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Malachite

Malachite

:This article is about the mineral. For the butterfly see Malachite (butterfly) Malachite (butterfly)] Malachite is a carbonate mineral, copper(II) carbonate hydroxide Cu2CO3(OH)2. Malachite has a hardness between 3.5 and 4. It crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagtitic masses. Malachite often results from weathering of copper ores and is often found together with azurite (Cu3(CO3)2(OH)2), goethite, and calcite. Except for the iridescent green colour, the properties of malachite are very similar to those of azurite and aggregates of the two minerals together are frequently found, although malachite is more common than azurite. Typically associated with copper deposits associated with limestones, the source of the carbonate. It was used as a mineral pigment in green paints from antiquity until about 1800. The pigment is moderately lightfast, very sensitive to acids and varying in colour. The natural form was being replaced by its synthetic form, verditer amongst other synthetic greens. It is also used for decorative purposes, such as in the Malachite Room in the Hermitage which features a huge malachite vase. Large quantities of malachite have been mined in the Urals. It is found in the Democratic Republic of Congo; Tsumeb, Namibia; Ural mountains, Russia; Mexico; Broken Hill, New South Wales; England; Lyon; and in the Southwestern United States especially in Arizona at Bisbee and Morenci.

References


- Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0471805807
- [http://mineral.galleries.com/minerals/carbonat/malachit/malachit.htm Mineral Galleries]
- [http://www.hermitagemuseum.org/html_En/08/hm88_0_1_62.html Virtual tour of the Malachite Room] Category:Carbonate minerals

Malachite (butterfly)

Siproeta stelenes is the scientific name for the Malachite butterfly.

Carbonate minerals

Carbonate minerals are those minerals containing the carbonate ion: CO32-.

Example carbonates

Anhydrous carbonates


- Calcite group: Trigonal
  - Calcite CaCO3
  - Gaspeite (Ni,Mg,Fe2+)CO3
  - Magnesite MgCO3
  - Otavite CdCO3
  - Rhodochrosite MnCO3
  - Siderite FeCO3
  - Smithsonite ZnCO3
  - Sphaerocobaltite CoCO3
- Aragonite group: Orthorhombic
  - Aragonite CaCO3
  - Cerussite PbCO3
  - Strontianite SrCO3
  - Witherite BaCO3
  - Rutherfordine UO2CO3
  - Natrite Na2CO3

Anhydrous carbonates with compound formulas


- Dolomite group: Trigonal
  - Ankerite CaFe(CO3)2
  - Dolomite CaMg(CO3)2
  - Minrecordite CaZn(CO3)2
  - Barytocalcite BaCa(CO3)2

Carbonates with hydroxyl or halogen


- Carbonate with hydroxide: Monoclinic
  - Azurite Cu3(CO3)2(OH)2
  - Hydrocerussite Pb3(CO3)2(OH)2
  - Malachite Cu2CO3(OH)2
  - Rosasite (Cu,Zn)2CO3(OH)2
  - Phosgenite Pb2(CO3)Cl2
  - Hydrozincite Zn5(CO3)2(OH)6
  - Aurichalcite (Zn,Cu)5(CO3)2(OH)6

Hydrated carbonates


- Natron Na2CO3·10(H2O)
- Lansfordite MgCO3·5(H2O)
- Zellerite Ca(UO2)(CO3)2·5(H2O) The carbonate class in both the Dana and the Strunz classification systems includes the nitrates, the borates, and the iodates.

References


- Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0471805807
- [http://webmineral.com/danaclass.shtml Webmineral Dana Classification] Category:Carbonate minerals

Copper(II) carbonate

Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming most of the patina one sees on weathered brass, bronze, and copper. The color can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration. It was formerly much used as a pigment, and is still in use for artist's colours. It is also been used in some types of make-up, like lipstick, although it can also be extremely poisonous to humans. Basic copper(II) carbonate occurs naturally as malachite (CuCO3.Cu(OH)2) and azurite (Cu3(CO3)2(OH)2). Category:Carbonates Category:Copper compounds

Hydroxide

Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: :−O−H It has a charge of −1. Hydroxide is one of the simplest of the polyatomic ions. The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. Organic molecules containing a hydroxyl group are known as alcohols (the simplest of which have the formula CnH2n+1-OH). A group of bases containing hydroxide are called hydroxide bases. Hydroxide bases will dissociate into a cation and one or more hydroxide ions in water, making the solution basic. This makes hydroxides alkalis, which may undergo neutralisation reactions with acids. In general acid-alkali reactions can be simplified to :OH−(aq) + H+(aq) → H2O by omitting spectator ions. Hydrogen hydroxide is another name for water, as is hydrohydroxic acid. Both names are based on the hydroxide ion. Hydroxides and hydroxide ions are relatively common. Many useful chemicals and chemical processes involve hydroxides or hydroxide ions, such as sodium hydroxide - used in industry as a strong base - or potassium hydroxide - used in agriculture.

Hydroxyl radical

The hydroxyl radical, ·OH, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and consequently short lived, however they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydro-peroxides (ROOH) or, importantly in atmospheric chemistry, by the reaction of excited atomic oxygen with water. In the troposphere the hydroxyl radical acts like a detergent, reacting with carbon monoxide, methane and other hydrocarbons and so oxidizing them to form water and carbon dioxide. The very short in vivo half-life of approx. 10-9 s and its high reactivity renders it a very dangerous compound to the organism. Unlike superoxide which can be detoxified by superoxide dismutase it cannot be eliminated by an enzymatic reaction as this would require its diffusion to the enzyme's active site. As diffusion is slower than the half life of the molecule it will react with any oxidizable compound in vicinity. The only means to protect important cellular structures is the use of antioxidants such as glutathione and of effective repair systems.

See also


- Hydronium
- Potassium hydroxide
- Sodium hydroxide
- Iron hydroxide
- Oxide Category:Bases ja:ヒドロキシル基

Mohs scale of mineral hardness

Mohs' scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. It was created, in 1812, by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science. Mohs based the scale on ten minerals that are all readily available except the last one, diamond. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on Mohs scale is 4.5. The table below shows comparison with absolute hardness measures by a sclerometer. Mohs' is a purely ordinal scale with, for example, corundum being twice as hard as topaz, but diamond, almost four times as hard as corundum. On the Mohs scale, fingernail has hardness 2; copper penny, about 3; a knife blade, 5; window glass, 5.5; steel file, 6.5. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale. Some mnemonics traditionally taught to geology students to remember this table are "The Girls Can Flirt And Other Queer Things Can Do" or "To Get Candy From Aunt Fanny, Quit Teasing Cousin Danny". An alternative table is shown below which has been modified to incorporate additional substances that may fall in between two levels. Source: [http://www.amfed.org/t_mohs.htm American Federation of Mineralogical Societies: Mohs Scale of Mineral Hardness] Category:Materials science Category:Mineralogy Category:Scales ja:モース硬度

Copper

Copper is a chemical element in the periodic table that has the symbol Cu and atomic number 29.

