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30 novembre 2011 3 30 /11 /novembre /2011 01:59

Potassium is the chemical element with the symbol K (from Neo-Latin kalium) and atomic number19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Sony VAIO VPCEB17FX/G Battery

Potassium and sodium are chemically very similar. For this reason it took a long time before their salts were differentiated. The existence of multiple elements in their salts was suspected from 1702, and this was proven in 1807 when potassium and sodium were individually isolated from different salts by electrolysis. Sony VAIO VPCEB17FX/L Battery

Potassium in nature occurs only in ionic salts. As such, it is found dissolved in seawater (which is 0.04% potassium by weight ), and is part of many minerals.

Most industrial chemical applications of potassium employ the relatively high solubility in water of potassium compounds, such as potassium soaps. Sony VAIO VPCEB17FX/P Battery

Potassium metal has only a few special applications, being replaced in most chemical reactions with sodium metal.

Potassium ion is necessary for the function of all living cells. Potassium ion diffusion is a key mechanism in nerve transmission, and potassium depletion in animals, including humans, results in various cardiac dysfunctions. Sony VAIO VPCEB17FX/W Battery

Potassium is found in especially high concentrations within plant cells, and in a mixed diet, it is mostly concentrated in fruits. The high concentration of potassium in plants, associated with comparatively low amounts of sodium there, historically resulted in potassium first being isolated from potash, the ashes of plants, giving the element its name.Sony VAIO VPCEB190X Battery

Heavy crop production rapidly depletes soils of potassium, and agricultural fertilizers consume 95% of global potassium chemical production.

Potassium atoms have 19 electrons, which is one more than the extremely stable configuration of argon. A potassium atom is thus much more likely to lose the "extra" electron than to gain one; however, the alkalide ions, K–, are known.Sony VAIO VPCEB19FX Battery

Because of the low first ionization energy (418.8 kJ/mol) the potassium atom easily loses an electron and oxidizes into the monopositive cation, K+.[6]This process requires so little energy that potassium is readily oxidized by atmospheric oxygen. Sony VAIO VPCEB19GX Battery

In contrast the second ionization energy, is very high (3052 kJ/mol), because removal of two electrons breaks the stable noble gas electronic configuration.[6] Potassium therefore does not readily form compounds with the oxidation state of +2 (or higher).[5]

Potassium is the second least dense metal after lithium. Sony VAIO VPCEB1AFX Battery

It is a soft solid that has a low melting point and can easily be cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately after being exposed to air. In a flame test, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nm (see movie below).Sony VAIO VPCEB1AFX/B Battery

Chemical

Potassium is an extremely active metal, which reacts violently with oxygen and water in air. With oxygen, it converts to potassium peroxide and with water potassium hydroxide. The reaction of potassium with water is dangerous because of its violent and sufficient exothermic character and release of hydrogen gas. Sony VAIO VPCEB1AGX Battery

Hydrogen reacts again with atmospheric oxygen, producing water which reacts with the remaining potassium. This reaction requires only traces of water; because of this, potassium and its liquid alloy — NaK — are potent desiccants which can be used to dry solventsprior to distillation.Sony VAIO VPCEB1AGX/BI Battery

Because of the sensitivity of potassium to water and air, the reactions are only possible in inert atmosphere, such as argon gas using air-free techniques. Potassium does not react with most hydrocarbons, such as mineral oil or kerosene. It readily dissolves in liquid ammonia, up to 480 g per 1000 g of ammonia at 0 °C. Sony VAIO VPCEB1BGX Battery

Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals. In a pure solution, potassium slowly reacts with ammonia to form KNH2, but this reaction is accelerated by minute amounts of transition metal salts.Sony VAIO VPCEB1BGX/BI Battery

It can reduce the salts to the metal; potassium is often used as the reductant in the preparation of finely divided metals from their salts by the Rieke method. For example, the preparation of Rieke magnesium employs potassium as the reductant:

MgCl2 + 2 K ? Mg + 2 KCl  Sony VAIO VPCEB1CGX Battery

Compounds

The only common oxidation state for potassium is +1. Potassium metal is a powerful reducing agent which is easily oxidized to the monopositive cation, K+. Once oxidized, it is very stable and difficult to reduce back to the metal.Sony VAIO VPCEB1CGX/BI Battery

Potassium hydroxide reacts readily with carbon dioxide to produce potassium carbonate, and is used to remove traces of the gas from air. Potassium compounds generally have excellent water solubility, owing to the high hydration energy of the K+ion. The potassium ion is colorless in water and is very difficult to precipitate;Sony VAIO VPCEB1DGX Battery

possible precipitation methods include reactions with sodium tetraphenylborate, hexachloroplatinic acid, and sodium cobaltinitrite.

Potassium oxidizes faster than most metals and forms oxides with oxygen-oxygen bonds; as do all alkali metals except lithium. Three species are formed during the reaction:Sony VAIO VPCEB1DGX/BI Battery

potassium oxide, potassium peroxide, and potassium superoxide, which contain three different oxygen-based ions: oxide (O2?), peroxide (O2?2), and superoxide (O?2). The last two species, especially thesuperoxide, are rare and are formed only in reaction with very electropositive metals; these species contain oxygen—oxygen bonds.Sony VAIO VPCEB1EGX Battery

All potassium—oxygen binary compounds are known to react with water violently, forming potassium hydroxide. This compound is a very strong alkali, and 1.21 kg of it can dissolve as much as a liter of water.

In aqueous solution

Potassium compounds are typically highly ionic and thus most of them are soluble in water. Sony VAIO VPCEB1EGX/BI Battery

The main species in water are the aquo complexes [K(H2O)n]+ where n = 6 and 7. Some of the few salts that are poorly soluble include potassium tetraphenylborate, potassium hexachloroplatinate, and potassium cobaltinitrite.

There are 24 known isotopes of potassium, three of which occur naturally: 39K (93.3%), 40K (0.0117%), and 41K (6.7%). Sony VAIO VPCEB1FGX Battery

Naturally occurring 40K has a half-life of 1.250×109 years. It decays to stable 40Ar by electron capture or positron emission (11.2%) or to stable 40Ca by beta decay (88.8%). The decay of 40K to 40Ar enables a commonly used method for dating rocks.Sony VAIO VPCEB1FGX/BI Battery

The conventional K-Ar dating method depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon (i.e., 40Ar) was quantitatively retained. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40Ar that has accumulated. Sony VAIO VPCEB1GGX Battery

The minerals that are best suited for dating include biotite, muscovite, metamorphic hornblende, and volcanic feldspar; whole rock samples from volcanic flows and shallow instrusives can also be dated if they are unaltered. Outside of dating, potassium isotopes have been used as tracers in studies of weathering and for nutrient cycling studies because potassium is a macronutrient required forlife.Sony VAIO VPCEB1GGX/BI Battery

40K occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C.Sony VAIO VPCEB1HGX Battery

In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second. The activity of natural potassium is 31 Bq/g.

Creation and occurrence

Potassium is formed in the universe by nucleosynthesis from lighter atoms. The stable form of potassium is created in supernovas via the explosive Oxygen-burning process.Sony VAIO VPCEB1HGX/BI Battery

Elemental potassium does not occur in nature because it reacts violently with water (see section Precautions below). As various compounds, potassium makes up about 2.6% of the weight of the Earth's crust and is the seventh most abundant element, similar in abundance to sodium at approximately 1.8% of the crust.Sony VAIO VPCEB1JFX Battery

In seawater, potassium at 0.39 g/L[2] (0.039 wt/v%) is far less abundant than sodium at 10.8 g/L (1.08 wt/v%).

Orthoclase (potassium feldspar) is a common rock-forming mineral. Granite for example contains 5% potassium which is well above the average in the Earth's crust. Sony VAIO VPCEB1JFX/B Battery

Sylvite (KCl), carnallite (KCl·MgCl2·6(H2O)), kainite (MgSO4·KCl·3H2O) and langbeinite (MgSO4·K2SO4)) are the minerals found in large evaporite deposits worldwide. The deposits often show layers starting with the least soluble at the bottom and the most soluble on top.Sony VAIO VPCEB1JFX/G Battery

Deposits of niter (potassium nitrate) are formed by decomposition of organic material in contact with atmosphere, mostly in caves; because of the good water solubility of niter the formation of larger deposits requires special environmental conditions.

