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Alkahest

Alkahest

Alkahest (or alcahest) is a hypothetical universal solvent, having the power to dissolve every other substance, including gold. It was much sought after by alchemists for its invaluable medicinal qualities. The name is believed to have been invented by Paracelsus (1493–1541), who modelled it on similar words taken from Arabic, such as ‘alkali’. Paracelsus' own recipe was based on caustic lime, alcohol, and carbonate of potash. In fact a universal solvent does not, and cannot, exist. The closest is likely to be aqua regia — or, depending on how one defines “dissolve”, antimatter. Category:Alchemy

Solvent

A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. The term organic solvent refers to most other solvents that are organic compounds and contain carbon atoms. Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, thereby leaving the dissolved substance behind. Solvents should therefore not react chemically with the dissolved compounds — they have to be inert. Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water. Solvents are usually clear and colorless liquids and most of them have a characteristic smell. The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximal amount of compound that is soluble in a certain volume of solvent at a specified temperature. Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene), as paint thinners (e.g. toluene, turpentine), as nail polish removers and glue solvents (acetone, methyl acetate, ethyl acetate), in spot removers (e.g. hexane, petrol ether), in detergents (citrus terpenes), in perfumes (ethanol), and in chemical syntheses.

Polarity, solubility, and miscibility

Solvents and solutes can be broadly classified into polar (hydrophilic) and non-polar (lipophilic). The polarity can be measured as the dielectric constant or the dipole moment of a compound. The polarity of a solvent determines what type of compounds it is able to dissolve and with what other solvents or liquid compounds it is miscible with. As a rule of thumb, polar solvents dissolve polar compounds best and non-polar solvents dissolve non-polar compounds best: "like dissolves like". Strongly polar compounds like inorganic salts (e.g. table salt) or sugars (e.g. sucrose) dissolve only in very polar solvents like water, while strongly non-polar compounds like oils or waxes dissolve only in very non-polar organic solvents like hexane. Similarly, water and hexane (or vinegar and salad oil) are not miscible with each other and will quickly separate into two layers even after being shaken well.

Protic and aprotic solvents

Polar solvents can be further subdivided into polar protic solvents and polar aprotic solvents. Water (H-O-H), ethanol (CH₃-CH₂-OH), or acetic acid (CH₃-C(=O)OH) are representative polar protic solvents. A polar aprotic solvent is acetone (CH₃-C(=O)-CH₃). In chemical reactions the use of polar protic solvents favors the S_N1 reaction mechanism, while polar aprotic solvents favor the S_N2 reaction mechanism.

Boiling point

Another important property of solvents is their boiling point that also determines the speed of evaporation. Small amounts of low-boiling solvents like diethyl ether, methylene chloride, or acetone will evaporate in seconds at room temperature, while high-boiling solvents like water or dimethylsulfoxide need higher temperatures, an air flow, or the application of vacuum for fast evaporation.

Density

Most organic solvents have a lower density than water. Therefore they are lighter and will separate on top of water. An important exception are many halogenated solvents like methylene chloride or chloroform that will sink to the bottom. This is important to remember when partitioning compounds between solvents and water in a separatory funnel during chemical syntheses.

Chemical interactions

A solvent will create various weak chemical interactions with the solute in order to solubilize it. The most common of these interactions are the relatively weak van der Waals interactions (induced dipole interactions), the stronger dipole-dipole interactions, and the even stronger hydrogen bonds (interaction between O-H or N-H hydrogens with O or N atoms).

Safety

Most organic solvents are flammable or highly flammable, depending on their volatility. Exceptions are some chlorinated solvents like methylene chloride and chloroform. Mixtures of solvent vapors and air can explode. Solvent vapors are heavier than air, they will sink to the bottom and can travel large distances nearly undiluted. Solvent vapors can also form in supposedly empty drums and cans, posing a flash fire hazard; hence empty containers of volatile solvents should be stored open and upside down. Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light. These peroxides will concentrate during distillation due to their higher boiling point. Ethers have to be stored in the dark in closed canisters in the presence of stabilizers like BHT or over sodium hydroxide. Many solvents can lead to a sudden loss of consciousness if inhaled in larger amounts. Solvents like diethyl ether and chloroform have been used in medicine as anesthetics and narcotics for a long time. Ethanol is a widely used and abused psychoactive drug. Diethyl ether, chloroform, and many other solvents (e.g. from gasoline or glues) are used recreationally in glue sniffing, often with harmful long term health effects like neurotoxicity or cancer. Some solvents including chloroform and benzene (an ingredient of gasoline) are carcinogenic. Many others can damage internal organs like the liver, the kidneys, or the brain. Methanol can cause internal damage to the eyes including permanent blindness.

General precautions

- Avoid the generation of solvent vapors by working in a fume hood or a well ventilated area
- Keep the storage containers tightly closed.
- Never use open flames near flammable solvents, use electrical heating instead.
- Never flush flammable solvents down the drain to avoid explosions and fires.
- Avoid the inhalation of solvent vapors.
- Avoid contact of the solvent with the skin — many solvents are easily absorbed through the skin.

Properties table of common solvents

The solvents are grouped into non-polar, polar aprotic, and polar protic solvents and ordered by increasing polarity. The polarity is given as the dielectric constant. The density of unpolar solvents that are heavier than water is bolded.

Solvent	Chemical Formula	Boiling point	Polarity	Density
Non-Polar Solvents
Hexane	CH₃-CH₂-CH₂-CH₂-CH₂-CH₃	69 °C	2.0	0.655 g/ml
Benzene	C₆H₆	80 °C	2.3	0.879 g/ml
Toluene	C₆H₅-CH₃	111 °C	2.4	0.867 g/ml
Diethyl ether	CH₃CH₂-O-CH₂-CH₃	35 °C	4.3	0.713 g/ml
Chloroform	CHCl₃	61 °C	4.8	1.498 g/ml
Ethyl acetate	CH₃-C(=O)-O-CH₂-CH₃	77 °C	6.0	0.894 g/ml
Tetrahydrofuran (THF)	/-CH₂-CH₂-O-CH₂-CH₂-\	66 °C	7.5	0.886 g/ml
Methylene chloride	CH₂Cl₂	40 °C	9.1	1.326 g/ml
Polar Aprotic Solvents
Acetone	CH₃-C(=O)-CH₃	56 °C	21	0.786 g/ml
Acetonitrile (MeCN)	CH₃-C≡N	82 °C	37	0.786 g/ml
Dimethylformamide (DMF)	H-C(=O)N(CH₃)₂	153 °C	38	0.944 g/ml
Dimethyl sulfoxide (DMSO)	CH₃-S(=O)-CH₃	189 °C	47	1.092 g/ml
Polar Protic Solvents
Acetic acid	CH₃-C(=O)OH	118 °C	6.2	1.049 g/ml
n-Butanol	CH₃-CH₂-CH₂-CH₂-OH	118 °C	18	0.810 g/ml
Isopropanol	CH₃-CH(-OH)-CH₃	82 °C	18	0.785 g/ml
n-Propanol	CH₃-CH₂-CH₂-OH	97 °C	20	0.803 g/ml
Ethanol	CH₃-CH₂-OH	79 °C	24	0.789 g/ml
Methanol	CH₃-OH	65 °C	33	0.791 g/ml
Formic acid	H-C(=O)OH	100 °C	58	1.21 g/ml
Water	H-O-H	100 °C	80	0.998 g/ml