History

In Greek times, the metal was known by the name chalkos (χαλκός). Copper was a very important resource for the Romans and Greeks. In Roman times, it became known as aes Cyprium (aes being the generic Latin term for copper alloys such as bronze and other metals, and Cyprium because so much of it was mined in Cyprus). From this, the phrase was simplified to cuprum and then eventually Anglicized into the English copper. Copper was known to some of the oldest civilizations on record, and has a history of use that is at least 10,000 years old. A copper pendant was found in what is now northern Iraq that dates to 8700 BC. By 5000 BC there are signs of copper smelting, the refining of copper from simple copper oxides such as malachite or azurite. The earliest signs of gold use, by contrast, appear around 4000 BC. There are copper and bronze artifacts from Sumerian cities that date to 3000 BC, and Egyptian artifacts in copper and copper alloyed with tin nearly as old. In one pyramid, a copper plumbing system was found that is 5000 years old. tin The Egyptians found that adding a small amount of tin made the metal easier to cast, so bronze alloys are found in Egypt almost as soon as copper is found. Use of copper in ancient China dates to at least 2000 BC. By 1200 BC excellent bronzes were being made in China. Note that these dates are affected by wars and conquest, as copper is easily melted down and reused. In Europe, Oetzi the Iceman, a well preserved male dated to 3200 BC, was found with a copper tipped axe whose metal was 99.7% pure. High levels of arsenic in his hair suggests he was involved in copper smelting. The use of bronze was so pervasive in a certain era of civilization that it has been named the Bronze Age. The transitional period in certain regions between the preceding Neolithic period and the Bronze Age is termed the Chalcolithic, with some high purity copper tools being used alongside stone tools. Chalcolithic Brass, an alloy of zinc and copper, was known to the Greeks but first used extensively by the Romans. Copper was associated with the goddess Aphrodite/Venus in mythology and alchemy, owing to its lustrous beauty, its ancient use in producing mirrors, and its association with Cyprus, which was sacred to the goddess. In alchemy the symbol for copper was also the symbol for the planet Venus.

Biological role

Copper is essential in all higher plants and animals. Copper is carried mostly in the bloodstream on a plasma protein called ceruloplasmin. When copper is first absorbed in the gut it is transported to the liver bound to albumin. Copper is found in a variety of enzymes, including the copper centers of cytochrome c oxidase and the enzyme superoxide dismutase (containing copper and zinc), and is the central metal in the oxygen carrying pigment hemocyanin. The blood of the horseshoe crab, Limulus polyphemus, uses copper rather than iron for oxygen transport. [http://www.ocean.udel.edu/horseshoecrab/funFacts.html] It is believed that zinc and copper compete for absorption in the digestive tract so that a diet that is excessive in one of these minerals may result in a deficiency in the other. The RDA for copper in normal healthy adults is 0.9 mg/day.

Toxicity

All copper compounds, unless otherwise known, should be treated as if they were toxic. 30g of copper sulfate is potentially lethal in humans. The suggested safe level of copper in drinking water for humans varies depending on the source, but tends to be pegged at 1.5 to 2 mg/l. The DRI Tolerable Upper Intake Level for adults of dietary copper from all sources is 10 mg/day.In toxicity, copper can inhibit the enzyme dihydrophil hydratase, an enzyme involved in haemopoesis An inherited condition called Wilson's disease causes the body to retain copper, since it is not excreted by the liver into the bile. This disease, if untreated, can lead to brain and liver damage. In addition, studies have found that people with mental illnesses such as schizophrenia had heightened levels of copper in their systems. However it is unknown at this stage whether the copper contributes to the mental illness, whether the body attempts to store more copper in response to the illness, or whether the high levels of copper are the result of the mental illness.

Miscellaneous hazards

The metal, when powdered, is a fire hazard. At concentrations higher than 1 mg/L, copper can stain clothes and items washed in water.

Physical characteristics

fire hazard Copper is a reddish-coloured metal, with a high electrical and thermal conductivity (among pure metals at room temperature, only silver has a higher electrical conductivity). Copper has its characteristic color because it reflects red and orange light and absorbs other frequencies in the visible spectrum, due to its band structure. There are two stable isotopes, 63Cu and 65Cu, along with a couple dozen radioisotopes. The vast majority of radioisotopes have half lives on the order of minutes or less; the longest lived, 64Cu, has a half life of 12.7 hours, with two decay modes, leading to two separate products. There are numerous alloys of copper - speculum metal is a copper/tin alloy, brass is a copper/zinc alloy, and bronze is a copper/tin alloy. Monel metal is a copper/nickel alloy, also called cupronickel.

Compounds

cupronickel Common oxidation states of copper include the less stable copper(I) state, Cu+1; and the more stable copper(II) state, Cu+2, which forms lovely blue or blue-green salts. Under unusual conditions, a +3 state can be obtained. Copper(II) carbonate is green from which arises the unique appearance of copper-clad roofs or domes on some buildings. Copper(II) sulfate forms a blue crystalline pentahydrate which is perhaps the most familiar copper compound in the laboratory. It is used as a fungicide, known as Bordeaux mixture. There are two stable copper oxides, copper(II) oxide (CuO) and copper(I) oxide (Cu2O). Copper oxides are used to make yttrium barium copper oxide (YBa2Cu3O7-δ) or YBCO which forms the basis of many unconventional superconductors. Copper (I) compounds : copper(I) chloride, copper(I) oxide. Copper (II) compounds : copper(II) carbonate, copper(II) chloride, copper(II) hydroxide, copper(II) nitrate, copper(II) oxide, copper(II) sulfate, copper(II) sulfide. Copper (I) and Copper (II) can also be referred to by their common names cuprous and cupric.

Occurrence

copper(II) sulfide :See Copper extraction for the main article. Copper can be found as native copper in mineral form. Minerals such as the carbonates azurite (Cu3(CO3)2(OH)2) and malachite (Cu2CO3(OH)2) are sources of copper, as are sulfides such as chalcopyrite (CuFeS2), bornite (Cu5FeS4), covellite (CuS), chalcocite (Cu2S) and oxides like cuprite (Cu2O). Most copper ore is mined or extracted from large open pit mines in copper porphyry deposits that contain 0.4 to 1.0 percent copper. Examples include: Chuquicamata in Chile and El Chino mine in New Mexico. The average abundance of copper found within crustal rocks is approximately 68000 parts per billion by mass, and 22000 parts per billion by atoms. The Intergovernmental Council of Copper Exporting Countries (CIPEC), defunct since 1992, once tried to play a similar role for copper as OPEC does for oil, but never achieved the same influence, not least because the second-largest producer, the United States, was never a member. Formed in 1967, its principal members were Chile, Peru, Zaire, and Zambia.