Neither elemental potassium nor potassium salts (as separate entities from other salts) were known in Roman times, and the Latin name of the element is not Classical Latin but rather neo-Latin. Sony VAIO VPCEB1JFX/L Battery

The Latin name kalium was taken from the word "alkali", which in turn came from Arabic: ?????????? al-qalyah "plant ashes." The similar-sounding English term alkali is from this same root (potassium in Modern Standard Arabic is ???????? ‹bootasyoom›).

The English name for the element potassium comes from the word "potash", Sony VAIO VPCEB1JFX/P Battery

referring to the method by which potash was obtained – leaching the ash of burnt wood or tree leaves and evaporating the solution in a pot. Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant's major mineral content consists of calcium salts of relatively low solubility in water. Sony VAIO VPCEB1JFX/W Battery

While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. Georg Ernst Stahl obtained experimental evidence which led him to suggest the fundamental difference of sodium and potassium salts in 1702,and Henri Louis Duhamel du Monceauwas able to prove this difference in 1736.Sony VAIO VPCEB1KGX Battery

The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus Antoine Lavoisier did include the alkali in his list of chemical elements in 1789.

Potassium metal was first isolated in 1807 in England by Sir Humphry Davy, who derived it from caustic potash (KOH), Sony VAIO VPCEB1KGX/B Battery

by the use of electrolysis of the molten salt with the newly discovered voltaic pile. Potassium was the first metal that was isolated by electrolysis. Later in the same year, Davy reported extraction of the metal sodium from a mineral derivative (caustic soda, NaOH, or lye) rather than a plant salt, by a similar technique, demonstrating that the elements, and thus the salts, are different.Sony VAIO VPCEB1KGX/W Battery

Although the production of potassium and sodium metal should have shown that both are elements, it took some time before this view was universally accepted.

For a long time the only significant applications for potash were the production of glass, bleach, and soap.Sony VAIO VPCEB1LFX Battery

Potassium soaps from animal fats and vegetable oils were especially prized, as they tended to be more water-soluble and of softer texture, and were known as soft soaps.The discovery by Justus Liebig in 1840 that potassium is a necessary element for plants and that most types of soil lack potassium caused a steep rise in demand for potassium salts. Sony VAIO VPCEB1LFX/BI Battery

Wood-ash from fir trees was initially used as a potassium salt source for fertilizer, but with the discovery in 1868 of mineral deposits containing potassium chloride near Staßfurt, Germany, the production of potassium-containing fertilizers began at an industrial scale. Other potash deposits were discovered, and by the 1960s Canada became the dominant producer.Sony VAIO VPCEB1LFX/WI Battery

Commercial production

Potassium salts such as carnallite, langbeinite, polyhalite, and sylvite form extensive deposits in ancient lake and seabeds, making extraction of potassium salts in these environments commercially viable. Sony VAIO VPCEB1MFX Battery

The principal source of potassium – potash – is mined in Canada, Russia, Belarus, Germany, Israel, United States, Jordan, and other places around the world. The first mined deposits were located near Staßfurt, Germany, but the deposits span from Great Britain over Germany into Poland. Sony VAIO VPCEB1MFX/BI Battery

They are located in the Zechstein and were deposited in the Middle to Late Permian. The largest deposits ever found lie 1000 meters (3000 feet) below the surface of the Canadian province of Saskatchewan. The deposits are located in the Elk Point Group produced in the Middle Devonian. Sony VAIO VPCEB1NFX Battery

Saskatchewan, where several large mines have operated since the 1960s, pioneered the use of freezing of wet sands (the Blairmore formation) in order to drive mine shafts through them. The main potash mining company in Saskatchewan is the Potash Corporation of Saskatchewan.Sony VAIO VPCEB1NFX/B Battery

The water of the Dead Sea is used by Israel and Jordan as a source for potash, while the concentration in normal oceans is too low for commercial production.

Several methods are applied to separate the potassium salts from the present sodium and magnesium compounds.Sony VAIO VPCEB1NFX/L Battery

The mostly used method is to precipitate some compounds relying on the solubility difference of the salts at different temperatures. Electrostatic separation of the ground salt mixture is also used in some mines. The resulting sodium and magnesium waste is either stored underground or piled up in slag heaps. Sony VAIO VPCEB1NFX/P Battery

Most of the mined potassium minerals end up as potassium chloride after processing. The mineral industry refers to potassium chloride either as potash, muriate of potash or simply MOP.

Pure potassium metal can be isolated by electrolysis of its hydroxide in a process that has changed little since Davy. Sony VAIO VPCEB1NFX/W Battery

Although the electrolysis process was developed and used in industrial scale in the 1920s the thermal method by reacting sodium withpotassium chloride in a chemical equilibrium reaction became the dominant method in the 1950s. The production of sodium potassium alloys is possible by changing the reaction time and the amount of sodium used in the reaction. Sony VAIO VPCEB1PFX Battery

The Griesheimer process employing the reaction of potassium fluoride with calcium carbide was also used to produce potassium.

Na + KCl ? NaCl + K                      (Thermal method)

2 KF + CaC2 ? 2K + CaF2 + 2 C       (Griesheimer process)

Reagent-grade potassium metal cost about $10.00/pound ($22/kg) in 2010 when purchased in tonne quantities. Sony VAIO VPCEB1PFX/B Battery

Lower purity metal is considerably cheaper. The market is volatile due to the difficulty of the long-term storage of the metal. It must be stored under a dry inert gas atmosphere or anhydrous mineral oil to prevent the formation of a surface layer of potassium superoxide. Sony VAIO VPCEB1QGX Battery

This superoxide is a pressure-sensitive explosive which will detonate when scratched. The resulting explosion will usually start a fire which is difficult to extinguish.

Potassium is the eighth or ninth most common element by mass (0.2%) in the human body, so that a 60 kg adult contains a total of about 120 grams of potassium.Sony VAIO VPCEB1QGX/BI Battery

The body has about as much potassium as sulfur and chlorine, and only the major minerals calcium and phosphorus are more abundant. Sony VAIO VPCEB1RGX/BI Battery

Potassium cations are important in neuron (brain and nerve) function, and in influencing osmotic balancebetween cells and the interstitial fluid, with their distribution mediated in all animals (but not in all plants) by the so-called Na+/K+-ATPase pump.Sony VAIO VPCEB1RGX Battery

This ion pump uses ATP to pump three sodium ions out of the cell and two potassium ions into the cell, thus creating an electrochemical gradient over the cell membrane. In addition, the highly selective potassium ion channels (which are tetramers) are crucial for the hyperpolarization, in for example neurons, after an action potential is fired. Sony VAIO VPCEB20 Battery

The most recently resolved potassium ion channel is KirBac3.1, which gives a total of five potassium ion channels (KcsA, KirBac1.1, KirBac3.1, KvAP, and MthK) with a determined structure. All five are fromprokaryotic species.

