Lead

Rather, plum is derived from the Old English word plume. In astrology Polaris is one of the Behenian fixed stars and has the symbol . The plum, however, does not get its name from this root. However, the bright Southern Cross (Crux) points towards the south celestial pole. The Latin plumbum has given birth to a number of terms in the English language:. The star visible to the naked eye that is closest to the south celestial pole is the dim Sigma Octantis, sometimes called Polaris Australis. The earliest pencils actually used lead, though 'pencil leads' have been made for the last couple of centuries from graphite, a naturally occurring form (allotrope) of carbon. There is no real southern pole star.

For that reason many universities do not hand out lead-containing samples to women for instructional laboratory analyses. The astronomer Edward Guinan considers this to be a remarkable rate of change and is on record as saying that "If they are real, these changes are 100 times larger than [those] predicted by current theories of stellar evolution". Lead is considered to be particularly harmful for women's ability to reproduce. Recent research reported in Science suggests that Polaris is 2.5 times brighter today than when Ptolemy observed it. 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. The star is also about 15% brighter (on average) than it was in 1900; the period has also lengthened by about 8 seconds each year since then. 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. As of 2005, the variations are about 2% from peak to trough.

Paint containing lead has been withdrawn from sale in industralised countries, though many older houses may still contain substantial lead in their old paint: it is generally recommended that old paint should not be stripped by sanding, as this generates inhalable dust. Around 1900, the star varied between being 8% brighter than its average luminosity and 8% dimmer (0.15 magnitudes in total) with a 3.97 day period. The concern about lead's role in mental retardation in children has brought about widespread reduction in its use (lead exposure has been linked to schizophrenia). The main star is a Population II cepheid variable, the pulsations of which cause it to cycle steadily. Main article: lead poisoning. It is an F7 supergiant (Ib) or bright giant (II), with two smaller companions: an F3 V main sequence star about 2700 AU away and a close companion about 20 AU distant. Although this has been banned in industrialized nations, there was a recent scandal involving lead-laced Mexican candy being eaten by children in California (http://www.ocregister.com/investigations/2004/lead/part1_printable.html). Polaris is 431 light years (132 parsecs) from Earth, according to measurements made by the Hipparcos satellite.

At one point in time, some lead compounds, because of their sweetness, were used by candy makers. See List of brightest stars. The historical use of lead acetate (also known as sugar of lead) by the Roman Empire as a sweetener for wine is considered by some to be the cause of the dementia which affected many of the Roman Emperors. The brightest star in the sky (besides the Sun) is Sirius. Long term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO₂) can cause nephropathy, and colic-like abdominal pains. Although Polaris is a relatively bright star and is conspicuous since no other stars of similar brightness are close to it, it is nowhere near the brightest; it is actually the 46th brightest star in the night sky. Lead is a poisonous metal that can damage nervous connections (especially in young children) and cause blood and brain disorders. Polaris's fame as the North Star has given rise to a persistent misconception that it is the brightest star in the sky.

The ranges of isotopic ratios for most natural materials are 14.0 - 30.0 for ²⁰⁶Pb/²⁰⁴Pb, 15.0 - 17.0 for ²⁰⁷Pb/²⁰⁴Pb, and 35.0 - 50.0 for ²⁰⁸Pb/²⁰⁴Pb, although numerous examples outside these ranges are reported in the literature. Polaris is not normally visible from the Southern Hemisphere. Each is reported relative to ²⁰⁴Pb, the only non-radiogenic stable isotope. One can also follow the central point of the W shape of Cassiopeia. The corresponding half-lives of these decay schemes vary markedly: 4.47 × 10⁹, 7.04 × 10⁸ and 1.4 × 10¹⁰ years, respectively. In the Northern Hemisphere, it is easy to find Polaris by following the line traced from Merak to Dubhe (β and α Ursae Majoris, also known as the Pointers), the two stars at the end of the bowl of the Big Dipper. ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb are all radiogenic, and are the end products of complex decay chains that begin at ²³⁸U, ²³⁵U and ²³²Th, respectively. Polaris is due to become an even more accurate pole star in the near future — the distance between Polaris and the pole will reach a minimum (of just under 1/2 degree) in 2100.

Lead has four stable, naturally occurring isotopes: ²⁰⁴Pb (1.4%), ²⁰⁶Pb (24.1%), ²⁰⁷Pb (22.1%), and ²⁰⁸Pb (52.4%). Other stars have been the pole star in the past and will be again in the future, including Thuban and Vega. Main Article: Isotopes of lead. This is due to precession of the equinox over thousands of years. The molten lead bullion is then refined by additional smelting with air being passed over the lead to form a slag layer containing any remaining impurities and producing 99.9% pure lead. Although Shakespeare wrote "I am as constant as the northern star", Polaris will not always be the pole star. The lead is then cooled in stages which causes the lighter impurites (dross) to rise to the surface where they can be removed. Only twice during every sidereal day does Polaris accurately define the true north azimuth; the rest of the time it is only an approximation and must be corrected using tables.

The concentrate is sintered before being smelted in to produce a 97% lead concentrate. At present, Polaris is slightly under 1° away from the pole of rotation (about twice the apparent diameter of the Moon) and hence revolves around the pole in a small circle almost 2° in diameter. The concentrate, which can range from 50% to 60% lead, is dried and then treated using pyrometallurgy. The antiquity of the use of this star is attested to by the fact that it is found represented on the earliest known Assyrian tablets. The Froth flotation process separates the lead and other minerals from the waste rock (tailings) to form a concentrate. Therefore, it makes an excellent fixed point from which to draw measurements for celestial navigation. The ore is then treated using extractive metallurgy. Because it lies nearly in a direct line with the axis of the Earth's rotation "above" the North Pole—the north celestial pole—Polaris is apparently motionless from the Earth, and all the stars of the Northern sky appear to rotate around it.