Tests for copper2+ ion

Add aqueous sodium hydroxide. A blue precipitate of copper(II) hydroxide should form, by the displacement of the copper ions by sodium ions. Ionic equation: :Cu2+(aq) + 2OH-(aq) -> Cu(OH)2 (s) Add aqeuous ammonia. A precipitate should form, which then dissolves upon adding excess ammonia, to form an ammonia complex, tetraaminecopper(II). Ionic equation: :Cu2+(aq) + 4NH3 (aq) -> Cu(NH3)42+(aq)

Applications

Copper is malleable and ductile, and is used extensively, in products such as:
- Copper wire.
- Copper plumbing.
- Doorknobs and other fixtures in houses.
- Statuary: The Statue of Liberty, for example, contains 179,200 pounds (81.3 tonnes) of copper.
- Electromagnets.
- Motors, especially electromagnetic motors.
- Watt's steam engine.
- Electrical relays, electrical busbars and electrical switches.
- Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
- Wave guides for microwave radiation.
- There is increasing use of copper in integrated circuits, replacing aluminium because of its superior conductivity.
- Alloyed with nickel, e.g. cupronickel and Monel, used as corrosive resistant materials in shipbuilding.
- As a component of coins, often as cupronickel alloy.
- In cookware, such as frying pans.
- Most flatware (knives, forks, spoons) contains some copper (nickel silver).
- Sterling silver, if it is to be used in dinnerware, must contain a few percent copper.
- As a component in ceramic glazes, and to color glass.
- Musical instruments, especially brass instruments.
- As a biostatic surface in hospitals, and to line parts of ships to protect against barnacles and mussels, originally used pure, but superceded by Muntz Metal. Bacteria will not grow on a copper surface because it is biostatic. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaire's Disease is supressed by copper tubing in air-conditioning systems.
- Compounds, such as Fehling's solution, have applications in chemistry.
- Copper(II) sulfate is used as a poison and a water purifier. It is used in gardening powders and sprays to kill mildew.
- As a material in the manufacture of computer heatsinks, as a result of its superior heat dissipation capacity to aluminium.

References


- [http://periodic.lanl.gov/elements/29.html Los Alamos National Laboratory - Copper]
- Copper: Technology & Competitiveness (Summary) Chapter 6: Copper Production Technology; Author: Office of Technology Assessment 2005
- [http://www.ocean.udel.edu/horseshoecrab/funFacts.html NOAA and Univ. of Delaware, Horseshoe Crab Fun Facts] Accessed 12-12-2005.

External links


- [http://www.webelements.com/webelements/elements/text/Cu/index.html WebElements.com – Copper]
- [http://www.healingedge.net/briefs_copper_tox.html Copper Toxicity Syndrome]
- [http://www.best-home-remedies.com/minerals/copper.htm Copper- Benefits, Deficiency Symptoms And Food Sources]
- [http://www.copper.org/ The Copper Page]
- [http://y2u.co.uk/&002_Images/Parys_Mountain_01.htm Photos of the Parys Mountain Copper Mine near Amlwch, Anglesey, Wales]
- [http://www.gindre.com/cours_du_cuivre/l_home.htm Current copper price] as at June 2005, about USD$3,500 / tonne.
- [http://www.indexmundi.com/en/commodities/minerals/copper/copper_t20.html World mine production of copper by country] Category:Chemical elements Category:Transition metals ko:구리 ja:銅 simple:Copper th:ทองแดง

Azurite

Azurite is a carbonate mineral with chemical composition Cu3(CO3)2(OH)2, (copper carbonate hydroxide). Azurite is often found in association with the green mineral malachite as a result of the weathering and oxidation of copper sulfide minerals. The name azurite comes from the Arabic word for blue. Azurite is used in jewelry and also collected as a beautiful mineral specimen.

Use as a pigment

Azurite has been used as a blue mineral pigment for centuries. It was formerly known as Azurro Della Magna (from Italian). When mixed with oil it turns slightly green. When mixed with egg yolk it turns green-grey. It is also known by the names Blue Bice and Blue Verditer.

See also


- list of minerals Category:Carbonate minerals Category:Pigments

Calcite

The carbonate mineral calcite is a calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earth's surface. It is a common constituent of sedimentary rocks, limestone in particular. It is also the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and also occurs in caverns as stalactites and stalagmites. Calcite is often the primary constituent of the shells of marine organisms (e.g. plankton, bivalves, etc.). Calcite represents the stable form of calcium carbonate; aragonite will change to calcite at 470°C.

Properties

Calcite crystals are hexagonal-rhombohedral, though actual calcite rhombohedrons are rare as natural crystals. However, they show a remarkable variety of habit including acute to obtuse rhombohedrons, tabular forms, prisms, or various scalenohedrons. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain. It has a Mohs hardness of 3, a specific gravity of 2.71, and its luster is vitreous in crystallized varieties. Colour is white or colourless, though shades of gray, red, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities. Calcite reacts when it comes into contact with dilute hydrochloric acid causing effervescence and the release of carbon dioxide gas. This is the only mineral to do so, and limestone and marble, rocks composed of calcite, will also react with acid. marble Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. It is perhaps best known because of its power to produce strong double refraction of light, such that objects viewed through a clear piece of calcite appear doubled in all of their parts - a phenomenon first described by Rasmus Bartholin. A beautifully transparent variety used for optical purposes comes from Iceland, called Iceland spar. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar". Iceland Iceland

See also


- List of minerals
- lysocline
- Ocean acidification

External link


- [http://mineral.galleries.com/minerals/carbonat/calcite/calcite.htm Calcite information and images] Category:Carbonate minerals ja:方解石

Iridescence

Iridescence is an optical phenomenon characterized as the property of surfaces in which hue changes according to the angle from which the surface is viewed, such as soap bubbles and butterfly wings. butterfly Iridescence is caused by multiple reflections from multi-layered, semi-transparent surfaces where the subsequent phase shift and interference of the reflections modulates the incident light (by amplifying or attenuating different frequencies). The word is derived in part from the Greek word iris (pl. irides), meaning "rainbow", which in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods. See also thin-film optics.

External links

thin-film optics Category:Optics Category:Optical phenomena

Limestone

, Tennessee]] Limestone is a chemical sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3). Limestones often contain variable amounts of silica in the form of chert or flint, as well as amounts of clay, silt and sand as disseminations, nodules, or layers within the rock unit. The primary source of this calcite is most commonly marine organisms. These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze (see lysocline for information on calcite dissolution). Secondary calcite may also be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems such as stalagmites and stalactites. Another form is composed of oolites (oolitic limestone) and can be recognised by its granular appearance. Limestone makes up about 10 percent of the total volume of all sedimentary rocks. oolites Pure limestones are white or almost white. Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. Travertine is a banded, compact variety of limestone formed along streams, particularly where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution that is supersaturated with chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group.

Limestone landscape

Limestone is partially soluble, especially in acid, and therefore forms many erosion landforms. These include limestone pavements, pot holes, caves and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. Limestone is therefore usually associated with hills and downland and occurs in regions with other sedimentary rocks, typically clays. clay Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. Examples include the Burren in Co. Clare, Ireland; the Verdon Gorge in France; Malham Cove in North Yorkshire, England; and the Ha Long Bay National Park in [[Vietnam{commonscat|Limestone

Acid

An acid (often represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound. In common usage an acid is any substance that, when dissolved in water, gives a solution with a pH of less than 7. In general scientific usage an acid is a molecule or ion that is able to give up a proton (H+ ion) to a base, or accept an unshared pair of electrons from a base. An acid reacts with a base in a neutralization reaction to form a salt.