Potassium can be detected by taste because it triggers three of the five types of taste sensations, according to concentration. Sony VAIO VPCEC20 Battery

Dilute solutions of potassium ions taste sweet, allowing moderate concentrations in milk and juices, while higher concentrations become increasingly bitter/alkaline, and finally also salty to the taste. The combined bitterness and saltiness of high-potassium solutions makes high-dose potassium supplementation by liquid drinks a palatability challenge.Sony VAIO VPCEE20 Battery

Membrane polarization

Potassium is also important in preventing muscle contraction and the sending of all nerve impulses in animals through action potentials.Sony VAIO VPCEF20 Battery

By nature of their electrostatic and chemical properties, K+ ions are larger than Na+ ions, and ion channels and pumps in cell membranes can distinguish between the two types of ions, actively pumping or passively allowing one of the two ions to pass, while blocking the other. Sony VAIO VPCF112FX/B Battery

A shortage of potassium in body fluids may cause a potentially fatal condition known as hypokalemia, typically resulting from vomiting, diarrhea, and/or increased diuresis. Deficiency symptoms include muscle weakness, paralytic ileus, ECG abnormalities, decreased reflex response and in severe cases respiratory paralysis,alkalosis and cardiac arrhythmia.Sony VAIO VPCF115FG/B Battery

Filtration and excretion

Potassium is an essential mineral micronutrient in human nutrition; it is the major cation (positive ion) inside animal cells, and it is thus important in maintaining fluid and electrolyte balance in the body. Sodium makes up most of the cations of blood plasma at a reference range of about 145 milliequivalents per liter (mEq/L; 3.345 grams), Sony VAIO VPCF116FGBI Battery

and potassium makes up most of the cell fluid cations at about 150 mEq/L (4.8 grams). Plasma is filtered through the glomerulus of the kidneys in enormous amounts, about 180 liters per day. Thus 602 grams of sodium and 33 grams of potassium are filtered each day. Sony VAIO VPCF117FJ/W Battery

All but the 1–10 grams of sodium and the 1–4 grams of potassium likely to be in the diet must be reabsorbed. Sodium must be reabsorbed in such a way as to keep the blood volume exactly right and the osmotic pressure correct; potassium must be reabsorbed in such a way as to keep serum concentration as close as possible to 4.8 mEq/L (about 0.190 g/L).Sony VAIO VPCF117HG/BI Battery

Sodium pumps in the kidneys must always operate to conserve sodium. Potassium must sometimes be conserved also, but as the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about thirty times as large, the situation is not so critical for potassium. Sony VAIO VPCF118FJ/W Battery

Since potassium is moved passively in counter flow to sodium in response to an apparent (but not actual) Donnan equilibrium, the urine can never sink below the concentration of potassium in serum except sometimes by actively excreting water at the end of the processing. Sony VAIO VPCF119FC Battery

Potassium is secreted twice and reabsorbed three times before the urine reaches the collecting tubules. At that point, it usually has about the same potassium concentration as plasma. At the end of the processing, potassium is secreted one more time if the serum levels are too high.Sony VAIO VPCF119FC/BI Battery

If potassium were removed from the diet, there would remain a minimum obligatory kidney excretion of about 200 mg per day when the serum declines to 3.0–3.5 mEq/L in about one week, and can never be cut off completely, resulting in hypokalemia and even death.Sony VAIO VPCF119FJ/BI Battery

The potassium moves passively through pores in the cell membrane. When ions move through pumps there is a gate in the pumps on either side of the cell membrane and only one gate can be open at once. As a result, approximately 100 ions are forced through per second. Sony VAIO VPCF11AFJ Battery

Pores have only one gate, and there only one kind of ion can stream through, at 10 million to 100 million ions per second.The pores require calcium in order to open although it is thought that the calcium works in reverse by blocking at least one of the pores.Sony VAIO VPCF11AGJ Battery

Carbonyl groups inside the pore on the amino acids mimic the water hydration that takes place in water solution by the nature of the electrostatic charges on four carbonyl groups inside the pore.

Adequate intake

A potassium intake sufficient to support life can generally be guaranteed by eating a variety of foods. Sony VAIO VPCF11AHJ Battery

Clear cases of potassium deficiency (as defined by symptoms, signs and a below-normal blood level of the element) are rare in healthy individuals. Foods rich in potassium include parsley, dried apricots, dried milk, chocolate, various nuts (especially almonds and pistachios),Sony VAIO VPCF11JFX/B Battery

potatoes, bamboo shoots, bananas, avocados, soybeans, and bran, although it is also present in sufficient quantities in most fruits, vegetables, meat and fish.

Optimal intake

Epidemiological studies and studies in animals subject to hypertension indicate that diets high in potassium can reduce the risk of hypertension and possibly stroke Sony VAIO VPCF11M1E Battery

(by a mechanism independent of blood pressure), and a potassium deficiency combined with an inadequate thiamine intake has produced heart disease in rats. There is some debate regarding the optimal amount of dietary potassium. For example, the 2004 guidelines of the Institute of Medicine specify a DRI of 4,000 mg of potassium (100 mEq),Sony VAIO VPCF11M1E/H Battery

though most Americans consume only half that amount per day, which would make them formally deficient as regards this particular recommendation. Similarly, in the European Union, particularly in Germany and Italy, insufficient potassium intake is somewhat common.Sony VAIO VPCF11MFX/B Battery

Italian researchers reported in a 2011 meta-analysis that a 1.64 g higher daily intake of potassium was associated with a 21% lower risk of stroke.

Medical supplementation and disease

Supplements of potassium in medicine are most widely used in conjunction with loop diuretics and thiazides,Sony VAIO VPCF11S1E Battery

classes of diuretics which rid the body of sodium and water, but have the side effect of also causing potassium loss in urine. A variety of medical and non-medical supplements are available. Potassium salts such as potassium chloride may be dissolved in water, but the salty/bitter taste of high concentrations of potassium ion make palatable high concentration liquid supplements difficult to formulate. Sony VAIO VPCF11S1E/B Battery

Typical medical supplemental doses range from 10 mEq (400 mg, about equal to a cup of milk or 6 US fl oz (180 ml). of orange juice) to 20 mEq (800 mg) per dose. Potassium salts are also available in tablets or capsules, which for therapeutic purposes are formulated to allow potassium to leach slowly out of a matrix, Sony VAIO VPCF11Z1E Battery

as very high concentrations of potassium ion (which might occur next to a solid tablet of potassium chloride) can kill tissue, and cause injury to the gastric or intestinal mucosa. For this reason, non-prescription supplement potassium pills are limited by law in the US to only 99 mg of potassium.Sony VAIO VPCF11Z1E/BI Battery

Individuals suffering from kidney diseases may suffer adverse health effects from consuming large quantities of dietary potassium. End stage renal failure patients undergoing therapy by renal dialysis must observe strict dietary limits on potassium intake, Sony VAIO VPCF11ZHJ Battery

as the kidneys control potassium excretion, and buildup of blood concentrations of potassium (hyperkalemia) may trigger fatal cardiac arrhythmia.

Potassium ions are an essential component of plant nutrition and are found in most soil types.Sony VAIO VPCF127HGBI Battery

They are used as a fertilizer inagriculture, horticulture, and hydroponic culture in the form of chloride (KCl), sulfate (K2SO4), or nitrate (KNO3). Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl.Sony VAIO VPCF137HG/BI Battery

The potassium content of most plants range from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount ofK2O. Modern high-yield agriculture depends upon fertilizers to replace the potassium lost at harvest. Most agricultural fertilizers contain potassium chloride, while potassium sulfate is used for chloride-sensitive crops or crops needing higher sulfur content.Sony VAIO VPC-P111KX/B Battery

The sulfate is mostly produced by decomposition of the complex minerals kainite (MgSO4·KCl·3H2O) and langbeinite(MgSO4·K2SO4). Only a very few fertilizers contain potassium nitrate. In 2005, about 93% of world potassium production was consumed by the fertilizer industry.Sony VAIO VPC-P111KX/D Battery

Food

The potassium cation is a nutrient necessary for human life and health. Potassium chloride is used as a substitute for table saltby those seeking to reduce sodium intake so as to control hypertension. The USDA lists tomato paste, orange juice, beet greens,white beans, potatoes, bananas and many other good dietary sources of potassium, ranked in descending order according to potassium content.Sony VAIO VPC-P111KX/G Battery

Potassium sodium tartrate (KNaC4H4O6, Rochelle salt) is the main constituent of baking powder; it is also used in the silvering of mirrors. Potassium bromate (KBrO3) is a strong oxidizer (E924), used to improve dough strength and rise height. Potassium bisulfite (KHSO3) is used as a food preservative, for example in wine and beer-making (but not in meats).Sony VAIO VPC-P111KX/P Battery

It is also used to bleach textiles and straw, and in the tanning of leathers.