External links

- [http://www.speckanalytical.co.uk/products/Tips/bps.html Table] Properties of common organic solvents
- [http://www.usm.maine.edu/~newton/Chy251_253/Lectures/Solvents/Solvents.html Table and text] O-Chem Lecture
- [http://virtual.yosemite.cc.ca.us/smurov/orgsoltab.htm Tables] Properties and toxicities of organic solvents Category:Solutions Category:Chemical compounds ko:용매 ja:溶媒

Solubility

A substance is soluble in a fluid if it dissolves in that fluid. The dissolved substance is called the solute and the dissolving fluid (usually present in excess) is called the solvent, which together form a solution. The process of dissolving is called solvation, or hydration if the solvent is water. A solution at equilibrium cannot hold any more solute and is said to be saturated. Solutions may, under special conditions, hold more solute than the solvent can normally dissolve. This is called supersaturation. The maximum equilibrium amount of solute which can normally dissolve per amount of solvent (or solution) is the solubility of that solute in that solvent. It is often expressed as a maximum concentration of a saturated solution. The solubility of one substance dissolving in another is determined by the intermolecular forces between the solvent and solute, temperature, the entropy change that accompanies the solvation, the presence and amount of other substances, and sometimes pressure or partial pressure of a solute gas. For salts, solubility in aqueous solutions is often dependent on a solubility constant. The solubility constant is a special case of an equilibrium constant for the reaction of dissolving the salt in question, with the concentration of undissolved compound not in the expression because it is not in the aqueous phase. The solubility constant is also "applicable" (i. e. useful) to precipitation, the reverse of the dissolving reaction. As with other equilibrium constants, temperature can affect the numerical value of solubility constant. Solvents are normally characterized as polar or nonpolar. Polar solvents will dissolve ionic compounds and covalent compounds which ionize, while nonpolar solvents will dissolve nonpolar covalent compounds. For example, ordinary table salt, an ionic compound, will dissolve in water, but not in ethanol. Common solvents used in organic chemistry include acetone, ethanol, water, and benzene. Water and nonpolar solvents are immiscible; they do not form homogeneous mixtures but separate into two distinct phases or form milky emulsions. While solutions are typically thought of as solids being mixed into liquids, any two states of matter can be mixed and be called a solution. Carbonated water is a solution of a gas in a liquid, hydrogen (a gas) can dissolve in palladium (a solid), and stainless steel is a solution of a solid in a solid (called an alloy).

Solubility of bonding type in water

Bonding type	Solubility in water	Example
ionic	most soluble	See below
metallic	insoluble	Fe
metallic	unless they react with water	K
polar covalent	soluble if it H bonds	glucose
	soluble by reaction	HCl
	insoluble otherwise	ether
non-polar covalent	most insoluble	benzene
non-polar covalent	some slightly soluble	O₂
covalent lattice	insoluble	diamond

Solubility of ionic compounds

Soluble	Insoluble
Group 1 and NH₄⁺ compounds	carbonates (except Group 1 and NH₄⁺ compounds)
nitrates	sulfites (except Group 1 and NH₄⁺ compounds)
acetates (ethanoates)	phosphates (except Group 1 and NH₄⁺ compounds)
chlorides, bromides and iodides (except Ag⁺, Pb²⁺, Cu⁺ and Hg₂²⁺)	hydroxides and oxides (except Group 1, NH₄⁺, Ba²⁺, Sr²⁺ and Ca²⁺)
sulfates (except Ag⁺, Pb²⁺, Ba²⁺, Sr²⁺ and Ca²⁺)	sulfides (except Group 1, Group 2 and NH₄⁺ compounds)

Software tools for prediction of solution

One of the most recent and prominent solution (solubility) prediction technologies is applied in [http://www.q-pharm.com/home/contents/drug_d/soft/ Quantum 3.1] that is a suite of Molecular Modeling software for Linux and Windows. The software calculates the solvation energy and solubility for a molecule or a library of molecules in a number of solvents (e.g. water and DMSO). The Quantum 3.1 [http://www.q-pharm.com/home developer] is also a service provider.

Gold

Gold is a chemical element in the periodic table that has the symbol Au (L. aurum) and atomic number 79. A soft, shiny, yellow, dense, malleable, ductile (trivalent and univalent) transition metal, gold does not react with most chemicals but is attacked by chlorine, fluorine and aqua regia. The metal occurs as nuggets or grains in rocks and in alluvial deposits and is one of the coinage metals. For millennia, gold has served as money and is also used in jewelry, dentistry, and in electronics. Gold forms the basis for a monetary standard used by the International Monetary Fund (IMF) and the Bank for International Settlements (BIS). Its ISO currency code is XAU.

Notable characteristics

Gold is a metallic element with a characteristic yellow color, but can also be black or ruby when finely divided, while colloidal solutions are intensely colored and often purple. These colors are the result of gold's plasmon frequency lying in the visible range (due to a relativistic effect), which causes red and yellow light to be reflected, and blue light to be absorbed. It is one of only three metals which have an actual easily-identifiable color; the other two are copper, which is red, and caesium, which has a pale golden color. It is the most malleable and ductile metal known; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square feet. A soft metal, gold will readily form alloys with many other metals. This can be done to increase its strength, or create several exotic colors, sold for instance in the western United States to the tourist trade as "Black Hills" gold. Adding copper yields a redder metal, iron blue, Silver produces green, aluminium purple, platinum metals white, and natural bismuth together with silver alloys produce black. Native gold contains usually eight to ten per cent silver, but often much more — alloys with a silver content over 20% are called electrum. As the amount of silver increases, the color becomes whiter and the specific gravity lower. Gold is a good conductor of heat and electricity, and is not affected by air and most reagents. Heat, moisture, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; conversely, halogens will chemically alter gold, and aqua regia dissolves it. Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated out as gold metal by the addition of virtually any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate. Recent research undertaken by Frank Reith of the Australian National University shows that microbes play an important role in the formation of gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits. [http://www.abc.net.au/science/news/enviro/EnviroRepublish_1032376.htm]