In mining, the ore is extracted by drilling or blasting and then crushed and ground. Other names include the "North Star", the "Lode Star", or sometimes "Polaris Borealis". But more than half of the lead used currently comes from recycling. "Polaris" comes from Stella Polaris, the Latin form of its common name "Pole Star." The Greek name Cynosura (Κυνόσουρα) means "tail of the dog" and is the source of the English word cynosure. Other common varieties are cerussite (PbCO₃) and anglesite (PbSO₄). The nearer dwarf star is in an orbit of only 20 AU (3 billion km) from Polaris A, explaining why its light is swamped by its close and much brighter companion. The main lead mineral is galena (PbS), which contains 86.6% lead. In January 2006, NASA released images from the Hubble telescope, directly showing all three members of the Polaris trinary system.

Currently lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. In 1929, it was discovered by examining the spectrum of Polaris A that it had another very close dwarf companion (variously α UMi P, α UMi a or α UMi Ab). Native lead does occur in nature, but it is rare. Polaris B can be seen with even a modest telescope and was first noticed by William Herschel in 1780. Recently, lead use is being further curtailed by the RoHS directive. Polaris is a trinary system, consisting of a large yellow Cepheid variable (α UMi A), distantly (about 2700 AU or 380 billion km) orbited by a bright yellow dwarf (α UMi B). 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. Much more rarely, it is called Cynosura.

Much of this shift was a result of the U.S. It is also very close to the north celestial pole, making it the current north pole star. By the mid-1980s, a significant shift in lead end-use patterns had taken place. Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris) is the brightest star in the constellation Ursa Minor. The English word "plumbing" also derives from this Latin root. Lead's symbol Pb is an abbreviation of its Latin name plumbum.

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. Alchemists thought that lead was the oldest metal and associated it with the planet Saturn. Lead was mentioned in the Book of Exodus. In the early bronze age lead was used with antimony and arsenic.

Lead has been used by humans for at least 7000 years, because it was (and continues to be) widespread and easy to extract, as well as easy to work with, being both highly malleable and ductile as well as easy to smelt. Lead is the only metal in which there is zero Thomson effect. Lead can be toughened by adding a small amount of antimony or other metals to it. sulfuric acid).

Because of this property, it is used to contain corrosive liquids (e.g. This true metal is highly resistant to corrosion. Lead has a bright luster and is a dense, ductile, very soft, highly malleable, bluish-white metal that has poor electrical conductivity. .

(But see the article on Bismuth, which has a half life so long it can be considered stable.). Lead has the highest atomic number of all stable elements. Lead is used in building construction, lead-acid batteries, bullets and shot, and is part of solder, pewter, and fusible alloys. A soft, heavy, toxic and malleable poor metal, lead is bluish white when freshly cut but tarnishes to dull gray when exposed to air.

plumbum) and atomic number 82. Lead is a chemical element in the periodic table that has the symbol Pb (L.
. Los Alamos National Laboratory - Lead.

A Small Dose of Toxicology:Lead. 41-52, 1968. 1., p. In: Curator, 11, No.

Keisch, B: Discriminating Radioactivity Measurements of Lead: New Tool for Authentication. 413-415, 1968. In: Science, 160, p. Keisch, B: Dating Works of Art Trough their Natural Radioactivity: Improvements and Applications.

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S., and Edwards, R. L., Levine, A. Keisch, B., Feller, R. Aplomb comes from the French à plomb, meaning plumb vertical, and therefore confident and cool.

Plumbism is the medical term for lead poisoning. sense of plum (derived from plumb) meaning 'completely'. Plumb crazy may derive from the fact that lead poisoning can cause insanity; or, according to the Oxford English Dictionary, from a U.S. Plumbing the depths derives from the use of the lead weight to draw the sounding line down to the bottom of the water body (or to the end of the line if the water's really deep!).

Plumb wall is so-said because a plumb bob is used to find the vertical. Plumb bob or plummet, a small, pointed body of metal the weight of which is used to draw a string vertical under tension, refers to the fact that they were originally made from lead. Plumbing, or system of piping, derives from the fact that pipes were once made of lead. see isotope geochemistry.

See Category:Lead minerals. Lead is used as electrodes in the process of electrolysis. Tetraethyl lead has been used in leaded fuels to reduce engine knocking; however, this is no longer common practice in the Western World due to health concerns. It changes the optical characteristics of the glass and reduces the transmission of radiation.

Lead glass is comprised of 12-28% lead. for lead cooled fast reactors. Molten lead is used as a coolant, eg. Lead is used as shielding from radiation.

[1]. Because of the dangers, European and North American manufacturers use more expensive alternatives such as zinc. Lead is used in some candles to treat the wick to ensure a longer, more even burn. Lead is used as projectiles for firearms and fishing sinkers because of its density, low cost verse alternative products and ease of use due to relatively low melting point.

Lead sticks were used as pencils but has been replaced by graphite for the last 450 years. Lead was used for plumbing in Ancient Rome and water mains and service pipes up until the early 1970's. Lead is used as a coloring element in ceramic glazes, notably in the colors red and yellow. Lead was used as a pigment in Lead paint for white as well as yellow and red colors.

Lead is a major constituent of the Lead-acid battery used extensively in car batteries.