Industrial

Major potassium chemicals are potassium hydroxide, potassium carbonate, potassium sulfate, and potassium chloride. Megatons of these compounds are produced annually.Sony VAIO VPC-P111KX/W Battery

Potassium hydroxide KOH is a strong base, which is used in industry to neutralize strong and weak acids, to control pH and to manufacture potassium salts. It is also used to saponify fats and oils, in industrial cleaners, and in hydrolysis reactions, for example of esters.Sony VAIO VPC-P112KX/B Battery

Potassium nitrate (KNO3) or saltpeter is obtained from natural sources such as guano and evaporites or manufactured via the Haber process; it is the oxidant ingunpowder (black powder) and an important agricultural fertilizer. Potassium cyanide (KCN) is used industrially to dissolve copper and precious metals, particularlysilver and gold, by forming complexes. Sony VAIO VPC-P112KX/D Battery

Its applications include gold mining, electroplating, and electroforming of these metals; it is also used in organic synthesisto make nitriles. Potassium carbonate (K2CO3 or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments.Sony VAIO VPC-P112KX/G Battery

Potassium permanganate (KMnO4) is an oxidizing, bleaching and purification substance and is used for production of saccharin. Potassium chlorite (KClO3) is added to matches and explosives. Potassium bromide (KBr) was formerly used as a sedative and in photography.Sony VAIO VPC-P112KX/P Battery

Potassium chromate (K2CrO4) is used in inks, dyes, stains (bright yellowish-red color); in explosives and fireworks; in the tanning of leather, in fly paper andsafety matches, but all these uses are due to the properties of chromate ion containment rather than potassium ions.Sony VAIO VPC-P112KX/W Battery

Niche uses

Potassium compounds are so pervasive that thousands of small uses are in place. The superoxide KO2 is an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber. It is widely used in respiration systems in mines, submarines and spacecraft as it takes less volume than the gaseous oxygen.Sony VAIO VPCP113KX/B Battery

4 KO2 + 2 CO2 ? 2 K2CO3 + 3 O2

Potassium cobaltinitrite K3[Co(NO2)6] is used as artist's pigment under the name of Aureolin or Cobalt yellow.

Laboratory uses

An alloy of sodium and potassium, NaK is a liquid used as a heat-transfer medium and a desiccant for producing dry and air-free solvents. It can also be used inreactive distillation.Sony VAIO VPC-P113KX/B Battery

The ternary alloy of 12% Na, 47% K and 41% Cs has the lowest melting point of ?78 °C of any metallic compound.

Metallic potassium is used in several types of magnetometers.

Precautions

Potassium reacts very violently with water producing potassium hydroxide (KOH) and hydrogen gas.Sony VAIO VPCP113KX/D Battery

2 K (s) + 2 H2O (l) ? 2 KOH (aq) + H2? (g)

This reaction is exothermic and releases enough heat to ignite the resulting hydrogen. It in turn may explode in the presence of oxygen. Potassium hydroxide is a strong alkali which causes skin burns. Finely divided potassium will ignite in air at room temperature. The bulk metal will ignite in air if heated.Sony VAIO VPC-P113KX/D Battery

Because its density is 0.89 g/cm3, burning potassium floats in water that exposes it to atmospheric oxygen. Many common fire extinguishing agents, including water, are either ineffective or make a potassium fire worse. Nitrogen, argon, Sodium chloride (table salt), sodium carbonate (soda ash), and silicon dioxide (sand) are effective if they are dry. Sony VAIO VPCP113KX/G Battery

Some Class D dry powder extinguishers designed for metal fires are also effective. These agents deprive the fire of oxygen and cool the potassium metal.

Potassium reacts violently with halogens and will detonate in the presence of bromine. It also reacts explosively with sulfuric acid. During combustion potassium forms peroxides and superoxides. Sony VAIO VPC-P113KX/G Battery

These peroxides may react violently with organic compounds such as oils. Both peroxides and superoxides may react explosively with metallic potassium.

Because potassium reacts with water vapor present in the air, it is usually stored under anhydrous mineral oil or kerosene.Sony VAIO VPCP113KX/P Battery

Unlike lithium and sodium, however, potassium should not be stored under oil for longer than 6 months, unless in an inert (oxygen free) atmosphere, or under vacuum. After prolonged storage in air dangerous shock-sensitive peroxides can form on the metal and under the lid of the container, and can detonate upon opening.Sony VAIO VPC-P113KX/P Battery

Because of the highly reactive nature of potassium metal, it must be handled with great care, with full skin and eye protection and preferably an explosion-resistant barrier between the user and the metal. Ingestion of large amounts of potassium compounds can lead to hyperkalemia strongly influencing the cardiovascular system.Sony VAIO VPCP113KX/W Battery

Potassium chloride is used in the United States for death penalty via lethal injection.

Sir Humphry Davy, 1st Baronet FRS MRIA (17 December 1778 – 29 May 1829) was a British chemist and inventor. He is probably best remembered today for his discoveries of several alkali and alkaline earth metals, Sony VAIO VPC-P113KX/W Battery

as well as contributions to the discoveries of the elemental nature of chlorine and iodine. Berzelius called Davy's 1806 Bakerian Lecture On Some Chemical Agencies of Electricity "one of the best memoirs which has ever enriched the theory of chemistry." This paper was central to any chemical affinity theory in the first half of the nineteenth century.Sony VAIO VPC-P114KX/B Battery

In 1815 he invented the Davy lamp, which allowed miners to work safely in the presence of flammable gases.

Davy was born in Penzance in Cornwall, United Kingdom, on 17 December 1778. The parish register of Madron (the parish church) records ‘Humphry Davy, son of Robert Davy, baptized at Penzance, January 22nd, 1779.’ Sony VAIO VPC-P114KX/D Battery

inal-sony-vaio-vpc-p114kx-d-battery-27610.htm" title="Sony VAIO VPC-P114KX/D laptop battery">Robert Davy was a wood carver at Penzance, who pursued his art rather for amusement than profit. As the representative of an old family (monuments to his ancestors in Ludgvan Church date as far back as 1635), he became possessor of a modest patrimony. His wife, Grace Millet, came from an old but no longer wealthy family. Sony VAIO VPC-P114KX/G Battery

Her parents died within a few hours of each other from malignant fever, whereupon Grace and her two sisters were adopted by John Tonkin, an eminent surgeon in Penzance. Robert Davy and his wife became the parents of five children — two boys, Humphry, the eldest, and John, and three girls.Sony VAIO VPC-P114KX/P Battery

In Davy's childhood the family moved from Penzance to Varfell, their family estate in Ludgvan. Davy's boyhood was spent partly with his parents and partly with Tonkin, who placed him at a preparatory school kept by a Mr. Bushell, who was so much struck with the boy's progress that he persuaded Davy's father to send him to a better school.Sony VAIO VPC-P114KX/W Battery

Davy was at an early age placed at the Penzance Grammar School, then under the care of the Rev. J. C. Coryton. Numerous anecdotes show that Davy was a precocious boy, possessing a remarkable memory and being singularly rapid in acquiring knowledge of books. He was especially attracted by John Bunyan's The Pilgrim's Progress, and he delighted in reading history. Sony VAIO VPCP115JC Battery

When but eight years of age he would collect a number of boys, and standing on a cart in the market-place address them on the subject of his latest reading. He delighted in the folklore of this remote district, and became, as he himself tells us, a ‘tale-teller.’ The ‘applause of my companions,’ he says, ‘was my recompense for punishments incurred for being idle.Sony VAIO VPCP115JC/B Battery

’ These conditions developed a love of poetry and the composition of verses and ballads.