Applications

Pure gold is too soft for ordinary use and is hardened by alloying with silver, copper, and other metals. Gold and its many alloys are most often used in jewelry, coinage and as a standard for monetary exchange in many countries. Because of its high electrical conductivity and resistance to corrosion and other desirable combinations of physical and chemical properties, gold also emerged in the late 20th century as an essential industrial metal.
- Gold can be made into thread and used in embroidery.
- Gold performs critical functions in computers, communications equipment, spacecraft, jet aircraft engines, and a host of other products.
- The resistance to oxidation of gold has led to its widespread use as thin layers electroplated on the surface of electrical connectors to ensure a good connection.
- Gold is used in restorative dentistry especially in tooth restorations such as crowns and bridges.
- Colloidal gold (a gold nanoparticle) is an intensely colored solution that is currently studied in many labs for medical, biological and other applications. It is also the form used as gold paint on ceramics prior to firing.
- Chlorauric acid is used in photography for toning the silver image.
- Gold(III) chloride is used as a catalyst in organic chemistry. It is also the usual starting point for making other gold compounds.
- Disodium aurothiomalate is a treatment for rheumatoid arthritis (administered intramuscularly). It inhibits lymphocyte proliferation, lysosomal enzyme release, the release of reactive oxygen species from macrophages, and IL-1 production. However, it can also cause photosensitive rashes, gastrointestinal disturbance, and kidney damage.
- The gold isotope Au-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.
- Gold is used as a coating enabling biological material to be viewed under a scanning electron microscope.
- Many competitions and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner (with silver to the second-place finisher, and bronze to the third.)
- Since it is a good reflector of both infrared and visible light, it is used for the protective coatings on many artificial satellites.
- Gold flake is used on and in some gourmet sweets and drinks. Having no reactivity it adds no taste but is taken as a delicacy.
- White gold (an alloy of gold with platinum, palladium, nickel, and/or zinc) serves as a substitute for platinum.
- Green gold (a gold/silver alloy) is used in specialized jewelry while gold alloys with copper (reddish color) are more widely used for that purpose (rose gold).

History

rose gold Gold (Sanskrit jval, Greek χρυσος [khrusos], Latin aurum for "shining dawn", Anglo-Saxon gold, Chinese 金 [jīn]) has been known and highly valued since prehistoric times. It may have been the first metal used by humans and was valued for ornamentation and rituals. Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was as "common as dust" in Egypt. Egypt and Nubia had the resources to make them major gold-producing areas for much of history. Gold is also mentioned several times in the Old Testament. The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia between 643 and 630 BC. The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in Central America, Peru, and Colombia. Gold has long been considered one of the most precious metals, and its value has been used as the standard for many currencies (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties (see gold album). Gold in antiquity was relatively easy to obtain geologically; however, 75% of all gold ever produced has been extracted since 1910.[http://www.goldsheetlinks.com/production2.htm] It has been estimated that all the gold in the world that has ever been refined would form a single cube 20 m (66 ft) a side. The primary goal of the alchemists was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called the philosopher's stone. Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today's chemistry. Their symbol for gold was the circle with a point at its center (☉), which was also the astrological symbol, the Egyptian hieroglyph and the ancient Chinese character for the Sun (now 日). For modern attempts to produce artificial gold, see gold synthesis. During the 19th century gold rushes occurred whenever large gold deposits were discovered, including the California, Colorado, Otago, Australia, Witwatersrand, Black Hills, and Klondike gold rushes. Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another.

Value

Klondike] Klondike Like other precious metals, gold is measured by troy weight and by grams. When it is alloyed with other metals the term carat or karat is used to indicate the amount of gold present, with 24 carats being pure gold and lower ratings proportionally less. The purity of a gold bar can also be expressed as a decimal figure ranging from 0 to 1, known as the millesimal fineness, such as 0.995. The price of gold is determined on the open market, but a procedure known as the Gold Fixing in London, originating in 1919, provides a twice-daily benchmark figure to the industry. Historically gold was used to back currency in an economic system known as the gold standard in which one unit of currency was equivalent to a certain weight of gold. As part of this system, governments and central banks attempted to control the price of gold by setting values at which they would exchange it for currency. For a long period the United States government set the price of gold at $20.67 per troy ounce ($664.56/kg) but in 1934 the price of gold was set at $35.00 per troy ounce ($1125.27/kg). By 1961 it was becoming hard to maintain this price, and a pool of US and European banks began to act together to defend the price against market forces. On March 17 1968, economic circumstances caused the collapse of the gold pool, and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. Central banks still hold historical gold reserves as a reserve asset although the level has generally been declining. The largest gold depository in the world is that of the U.S. Federal Reserve Bank, held at Fort Knox. Since 1968 the price of gold on the open market has ranged widely, with a record high of $850/oz ($27,300/kg) on 21 January 1980, to a low of $252.90/oz ($8,131/kg) on 21 June 1999 (London Fixing). Prices have risen to the $500/oz mark in late 2005, due to a depreciation of the US dollar and inflation due to rising energy costs.

Gold and the money supply

In January 1959 US M3 money supply was $288.8 billion, and the Official Gold Holdings of the United States was then 17,335.1 Tonnes, or about 557 million ounces (there are 32,150.7 Troy Ounces in a Tonne). That means that in 1959, there were $518 in circulation for every ounce of gold reserves held by the USA. Although the theoretical price should then have been $518 per ounce, the actual price, as fixed under the gold standard was only $35 an ounce. By August 2005, the US M3 money supply had risen to $9,873.9 billion, whilst at the same time the Official Gold Holdings of the United States had fallen to just 8,133.5 Tonnes, or about 261 million Troy Ounces. This means that today, in 2005, there are $37,831 in circulation for every ounce of gold held by the United States. The above numbers show the falling influence of gold in the monetary system of the world today. Goldbugs believe, or even hope, that one day gold's importance will return as the printing of paper money gets out of control and we end in a hyper-inflationary fiat money collapse.

Restrictions on gold ownership

Because of its use as a reserve store of value, the possession of gold is sometimes restricted or banned. Within the United States, the private possession of gold except as jewelry and coin collecting was banned between 1933 and 1975. President Franklin D. Roosevelt confiscated gold by [http://www.the-privateer.com/1933-gold-confiscation.html Executive Order 6102], and President Richard Nixon closed the gold window by which foreign countries could exchange American dollars for gold at a fixed rate.

Return of a Gold Standard?