Chemical characteristics

In water the following reversible reaction occurs between an acid (HA) and water, which acts as a base: :\mbox +\mbox_2\mbox \leftrightarrow \mbox_3\mbox^+ + \mbox^- The acidity constant (or acid dissociation constant) is the equilibrium constant for the reaction of HA with water: :K_a = Strong acids have large Ka values (i.e. the reaction equilibrium lies far to the right, lots of H3O+ present; the acid is almost completely dissociated). For example, the Ka value for hydrochloric acid (HCl) is 107. Weak acids have small Ka values (i.e. at equilibrium significant amounts of HA and A− exist together in solution; modest levels of H3O+ are present; the acid is only partially dissociated). For example, the Ka value for acetic acid is 1.8 x 10-5. Strong acids include the hydrohalic acids - HCl, HBr, and HI. (However, hydrofluoric acid, HF, is relatively weak.) Oxoacids, which tend to contain central atoms in high oxidation states surrounded by oxygen, are also quite strong and include HNO3, H2SO4, HClO4. Most organic acids are weak acids. A few clarifications:
- The terms "hydrogen ion" and "proton" are used interchangebly; both refer to H+.
- In chemical equations H+ is often written, although in water it will actually be H3O+ and related ions.
- The strength of an acid is measured by its Ka value. pH measures how many hydrogen ions are present, which depends on both the type of acid (or base) and how much is there.
- Acid strength is also defined by pKa= - log(Ka).

Number of acid dissociations

Some acid molecules are able to give up more than one H+ ion (proton). Those acids which can give up only one H+ ion per molecule are called monoprotic acids, those acid molecules that can give up two H+ ions are diprotic acids, those that can give up three are triprotic acids, etc. A monoprotic acid can undergo one dissociation (sometimes called ionization) as follows and simply has one acid dissociation constant as shown above: :::::HA + H2O H3O+ + A−         Ka A diprotic acid (here symbolized by H2A) can undergo one or two dissociations depending on the conditions (namely pH). Each dissociation has its own dissociation constant, Ka1 and Ka2. :::::H2A + H2O H3O+ + HA−       Ka1 :::::HA− + H2O H3O+ + A2−       Ka2 The first dissociation constant is typically greater than the second; i. e. Ka1 > Ka2 . For example, sulfuric acid (H2SO4) can give up one H+ to form the singly charged bisulfate anion (HSO4−), for which Ka1 is very large; then it can give up a second H+ to form the doubly charged sulfate anion (SO42−) where the Ka2 is intermediate strength. The large Ka1 for the first dissociation makes sulfuric a strong acid. Similarly, the weak unstable carbonic acid (H2CO3) can lose one H+ to form a singly charged bicarbonate anion (HCO3−) and lose a second to form a doubly charged carbonate anion (CO32−). Both Ka values are small, but Ka1 > Ka2 . Analogously, a triprotic acid (H3A) can undergo one, two, or three dissociations and has three dissociation constants, where Ka1 > Ka2 > Ka3 . :::::H3A + H2O H3O+ + H2A−        Ka1 stop :::::H2A− + H2O H3O+ + HA2−       Ka2 :::::HA2− + H2O H3O+ + A3−         Ka3 An inorganic example of a triprotic acid is orthophosphoric acid (H3PO4), usually just called phosphoric acid. All three of its H atoms can be successively lost as H+ (or H3O+ in water) to yield H2PO4−, then HPO42−, and finally PO43− , the triply charged orthophosphate ion, usually just called phosphate. An organic example of a triprotic acid is citric acid, which can successively lose three H+ ions to finally form the triply charged citrate ion. Even though the positions of the H atoms on the original molecule may be equivalent, the successive Ka values will differ since it is energetically less favorable to lose a positive H+ if the ion is more negatively charged.

Characteristics of acids


- Taste: generally sour when dissolved in water
- Touch: produce a stinging feeling (strong acids)
- Reactivity: react aggressively with many metals
- Electrical conductivity: are electrolytes Strong acids are very dangerous. They are extremely reactive with metals, and can cause serious burns just by touching them for an instant. If contact with a strong acid should occur rinse abundantly with water immediately and seek medical attention.

Different definitions of acid/base

The word acid comes from the Latin acidus meaning sour but in chemistry the term acid has a more specific meaning. There are three common ways to define an acid - namely, the Arrhenius, the Brønsted-Lowry and the Lewis definitions. Around 1800, many French chemists, including Antoine Lavoisier, incorrectly believed that all acids contained oxygen. English chemists, including Sir Humphry Davy at the same time believed all acids contained hydrogen. The Swedish chemist Svante Arrhenius used this belief to define an acid to be a substance that gives up hydrogen ions (H+) when dissolved in water (the product of the solution, H2O + H+, is called a hydronium ion, H3O+), while bases are substances that give up hydroxide ions (OH-). This definition limits acids and bases to substances that can dissolve in water. Later on, Brønsted and Lowry defined an acid to be a proton donor and a base to be a proton acceptor. In this definition, even substances that are insoluble in water can be acids and bases. The most general definition of acids and bases is the Lewis definition, given by the American chemist Gilbert N. Lewis. Lewis theory defines a "Lewis acid" as an electron-pair acceptor and a "Lewis base" as an electron-pair donor. Lewis acids include acids that do not contain any hydrogen atoms, such as iron(III) chloride. Acid/base systems are different from redox reactions in that there is no change in oxidation state. The Lewis definition can also be explained with molecular orbital theory. In general an acid can receive an electron pair in its lowest unoccupied orbital (LUMO) from the highest occupied orbital (HOMO) of a base. That is, the HOMO from the base and the LUMO from the acid combine to a bonding molecular orbital. The Brønsted-Lowry definition, where an acid is treated as a proton donor, is sufficient for many situations. In this case, the proton (H+) is the actual acid and the acidity of the proton-donating-compound, such as an organic acid, is determined by its stability when it donates protons to the solution it is embedded in. So if the organic acid likes letting protons go, it has high acidity, because it donates protons with empty molecular orbitals to the solution. This is how organic acids such as carboxylic acids work. Here the Brønsted definition is nice for calculations, while the Lewis definition is good for understanding.

Acid number

The Acid number is used to quantify the amount of acid present, for example in a sample of biodiesel. It is the quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize the acidic constituents in 1 g of sample. AN = (Veq-beq)×N×56.1/Woil. Veq is the amount of titrant (ml) consumed by the crude oil sample and 1ml spiking solution at the equivalent point, and beqbeq is the amount of titrant (ml) consumed by 1ml spiking solution at the equivalent point. The molarity concentration of titrant (N) is calculated as such: N = 1000×WKHP/(204.23×Veq). In which, WKHP is the amount (g) of KHP in 50ml of KHP standard solution, and Veq is the amount of titrant (ml) consumed by 50ml KHP standard solution at the equivalent point. Acid number (mgKOH/g oil) for biodiesel is preferred to be lower than 3.

Neutralization

Neutralization is a type of reaction between an acid and a base. The products include a salt and water. So, it is also called a water forming reaction acid + base \rarr water + salt
Example: HCl + NaOH \rarr H_2O + NaCl This type of reaction forms the basis of titration methods for analyzing acids, where a pH indicator shows the point of neutralization.

Naming acids

Acids are named according to the ending of their anion. That ionic ending is dropped and replaced with a new suffix according to the table below. For example, HCl has chloride as its anion, so the -ide suffix makes it take the form hydrochloric acid.

