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Sodium Chloride

Sodium chloride

Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the formula Na Cl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. As the main ingredient in edible salt, it is commonly used as a condiment and food preservative.

Crystal structure

preservative⁻]] Sodium chloride forms crystals with cubic symmetry. In these, the larger chloride ions are arranged in a cubic close-packing, while the smaller sodium ions fill the octahedral gaps between them. Each ion is surrounded by six of the other kind. This same basic structure is found in many other minerals, and is known as the halite structure.

Biological importance

Sodium chloride is essential to life on Earth. Most biological tissues and body fluids contain a varying amount of salt. The concentration of sodium ions in the blood is directly related to the regulation of safe body-fluid levels. Propagation of nerve impulses by signal transduction is regulated by sodium ions. (Potassium, a metal closely related to Sodium, is also a major component in the same bodily systems). 0.9% sodium chloride in water is called a physiological solution because it is isotonic with blood plasma. It is known medically as normal saline. Physiological solution is the mainstay of fluid replacement therapy that is widely used in medicine in prevention or treatment of dehydration, or as an intravenous therapy to prevent hypovolemic shock due to blood loss. Humans are unusual among primates in secreting large amounts of salt by sweating.

Salt throughout history

sweating Salt's preservative ability was a foundation of civilization. It eliminated dependency on the seasonal availability of food and allowed travel over long distances. By the Middle Ages, caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt, sometimes trading it for slaves. Until the 1900s, salt was one of the prime movers of national economies and wars. Salt has played a prominent role in determining the power and location of the world's great cities. Timbuktu was once a huge salt market. Liverpool rose from just a small English port to become the prime exporting port for the salt dug in the great Cheshire salt mines and thus became the source of the world's salt in the 1800s. Salt created and destroyed empires. The salt mines of Poland led to a vast kingdom in the 1500s, only to be destroyed when Germans brought sea salt (often, to most of the world, considered 'superior' to rock salt). Venice fought and won a war with Genoa over salt. Genoa, however, had the last laugh. Genovites Christopher Columbus and Giovanni Caboto destroyed the Mediterranean trade by introducing the new world to the market. Salt was once one of the most valuable commodities known to man. Salt was taxed, from as far back as the 20th century BC in China. In the Roman Empire, salt was sometimes even used as a currency, giving us the term salary ("salt money", see below for etymology). The Roman Republic and Empire controlled the price of salt, increasing it to raise money for wars, or lowering it to be sure that the poorest citizens could easily afford this important part of the diet. Throughout much of history, it influenced the conduct of wars, the fiscal policies of governments, and even the inception of revolutions. In the empire of Mali, merchants in 12th-century Timbuktu—the gateway to the Sahara Desert and the seat of scholars—valued salt enough to buy it for its weight in gold; this trade led to the legends of the incredibly wealthy city of Timbuktu, and fueled inflation in Europe, which was exporting the salt. In later times, for instance during the British colonial period, salt production and transport were controlled in India as a means of generating enormous tax revenues. This ultimately led to the Salt March to Dandi, led by Mahatma Gandhi in 1930 in which thousands of Indians went to the sea to illegally produce their own salt in protest of the British tax on salt. The salt trade was based on one fact — it is more profitable to sell salted foodstuffs than to sell just salt. Thus sources of food to salt went hand in hand with salt making. Before the salt mines of Cheshire were discovered, a huge trade in British fish for French salt existed. This was not a happy accord, for each nation did not want to be dependent on each other. The search for fish and salt led to the Seven Years War between the two. With the British in control of saltworks in the Bahamas and North American cod, their sphere of influence quickly covered the world. The search for oil in the late 1800s and early 1900s used the technology and methods pioneered by salt miners, even to the degree that they looked for oil where salt domes were located.

In religion

There are thirty-two references to salt in the Bible, the most familiar probably being the story of Lot's wife, who was turned into a pillar of salt when she disobeyed the angels and looked back at the wicked city of Sodom (Genesis 19:26). Jesus also referred to his followers as the "salt of the earth" (Matthew 5:13), a reference to salt's great value in the ancient world. In the native Japanese religion shinto, salt is seen as "pure" and can be used to purify (bless) locations and people.

