead without a wooden holder.^[69] When the pencil originated as a wrapped graphite writing tool, the particular type of graphite being used was named plumbago (lit. act for lead, or lead mockup).

Health effects[link]

Lead is highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO₂) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles. Lead exposure also causes small increases in blood pressure, particularly in middle-aged and older people and can cause anemia. Exposure to high lead levels can severely damage the brain and kidneys in adults or children and ultimately cause death. In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure have shown to reduce fertility in males.^[70] Lead also damages nervous connections (especially in young children) and cause blood and brain disorders. Lead poisoning typically results from ingestion of food or water contaminated with lead; but may also occur after accidental ingestion of contaminated soil, dust, or lead-based paint.^[71] It is rapidly absorbed into the bloodstream and is believed to have adverse effects on the central nervous system, the cardiovascular system, kidneys, and the immune system.^[72] The component limit of lead (1.0 μg/g) is a test benchmark for pharmaceuticals, representing the maximum daily intake an individual should have. However, even at this low level, a prolonged intake can be hazardous to human beings.^[73][74] The treatment for lead poisoning consists of dimercaprol and succimer.^[75]

NFPA 704
1 3 0
Fire diamond for lead granules

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 learning disabilities).^[76] Most cases of adult elevated blood lead levels are workplace-related.^[77] High blood levels are associated with delayed puberty in girls.^[78] Lead has been shown many times to permanently reduce the cognitive capacity of children at extremely low levels of exposure.^[79]

During the 20th century, the use of lead in paint pigments was sharply reduced because of the danger of lead poisoning, especially to children.^[80][81] 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 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 Chinese brass. 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. 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 acidic drinks, such as fruit juices, have leached lead ions out of the glaze.^[82] 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. Lead(II) 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 and even be a partial reason for the Roman Empire's fall (see Decline of the Roman Empire#Lead poisoning).^[83]

Biochemistry of poisoning[link]

In the human body, lead inhibits porphobilinogen synthase 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.^[84] At lower levels, it acts as a calcium analog, interfering with ion channels during nerve conduction. This is one of the mechanisms by which it interferes with cognition. Acute lead poisoning is treated using disodium calcium edetate: the calcium chelate of the disodium salt of ethylene-diamine-tetracetic acid (EDTA). This chelating agent has a greater affinity for lead than for calcium and so the lead chelate is formed by exchange. This is then excreted in the urine leaving behind harmless calcium.^[85]

Exposure to lead and lead chemicals can occur through inhalation, ingestion and dermal contact. Most exposure occurs through ingestion or inhalation; in the U.S. the skin exposure is unlikely as leaded gasoline additives are no longer used. Lead exposure is a global issue as lead mining and lead smelting are common in many countries. Most countries have stopped using lead-containing gasoline by 2007.^[86]

Lead exposure mostly occurs through ingestion. Lead paint is the major source of lead exposure for children. As lead paint deteriorates, it peels, is pulverized into dust and then enters the body through hand-to-mouth contact or through contaminated food, water or alcohol. Ingesting certain home remedy medicines may also expose people to lead or lead compounds.^[86] Lead can be ingested through fruits and vegetables contaminated by high levels of lead in the soils they were grown in. Soil is contaminated through particulate accumulation from lead in pipes, lead paint and residual emissions from leaded gasoline that was used before the Environment Protection Agency issue the regulation around 1980.^[87]

Inhalation is the second major pathway of exposure, especially for workers in lead-related occupations. Almost all inhaled lead is absorbed into the body, the rate is 20–70% for ingested lead; children absorb more than adults.^[86]

Dermal exposure may be significant for a narrow category of people working with organic lead compounds, but is of little concern for general population. The rate of skin absorption is also low for inorganic lead.^[86]

According to Agency for Toxic Substance and Disease Registry, a small amount of lead (1%) will store itself in bones and the rest will be excreted through urine and feces within a few weeks of exposure. Children have a harder time excreting lead. Only about 32% of lead will be excreted by a child.^[88]

See also[link]

• Lead Poisoning
• Adult Blood Lead Epidemiology and Surveillance
• Lead-Free Toys Act
• Medical geology
• Plumbosolvency
• RoHS directive
• Banning of leaded petrol

Books View or order collections of articles	Lead Period 6 elements Carbon group Chemical elements (sorted alphabetically) Chemical elements (sorted by number)
Portals Access related topics	Chemistry portal
Find out more on Wikipedia's Sister projects	Images and media from Commons Definitions from Wiktionary

References[link]

Bibliography[link]

• Lide, D. R., ed. (2004). CRC Handbook of Chemistry and Physics (84th ed.). Boca Raton (FL): CRC Press. ISBN 978-0-8493-0484-2. 
• Polyanskiy, N. G. (1986). Fillipova, N. A. ed (in Russian). Аналитическая химия элементов: Свинец [Analytical Chemistry of the Elements: Lead]. Nauka. 