Common acids

Strong inorganic acids


- Hydrobromic acid
- Hydrochloric acid
- Hydroiodic acid
- Nitric acid
- Sulfuric acid
- Perchloric acid

Medium to weak inorganic acids


- Boric acid
- Carbonic acid
- Chloric acid
- Hydrofluoric acid
- Phosphoric acid
- Pyrophosphoric acid

Weak organic acids


- Acetic acid
- Benzoic acid
- Butyric acid
- Citric acid
- Formic acid
- Lactic acid
- Malic acid
- Methanethiol
- Propionic acid
- Pyruvic acid
- Valeric acid
- mandellic acid

Acids in food


- Acetic acid: (E260) found in vinegar
- Adipic acid: (E355)
- Alginic acid: (E400)
- Benzoic acid: (E210)
- Boric acid: (E284)
- Ascorbic acid (vitamin C): (E300) found in fruits
- Citric acid: (E330) found in citrus fruits
- Carbonic acid: (E290) found in carbonated soft drinks
- Carminic acid: (E120)
- Cyclamic acid: (E952)
- Erythorbic acid: (E315)
- Erythorbin acid: (E317)
- Formic acid: (E236)
- Fumaric acid: (E297)
- Gluconic acid: (E574)
- Glutamic acid: (E620)
- Guanylic acid: (E626)
- Hydrochloric acid: (E507)
- Inosinic acid: (E630)
- Lactic acid: (E270) found in dairy products such as yoghurt and sour milk, also is product of cellular fermentation, the reason muscles burn
- Malic acid: (E296)
- Metatartaric acid: (E353)
- Methanethiol: found in cheese and some other fermented foods.
- Nicotinic acid: (E375)
- Oxalic acid: found in spinach and rhubarb
- Pectic acid: found in fruits and some vegetables
- Phosphoric acid: (E338)
- Propionic acid: (E280)
- Sorbic acid: (E200) found in foods and drinks
- Stearic acid: (E570), a type of fatty acid.
- Succinic acid: (E363)
- Sulfuric acid: (E513)
- Tannic acid: found in tea
- Tartaric acid: (E334) found in grapes

Sources


- [http://www.csudh.edu/oliver/chemdata/data-ka.htm Listing of strengths of common acids and bases]
- Zumdahl, Chemistry, 4th Edition. Category:Chemical substances
- ko:산 (화학) ja:酸と塩基 simple:Acid th:กรด

Hermitage Museum

The Hermitage Museum (Эрмитаж) in St. Petersburg, Russia is one of the largest, oldest and most important art galleries in the world. The vast Hermitage collections are displayed in six buildings, the main one being the Winter Palace which used to be the official residence of the Russian Tsars. Strong points of the Hermitage collection of Western art include Michelangelo, Leonardo, Rubens, Van Dyck, Rembrandt, Poussin, Claude Lorraine, Watteau, Tiepolo, Canaletto, Canova, Rodin, Monet, Pissarro, Renoir, Cezanne, Van Gogh, Gauguin, Picasso, and Matisse. But there is actually much more to see - the Russian imperial regalia, a superb assortment of Faberge jewellery, and a breathtaking collection of ancient gold.

Origin

Catherine the Great started things off in 1764, when she purchased more than 250 paintings in Europe. Russian ambassadors in foreign capitals were commissioned to acquire the best collections offered for sale: Brühl's collection in Saxony, Crozat's in France and the Walpole gallery in England. Catherine called her art gallery my hermitage, as very few people were allowed within to see its riches. In one of her letters she lamented that "only the mice and I can admire all this."

Expansion in the 19th century

England Gradually imperial collections were enriched by relics of Greek and Scythian culture, unearthed during excavations on ancient burial mounds in southern Russia. Thus started one of the world's richest collections of ancient gold, which now includes a substantial part of Troy's treasures unearthed by Heinrich Schliemann and seized from Berlin museums by the Red Army in 1945. To house the ever-expanding collection of Greek, Roman, and Egyptian antiquities, Nicholas I commissioned the fashionable German architect Leo von Klenze to design a building for the public museum. Probably the first purpose-built art gallery in Eastern Europe, the New Hermitage was opened to the public in 1852. As the Russian tsars continued to amass their art holdings, several works of Leonardo da Vinci, Jan van Eyck, and Raphael were bought in Italy. The Hermitage collection of Rembrandts was considered the largest in the world; its quality is still unsurpassed. Rembrandt

Vicissitudes in the 20th century

The imperial Hermitage was proclaimed public property during the Revolution. The range of its exhibits was further expanded when private art collections were being nationalized. Particularly remarkable was the influx of modern art from collections of Sergei Shchukin and Ivan Morozov. New acquisitions included most of Gauguin's later ouevre, a lot of Cubistic works by Picasso, and such icons of modern art as Matisse's La danse and Vincent van Gogh's Night Cafe. The Soviet government did not pay much attention to maintenance of "bourgeois and decadent" art. What is worse, Stalin ordered some of the most precious Hermitage works to be sold abroad. These included unqualified masterpieces like Raphael's Madonna Alba, Titian's Venus with a Mirror and Jan van Eyck's Annunciation. Acquired by Andrew W. Mellon, most of these works formed a nucleus of the National Gallery of Art in Washington, D.C.. There were other losses, though somewhat less irreplaceable: thousands of works were moved from the Hermitage collection to the Pushkin Museum in Moscow and other museums across the USSR. Moscow The tragic period in Hermitage's history came to an end in 1945. At that time the government attempted to compensate recent losses by transferring to the museum some of the art looted by the Red Army in Germany during World War II. By far the most precious part of that booty were Impressionist and Post-Impressionist paintings taken from private collections of German business elite. These paintings were considered lost until 1995 when the museum unveiled them to the public. The Russian government maintains that these works provide just a small compensation for irreparable losses inflicted on Russian cultural heritage by the German invasion, including the almost complete destruction of Peterhof and Tsarskoe Selo. Moreover, the State Duma passed a law forbidding return of disputed works to their owners in case they were guilty of financing the Nazi regime.

In the 21st century

In recent years, Hermitage expanded to the nearby building of the General Staff and launched several ambitious projects abroad, including the Guggenheim Hermitage Museum in Las Vegas, the Hermitage Rooms in London's Somerset House, and the Hermitage Amsterdam in the former Amstelhof, Amsterdam. The Hermitage was featured in the film Russian Ark, an incredible single shot walk through with period reenactments spanning three hundred years of court meetings, balls, and family life in the Winter Palace. Russian Ark

Hermitage directors


- Florian Antonovich Gilles
- Stepan Alexandrovich Gedeonov (1863 - 1878)
- Alexander Alexeyevich Vasilchikov (1879 - 1888)
- Sergei Nikitich Trubetskoi (1888 - 1899)
- Ivan Alexandrovich Vsevolozhsky (1899 - 1909)
- Dmitry Ivanovich Tolstoi (1909 - 1918)
- Mikhail Artamonov (1951-1964)
- Boris Borisovich Piotrovsky
- Boris Borisovich Piotrovsky (son) since July 1992

External links


- [http://www.hermitage.ru Official web site]
- [http://www.hermitage.nl Hermitage Amsterdam]
- [http://www.guggenheimlasvegas.org Guggenheim Hermitage Museum]
- [http://www.hermitagerooms.com Hermitage rooms in London] Category:Art museums and galleries in Russia Category:Museums in Saint Petersburg ja:エルミタージュ美術館