In the first few years of the 21st century, reports started to circulate that Malaysia was planning a return to the gold standard -- to issue and use gold dinars as currency in international trade. The purported purpose of this move would be to reduce dependence on the United States dollar as a reserve currency, and to establish a non-debt-backed currency in accord with Islamic law against the charging of interest. [http://www.islamidag.dk/ulamaongold.html] Nonetheless, gold dinar currency has not yet emerged. [http://english.aljazeera.net/NR/exeres/E7515CEE-880E-492F-B225-A94E21D90D2B.htm] [http://www.mineweb.net/columns/american_notes/336075.htm]

Gold in investment portfolios

As a tangible investment gold is sometimes held as part of a portfolio because over the long term gold has an extensive history of maintaining its value. It has in the last century gained ground in relation to fiat currencies owing to inflation. Gold becomes particularly desirable in times of extremely weak confidence and during hyperinflation because gold maintains its value even as fiat money becomes worthless. People who enjoy investing in gold are known as goldbugs. Futures contracts based on gold currently trade on various exchanges around the world. In the US this occurs primarily on COMEX (Commodity Exchange) which is a subsidiary of the New York Mercantile Exchange. Speculation about the future price of gold and other commodities is carried on at COMEX. Recently, gold-based ETFs like [http://finance.yahoo.com/q?s=GLD GLD] have emerged as a more convenient investment vehicle. In some countries such as Switzerland, it is possible to hold physical gold as part of an investment portfolio, due to the absence of taxes and narrow bid-ask spreads, however in other countries portfolio managers sometimes hold gold shares or gold bullion securities as a proxy for the metal itself. Exchange Traded Funds such as Gold Bullion Securities are securities sponsored by the World Gold Council and which are fully backed up by allocated gold held by a custodian. The main Gold Bullion Securities are as follows:
- New York Stock Exchange (NYSE), Symbol:GLD (Streettracks Gold Shares, ISIN No. US8633071043)
- London Stock Exchange (LSE) Symbol GBS (Gold Bullion Securities ISIN No. GB00B00FHZ82)
- Euronext France Symbol:GBS (Gold Bullion Securities ISIN No. GB00B00FHZ82 )
- Australian Stock Exchange (ASX), Symbol:GOLD (Gold Bullion Securities ISIN No. AU00000GOLD7)
- Johannesburg Securities Exchange (JSE), Symbol:GLD (New Gold Debentures ISIN No. ZAE000060067 )

Occurrence

Exchange Traded Fund Due to its relative chemical inertness gold is usually found as the native metal or alloy. Occasionally large accumulations of native gold (also known as nuggets) occur but usually gold occurs as minute grains. These grains occur between mineral grain boundries or as inclusions within minerals. Common gold associations are quartz often as veins and sulfide minerals. The most common sulfide associations are pyrite, chalcopyrite, galena, sphalerite, arsenopyrite, stibnite and pyrrhotite. Rarer mineral associations are petzite, calaverite, sylvanite, muthmannite, nagyagite and krennerite. Gold is widely distributed in the Earth's crust at a background level of 0.03 g/1000 kg (0.03 ppm by weight). Hydrothermal ore deposits of gold occur in metamorphic rocks and igneous rocks; alluvial deposits and placer deposits originate from these sources. The primary source of gold is usually igneous rocks or surface concentrations. A deposit usually needs some form of secondary enrichment to form an economically viable ore deposit: either chemical or physical processes like erosion or solution or more generally metamorphism, which concentrates the gold in sulfide minerals or quartz. There are several primary deposit types, common ones are termed reef or vein. Primary deposits can be weathered and eroded, with most of the gold being transported into stream beds where it congregates with other heavy minerals to form placer deposits. In all these deposits the gold is in its native form. Another important ore type is in sedimentary black shale and limestone deposits containing finely disseminated gold and other platinum group metals. Gold occurs in sea water at 0.1 to 2 mg/t (0.1 to 2 ppb by weight) depending on sample location.

Production

ppb Economic gold extraction can be achieved from ore grades as little as 0.5 g/1000 kg (0.5 ppm) on average in large easily mined deposits, typical ore grades in open-pit mines are 1–5 g/1000 kg (1-5 ppm), ore grades in underground or hard rock mines are usually at least 3 g/1000 kg (3 ppm) on average. Ore grades of 30 g/1000 kg (30 ppm) are usually needed before gold is visible to the naked eye, therefore in most gold mines you will not see any gold. It is claimed, that all the gold that has been mined throughout the history of mankind could be incorporated in a solid ball with a diameter of 27 metres. metre Since the 1880s South Africa has been the source for a large proportion of the world's gold supply. Production in 1970 accounted for 79% of the world supply, producing about 1,000 tonnes, however production in 2004 was 342 tonnes. This decline was due to the increasing difficulty of extraction and changing economic factors effecting the industry in South Africa. The city of Johannesburg was built atop the world's greatest gold finds. Gold fields in the Orange Free State and the Transvaal are deep and require the world's deepest mines. The Second Boer War of 1899–1901 between the British Empire and the white Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa. Other major producers are Canada, United States and Western Australia. Mines in South Dakota and Nevada supply two-thirds of gold used in the United States. Siberian regions of the USSR also used to be significant in the global gold mining industry. Kolar Gold Fields in India is another example of a city being built on the greatest gold deposits in India. In South America, the controversial project Pascua Lama aims at exploitation of rich fields in the high mountains of Atacama, at the border between Chile and Argentina. The idea of producing gold out of lesser metals or other cheap substances has fascinated people throughout the centuries. Scientists, kings and charlatans obsessed with the secret art of alchemy accidentally invented practically useful materials (e.g. porcelain), while searching in vain for the philosopher's stone, which was supposed to turn mercury into gold. Modern science has since proven the impossibility of making gold from other elements via chemical reactions. However, it is possible to obtain infinitesimally small amounts of gold by artificial nuclear transformations in particle accelerators The gold isotopes produced would likely be radioactive. No economically feasible method to manufacture gold artificially has been found and published yet. The possibility of cheap man-made gold would have unforeseen economic and political consequences.

Compounds/isotopes

Although gold is a noble metal, it can form many compounds, auric chloride (AuCl₃) and chlorauric acid (HAuCl₄) being the most common. Gold compounds can be aurous (univalent, +1) or auric (trivalent, +3). Gold also can under extreme conditions form a +5 state with fluorine (gold pentafluoride, AuF₅), as well as (unusually for a metal), a -1 state. Such compounds containing the Au^- anion are called aurides and include caesium auride, CsAu, rubidium auride, RbAu, and tetramethylammonium auride, (CH₃)₄N⁺ Au^-. Gold also forms:
- The AuCl₄^- ion after dissolving in aqua regia
- Gold halides (F,Cl,Br,I)
- Gold chalcogenides (O, S, Se,Te)
- Gold cluster compounds
- Gold hydrazide: an olive-green powder, AuN₂H₃, one of several explosive compounds known archaically as aurum fulminans There is only one stable isotope of gold, and 18 radioisotopes with Au-195 being the most stable with a half-life of 186 days.