At the same time Davy acquired a taste for experimental science. This was mainly due to a member of the Society of Friends namedRobert Dunkin, a saddler and a man of original mind. Dunkin constructed for himself an electrical machine, voltaic piles, and Leyden jars, and made models to illustrate mathematical principles. Sony VAIO VPCP115JC/D Battery

Using these he instructed Davy in the rudiments of experimental science. As professor at the Royal Institution Davy would later repeat many of the ingenious experiments which he had learned from his Quaker instructor. From the Penzance school Davy went in 1793 toTruro, and finished his education under the Rev.Sony VAIO VPCP115JC/G Battery

Dr. Cardew, who, in a letter to Davies Gilbert, says: ‘I could not discern the faculties by which he was afterwards so much distinguished.’ Davy says himself: ‘I consider it fortunate I was left much to myself as a child, and put upon no particular plan of study. … What I am I made myself.’ Sony VAIO VPCP115JC/P Battery

Apprentice and poet

After the death of Davy's father in 1794, Tonkin apprenticed the boy to John Bingham Borlase, a surgeon in large practice at Penzance. Davy's indenture is dated 10 February 1795. In the apothecary's dispensary Davy became a chemist, and a garret in Tonkin's house was the scene of his earliest chemical operations. Sony VAIO VPCP115JC/W Battery

Davy's friends would often say: ‘This boy Humphry is incorrigible. He will blow us all,’ and his eldest sister complained of the ravages made on her dresses by corrosive substances.

Much has been said of Davy as a poet, and John Ayrton Paris somewhat hastily says that his verses ‘bear the stamp of lofty genius.’Sony VAIO VPCP115KG Battery

Davy's first production preserved bears the date of 1795. It is entitled ‘The Sons of Genius,’ and is marked by the usual immaturity of youth. The poems, produced in the following years, especially those ‘On the Mount's Bay’ and ‘St. Michael's Mount,’ are pleasingly descriptive verses, showing sensibility, but no true poetic imagination. Sony VAIO VPCP116KG Battery

Davy was also a painter and three paintings of circa 1796 have been donated to the Penlee House museum, Penzance. One picture is of the view from above Gulval showing the church, Mount's Bay and the mount and the other two depict Loch Lomond in Scotland.Sony VAIO VPC-P116KX/B Battery

Davy soon abandoned poetry for science. While writing verses at the age of seventeen in honour of his first love, he was eagerly discussing with his Quaker friend the question of the materiality of heat. Robert Dunkin once remarked: ‘I tell thee what, Humphry, thou art the most quibbling hand at a dispute I ever met with in my life.’ Sony VAIO VPC-P116KX/D Battery

One winter day he took Dunkin to Larigan river, to show him that the rubbing of two plates of ice together developed sufficient energy by motion to melt them, and that the motion being suspended the pieces were united by regelation. This was, in a rude form, an elementary version of an analogous experiment later exhibited by Davy in the lecture-room of the Royal Institution, which excited considerable attention. Sony VAIO VPC-P116KX/G Battery

Early scientific interests

Davies Giddy, afterwards Davies Gilbert, accidentally saw Davy in Penzance, carelessly swinging on the half-gate of Dr Borlase's house. Gilbert was interested by the lad's talk, offered him the use of his library, and invited him to his house at Tredrea. Sony VAIO VPC-P116KX/P Battery

This led to an introduction to Dr Edwards, who then resided at Hayle Copper House, and was also chemical lecturer in the school of St. Bartholomew's Hospital. Dr Edwards permitted Davy to use the apparatus in his laboratory, and appears to have directed his attention to the floodgates of the port of Hayle, which were rapidly decaying from the contact of copper and iron under the influence of seawater.Sony VAIO VPC-P116KX/W Battery

Galvanic corrosion was not then understood, but the phenomenon prepared the mind of Davy for his experiments on the copper sheathing of ships in later days. Gregory Watt, the son of James Watt, visited Penzance for his health's sake, and lodging at Mrs Davy's house became a friend of her son and gave him instructions in chemistry. Sony VAIO VPCP118JC Battery

Davy also formed a useful acquaintance with the Wedgwood family, who spent a winter at Penzance.

Dr Thomas Beddoes and Professor Hailstone were engaged in a geological controversy upon the rival merits of the Plutonian and the Neptunist hypotheses. Sony VAIO VPCP118JC/B Battery

They travelled together to examine the Cornish coast accompanied by Davies Gilbert, and thus made Davy's acquaintance. Beddoes, who had recently established at Bristol a ‘Pneumatic Institution,’ required an assistant to superintend the laboratory.Sony VAIO VPCP118JC/P Battery

Gilbert recommended Davy for the post, and Gregory Watt, in 1798, showed Beddoes the ‘Young man's Researches on Heat and Light,’ which were subsequently published by him in the first volume of ‘West-Country Contributions.’ Prolonged negotiations were carried on, mainly by Gilbert.Sony VAIO VPCP118JC/W Battery

Mrs Davy and Borlase consented to Davy's departure, but Tonkin desired to fix him in his native town as a surgeon, and actually altered his will when he found that Davy insisted on going to Dr Beddoes.

The Pneumatic Institution

On 2 October 1798, Davy joined the ‘Pneumatic Institution’ at Bristol.Sony VAIO VPC-P118KX/B Battery

This institution had been established for the purpose of investigating the medical powers of factitious airs and gases, and to Davy was committed the superintendence of the various experiments. The arrangement concluded between Dr. Beddoes and Davy was a liberal one, and enabled Davy to give up all claims upon his paternal property in favour of his mother.Sony VAIO VPC-P118KX/D Battery

He did not intend to abandon the profession of medicine, being still determined to study and graduate at Edinburgh, but he soon began to fill parts of the Institution with voltaic batteries. During his residence at Bristol, Davy formed the acquaintance of the Earl of Durham, who became a resident for his health in the Pneumatic Institution,Sony VAIO VPC-P118KX/G Battery

and close friendships with Gregory Watt, James Watt, Samuel Taylor Coleridge and Robert Southey, all of whom became regular users of Davy's nitrous oxide (laughing gas), to which Davy would become addicted. The gas was first synthesized by English natural philosopher and chemist Joseph Priestley in 1772, who called it phlogisticated nitrous air (see phlogiston).Sony VAIO VPC-P118KX/P Battery

Priestley published his discovery in the book Experiments and Observations on Different Kinds of Air (1775), where he described how to produce the preparation of "nitrous air diminished", by heating iron filings dampened with nitric acid.Sony VAIO VPC-P118KX/W Battery

James Watt built a portable gas chamber for the purpose of Davy's nitrous oxide inhalation experiments, which at one point were combined with wine to judge the efficacy of nitrous oxide as a cure for hangovers (his laboratory notebook indicated success).Sony VAIO VPCP119JC Battery

Despite the popularity of the gas among Davy's friends and acquaintances and his copious notes about the ability of the gas to entirely take away the sensation of pain, Davy seems never to have considered the use of nitrous oxide as an anesthetic, missing a huge opportunity. Anesthetics would not be regularly used in medicine or dentistry until decades after Davy's death. Sony VAIO VPCP119JC/BI Battery

Davy threw himself energetically into the labours of the laboratory and formed a long romantic friendship with Mrs Anna Beddoes who acted as his guide on walks and other fine sights of the locality. In December 1799 Davy visited London for the first time, and his circle of friends was there much extended.Sony VAIO VPCP11S1E/B Battery

In these gas experiments Davy ran considerable risks. His respiration of nitric oxide may have led, by its union with common air in the mouth, to the formation ofnitric acid (HNO3), which severely injured the mucous membrane, and in Davy's attempt to inhale four quarts of 'pure hydrocarbonate' gas in an experiment with carbon monoxide he ‘seemed sinking into annihilation.’ Sony VAIO VPC-P11S1E/B Battery

On being removed into the open air, Davy faintly articulated, ‘I do not think I shall die,’ but some hours elapsed before the painful symptoms ceased.[5] Davy was still able to take his own pulse as he staggered out of the laboratory and into the garden, and he described it in his notes as 'threadlike and beating with excessive quickness'.Sony VAIO VPCP11S1E/D Battery

In this year the first volume of the ‘West-Country Collections’ was issued. Half of the volume consisted of Davy's essays ‘On Heat, Light, and the Combinations of Light,’ ‘On Phos-oxygen and its Combinations,’ and on the ‘Theory of Respiration.’ On 22 February 1799 Davy, writing to Davies Gilbert, says:Sony VAIO VPC-P11S1E/D Battery

‘I am now as much convinced of the non-existence of caloric as I am of the existence of light.’ In another letter written to Davies Gilbert, on 10 April, Davy informs him: I made a discovery yesterday which proves how necessary it is to repeat experiments. The gaseous oxide of azote (the laughing gas) is perfectly respirable when pure.Sony VAIO VPCP11S1E/G Battery

It is never deleterious but when it contains nitrous gas. I have found a mode of making it pure.’ He then says that he breathed sixteen quarts of it for nearly seven minutes, and that it ‘absolutely intoxicated me.’ During this year Davy published his ‘Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration.’ Sony VAIO VPC-P11S1E/G Battery

In after years Davy regretted that he had ever published these immature hypotheses, which he himself subsequently designated as ‘the dreams of misemployed genius which the light of experiment and observation has never conducted to truth.’