Urals

The Ural Mountains (Russian: Уральские горы = Урал) also known simply as the Urals and as the Riphean Mountains in Greco-Roman antiquity, is a mountain range that runs roughly north and south through western Russia. The Urals extend 2500 km from the Kazakh steppes along the northern border of Kazakhstan to the coast of the Arctic ocean. The island of Novaya Zemlya forms a further continuation of the chain. Geographically this range marks the northern part of the (arbitrary) border between Asian and European sections of the Eurasian continent. Its highest peak is Mount Narodnaya (Poznurr, 1895 m). Erosion has exposed considerable mineral wealth in the Urals, including gems such as topaz and beryl. The Virgin Komi Forests in the northern Urals are recognized as a World Heritage site. Yekaterinburg is the self-proclaimed capital of the Urals, though "Urals" is a geographical term, not an administrative one. The Urals are among the world's oldest extant mountain ranges. They were formed in the late Carboniferous period, when a continent consisting largely of Siberia collided with the supercontinent that contained much of the world's land at the time: the combination of Laurasia (Europe and North America) and Gondwana. Europe and Siberia have remained joined together ever since. Geographers have divided the Urals into five regions: South, Middle, North, Subarctic and Arctic Urals.

External links


- [http://wikitravel.org/en/Urals Wikitravel article] Category:Mountain ranges of the Russian Federation Category:Mountains of Russia ko:우랄 산맥 ja:ウラル山脈

Democratic Republic of Congo

The Democratic Republic of the Congo — also referred to as DRC, DRC Congo, DR Congo, Congo and Congo-Kinshasa — (formerly Zaire) is a nation in central Africa and the third largest country on the continent. It borders the Central African Republic and Sudan on the north, Uganda, Rwanda, Burundi, and Tanzania on the east, Zambia and Angola on the south, and the Republic of the Congo on the west. The country enjoys access to the sea through a narrow forty kilometre stretch, following the Congo river into the Gulf of Guinea. The name "Congo" (meaning "hunter") is coined after the Bakongo tribe, living in the Congo river basin. Formerly, the Belgian colony of the Belgian Congo, the country's post-independence name was changed in 1971, from Congo-Kinshasa (after its capital, to distinguish it from the Republic of Congo, or Congo-Brazzaville) to Zaire, until 1997. Since 1998, the country has suffered greatly from the devastating Second Congo War (sometimes referred to as the African World War), the deadliest conflict since World War II.

History

Congolese pre-history

From 2000 BC to AD 500, waves of Bantu migrations moved into what is now the Democratic Republic of the Congo (Although the term "Congo" usually encompasses neighboring Congo-Brazzaville as well) from the northwest, adding to and displacing the indigenous Pygmy populations into the southern regions of the modern DRC state. Subsequent migrations from the Darfur and Kordofan regions of Sudan into the northeast, as well as East Africans migrating into the eastern Congo added to the mix of ethnic groups. The Bantus imported agriculture and iron-working techniques from West Africa into the area, as well as establishing the Bantu language family as the primary set of tongues for the Congolese. In the fifth century, a society began to develop in a region that initially encompassed only a 200 kilometre (125 mi) area along the banks of the Lualaba River in the modern day Katanga province. This culture, known as the Upemba, would eventually evolve into the more significant Luba kingdom. The process in which the original Upemba societies transitioned into the Luba kingdom was gradual and complex. This transition ran without interruption, with several distinct societies developing out of the Upemba culture prior to the genesis of the Luba. Each of these kingdoms became very wealthy due mainly to the region's mineral wealth, especially in ores. The civilization began to develop and implement iron and copper technology, in addition to trading in ivory and other goods. The Luba established a strong commercial demand for their metal technologies and were able to institute a primitive but long-range commercial net (the business connections extended over 1,500 kilometres (930 mi), all the way to the Indian Ocean). By the 1500s the kingdom had an established strong central government based on chieftainship.

Medieval kingdoms

The Kongo Empire

By the fifteenth century, the dominant political force of the Congo region was the Kongo Empire. The Kongo was a highly developed state located primarily in the southwest portion of the modern Congo, in addition to occupying portions of northern Angola and Cabinda. The state was particularly noted by Europeans on their arrival as having developed an intricate system of taxation. At its greatest extent, the empire reached from the Atlantic Ocean in the west to the Kwango River in the east, and from the Congo River in the north to the Loje River in the south. The kingdom was headed by a king known as the Manikongo who exercised his authority over the Bakongo (Kongo peoples) from his capital in Mbanza-Kongo, which grew into the present day city of Sao Salvador. The empire established itself as the hub of an extensive Central African trade network in which it traded slaves especially, along with other natural resources. The Kongo would eventually sell so many people into slavery that the empire collapsed due to lack of human resources and war with the Portuguese.

Other states

There were numerous other, but much smaller states scattered throughout the territory in the north and northeast of the basin, with Pygmies and other primarily hunter-gatherer populations located mostly in the southern portions of the region. Of particular note is that the populations of the Eastern regions of the premordial Congo were heavily disrupted by constant slaving, mainly from Zanzibari slave dealers. The slave trade in this portion of Africa was primarily Arab in nature (as opposed to the European or Atlantic slave trade) and captured persons were typically shipped off to the Middle East or holdings of Arabian kingdoms for labor.

European exploration and administration (1870–1960)

Arabian European exploration and administration took place from the 1870s until the 1920s. The area was first mapped by the British explorer Henry Morton Stanley. He prepared the region for European colonization. Stanley had undertaken his explorations mainly under the sponsorship of King Leopold II of Belgium, who desired what was to become the Congo as a colony. In a succession of negotiations Leopold, professing humanitarian objectives in his capacity as chairman of the Association Internationale Africaine, played one European rival against the other. The Congo territory was acquired formally by Leopold at the Conference of Berlin in 1885. He made the land his private property and named it the Congo Free State. Leopold's regime began undertaking various development projects, such as the railway that ran from the coast to Leopoldville (now Kinshasa) which took years to complete. Nearly all of these projects were aimed at increasing the capital Leopold and his cohorts could extract from the colony, leading to atrocious exploitation of Africans. In the Free State, the local population was brutalized in exchange for rubber, a growing market with the development of rubber tires. The selling of the rubber made a fortune for Leopold, who built several buildings in Brussels and Ostend to honour himself and his country. During the period between 1885 and 1908, between five and fifteen (the commonly accepted figure is about ten) million Congolese died as a consequence of exploitation and diseases. To enforce the rubber quotas, the Force Publique (FP) was called in. The FP was an army, but its aim was not to defend the country, but to terrorise the local population The Force Publique made the practice of cutting off the limbs of the natives as a means of enforcing rubber quotas a matter of policy; this practice was disturbingly widespread. However, there were international protests spearheaded mainly by E. D. Morel and British diplomat/Irish patriot Roger Casement, whose 1904 report on the Congo condemned the practice, as well as famous writers such as Mark Twain. Joseph Conrad's novella Heart of Darkness also takes place in Congo Free State. In 1908, the Belgian parliament bowed to international pressure in order to save their last bit of prestige in Europe, forcibly adopting the Free State as a Belgian colony from the king. From then on, it became the Belgian Congo, but in practical terms, things changed only slightly. During World War II the small Congolese army achieved several victories against the Italians in north Africa. The Belgian Congo, which was also rich in uranium deposits, supplied the uranium that was used to build the American atom bombs that destroyed Hiroshima and Nagasaki, Japan, helping bring World War II to an end. Political Crises (1960-1965) In 1959,Patrice Lumumba, with the MNC party or Mouvement National Congolais, won the first free legislative elections. He was therefore appointed Prime Minister, while Joseph Kasavubu was elected President by the parliament. His party was the ABAKO (Alliance des Bakongo). Other partis that emerged include the PSA or Parti Solidaire Africain (Antoine Gizenga), the PNP or Parti National du Peuple (Albert Delvaux, Laurent Mbariko). Shortly after independence the provinces of Katanga (with Moise Tshombe) and South Kasai seceded. Subsequent events led to a crisis between the President and the Prime Minister. On September 5th 1960, the President dismissed the Prime Minister who will later be killed in Katanga on January 17th 1961. Several gouvernments successively took over in the widespread confusion. They were led by technicians (College des Commissaires), Joseph Ileo, Cyrille Adoula, Moise Tshombe, and Evariste Kimba.