Precautions

The human body does not absorb gold very well, thus compounds of gold are not normally very toxic. Liver and kidney damage has, however, been reported for up to 50% of arthritis patients treated with gold-containing drugs. Gold used in dentistry is widely regarded as the safest form of restorative material, as well as the most successful.

Symbolism

Gold has been associated with the extremities of utmost evil and great sanctity throughout history. The Golden Calf is a widely-recognised symbol of idolatry and revolt against God; concentration camp guards removed the golden teeth from the mouths of gassed Holocaust victims. In Communist propaganda, the golden pocket watch and its fastening golden chain were the characteristic accessories of the class enemy, the bourgeois and the industrial tycoons. On the other hand, eminent orators such as John Chrysostom were said to have a mouth of gold with a silver tongue. Gold is associated with notable anniversaries, particularly in a 50 year cycle, such as a golden wedding anniversary, golden jubilee, etc. Great human achievements are frequently rewarded with gold, in the form of medals and decorations. Winners of races and prizes are usually awarded the gold medal (such as the Olympic Games and the Nobel Prize), while many award statues are depicted in gold (such as the Academy Awards, the Emmy Awards and the British Academy Film Awards). In the software development cycle "going gold" means releasing a version that is ready for distribution to customers, rather than a buggy beta version. Medieval kings were inaugurated under the signs of sacred oil and a golden crown, the latter symbolizing the eternal shining light of heaven and thus a Christian king's divinely inspired authority. Wedding rings are traditionally made of gold; since it is long-lasting and unaffected by the passage of time, it is considered a suitable material for everyday wear as well as a metaphor for the relationship. In Orthodox Christianity, the wedded couple is adorned with a golden crown during the ceremony, an amalgamation of symbolic rites. The symbolic value of gold varies wildly around the world, even within geographic regions. For example, gold is quite common in Turkey but considered a most valuable gift in Sicily.

References

- [http://periodic.lanl.gov/elements/79.html Los Alamos National Laboratory – Gold]
- [http://www.infoplease.com/ce6/sci/A0821152.html The Columbia Electronic Encyclopedia, 6th ed]

External links

- [http://www.webelements.com/webelements/elements/text/Au/index.html WebElements.com – Gold] (also used as a reference)
- [http://mineral.galleries.com/minerals/elements/gold/gold.htm Mineral Galleries - Native Gold]
- [http://www.lateralscience.co.uk/gold/auriferous.html Getting Gold 1898 book]
- Gold Category:Chemical elements Category:Transition metals Category:Numismatics Category:Historical trading items ms:Emas ja:金 simple:Gold th:ทองคำ

Medicine

Medicine is a branch of health science concerned with maintaining human health and restoring it by treating disease and injury; it is both an area of knowledge, a science of body systems and diseases and their treatment, and the applied practice of that knowledge. The practice of medical care is shared between the medical profession—physicians or doctors—and other groups of professionals, such as nurses or pharmacists (sometimes called allied health professions). Historically, only members of the medical profession proper have been considered to actually practice medicine in the strictest sense, in contrast to the allied fields of health care professionals. Clinicians can be physicians, nurses, or physician assistants -- those who provide health care or otherwise tend to their patients. The medical profession is the social and occupational structure of the group of people formally trained and authorized to apply medical knowledge. Many countries and legal jurisdictions have legal limitations on who may practice medicine or the allied medical fields. Medicine is typically seen as composed of various specialized sub-branches, such as pediatrics, gynecology, neurology, dealing with particular body systems, diseases, or areas of health. Systems of medical and healthcare practices have existed among human societies since at least the dawn of recorded history. These systems have developed in various ways in different cultures and regions. Medicine as understood in the modern period has historically been considered to be the mainstream tradition which developed in the Western world since the early modern age. Many other traditions of medicine and healthcare are still widely practiced throughout the world, most of which are still considered to be separate and distinct from Western medicine, also called biomedicine or the Hippocratic tradition. The most highly developed systems of medicine outside the Western system are the Ayurvedic tradition of India and traditional Chinese medicine. Various non-mainstream traditions of health care have also developed in the Western world distinct from mainstream medicine. The various other systems practiced among various cultures are sometimes practiced alongside or in cooperation with Western medicine, while sometimes being seen as competing traditions. Medicine is also often used amongst medical professionals as shorthand for Internal Medicine. Veterinary medicine is the practice of health care specialized for other animal species.

History of medicine

Medicine as it is practiced now is rooted in various traditions, but developed mainly in the late 18th and early 19th century in Germany (Rudolf Virchow) and France (Jean-Martin Charcot, Claude Bernard and others). The new, "scientific" medicine replaced earlier Western traditions of medicine, mostly based on the "four humours" and other pre-modern theories. The focal points of development of clinical medicine shifted to the United Kingdom and the USA by the early 1900s (Sir William Osler, Harvey Cushing). Evidence-based medicine is the recent movement to link the practice and the science of medicine more closely through the use of the scientific method and modern information science. Genomics and knowledge of human genetics is already having a large influence on medicine, as the causative genes of most monogenic genetic disorders have now identified, and the development of techniques in molecular biology and genetics are influencing medical practice and decision-making.

Practice of medicine

The practice of medicine combines both science and art. Science and technology are the evidence base for many clinical problems for the general population at large. The art of medicine is the application of this medical knowledge in combination with intuition and clinical judgment to determine the proper diagnoses and treatment plan for this unique patient and to treat the patient accordingly. Central to medicine is the patient-doctor relationship established when a person with a health concern or problem seeks the help of a physician (i.e. the medical encounter). Other health professionals similarly establish a relationship with a patient and may perform interventions from their perspective, e.g. nurses, radiographers and therapists. As part of the medical encounter, the doctor needs to:
- develop a relationship with the patient
- gather data (medical history and physical examination combined with laboratory or imaging studies)
- analyze and synthesize that data (assessment and/or differential diagnosis), and then
- develop a treatment plan (further testing, therapy, watchful observation, referral and follow-up)
- treat the patient accordingly
- assess the progress of treatment and alter the plan as necessary. The medical encounter is documented in a medical record, which is a legal document in many jurisdictions. One method that is used is called the problem-oriented medical record (POMR), which includes a problem list of diagnoses and a "SOAP" method of documentation for each visit:
- S - Subjective, the medical history of the problem from the point-of-view of the patient.
- O - Objective, the physical examination and any laboratory or imaging studies.
- A - Assessment, is the medical decision-making process including the differential diagnoses and most probable diagnoses.
- P - Plan, the way resolve the problem and monitor progress

Medical systems

Medicine is practiced within the medical system of a particular culture or government. Leaving aside tribal cultures, the most significant divide in developed countries is that between universal health care and the market based health care (such as practiced in the U.S.).