Further reading[link]

• Keisch, B.; Feller, R. L.; Levine, A. S.; Edwards, R. R. (1967). "Dating and Authenticating Works of Art by Measurement of Natural Alpha Emitters". Science 155 (3767): 1238–1242. Bibcode 1967Sci...155.1238K. DOI:10.1126/science.155.3767.1238. PMID 17847535. 
• Keisch, B (1968). "Dating Works of Art Through their Natural Radioactivity: Improvements and Applications". Science 160 (3826): 413–415. Bibcode 1968Sci...160..413K. DOI:10.1126/science.160.3826.413. PMID 17740234. 
• Keisch, B (1968). "Discriminating Radioactivity Measurements of Lead: New Tool for Authentication". Curator 11 (1): 41–52. DOI:10.1111/j.2151-6952.1968.tb00884.x. 
• Casas, Jose S.; Sordo, Jose, eds. (2006). Lead Chemistry, Analytical Aspects. Environmental Impacts and Health Effects. Elsevier. ISBN 0-444-52945-4. http://www.google.com/books?id=D9nYWCv_FE4C&printsec=frontcover. 

External links[link]

• Toxicological Profile for Lead (Update) Agency for Toxic Substances and Disease Registry (ATSDR). 2007. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
• Lead at the Open Directory Project
• Chemistry in its element podcast (MP3) from the Royal Society of Chemistry's Chemistry World: Lead
• Lead-Free Wheels
• National Lead Free Wheel Weight Initiative| Waste Minimization|Wastes|US EPA

lez:Кьуркьушумvep:Hahktin

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2007)

A youth hostel room in Japan

A room is any distinguishable space within a structure. Usually, a room is separated from other spaces or passageways by interior walls; moreover, it is separated from outdoor areas by an exterior wall, sometimes with a door. Historically the use of rooms dates at least to early Minoan cultures about 2200 BC, where excavations on Santorini, Greece at Akrotiri reveal clearly defined rooms within certain structures.^[1]

Historical room types[link]

A living room

In early structures, diverse room types could be identified to include bedrooms, kitchens, bathing rooms, reception rooms, and other specialized uses. The aforementioned Akrotiri excavations reveal rooms sometimes built above other rooms connected by staircases, bathrooms with alabaster appliances such as washbasins, bathing tubs, and toilets, all connected to an elaborate twin plumbing systems of ceramic pipes for cold and hot water separately.^[1] Ancient Rome manifested very complex building forms with a variety of room types, including some of the earliest examples of rooms for indoor bathing. The Anasazi civilization also had an early complex development of room structures, probably the oldest in North America, while the Maya of Central America had very advanced room configurations as early as several hundred AD. By at least the early Han Dynasty in China (e.g. approximately 200 BC), complex multi-level building forms emerged, particularly for religious and public purposes; these designs featured many roomed structures and included vertical connections of rooms.

Box-room[link]

A hospital room

Many houses are built to contain a box-room (box room or boxroom) that is easily identifiable, being smaller than the others. The small size of these rooms limits their use, and they tend to be used as a small single bedroom, small child's bedroom, or as a storage room. Other box rooms may house a live-in domestic worker.

Traditionally, and often seen in country houses and larger suburban houses up until the 1930s in Britain, the box room was literally for the storage of boxes, trunks, portmanteaux, and the like, rather than for bedroom use.^{[citation needed]}

See also[link]

• Entryway
• Great hall
• Room number

Notes[link]

John Mayer
Mayer at the Mile High Music Festival on July 20, 2008
Background information
Birth name	John Clayton Mayer
Born	(1977-10-16) October 16, 1977 (age 34) Bridgeport, Connecticut United States
Genres	Pop rock, blues rock, acoustic rock, blue-eyed soul
Occupations	Musician, songwriter, record producer, columnist, graphic designer, photographer, comedian, television host
Instruments	Guitar, vocals, omnichord, piano, vibraphone, harmonica, percussion, clarinet, violin
Years active	1998 (1998)–present
Labels	Arista, Aware, Columbia
Associated acts	John Mayer Trio, Fall Out Boy
Website	johnmayer.com
Notable instruments
Fender Stratocaster Martin Guitars Gibson Guitars