Production and use

shintoi salt evaporation ponds at the south end of the Dead Sea]] Nowadays, salt is produced by evaporation of seawater or brine from other sources, such as brine wells and salt lakes, and by mining rock salt, called halite. While most people are familiar with the many uses of salt in cooking, they might be unaware that salt is used in a plethora of applications, from manufacturing pulp and paper to setting dyes in textiles and fabric, to producing soaps and detergents. In most of Canada and the northern USA, large quantities of rock salt are used to help clear highways of ice during winter, although "Road Salt" loses its melting ability at temperatures below -15°C to -20°C (5°F to -4°F). Salt is also the raw material used to produce chlorine which itself is required for the production of many modern materials including PVC and pesticides.

Flavor enhancer

Salt is commonly used as a flavor enhancer for food and has been identified as one of the basic tastes. Unfortunately, given its history, this has resulted in large sections of the developed world ingesting salt massively in excess of the required intake, particularly in colder climates where the required intake is much lower. This causes elevated levels of blood pressure in some, which in turn is associated with increased risks of heart attack and stroke.

Biological uses

Many microorganisms cannot live in an overly salty environment: water is drawn out of their cells by osmosis. For this reason salt is used to preserve some foods, such as smoked bacon or fish. It has also been used to disinfect wounds. preserve

De-icing

While salt was a scarce commodity in history, industrialised production has now made salt plentiful. About 51% of world output is now used by cold countries to de-ice roads in winter, see Grit bin. This works because salt and water form a eutectic mixture that has about a 10°C lower freezing point than pure water: the ions prevent regular ice crystals from forming (below −10°C salt will not prevent water from freezing). Concerns are arising that this use may be harmful to the environment though, and, in Canada, norms were developed to minimize the use of salt in de-icing.

Additives

The salt one buys for consumption today is not purely sodium chloride as most people assume. In 1911 Magnesium carbonate was first added to salt to make it flow more freely. In 1924 trace amounts of iodine in form of sodium iodide, potassium iodide or potassium iodate were first added, creating iodized salt to reduce the incidence of simple goiter.

Etymology

goiter, USA]] Salt has also had influence on the English language. Many of its effects can still be seen today. Words and expressions related to salt mostly come from the Roman and Greek civilizations when salt was still a valuable commodity. Roman soldiers were given a particular allowance to purchase salt (Latin: sal), salarium argentum, from which we take our English word salary. The Romans also preferred salting of their greens, which led to the Latin word for salt being integrated in the word salad (in Vulgar Latin salata literally meant "salted"). Also the expression "He is not worth his salt" can be traced back to ancient Greece where salt was traded for slaves. It is worth noting that apparently, the English word doesn't come from the Latin word, but they both derive from a common ancestral PIE root-word
- sal, which meant 'salt' in the Proto-Indo-European language, which is estimated to have been spoken over eight thousand years ago.

Other facts

- Salty soil is generally unfit for agriculture, hence the practice of salting the earth.
- The superstition that spilling salt brings bad luck is said to have originated with the overturned salt cellar in front of Judas Iscariot at the Last Supper, immortalised in Leonardo Da Vinci’s famous painting.
- Due to its high concentration of salt, the Dead Sea has such a high density that some objects which are not normally buoyant can float on its surface. Humans float easily, having a density slightly less than that of pure water. (Only 8% of the salt in the Dead Sea is sodium chloride; 53% is magnesium chloride, 37% is potassium chloride.)
- The cities of Cincinnati, Detroit and Hutchinson are on top of active salt mines.
- The Third Reich stored vast amounts of money, paintings and artworks in salt mines and many important documents and items continue to be stored in former salt mines to this day. They are also used to store nuclear waste.