Patient-doctor relationship

The doctor-patient relationship and interaction is a central process in the practice of medicine. There are many perspectives from which to understand and describe it. An idealized physician's perspective, such as is taught in medical school, sees the core aspects of the process as the physician learning from the patient his symptoms, concerns and values; in response the physician examines the patient, interprets the symptoms, and formulates a diagnosis to explain the symptoms and their cause to the patient and to propose a treatment. In more detail, the patient presents a set of complaints or concerns about his health to the doctor, who then obtains further information about the patient's symptoms, previous state of health, living conditions, and so forth, and then formulates a diagnosis and enlists the patient's agreement to a treatment plan. Importantly, during this process the doctor educates the patient about the causes, progression, outcomes, and possible treatments of his ailments, as well as often providing advice for maintaining health. This teaching relationship is the basis of calling the physician doctor, which originally meant "teacher" in Latin. The patient-doctor relationship is additionally complicated by the patient's suffering (patient derives from the Latin patiens, "suffering") and limited ability to relieve it on his own. The doctor's expertise comes from his knowledge about, or experience with, other people who have suffered similar symptoms, and his presumed ability to relieve it with medicines or other therapies about which the patient may initially have little knowledge. The doctor-patient relationship can be analyzed from the perspective of ethical concerns, in terms of how well the goals of non-maleficence, beneficence, autonomy, and justice are achieved. Many other values and ethical issues can be added to these. In different societies, periods, and cultures, different values may be assigned different priorities. For example, in the last 30 years medical care in the Western World has increasingly emphasized patient autonomy in decision making. The relationship and process can also be analyzed in terms of social power relationships (e.g., by Michel Foucault), or economic transactions. Physicians have been accorded gradually higher status and respect over the last century, and they have been entrusted with control of access to prescription medicines as a public health measure. This represents a concentration of power and carries both advantages and disadvantages to particular kinds of patients with particular kinds of conditions. A further twist has occurred in the last 25 years as costs of medical care have risen, and a third party (an insurance company or government agency) now often insists upon a share of decision-making power for a variety of reasons, reducing freedom of choice of both doctors and patients in many ways. The quality of the patient-doctor relationship is important to both parties. The better the relationship in terms of mutual respect, knowledge, trust, shared values and perspectives about disease and life, and time available, the better will be the amount and quality of information about the patient's disease transferred in both directions, enhancing accuracy of diagnosis and increasing the patient's knowledge about the disease. In some settings, e.g. the hospital ward, the patient-doctor relationship is much more complex, and many other people are involved when somebody is ill: relatives, neighbors, rescue specialists, nurses, technical personnel, social workers and others.

Clinical skills

Main articles: Medical history, Physical examination. A complete medical evaluation includes a medical history, a physical examination, appropriate laboratory or imaging studies, analysis of data and medical decision making to obtain diagnoses, and treatment plan. The components of the medical history are:
- Chief complaint (CC) - the reason for the current medical visit.
- History of present illness (HPI) - the chronological order of events of symptoms. A mnemonic PQRST is sometimes helpful in obtaining the history:
- Provocative-palliative factors - what makes a symptom worse or better.
- Quality - description of the symptom
- Region - which part of the body is affected
- Severity - what is the intensity of the symptom; using a scale of 0-10 (10 worst)
- Timing - what is the course of the symptom
- Current activity - occupation, hobbies, what the patient actually does.
- Medications - what drugs including OTCs, and home remedies, as well as herbal remedies such as St. John's Wort. Allergies are recorded.
- Past medical history (PMH/PMHx) - other medical diagnoses, past hospitalizations and operations, injuries, past infectious diseases and/or vaccinations, history of known allergies.
- Review of systems (ROS) - an outline of additional symptoms to ask which may be missed on HPI, generally following the body's main organ systems (heart, lungs, digestive tract, urinary tract, etc).
- Social history (SH) - birthplace, residences, marital history, social and economic status, habits (including diet, medications, tobacco, alcohol).
- Family history (FH) - listing of diseases in the family that may impact the patient. A family tree is sometimes used. The physical examination is the examination of the patient looking for signs of disease. The doctor uses his senses of sight, hearing, touch, and sometimes smell (taste has been made redundant by the availability of modern lab tests). Four chief methods are used: inspection, palpation, percussion, and auscultation; smelling may be useful (e.g. infection, uremia, diabetic ketoacidosis). The clinical examination involves study of:
- Vital signs include height, weight, body temperature, blood pressure, pulse, respiration rate, hemoglobin oxygen saturation
- General appearance of the patient
- Skin
- Head, eye, ear, nose, and throat (HEENT)
- Cardiovascular - heart and blood vessels
- Respiratory - lungs
- Abdomen and rectosigmoid
- Genitalia
- Spine and extremities - musculoskeletal
- Neurological and psychiatric Laboratory and imaging studies results may be obtained, if ncessary. The medical decision-making (MDM) process involves analysis and synthesis of all the above data to come up with a list of possible diagnoses (the differential diagnoses), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient's problem. The treatment plan may include ordering additional laboratory tests and studies, starting therapy, referral to a specialist, or watchful observation. Follow-up may be advised. This process is used by primary care providers as well as specialists. It may take only a few minutes if the problem is simple and straightforward. On the other hand, it may take weeks in a patient who has been hospitalized with multi-system problems, with involvement by several specialists. On subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, and lab or imaging results or specialist consultations.

Settings where medical care is delivered

See also clinic, hospital, and hospice Medicine is a diverse field and the provision of medical care is therefore provided in a variety of locations. Primary care medical services are provided by physicians or other health professionals who has first contact with a patient seeking medical treatment or care. These occur in physician's office, clinics, nursing homes, schools, home visits and other places close to patients. About 90% of medical visits can be treated by the primary care provider. These include treatment of acute and chronic illnesses, preventive care and health education for all ages and both sex. Secondary care medical services are provided by medical specialists in their offices or clinics or at local community hospitals for a patient referred by a primary care provider who first diagnosed or treated the patient. Referrals are made for those patients who required the expertise or procedures performed by specialists. These include both ambulatory care and inpatient services, emergency rooms, intensive care medicine, surgery services, physical therapy, labor and delivery, endoscopy units, diagnostic laboratory and medical imaging services, hospice centers, etc. Some primary care providers may also take care of hospitalized patients and deliver babies in a secondary care setting. Tertiary care medical services are provided by specialist hospitals or regional centers equipped with diagnostic and treatment facilities not generally available at local hospitals. These include trauma centers, burn treatment centers, advanced neonatology unit services, organ transplants, high-risk pregnancy, radiation oncology, etc. Modern medical care also depends on information - still delivered in many health care settings on paper records, but increasingly nowadays by electronic means.