John Clayton Mayer ( /ˈmeɪ.ər/ MAY-ər;^[1] (born October 16, 1977) is an American pop and blues rock musician, singer-songwriter, recording artist, and music producer.^[2] Born in Bridgeport, Connecticut and raised in Fairfield, Connecticut, he attended Berklee College of Music in Boston. He moved to Atlanta in 1997, where he refined his skills and gained a following, and he now lives in New York City.^[3][4] His first two studio albums, Room for Squares and Heavier Things, did well commercially, achieving multi-platinum status. In 2003, he won a Grammy Award for Best Male Pop Vocal Performance for "Your Body Is a Wonderland."^[5]

Mayer began his career performing mainly acoustic rock, but gradually began a transition towards the blues genre in 2005 by collaborating with renowned blues artists such as B. B. King, Buddy Guy, and Eric Clapton, and by forming the John Mayer Trio. The blues influence can be heard throughout his 2005 live album Try! with the John Mayer Trio and his third studio album Continuum, released in September 2006. At the 49th Annual Grammy Awards in 2007 Mayer won Best Pop Vocal Album for Continuum and Best Male Pop Vocal Performance for "Waiting on the World to Change". He released his fourth studio album, Battle Studies, in November 2009. His fifth album, Born and Raised, was released on May 22, 2012. He has sold over 10 million albums in the U.S. and 20 million albums worldwide.

Early life[link]

John Clayton Mayer was born on October 16, 1977 in Bridgeport, Connecticut to Margaret, an English teacher, and Richard, a high school principal.^[6] He grew up in Fairfield, Connecticut, the second of three children.^[7] His father is Jewish, and Mayer has said that he "relat[es] to Judaism".^[8] He attended Fairfield High School in Fairfield^[9] although he was enrolled in the Center for Global Studies at Brien McMahon High School in Norwalk for his junior year (then known as the Center for Japanese Studies Abroad, it is a magnet program for students wanting to learn Japanese).^[10]

After watching Michael J. Fox's guitar performance as Marty McFly in Back to the Future, Mayer became fascinated with the instrument, and when he turned 13, his father rented one for him.^[11][12] A neighbor gave Mayer a Stevie Ray Vaughan cassette, which cultivated Mayer's love of blues music.^[13]a[›] Mayer started taking lessons from a local guitar-shop owner, Al Ferrante, and soon became consumed with playing the instrument.^[3][14] His singular focus concerned his parents, and they took him twice to see a psychiatrist—but Mayer was determined to be fine.^[3][14] Mayer says that the contentious nature of his parents' marriage led him to "disappear and create my own world I could believe in".^[3] After two years of practice, he started playing at blues bars and other venues in the area, while he was still in high school.^[10][12] In addition to performing solo, he was a member of a band called Villanova Junction (named for a Jimi Hendrix song) with Tim Procaccini, Joe Beleznay, and Rich Wolf.^[3][15] Mayer considered skipping college to pursue his music, but the disapproval of his parents dissuaded him from doing so.^[3]

When Mayer was seventeen, he was stricken with cardiac dysrhythmia and was hospitalized for a weekend. Reflecting on the incident, Mayer said, "That was the moment the songwriter in me was born," and he penned his first lyrics the night he got home from the hospital.^[4] Shortly thereafter, he began suffering from panic attacks, and lived with the fear of having to enter a mental institution.^[3] He continues to manage such episodes with Xanax, an anti-anxiety drug.^[4][16] After graduation, he worked for fifteen months at a gas station until he saved enough money to buy a 1996 Stevie Ray Vaughan signature Stratocaster.^[17]

Career[link]

Early career[link]

Mayer enrolled in the Berklee College of Music in Boston, Massachusetts, aged 19.^[7] However, at the urging of his college friend an Atlanta, Georgia native, Clay Cook, he left school after two semesters and moved with Cook to Atlanta.^[18] In Atlanta they formed a two-man band called LoFi Masters and began performing in local coffee houses and club venues such as Eddie's Attic.^[12] According to Cook, they began to experience musical differences due to Mayer’s desire to move more towards pop music.^[19] As a result, the two parted ways, and Mayer embarked on a solo career.^[18]

With the help of local producer and engineer Glenn Matullo, Mayer recorded the independent EP Inside Wants Out. Cook co-wrote many of the songs from the EP including Mayer's first commercial single release, "No Such Thing".^[19] The EP includes eight songs with Mayer on lead vocals and guitars. However, Cook's only contribution was backing vocals on the song "Comfortable". For the opening track, "Back To You", a full band was enlisted, including the EP’s co-producer David "DeLa" LaBruyere on bass guitars.^[20] Mayer and LaBruyere then began to perform throughout Georgia and nearby states.