Davy's later time at the Pneumatic Institution was spent partially in experimentation In 1800, Sony VAIO VPCP11S1E/P Battery

Davy informed Davies Gilbert that he had been ‘repeating the galvanic experiments with success’ in the intervals of the experiments on the gases, which ‘almost incessantly occupied him from January to April.’

The Royal Institution

In 1799, Count Rumford had proposed the establishment in London of an ‘Institution for Diffusing Knowledge’, i.e. the Royal Institution.Sony VAIO VPCP11S1E/W Battery

The house in Albemarle Street was bought in April 1799. Rumford became secretary to the institution, and Dr. Garnett was the first lecturer.

Davy's ‘Researches,’ which was full of striking and novel facts, and rich in chemical discoveries, soon attracted the attention of natural philosophers, and Davy now made his grand move in life. Sony VAIO VPC-P11S1E/W Battery

Joseph Banks had long had his eye on Davy, and in February 1801 Davy was officially interviewed by Banks,Benjamin Thompson (who had been appointed Count Rumford) and Henry Cavendish, the Committee of the Royal Institution. Davy wrote to Davies Giddy on March 8, 1801 about the offers made by Banks and Thompson, Sony VAIO VPCP11Z9E/B Battery

a possible move to London and the promise of funding for Davy's work in galvanism. In that letter he also mentioned that he might not be collaborating further with Beddoes on therapeutic gases. The next day Davy left Bristol to take up his new post at the Royal Institution,Sony VAIO VPCS111FM/S Battery

it having been resolved ‘that Humphry Davy be engaged in the service of the Royal Institution in the capacity of assistant lecturer in chemistry, director of the chemical laboratory, and assistant editor of the journals of the institution, and that he be allowed to occupy a room in the house, and be furnished with coals and candles, and that he be paid a salary of 100l. per annum.’Sony VAIO VPCS115EC Battery

On April 25, 1801, Davy gave his first lecture on the relatively new subject of 'Galvanism'. He and his good friend Coleridge had had many conversations about the nature of human knowledge and progress, and Davy's lectures gave his audience a vision of human civilization brought forward by scientific discovery. Sony VAIO VPCS115FG Battery

"It [science] has bestowed on him powers which may almost be called creative; which have enabled him to modify and change the beings surrounding him, and by his experiments to interrogate nature with power, not simply as a scholar, passive and seeking only to understand her operations, but rather as a master, active with his own instruments."Sony VAIO VPCS117GG Battery

The first lecture garnered rave reviews, and by the June lecture Davy wrote to John King that his last lecture had attendance of nearly 500 people. "There was Respiration, Nitrous Oxide, and unbounded Applause. Amen!"

Davy's lectures also included spectacular and sometimes dangerous chemical demonstrations for his audience, a generous helping of references to divine creation, and genuine scientific information.Sony VAIO VPCS117GGB Battery

Not only a popular lecturer, the young and handsome Davy acquired a huge female following around London, and nearly half of the attendees pictured in Gillray's cartoon are female. When Davy's lecture series on Galvanism ended, he progressed to a new series on Agricultural Chemistry, and his popularity continued to skyrocket. Sony VAIO VPCS118EC Battery

By June 1802, after just over a year at the Institution and at the age of 23, Davy was nominated to full lecturer at the Royal Institution of Great Britain. Garnett quietly resigned, citing health reasons.

In November 1804 Davy became a Fellow of the Royal Society, over which he would later preside. In 1810, he was elected a foreign member of the Royal Swedish Academy of Sciences.Sony VAIO VPCS119FJ/B Battery

Discovery of new elements

Davy was a pioneer in the field of electrolysis using the voltaic pile to split up common compounds and thus prepare many new elements. He went on to electrolyse molten salts and discovered several new metals, especially sodium andpotassium, highly reactive elements known as the alkali metals. Sony VAIO VPCS119GC Battery

Potassium was discovered in 1807 by Davy, who derived it from caustic potash (KOH). Before the 18th century, no distinction was made between potassium and sodium. Potassium was the first metal that was isolated by electrolysis. Sodium was first isolated by Davy in the same year by passing an electric current through molten sodium hydroxide. Sony VAIO VPCS11AFJ Battery

Davy went on to discover calcium in 1808 by electrolyzing a mixture of lime and mercuric oxide.Davy was trying to isolate calcium; when he heard that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. He worked with electrolysis throughout his life and also discovered magnesium, boron and barium.Sony VAIO VPCS11AGJ Battery

Discovery of chlorine

Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, who called it "dephlogisticated marine acid"(see phlogiston theory) and mistakenly thought it contained oxygen. Scheele had produced chlorine by reacting manganese dioxide (MnO2) with hydrogen chloride (HCl).Sony VAIO VPCS11AHJ Battery

4 HCl + MnO2 ? MnCl2 + 2 H2O + Cl2

Scheele observed several properties of chlorine gas, such as its bleaching effect on litmus, its deadly effect on insects, its yellow-green colour, and the similarity of its smell to that of aqua regia. However, Scheele was unable to publish his findings at the time.Sony VAIO VPCS11AVJ Battery

In 1810, chlorine was given its current name by Humphry Davy, who insisted that chlorine was in fact an element. He also showed thatoxygen could not be obtained from the substance known as oxymuriatic acid (HCl solution). This discovery overturned Lavoisier's definition of acids as compounds of oxygen.Sony VAIO VPCS11J7E/B Battery

Popular public figure

Davy revelled in his public status, as his lectures gathered many spectators. He became well known due to his experiments with the physiological action of some gases, including laughing gas (nitrous oxide), once stating that its properties bestowed all of the benefits of alcohol but was devoid of its flaws.Sony VAIO VPCS11M1E/W Battery

Davy later damaged his eyesight in a laboratory accident with nitrogen trichloride.[17] Pierre Louis Dulong first prepared this compound in 1812, and lost two fingers and an eye in two separate explosions with it. Davy's own accident induced him to hire Michael Faraday as a coworker.Sony VAIO VPCS11V9E Battery

European travels

In 1812, Davy was knighted, gave a farewell lecture to the Royal Institution, and married a wealthy widow, Jane Apreece. (While generally acknowledged as being faithful to his wife, their relationship was stormy, and in his later years Davy travelled to continental Europe alone.) Sony VAIO VPCS11V9E/B Battery

In October 1813, he and his wife, accompanied byMichael Faraday as his scientific assistant (and valet), travelled to France to collect a medal that Napoleon Bonaparte had awarded Davy for his electro-chemical work. While in Paris, Davy was asked by Gay-Lussac to investigate a mysterious substance isolated by Bernard Courtois. Sony VAIO VPCS11X9E/B Battery

Davy showed it to be an element, which is now called iodine.