Branches of medicine

Working together as an interdisciplinary team, many highly trained health professionals besides medical practitioners are involved in the delivery of modern health care. Some examples include: nurses, laboratory scientists, pharmacists, physiotherapists, speech therapists, occupational therapists, dietitians and bioengineers. The scope and sciences underpinning human medicine overlap many other fields. Dentistry and psychology, while separate disciplines from medicine, are sometimes also considered medical fields. Physician assistants, nurse practitioners and midwives treat patients and prescribe medication in many legal jurisdictions. Veterinary medicine applies similar techniques to the care of animals. Medical doctors have many specializations and subspecializations which are listed below.

Basic sciences

- Anatomy is the study of the physical structure of organisms. In contrast to macroscopic or gross anatomy, cytology and histology are concerned with microscopic structures.
- Biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components.
- Biostatistics is the application of statistics to biological fields in the broadest sense. A knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. It is also fundamental to epidemiology and evidence-based medicine.
- Cytology is the microscopic study of individual cells.
- Embryology is the study of the early development of organisms.
- Epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics.
- Genetics is the study of genes, and their role in biological inheritance.
- Histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry.
- Immunology is the study of the immune system, which includes the innate and adaptive immune system in human, for example.
- Microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses.
- Neuroscience is a comprehensive term for those disciplines of science that are related to the study of the nervous system. A main focus of neuroscience is the biology and physiology of the human brain.
- Nutrition is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. Medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition and neoplastic diseases.
- Pathology is the study of disease - the causes, course, progression and resolution thereof.
- Pharmacology is the study of drugs and their actions.
- Physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms.
- Toxicology is the study of hazardous effects of drugs and poisons.

Diagnostic specialties

- Clinical laboratory sciences are the clinical diagnostic services which apply laboratory techniques to diagnosis and management of patients. In the United States these services are supervised by a Pathologist. The personnel that work in these medical laboratory departments are technically trained staff, each of whom usually hold a medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services.
- Transfusion medicine is concerned with the transfusion of blood and blood component, including the maintenance of a "blood bank".
- Cellular pathology is concerned with diagnosis using samples from patients taken as tissues and cells using histology and cytology.
- Clinical chemistry is concerned with diagnosis by making biochemical analysis of blood, body fluids and tissues.
- Hematology is concerned with diagnosis by looking at changes in the cellular composition of the blood and bone marrow as well as the coagulation system in the blood.
- Clinical microbiology is concerned with the in vitro diagnosis of diseases caused by bacteria, viruses, fungi, and parasites.
- Clinical immunology is concerned with disorders of the immune system and related body defenses. It also deals with diagnosis of allergy.
- Radiology is concerned with imaging of the human body, e.g. by x-rays, x-ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography.
- Interventional radiology is concerned with using imaging of the human body, usually from CT, ultrasound, or fluoroscopy, to do biopsies, place certain tubes, and perform intravascular procedures.
- Nuclear Medicine uses radioactive substances for in vivo and in vitro diagnosis using either imaging of the location of radioactive substances placed into a patient, or using in vitro diagnostic tests utilizing radioactive substances.