Major label success[link]

	"City Love" excerpt noicon From the album Room for Squares.
Problems listening to this file? See media help.

Mayer’s reputation began to build, and a March 2000 appearance at South by Southwest brought him to the attention of "launch" label, Aware Records.^[14][21][22] After including him in the Aware Festival concerts and having his songs included on Aware compilations, in early 2001, Aware released Mayer's internet-only album titled, Room for Squares. During this time, Aware inked a deal with Columbia Records that gave Columbia first pick in signing Aware artists, and so in September of the same year, Columbia remixed and re-released Room for Squares.^[23] As part of the major label "debut", the album's artwork was updated, and the track "3x5" was added. The re-release also included reworked studio versions of the first four songs from his indie album, Inside Wants Out.^[24]

By the end of 2002, Room for Squares had spawned several radio hits, including "No Such Thing," "Your Body Is a Wonderland", and ultimately, "Why Georgia". In 2003, Mayer won a Grammy for Best Male Pop Vocal Performance for "Your Body Is a Wonderland." In his acceptance speech he remarked, "This is very, very fast, and I promise to catch up."^[25] He also figuratively referred to himself as being sixteen, a remark that many mistook to mean that he was only sixteen years old at the time.^[26]

In 2003, Mayer released a live CD and DVD of a concert in Birmingham, Alabama titled Any Given Thursday. The concert featured songs previously not recorded, such as "Man on the Side" (co-written with Cook) and "Something's Missing", which later appeared on Heavier Things. The concert also included "Covered In Rain". According to the accompanying DVD documentary, this song is "part two" of the song "City Love", which features the line "covered in rain". Commercially, the album quickly peaked at number seventeen on the Billboard 200 chart. The CD/DVD received conservative, although consistent, praise, with critics torn between his pop-idol image, and (at the time) emerging guitar prowess. Erik Crawford (of Allmusic) asked "Is he the consummate guitar hero exemplified when he plays a cover of Stevie Ray Vaughan's 'Lenny', or is he the teen idol that the pubescent girls shriek for after he plays 'Your Body Is a Wonderland?'"^[27][28]

Heavier Things, Mayer's second album, was released in 2003 to generally favorable reviews. Rolling Stone, Allmusic and Blender all gave positive, although reserved, feedback. PopMatters said that it "doesn't have as many drawbacks as one might assume".^[29] The album was commercially successful, and while it did not sell as well as Room for Squares, it peaked at number one on the US Billboard 200 chart. Mayer earned his first number one single with the song "Daughters" as well as a 2005 Grammy for Song of the Year, beating out fellow contenders Alicia Keys and Kanye West. He dedicated the award to his grandmother, Annie Hoffman, who died in May 2004. He also won Best Male Pop Vocal Performance, beating Elvis Costello, Prince, and Seal for the award. In a February 9, 2009 interview on The Ellen DeGeneres Show, Mayer said that he thought he should not have won the Grammy for Song of the year because he thought that Alicia Keys' If I Ain't Got You was the better song. Because of this, he removed the top half of the Grammy and gave it to Keys, and kept the bottom part for himself. At the 37th Annual Songwriters Hall of Fame Induction Ceremony in 2006, Mayer was honored with the Hal David Starlight Award.^[30]

Mayer again recorded live concerts across seven nights of his U.S. tour in 2004. These recordings were released to the iTunes Store under the title As/Is, indicating that the errors were included along with the good moments. A few months later, a "best of" CD was compiled from the As/Is nights. The album included a previously unreleased cover of Marvin Gaye's song "Inner City Blues (Make Me Wanna Holler)", featuring a solo from Mayer's support act, jazz and blues turntablist DJ Logic. All the album covers of the As/Is releases feature drawings of anthropomorphic bunnies.^[31]

January 2005, left to right: David Ryan Harris, John Mayer and Steve Jobs at Macworld 11, SF Moscone Center.

With increased exposure, Mayer's talent came into demand in other areas. Steve Jobs invited Mayer to perform during the keynote address of Apple's annual Macworld Conference & Expo, in January 2004, as Jobs introduced the software application GarageBand.^[32] The gig led to Mayer becoming a fixture of the event. He rejoined Jobs on stage for a solo performance at Macworld 2007, following the announcement of the iPhone.^[33] Mayer has also done endorsements, such as a Volkswagen commercial for the Beetle's guitar outlet and for the BlackBerry Curve.^[34]

Change in musical direction[link]