External links

- [http://www.saltinstitute.org Salt Institute] website
- [http://salt.org.il/news_arch.htm Salt Archive] website
- [http://users.tpg.com.au/terrett/Downloads/snarfevsCCPLatticerotate.avi Video] of rotating rock salt unit cell (divx, 378kb) Category:Chlorides Category:Sodium compounds Category:Edible salt Category:Granular materials Category:metal halides Category:Condiments Category:Preservatives Category:Antiseptics ja:塩化ナトリウム

Halite

Halite is the mineral of sodium chloride, NaCl, commonly known as rock salt. Halite forms isometric crystals. The mineral is colorless to white, light blue, dark blue, and pink. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides and borates. Halite occurs in vast beds of sedimentary evaporite minerals that result from the drying up of enclosed lakes, playas, and seas. Salt beds may be up to 350 m thick and underlie broad areas. In the United States and Canada extensive underground beds extend from the Appalacian basin of western New York through parts of Ontario and under much of the Michigan basin. Other deposits are in Ohio, Kansas, New Mexico, Nova Scotia, and Saskatchewan. Salt domes are vertical diapirs or pipe-like masses of salt that have been essentially "squeezed up" from underlying salt beds by mobilization due to the weight of overlying rock. Salt domes contain anhydrite, gypsum, and native sulfur, in addition to halite and sylvite. They are common along the Gulf coasts of Texas and Louisiana and are often associated with petroleum deposits. Germany, Spain, Romania, and Iran also have salt domes. Salt glaciers exist in arid Iran where the salt has broken through the surface at high elevation and flows downhill. In all of these cases, halite is said to be behaving in the manner of a rheid. Unusual, purple, fibrous vein filling halite is found in France and a few other localities. Halite crystals termed hopper crystals appear to be "skeletons" of the typical cubes, with the edges present and stairstep depressions on, or rather in, each crystal face. In a rapidly crystallizing environment the edges of the cubes simply grow faster than the centers. Halite crystals form quite rapidly in some fast evaporating lakes resulting in modern artefacts with a coating or encrustation of halite crystals. Halite flowers are rare stalactites of curling fibers of halite that are found in certain arid caves of Australia's Nullarbor Plain. Halite stalactites and encrustations are also reported in the Quincy native copper mine of Hancock, Michigan.

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/halides/halite/halite.htm Mineral Galleries]
- [http://webmineral.com/data/Halite.shtml WebMineral]
- [http://www.minerals.net/mineral/halides/halite/halite.htm Minerals.net]
- [http://www.desertusa.com/mag99/jan/papr/geo_halite.html Desert USA]
- [http://www.minsocam.org/MSA/collectors_corner/arc/mihalite.htm Halite stalactites] Category:Halide minerals ko:암염 ja:岩塩

Chemical formula

A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. It identifies each type of chemical element by its element symbol and identifies the number of atoms of such element to be found in each discrete molecule of that compound. The number of atoms (if greater than one) is indicated as a subscript. For non-molecular substances the subscripts indicate the ratio of elements in the empirical formula. Chemical formula used for a series of compounds that differ from each other by a constant unit is called general formula. Such a series is called the homologous series, while its members are called homologs.

Elements

In organic chemistry most compounds consist of the following five chemical elements:
- C carbon
- H hydrogen
- N nitrogen
- O oxygen
- S sulfur For other element symbols see list of elements by symbol.

Molecular and structural formulas

For example methane, a simple molecule consisting of one carbon atom bonded to four hydrogen atoms has the chemical formula: : CH₄ and glucose with six carbon atoms, twelve hydrogen atoms and six oxygen atoms has the chemical formula: : C₆H₁₂O₆. A chemical formula may also supply information about the types and spatial arrangement of bonds in the chemical, though it does not necessarily specify the exact isomer. For example ethane consists of two carbon atoms single-bonded to each other, each having three hydrogen atoms bonded to it. Its chemical formula can be rendered as CH₃CH₃. If there were a double bond between the carbon atoms (and thus each carbon only had two hydrogens), the chemical formula may be written: CH₂CH₂, and the fact that there is a double bond between the carbons is assumed. However, a more explicit and correct method is to write H₂C:CH₂ or H₂C=CH₂. The two dots or lines indicate that a double bond connects the atoms on either side of them. A triple bond may be expressed with three dots or lines, and if there may be ambiguity, a single dot or line may be used to indicate a single bond. Molecules with multiple functional groups that are the same may be expressed in the following way: (CH₃)₃CH. However, this implies a different structure from other molecules that can be formed using the same atoms (isomers). The formula (CH₃)₃CH implies a chain of three carbon atoms, with the middle carbon atom bonded to another carbon: Carbon chain and the remaining bonds on the carbons all leading to hydrogen atoms. However, the same number of atoms (10 hydrogens and 4 carbons, or C₄H₁₀) may be used to make a straight chain: CH₃CH₂CH₂CH₃. The alkene 2-butene has two isomers which the chemical formula CH₃CH=CHCH₃ does not identify. The relative position of the two methyl groups must be indicated by additional notation denoting whether the methyl groups are on the same side of the double bond (cis or Z) or on the opposite sides from each other.(trans or E)