Clinical disciplines

- Anesthesiology (AE), Anaesthesia (BE), is the clinical discipline concerned with providing anesthesia. Pain medicine is often practiced by specialised anesthesiologists.
- Dermatology is concerned with the skin and its diseases.
- Emergency medicine is concerned with the diagnosis and treatment of acute or life-threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies.
- General practice, Family practice, family medicine or primary care is, in many countries, the first port-of-call for patients with non-emergency medical problems. Family doctors are usually able to treat over 90% of all complaints without referring to specialists.
- Hospital medicine is the general medical care of hospitalized patients. Doctors whose primary professional focus is hospital medicine are called hospitalists.
- Internal medicine is concerned with systemic diseases of adults, i.e. those diseases that affect the body as a whole , (restrictive ,current meaning) or with all adult non-operative somatic medicine (traditional , inclusive meaning) , thus excluding pediatrics , surgery , gynaecology & obstetrics and psychiatry. There are several subdisciplines of internal medicine:
- Cardiology is concerned with the heart and cardiovascular system and their diseases.
- Critical care medicine is concerned with the therapy of patients with serious and life-threatening disease or injury. Intensive care medicine employs invasive diagnostic techniques and (temporary) replacement of organ functions by technical means. Also known as Intensive care medicine. This field is often associated with Pulmonology.
- Endocrinology is concerned with the endocrine system, i.e. endocrine glands and hormones, usually Diabetes or Thyroid diseases.
- Gastroenterology is concerned with the alimentary tract.
- Geriatrics is concerned with medical care of the elderly.
- Hematology (or haematology) is concerned with the blood and its diseases.
- Hepatology is concerned with the liver and biliary tract, and is usually a part of Gastroenterology
- Infectious diseases is concerned with the study, diagnosis and treatment of diseases caused by biological agents.
- Nephrology is concerned with diseases of the kidneys.
- Oncology is devoted to the study, diagnosis and treatment of cancer and other malignant diseases, and is often grouped with Hematology.
- Pulmonology (or chest medicine, respiratory medicine or lung medicine) is concerned with diseases of the lungs and the respiratory system.
- Rheumatology is devoted to the diagnosis and treatment of inflammatory diseases of the joints and other organ systems, such as arthritis.
- Neurology is concerned with the diagnosis and treatment of nervous system diseases.
- Obstetrics and Gynecology (often abbreviated as Ob/Gyn) are concerned respectively with childbirth and the female reproductive and associated organs. Reproductive medicine and fertility medicine are generally practiced by gynecological specialists.
- Palliative care is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal diseases (cancer, heart failure).
- Pediatrics (or paediatrics) is devoted to the care of infants, children, and adolescents. Like internal medicine, there are many pediatric subspecialities for specific age ranges, organ systems, disease classes and sites of care delivery. Most subspecialities of adult medicine have a pediatric equivalent such as pediatric cardiology, pediatric endocrinology, pediatric gastroenterology, pediatric hematology, and pediatric oncology, pediatric ophthalmology, and neonatology.
- Physical medicine and rehabilitation (or physiatry) is concerned with functional improvement after injury, illness, or congenital abnormality.
- Preventive medicine is the branch of medicine concerned with preventing disease.
- Community health care or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis.
- Occupational medicines principal role is the provision of health advice to organisations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained.
- Psychiatry is a branch of medicine that studies and treats mental disorders. Related non-medical fields are psychotherapy and clinical psychology. There are several subdisciplines of Psychiatry:
- Child & adolescent psychiatry focuses on the care of children and adolescents with mental/emotional/learning problems (i.e., ADHD, Autism, family conflicts).
- Geriatric psychiatry focuses on the care of elderly people with mental illnesses (i.e., dementias, post stroke cognitive changes, depression).
- Addiction psychiatry focuses on substance abuse and its treatment.
- Forensic psychiatry focuses on the interface of psychiatry and the Law.
- Radiation therapy is concerned with the therapeutic use of ionizing radiation and high energy elementary particle beams in patient treatment.
- Surgical specialties - there are many medical disciplines that employ operative treatment. Some of these are highly specialized and are often not considered subdisciplines of surgery, although their naming might suggest so.
- General surgery is traditionally defined as the specialty of surgery of the skin, endocrine glands, and abdomen (and, sometimes, the mammary glands). In some countries, it is still deemed a pre-requisite training prior to progression to training in certain sub-specialties, but lately has evolved into its own sub-specialty.
- Cardiovascular surgery is the surgical specialty that is concerned with the heart and major blood vessels of the chest.
- Neurosurgery is concerned with the operative treatment of diseases of the nervous system.
- Maxillofacial surgery (technically a subspeciality of dentistry)
- Ophthalmology deals with the diseases of the eyes and their treatment.
- Orthopedic surgery consists on surgery of the locomotor system.
- Otolaryngology (or otorhinolaryngology or ENT/ear-nose-throat) is concerned with treatment of ear, nose and throat disorders. The term head and neck surgery defines a closely related specialty which is concerned mainly with the surgical management of cancer of the same anatomical structures.
- Pediatric surgery treats a wide variety of thoracic and abdominal (and sometimes urologic) diseases of childhood.
- Plastic surgery includes aesthetic surgery (operations that are done for other than medical purposes) as well as reconstructive surgery (operations to restore function and/or appearance after traumatic or operative mutilation).
- Surgical oncology is concerned with curative and palliative surgical approaches to cancer treatment.
- Urology focuses on the urinary tracts of males and females, and on the male reproductive system. It is often practiced together with andrology ("men's health").
- Vascular surgery is surgery of "peripheral" blood vessels, i.e. those outside of the chest (usually operated on by cardiovascular surgeons) and of the central nervous system (treated by neurosurgery).
- Urgent Care focuses on delivery of unscheduled, walk-in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department.
Interdisciplinary fields
Interdisciplinary sub-specialties of medicine are:
- Aerospace medicine deals with medical problems related to flying and space travel.
- Bioethics is a field of study which concerns the relationship between biology, science, medicine and ethics, philosophy and theology.
- Clinical pharmacology is concerned with how systems of therapeutics interact with patients.
- Conservation medicine studies the relationship between human and animal health, and environmental conditions. Also known as ecological medicine, environmental medicine, or medical geology.
- Diving medicine (or hyperbaric medicine) is the prevention and treatment of diving-related problems.
- Evolutionary medicine is a perspective on medicine derived through applying evolutionary theory.
- Forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death.
- Medical humanities includes the humanities (literature, philosophy, ethics, history and religion), social science (anthropology, cultural studies, psychology, sociology), and the arts (literature, theater, film, and visual arts) and their application to medical education and practice.
- Medical informatics and medical computer science are relatively recent fields that deal with the application of computers and information technology to medicine.
- Nosology is the classification of diseases for various purposes.
- Sports medicine deals with the treatment and preventive care of athletics, amateur and professional. The team includes specialty physicians and surgeons, athletic trainers, physical therapists, coaches, other personnel, and, of course, the athlete.
- Therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health [http://2.1911encyclopedia.org/T/TH/THERAPEUTICS.htm] [http://www.britannica.com/eb/article-9106176?query=Therapeutics&ct=].
- Travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different evironments.
Medical education
See also Medical doctor (BE), Physician (AE), and Medical school. Medical training involves several years of university study followed by several more years of residential practice at a hospital. Entry to a medical degree in some countries (such as the United States) requires the completion of another degree first, while in other countries (such as the United Kingdom, Australia and New Zealand) medical training can be commenced as an undergraduate degree immediately after secondary education. The name of the medical degree gained at the end varies: some countries (e.g. the US) call it "Doctor of Medicine" (abbreviated 'M.D.'), while other countries (mostly following the British Oxbridge system) call it "Medicinæ Baccalaureus & Baccalaureus Chirurgiæ" (Latin for "Bachelor of Medicine/Bachelor of Surgery", Old English: "Chirurgie"); this is technically a double degree, frequently abbreviated 'MB BChir', 'MB ChB', 'MB BS' (or variations thereof), dependent on the medical school. In either case, graduates of a medical degree may call themselves physician. In the US and some other countries there is a parallel system of medicine which is equal in all aspects of education, legality, and practice to M.D.'s. It is called osteopathic medicine (generic term: "osteopathy") which awards the degree of "Doctor of Osteopathic Medicine" (abbreviated 'D.O.'). In many countries, a doctorate of medicine does not involve original research as does, in distinction, a Ph.D.. Once graduated from medical school most physicians (both M.D.'s and D.O.'s) begin their residency/house post training, where skills in a speciality of medicine are learned, supervised by more experienced doctors. The first year of residency is known as the "intern" year (USA) or "junior/pre-registration house officer" year (UK). The duration of residency training depends on the speciality. A medical graduate can then enter general practice and become a general practitioner (or primary care internist in the USA); training for these is generally shorter, while specialist training is typically longer. Medical education is a never ending endeavor. In addition to continually reading relevant medical journals, physicians require a number of continuing medical education (CME)credits annually to be recertified. These can be acquired by attending conferences, lectures, online, and through other sources.
Medical devices
See also the main articles: implant, artificial limbs, corrective lenses, cochlear implants, ocular prosthetics, facial prosthetics, somato prosthetics, surgical prosthetics, maxillo-facial prosthetics and dental implants Medical devices are devices used by health professionals as tools in diagnosis, treatment, or other aspects of patient care.
Legal restrictions
In most countries, it is a legal requirement for medical doctors to be licensed or registered. In general, this entails a medical degree from a university and accreditation by a medical board or an equivalent national organization, which may ask the applicant to pass exams. This restricts the considerable legal authority of the medical profession to doctors that are trained and qualified by national standards. It is also intended as an assurance to patients and as a safeguard against charlatans that practice inadequate medicine for personal gain. While the laws generally require medical doctors to be trained in "evidence based", Western, or Hippocratic Medicine, they are not intended to discourage different paradigms of health and healing, such as