The party left Paris in December 1813, travelling south to Italy. They sojourned in Florence, where, in a series of experiments conducted with Faraday's assistance, Davy succeeded in using the sun's rays to ignitediamond, proving it is composed of pure carbon.Sony VAIO VPCS123FGB Battery

Davy's party continued to Rome, and also visited Naples and Mount Vesuvius. By June 1814, they were in Milan, where they met Alessandro Volta, and then continued north to Geneva. They returned to Italy via Munich and Innsbruck, and when their plans to travel to Greece andConstantinople (Istanbul) were abandoned after Napoleon's escape from Elba, they returned to England.Sony VAIO VPCS125EC Battery

Davy lamp

After his return to England in 1815, Davy experimented with lamps for use in coal mines. There had been many mining explosions caused byfiredamp or methane often ignited by open flames of the lamps then used by miners. Sony VAIO VPCS128EC Battery

In particular the Felling mine disaster in 1812 nearNewcastle caused great loss of life, and action was needed to improve underground lighting and especially the lamps used by miners. Davy conceived of using an iron gauze to enclose a lamp's flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere.Sony VAIO VPCS129GC Battery

Although the idea of the safety lamp had already been demonstrated by William Reid Clanny and by the then unknown (but later very famous) engineer George Stephenson, Davy's use of wire gauze to prevent the spread of flame was used by many other inventors in their later designs. Sony VAIO VPCS12C7E/B Battery

George Stephenson's lamp was very popular in the north-east coalfields, and used the same principle of preventing the flame reaching the general atmosphere, but by different means. Unfortunately, although the new design of gauze lamp initially did seem to offer protection, it gave much less light, and quickly deteriorated in the wet conditions of most pits. Sony VAIO VPCS12L9E/B Battery

Rusting of the gauze quickly made the lamp unsafe, and the number of deaths from firedamp explosions rose yet further.

There was some discussion as to whether Davy had discovered the principles behind his lamp without the help of the work of Smithson Tennant, but it was generally agreed that the work of both men had been independent. Sony VAIO VPCS12V9E/B Battery

Davy refused to patent the lamp, and its invention led to him being awarded the Rumford medal in 1816.

Acid-base studies

In 1815 Davy suggested that acids were substances that contained replaceable hydrogen – hydrogen that could be partly or totally replaced by metals. When acids reacted with metals they formed salts. Sony VAIO VPCW111XX/P Battery

Bases were substances that reacted with acids to form salts and water. These definitions worked well for most of the nineteenth century.

Last years and death

In January 1819, Davy was awarded a baronetcy, at the time the highest honour ever conferred on a man of science in Britain. A year later he became President of the Royal Society.Sony VAIO VPCW111XX/PC Battery

Davy's laboratory assistant, Michael Faraday, went on to enhance Davy's work and in the end he became the more famous and influential scientist – to the extent that Davy is supposed to have claimed Faraday as his greatest discovery. However, Davy later accused Faraday of plagiarism, Sony VAIO VPCW111XX/T Battery

causing Faraday (the first Fullerian Professor of Chemistry) to cease all research in electromagnetism until his mentor's death.

Of a sanguine, somewhat irritable temperament, Davy displayed characteristic enthusiasm and energy in all his pursuits. As is shown by his verses and sometimes by his prose, his mind was highly imaginative; Sony VAIO VPCW111XX/W Battery

the poet Coleridge declared that if he “had not been the first chemist, he would have been the first poet of his age,” and Southey said that “he had all the elements of a poet; he only wanted the art.” In spite of his ungainly exterior and peculiar manner, his happy gifts of exposition and illustration won him extraordinary popularity as a lecturer, Sony VAIO VPCW111XXP Battery

his experiments were ingenious and rapidly performed, and Coleridge went to hear him “to increase his stock of metaphors.” The dominating ambition of his life was to achieve fame, but though that sometimes betrayed him into petty jealousy, it did not leave him insensible to the claims on his knowledge of the “cause of humanity,Sony VAIO VPCW111XXT Battery

to use a phrase often employed by him in connection with his invention of the miners' lamp. Of the smaller observances of etiquette he was careless, and his frankness of disposition sometimes exposed him to annoyances which he might have avoided by the exercise of ordinary tact.Sony VAIO VPCW111XXW Battery

After spending many months attempting to recuperate, Davy died in Switzerland in 1829 of heart disease inherited from his father's side of the family. He spent the last months of his life writing "Consolations In Travel", an immensely popular, somewhat freeform compendium of poetry,Sony VAIO VPCW115XG Battery

thoughts on science and philosophy (and even speculation concerning alien life) which became a staple of both scientific and family libraries for several decades afterward. He is buried in the Plainpalais Cemetery in Geneva.

Legacy and honours

  • A plaque to honour him was included on the wall of the Royal Panopticon of Science and Arts in 1854.Sony VAIO VPCW115XGP Battery
  • A lunar crater (Davy) is named after Sir Humphry Davy. It has a diameter of 34 km and coordinates of 11.8S, 8.1W.
  • In his hometown of Penzance, Cornwall, a statue of Davy stands in front of the imposing Market House (now owned by Lloyds TSB) at the top of the town's main street Market Jew Street. Sony VAIO VPCW115XW/P Battery
  • Nearby is a house on which a commemorative plaque claims the location as the site of his birth.
  • Penzance also has a secondary school named Humphry Davy School. Like James Prescott Joule and Isaac Newton, Davy is also remembered in his hometown by a pub – "The Sir Humphry Davy" at 32 Alverton Street, west of the Market House.
  • Davy was the subject of the first ever clerihew.Sony VAIO VPCW115XW/T Battery
  • Davy was a founding Fellow of the Zoological Society of London
  • A satellite of the University of Sheffield at Golden Smithies Lane in Wath upon Dearne (Manvers) is called Humphry Davy House and is currently home to the School of Nursing and Midwifery, until April 2009.Sony VAIO VPCW115XW/W Battery
  • There is a street named after Sir Humphry Davy (Humphry-Davy-Straße) in the industrial quarter of the town of Cuxhaven, Schleswig-Holstein, Germany.
  • The University of Plymouth has named one of its science buildings after the chemist
  • The Royal Society of London has awarded the Davy Medal annually since 1877 "for an outstandingly important recent discovery in any branch of chemistry."Sony VAIO VPCW117XC/P Battery
  • Davy is the subject of a humorous song by Richard Gendall, recorded in 1980 by Cornish folk-singer Brenda Wootton, each verse of which recalls one of Davy's major discoveries.Sony VAIO VPCW117XC/T Battery
  • Cornish playwright Nick Darke wrote Laughing Gas (2005) a comedy script about the life of Sir Humphry Davy, unfinished at the time of Nick Darke's death; completed posthumously by Cornish actor and playwright Carl Grose and produced by the Truro-based production company O-region.Sony VAIO VPCW117XC/W Battery

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.

Along with sodium hydroxide (NaOH), this colorless solid is a prototypical strong base. It has many industrial and niche applications. Sony VAIO VPCW119XJ Battery

Most applications exploit its reactivity toward acids and its corrosive nature. In 2005, an estimated 700,000 to 800,000 tonnes were produced. Approximately 100 times more NaOH than KOH is produced annually.  KOH is noteworthy as the precursor to most soft and liquid soaps as well as numerous potassium-containing chemicals.Sony VAIO VPCW119XJ/P Battery

Properties and structure

Potassium hydroxide can be found in pure form by reacting sodium hydroxide with impure potassium. Potassium hydroxide is usually sold as translucent pellets, which will become tacky in air because KOH is hygroscopic. Sony VAIO VPCW119XJ/W Battery

Consequently, KOH typically contains varying amounts of water (as well as carbonates, see below). Its dissolution in water is strongly exothermic, meaning the process gives off significant heat. Concentrated aqueous solutions are sometimes called potassium lyes. Even at high temperatures, solid KOH does not dehydrate readily.Sony VAIO VPCW11AXJ Battery

Structure

At higher temperatures, solid KOH crystallizes in the NaCl crystal structure. The OH group is either rapidly or randomly disordered so that the OH? group is effectively a spherical anion of radius 1.53 Å (between Cl? and F? in size). Sony VAIO VPCW11S1E/P Battery