Zaire (1965–1996)

Following five years of extreme instability and civil unrest, Mobutu, now Lieutenant General, overthrew Kasavubu in a 1965 coup d'état. A one-party system was established, and Mobutu declared himself head of state. He would occasionally hold elections in which he was the only candidate. Relative peace and stability was achieved, but Mobutu's government was accused of human rights violations, repression, a cult of personality (every Congolese bank note displayed his image, his portrait was displayed in all public buildings, most businesses, and on billboards, and it was common for ordinary people to wear his likeness on their clothing) and excessive corruption — in 1984 he was said to have four billion U.S. dollars, an amount close to the country's national debt, stashed away in personal Swiss bank accounts. In an effort to spread African national awareness, starting on June 1 1966, Mobutu renamed the nation's cities (Leopoldville became Kinshasa [the country was now Democratic Republic of The Congo–Kinshasa], Stanleyville became Kisangani, and Elisabethville became Lumbumbashi). This city-renaming campaign was completed in the 1970s. In 1971, he renamed the country the Republic of Zaire, its fourth name change in eleven years and its sixth overall. The Congo River became the Zaire River. In 1972, Mobutu renamed himself Mobutu Sese Seko. Another way to promote the country's African heritage was to promote old African values and traditions. Following the collapse of the Soviet Union, U.S. relations with Kinshasa cooled, as Mobutu was no longer deemed a necessary Cold War ally, and his opponents within Zaïre stepped up demands for reform. This atmosphere contributed to Mobutu declaring the Third Republic in 1990, whose constitution was supposed to pave the way for democratic reform. The reforms turned out to be largely cosmetic, and Mobutu's rule continued until conflict forced him to flee Zaire.

War (1996–present)

Since 1994, the Congo has been rent by ethnic strife and civil war, touched off by a massive inflow of refugees from fighting in Rwanda and Burundi. The government of Mobutu Sese Seko was toppled by a rebellion led by Laurent-Désiré Kabila in May, 1997; he changed the country's name back to Democratic Republic of The Congo-Kinshasa. But when it became clear that the country had exchanged one corrupt dictator for another, his regime was challenged by a Rwandan and Ugandan-backed rebellion in August 1998. Troops from Zimbabwe, Angola, Namibia, Chad, and Sudan intervened to support the new regime in Kinshasa. See Foreign relations of Congo and First Congo War. First Congo War A cease-fire was signed on July 10 1999; nevertheless, fighting continues apace especially in the eastern part of the country, financed by revenues from the illegal extraction of minerals such as coltan, cassiterite and diamonds. Kabila was assassinated in January 2001 and his son Joseph Kabila was named head of state. The new president quickly began overtures to end the war. Fighting continued, even after an accord signed in South Africa in 2002. But by late 2003, a fragile peace prevailed. Kabila appointed four vice-presidents, two who had been fighting to oust him until July 2003.

Politics

2002 From the day King Leopold II established colonial authority in what is now Congo-Kinshasa to today, the country's government has been unstable. This is reflected in its seven name changes since 1885: (1) Congo Free State (1885–1908), (2) Belgian Congo (1908–60 [this, incidentally, was the longest period of tranquility the country has experienced]), (3) Republic of The Congo-Leopoldville (1960–64), (4) Democratic Republic of The Congo-Leopoldville (1964–66), (5) Democratic Republic of The Congo-Kinshasa (1966-71), (6) Republic of Zaire (1971–97), and (7) Democratic Republic of The Congo-Kinshasa (since 1997). The government of former president Mobutu Sese Seko was toppled by a rebellion led by Laurent Kabila in May 1997, with the support of Rwanda and Uganda. They were later to turn against Kabila and backed a rebellion against him in August 1998. Troops from Zimbabwe, Angola, Namibia, Chad, and Sudan intervened to support the Kinshasa regime. A cease-fire was signed on 10 July 1999 by the DROC, Zimbabwe, Angola, Uganda, Namibia, Rwanda, and Congolese armed rebel groups, but sporadic fighting continued. Kabila was assassinated on 16 January 2001 and his son Joseph Kabila was named head of state ten days later. In October 2002, the new president was successful in getting occupying Rwandan forces to withdraw from eastern Congo; two months later, an agreement was signed by all remaining warring parties to end the fighting and set up a government of national unity. Elections currently planned for June 2005 appear to have been put on hold as Congolese politicians have yet to approve the newly created constitution. Despite the peace deal: "After eighteen months in power, the transitional government of the Democratic Republic of Congo (DRC) remains fragile, far from its goals of peace and effective administration of this huge central African nation. Installed after five years of civil war, the uneasy coalition of former belligerents is plagued by mistrust, dissatisfaction among troops not yet fully integrated in a new national army—including an aborted rebellion by some of them, and challenges from armed groups outside the peace process. It also faces continued interference from neighboring countries, in particular Uganda and Rwanda [http://hrw.org/english/docs/2005/01/13/congo9855.htm]." The presence of UN troops has not stopped most of the eastern portion of the country from the rule of tyranical warlords such as those of the Nationalist and Integrationist Front (NFI), who have committed well-documented human rights abuses in their own economic interests [http://hrw.org/english/docs/2005/06/02/congo11041.htm]. The NFI has been accused in the killing of nine UN peacekeepers in February 2005 [http://www.nytimes.com/auth/login?URI=http://www.nytimes.com/2005/02/26/international/africa/26congo.html&OP=179510d7Q2FQ5C5XQ2FQ5CknUp)nnQ5E_Q5C_ZZ-Q5CZ_Q5C_6Q5CM2Q5EX)2(Q5EMn2(Q22Q5C(F)MU(Q5C_6Un2Q3EnuQ23Q5EdQ22], in addition to massive exploitation of regional mineral wealth, particularly gold [http://hrw.org/english/docs/2005/06/02/congo11041.htm]. According to the Human Rights Watch, the east is a human rights disaster area with, "soldiers of the national army and combatants of armed groups continu(ing) to target civilians, killing, raping, and otherwise injuring them, carrying out arbitrary arrests and torture, and destroying or pillaging their property. Tens of thousands of persons have fled their homes, several thousand of them across international borders. After the attempted rebellion and a massacre of Congolese refugees in neighboring Burundi, ethnically-based fear and hatred have risen sharply, emotions that are amplified and manipulated by politicians and some civil society leaders [http://hrw.org/english/docs/2005/01/13/congo9855.htm]." Continuing violence amongst civilians, ethnic hostility, economic explotation, and the violation of civil and political rights are amongst the many human rights abuses that plague the area. The new government has almost no control militarily over the country, especially in the chaotic eastern regions and particularly the Ituri district. The revamped Congolese "military" is a hodge-podge of Kabila's allies coalitioned with former rebel militias. A hundred members of one of these militias went on a rampage in a major town near Kinshasa, killing a number of civilians [http://allafrica.com/stories/200507051015.html] in July 2005. [http://fr.wikisource.org/wiki/Constitution_de_la_R%C3%A9publique_d%C3%A9mocratique_du_Congo View the proposed constitution of the Democratic Republic of the Congo. It is currently awaiting a referendum. (French)]