Polymers

For polymers, parentheses are placed around the repeating unit. For example, a hydrocarbon molecule that is described as: CH₃(CH₂)₅₀CH₃, is a molecule with 50 repeating units. If the number of repeating units is unknown or variable, the letter n may be used to indicate this: CH₃(CH₂)_nCH₃.

Ions

For ions, the charge on a particular atom may be denoted with a right-hand superscript. For example Na⁺, or Cu²⁺. The total charge on a charged molecule or a polyatomic ion may also be shown in this way. For example: hydronium, H₃O⁺ or sulfate, SO₄^2-.

Isotopes

Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with a left-hand superscript in a chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is ³²PO₄^3-. Also a study involving stable isotope ratios might include ¹⁸O:¹⁶O. A left-hand subscript is sometimes used to indicate redundantly, for convenience, the atomic number.

Empirical formula

In chemistry, the empirical formula of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in it. Empirical formulas are the standard for ionic compounds, such as CaCl₂, and for macromolecules, such as SiO₂. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The term empirical refers to the process of elemental analysis, a technique of analytical chemistry used to determine the relative percent composition of a pure chemical substance by element. For example, hexane could have a chemical formula of CH₃CH₂CH₂CH₂CH₂CH₃, implying that it has a straight chain structure, 6 carbon atoms, and 14 hydrogen atoms. However the empirical formula for the same molecule would be C₃H₇.

Sodium

Sodium is the chemical element in the periodic table that has the symbol Na (Natrium in Latin) and atomic number 11. Sodium is a soft, waxy, silvery reactive metal belonging to the alkali metals that is abundant in natural compounds (especially halite). It is highly reactive, burns with a yellow flame, reacts violently with water and oxidizes in air (which is why pure sodium must be stored in oil).

Notable characteristics

Like the other alkali metals, sodium is a soft, light-weight, silvery white, reactive element that is never found as a pure element in nature. Sodium floats in water, as well as decomposing it to release hydrogen gas and hydroxide ions. If ground to a fine enough powder, sodium will ignite spontaneously in water. Sodium is necessary for regulation of blood and body fluids, transmission of nerve impulses, heart activity, and certain metabolic functions. We consume much more than we actually need in the form of sodium chloride, or table salt. It is estimated that the average American only needs 500mg per day, but usually Americans get 6,000 to 12,000 mg per day. Under extreme pressure, sodium departs from standard rules for changing to a liquid state. Most materials need more thermal energy to melt under pressure than they do at normal atmospheric pressure. This is because the molecules are packed closer together and have less room to move. At a pressure of 30 gigapascals (300,000 times sea level atmospheric pressure), sodium's melting temperature begins to drop. At around 100 gigapascals, sodium will melt at near room temperature. A possible explanation for the aberrant behavior of sodium is that this element has one free electron that is pushed closer to the other 10 electrons when placed under pressure forcing interaction that is not normally present. While under pressure, solid sodium assumes several odd crystal structures suggesting that the liquid might have unusual properties such as superconduction or superfluidity. (Gregoryanz, et al., 2005)

Applications

Sodium in its metallic form is an essential component in the making of esters and in the manufacture of organic compounds. This alkali metal is also a component of sodium chloride (NaCl) which is vital to life. Other uses:
- In certain alloys to improve their structure.
- In soap, in combination with fatty acids.
- To descale metal (make its surface smooth).
- To purify molten metals.
- In sodium vapor lamps, an efficient means of producing light from electricity.
- As a heat transfer fluid in some types of nuclear reactors and inside the hollow valves of high-performance internal combustion engines. NaCl, a compound of sodium ions and chloride ions, is an important heat transfer material.