At room temperature, the OH? groups are ordered and the environment about the K+ centers is distorted, with K+—OH? distances ranging from 2.69 to 3.15 Å, depending on the orientation of the OH group. KOH forms a series of crystalline hydrates, namely the monohydrate KOH·H2O, the dihydrate KOH·2H2O, and the tetrahydrate KOH·4H2O.Sony VAIO VPCW11S1E/T Battery

Solubility and desiccating properties

Approximately 121 g of KOH will dissolve in 100 mL of water at room temperature (compared with 100 g of NaOH in the same volume). Lower alcohols such as methanol, ethanol, and propanols are also excellent solvents. The solubility in ethanol is about 40 g KOH/100 mL.Sony VAIO VPCW11S1E/W Battery

Because of its high affinity for water, KOH serves as a desiccant in the laboratory. It is often used to dry basic solvents, especially amines and pyridines: distillation of these basic liquids from a slurry of KOH yields the anhydrous reagent.Sony VAIO VPCW121AX Battery

Thermal stability

Like NaOH, KOH exhibits high thermal stability. The gaseous species is dimeric. Because of its high stability and relatively low melting point, it is often melt-cast as pellets or rods, forms that have low surface area and convenient handling properties.Sony VAIO VPCW126AG Battery

As a base

KOH is highly basic, forming strongly alkaline solutions in water and other polar solvents. These solutions are capable ofdeprotonating many acids, even weak ones. In analytical chemistry, titrations using solutions of KOH are used to assay acids.Sony VAIO VPCW127JC/P Battery

As a nucleophile in organic chemistry

KOH, like NaOH, serves as a source of OH?, a highly nucleophilic anion that attacks polar bonds in both inorganic and organic materials. In perhaps its most well-known reaction, aqueous KOH saponifies esters:Sony VAIO VPCW127JC/T Battery

KOH + RCO2R' ? RCO2K + R'OH

When R is a long chain, the product is called a potassium soap. This reaction is manifested by the "greasy" feel that KOH gives when touched — fats on the skin are rapidly converted to soap and glycerol.

Molten KOH is used to displace halides and other leaving groups. The reaction is especially useful for aromatic reagents to give the corresponding phenols.Sony VAIO VPCW127JC/W Battery

Reactions with inorganic compounds

Complementary to its reactivity toward acids, KOH attacks oxides. Thus, SiO2 is attacked by KOH to give soluble potassium silicates. KOH reacts with carbon dioxide to give bicarbonate:

KOH + CO2 ? KHCO3 Sony VAIO VPCW127JC/WZ Battery

Manufacture

Historically KOH was made by boiling a solution of potassium carbonate (potash) with calcium hydroxide (slaked lime), leading to a metathesis reaction which caused calcium carbonate to precipitate, leaving potassium hydroxide in solution:Sony VAIO VPCW12AAJ Battery

Ca(OH)2 + K2CO3 ? CaCO3 + 2 KOH

Filtering off the precipitated calcium carbonate and boiling down the solution gives potassium hydroxide ("calcinated or caustic potash"). This method used potash extracted from wood ashes using slaked lime. It was the most important method of producing potassium hydroxide until the late 19th century, Sony VAIO VPCW12AKJ Battery

when it was largely replaced by the current method of electrolysis of potassium chloride solutions, analogous to the method of manufacturing sodium hydroxide (see chloralkali process):

2 KCl + 2 H2O ? 2 KOH + Cl2 + H2

Hydrogen gas forms as a by-product on the cathode; concurrently, an anodic oxidation of the chloride ion takes place,Sony VAIO VPCW12AVJ Battery

formingchlorine gas as a byproduct. Separation of the anodic and cathodic spaces in the electrolysis cell is essential for this process.

Uses

KOH and NaOH can be used interchangeably for a number of applications, although in industry, NaOH is preferred because of its lower cost.Sony VAIO VPCW12S1E/P Battery

Precursor to other potassium compounds

Many potassium salts are prepared by neutralization reactions involving KOH. The potassium salts of carbonate, cyanide,permanganate, phosphate, and various silicates are prepared by treating either the oxides or the acids with KOH. Sony VAIO VPCW12S1E/T Battery

The high solubility of potassium phosphate is desirable in fertilizers.

Manufacture of biodiesel

Although more expensive than using sodium hydroxide, KOH works well in the manufacture of biodiesel by transesterification of the triglycerides in vegetable oil. Sony VAIO VPCW12S1E/W Battery

Glycerin from potassium hydroxide-processed biodiesel is useful as an inexpensive food supplement for livestock, once the toxic methanol is removed.

Manufacture of soft soaps

The saponification of fats with KOH is used to prepare the corresponding "potassium soaps", which are softer than the more common sodium hydroxide-derived soaps.Sony VAIO VPCW213AG/L Battery

Because of their softness and greater solubility, potassium soaps require less water to liquefy, and can thus contain more cleaning agent than liquefied sodium soaps.

As an electrolyte

Aqueous potassium hydroxide is employed as the electrolyte in alkaline batteries based on nickel-cadmium and manganese dioxide-zinc. Sony VAIO VPCW213AG/P Battery

Potassium hydroxide is preferred over sodium hydroxide because its solutions are more conductive. The Nickel Metal Hydride batteries in the Toyota Prius use a mixture of potassium hydroxide and sodium hydroxide.Sony VAIO VPCW213AG/W Battery

Niche applications

Like sodium hydroxide, potassium hydroxide attracts numerous specialized applications, virtually all of which rely on its properties as a strong chemical base with its consequent ability to degrade many materials.Sony VAIO VPCW213AG/T Battery

For example, in a process commonly referred to as "chemical cremation" or "resomation", potassium hydroxide hastens the decomposition of soft tissues, both animal and human, to leave behind only the bones and other hard tissues. Entomologists wishing to study the fine structure of insect anatomy may use a 10% aqueous solution of KOH to apply this process.Sony VAIO VPCW215AG/L Battery

An example of chemical cremation outside of a laboratory environment is the use of a potassium hydroxide solution as the principal agent in the resomation process, an alternative to the well-known, thermal cremationprocess for the disposal of human remains after death.Sony VAIO VPCW217JC Battery

In chemical synthesis, the choice between the use of KOH and the use of sodium hydroxide, NaOH, is guided by the solubility of the resulting salt.

The corrosive properties of potassium hydroxide make it a useful ing

redient in agents and preparations that clean and disinfect surfaces and materials that can themselves resist corrosion by KOH.Sony VAIO VPCW217JC/L Battery

Potassium hydroxide is often the main active ingredient in chemical "cuticle removers" used in manicure treatments.

Because aggressive bases like KOH damage the cuticle of the hair shaft, potassium hydroxide is used to chemically assist the removal of hair from animal hides.Sony VAIO VPCW217JC/P Battery

The hides are soaked for several hours in a solution of KOH and water to prepare them for the unhairing stage of the tanning process. This same effect is also used to weaken human hair in preparation for shaving. Sony VAIO VPCW217JC/T Battery

Pre-shave products and some shave creams contain potassium hydroxide to force open the hair cuticle and to act as a hygroscopic agent to attract and force water into the hair shaft, causing further damage to the hair. In this weakened state, the hair is more easily cut by a razor blade.Sony VAIO VPCW217JC/W Battery

Potassium hydroxide is used to identify certain kinds of mushrooms. A 3–5% aqueous solution of KOH is applied to the flesh of a mushroom and the researcher notes whether or not the color of the flesh changes. Certain species of boletes, polypores, and many gilled mushrooms are identified based on this color-change reaction.Sony VAIO VPCW218JC Battery,Sony VAIO VPCW218JC/L Battery,Sony VAIO VPCW218JC/P Battery,Sony VAIO VPCW218JC/T Battery,Sony VAIO VPCW218JC/W Battery,Sony VAIO VPCW219AJ/L Battery,Sony VAIO VPCW219AJ/P Battery,Sony VAIO VPCW219AJ/W Battery,Sony VAIO VPCW21AAJ Battery,Sony VAIO VPCW21AKJ Battery,Sony VAIO VPCW21AVJ Battery

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