Political divisions

Provinces

July 2005 The Congo is divided into ten provinces, and one independent city (Kinshasa). #Bandundu #Bas-Congo # Equateur #Kasai-Occidental #Kasai-Oriental #Katanga(During the Mobutu years, it was called the Shaba Province) #Kinshasa #Maniema #Nord-Kivu #Orientale (Congo) (Formerly Haut-Zaire) #Sud-Kivu

Major cities

Sud-Kivu Sud-Kivu]

- Bandundu (Banningville)
- Bukavu (Constermansville)
- Djokupunda (Charlesvilles)
- Ilebo (Port-Francqui)
- Isiro (Paulis)
- Kalemie (Albertville)
- Kananga (Luluabourg)
- Kinshasa (Léopoldville)
- Kisangani (Stanleyville)
- Kolwezi
- Likasi (Jadotville)
- Lubumbashi (Élisabethville)
- Lukutu (Élisabetha)
- Lusanga (Leverville)
- Mbandaka (Coquilhatville)
- Mbanza-Ngungu (Thysville)
- Moba (Baudoinville)
- Mobaye-Mbongo (Banzyville)
- Mbuji-Mayi (Bakwanga)
- Ubundu (Ponthierville)

Geography

Ubundu The Congo is situated at the heart of the west-central portion of sub-Saharan Africa and is bounded by (Clockwise from the west) Angola, the Republic of Congo, the Central African Republic, the Sudan, Uganda, Rwanda, Burundi, Tanzania across Lake Tanganyika, and Zambia. Its territory also straddles the Equator, with one-third to the north and two-thirds to the south. As a result of its equatorial location, the Congo experiences extremely high amounts of rainfall. The average rainfall for the entire country is about 1,070 millimeters (42 in), which have created the second largest rain forest in the world (after the Amazon). This massive expanse of lush jungle covers most of the vast, low-lying central basin of the river, which slopes toward the Atlantic Ocean in the west. This area is surrounded by plateaus merging into savannas in the south and southwest, by mountainous terraces in the west, and dense grasslands extending beyond the Congo River in the north. High mountains are found in the extreme eastern region. The tropical climate has also produced the Congo River system which dominates the region topographically along with the rainforest it flows through, (though they are not mutually exclusive). The name for the "Congo" state is derived from that of the river, along with that of the Kongo Empire which controlled much of the region in precolonial times. The river basin (meaning the Congo River and all of its myriad tributaries) occupy nearly the entire country and an area of nearly one million square kilometers (400,000 sq mi). The river and its tributaries (major offshoots include the Kasai, Sangha, Ubangi, Aruwimi, and Lulonga) form the backbone of Congolese economics and transportion, they have a drastic impact on the daily lives of the people. The sources of the Congo are in the highlands and mountains of the East African Rift, as well as Lake Tanganyika and Lake Mweru. The river flows generally west from Kisangani just below Boyoma Falls, then gradually bends southwest, passing by Mbandaka, joining with the Ubangi River, and running into the Pool Malebo (Stanley Pool). Kinshasa and Brazzaville are actually on opposite sides of the river at the Pool (see NASA image), then the river narrows and falls through a number of cataracts in deep canyons (collectively known as the Livingstone Falls), and then running past Boma into the Atlantic. The river also has the second-largest flow and the second-largest watershed of any river in the world (trailing the Amazon in both respects). The river provides the country's only outlet to the Atlantic, a narrow strip of land on its north bank, otherwise the Congo would be completely landlocked. The previously mentioned Great Rift Valley, in particular the Eastern Rift, plays a key role in shaping the Congo's geography. Not only is the northeastern section of the country much more mountainous, but due the rift's tectonic activities, this area also experiences low levels of volcanic activity. The rifting of the African continent in this area has also manifested itself as the famous Great Lakes which lie on the Congo's eastern frontier. The country is bordered in the east by two of these: Lake Albert and Lake Tanganyika. Perhaps most important of all, the Rift Valley has endowed most of the south and east of the Congo with an enormous amount of mineral wealth. These include cobalt, copper, cadmium, petroleum, industrial and gem diamonds, gold, silver, zinc, manganese, tin, germanium, uranium, radium, bauxite, iron ore, and coal. Unfortunately, this wealth has been both a blessing and a curse; the Congo people have not so far reaped the benefits of their country's tremendous mineral resources.

Economy

The economy of the Democratic Republic of the Congo—a nation endowed with vast potential wealth—has declined drastically since the mid-1980s. The two recent conflicts, which began in 1996, have dramatically reduced national output and government revenue, has increased external debt, and has resulted in the deaths from war, famine, and disease of perhaps 3.8 million people. Foreign businesses have curtailed operations due to uncertainty about the outcome of the conflict, lack of infrastructure, and the difficult operating environment. The war has intensified the impact of such basic problems as an uncertain legal framework, corruption, inflation, and lack of openness in government economic policy and financial operations. Conditions improved in late 2002 with the withdrawal of a large portion of the invading foreign troops. A number of IMF and World Bank missions have met with the government to help it develop a coherent economic plan, and President Joseph Kabila has begun implementing reforms. Much economic activity lies outside the GDP data.

Demographics

The population was estimated at 56.6 million in 2003, growing quickly from 46.7 million in 1997. As many as 250 ethnic groups have been distinguished and named. The most numerous people are the Kongo, Luba, and Mongo. Although 700 local languages and dialects are spoken, the linguistic variety is bridged both by the use of French and the intermediary languages Kikongo, Tshiluba, Swahili, and Lingala. About 80% of the Congolese population are Christian, predominantly Roman Catholic. Most of the non-Christians adhere to either traditional religions or syncretic sects. Traditional religions embody such concepts as monotheism, animism, vitalism, spirit and ancestor worship, witchcraft, and sorcery and vary widely among ethnic groups; none is formalized. The syncretic sects often merge Christianity with traditional beliefs and rituals. The most popular of these sects, Kimbanguism, was seen as a threat to the colonial regime and was banned by the Belgians. Kimbanguism, officially "the church of Christ on Earth by the prophet Simon Kimbangu," now has about 3 million members, primarily among the Bakongo of Bas-Congo and Kinshasa. Kinshasa

Languages

Kinshasa There is an estimated total of 242 languages spoken in the Democratic Republic of the Congo. Out of these, only 4 have the status of national languages: Kikongo, Lingala, Tshiluba and Swahili. Lingala was made the official language of the army under Mobutu, but since the rebel