History

Sodium (English, soda) has long been recognized in compounds, but was not isolated until 1807 by Sir Humphry Davy through the electrolysis of caustic soda. In medieval Europe a compound of sodium with the Latin name of sodanum was used as a headache remedy. Sodium's symbol, Na, comes for the neo-Latin name for a common sodium compound named natrium, which comes from the Greek nítron, a kind of natural salt. As early as 1860 Kirchhoff and Bunsen noted the sensitivity with which a flame test for Na could be. Stating in Annalen der Physik und der Chemie in the paper "Chemical Analysis by Observation of Spectra": "In a corner of our 60 cu.m. room farthest away from the apparatus, we exploded 3 mg. of sodium chlorate with milk sugar while observing the nonluminous flame before the slit. After a few minutes, the flame gradually turned yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium."

Occurrence

Sodium is relatively abundant in stars and the D spectral lines of this element are among the most prominent in star light. Sodium makes up about 2.6% by weight of the Earth's crust making it the fourth most abundant element overall and the most abundant alkali metal. At the end of the 19th century, sodium was chemically prepared by heating sodium carbonate with carbon to 1100 °C. :Na₂CO₃ (liquid) + 2C (solid, coke) → 2Na (vapor) + 3CO (gas). It is now produced commercially through the electrolysis of liquid sodium chloride. This is done in a Down's cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C. As calcium is more electropositive than sodium, no calcium will be formed at the cathode. This method is less expensive than the previous method of electrolyzing sodium hydroxide. Overview of a Downs cell for production of sodium metal. Metallic sodium cost about 15 to 20 US cents per pound (US$0.30/kg to US$0.45/kg) in 1997 but reagent grade (ACS) sodium cost about US$35 per pound (US$75/kg) in 1990.

Compounds

Sodium chloride, better known as common salt, is the most common compound of sodium, but sodium occurs in many other minerals, such as amphibole, cryolite, halite, soda niter and zeolite. Sodium compounds are important to the chemical, glass, metal, paper, petroleum, soap, and textile industries. Soap is generally a sodium salt of certain fatty acids. The sodium compounds that are the most important to industry are common salt (NaCl), soda ash (Na₂C O₃), baking soda (NaHCO₃), caustic soda (NaOH), Chile saltpeter (NaNO₃), di- and tri-sodium phosphates, sodium thiosulfate (hypo, Na₂S₂O₃ · 5H₂O), and borax (Na₂B₄O₇ · 10H₂O).

Isotopes

There are thirteen isotopes of sodium that have been recognized. The only stable isotope is Na-23. Sodium has two radioactive cosmogenic isotopes (Na-22, half-life = 2.605 years; Na-24, half-life ≈ 15 hours). Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable Na-23 in human blood plasma to Na-24. By measuring the concentration of this isotope, the neutron radiation dosage to the victim can be computed.

Precautions

criticality accident Sodium's powdered form is highly explosive in water and a poison combined and uncombined with many other elements. This metal should be handled carefully at all times. Sodium must be stored either in an inert atmosphere, or under mineral oil (normally under kerosene).

Physiology and sodium ions

Sodium ions play a diverse and important role in many physiological processes. Excitable cells, for example, rely on the entry of Na⁺ to cause a depolarization. An example of this is signal transduction in the human central nervous system. Some potent neurotoxins, such as batrachotoxin, increase the sodium ion permeability of the cell membranes in nerves and muscles, causing a massive and irreversible depolarization of the membranes, with potentially fatal consequences.

References

- [http://periodic.lanl.gov/elements/11.html Los Alamos National Laboratory – Sodium]
-
- Rebecca J. Donatelle. Health, The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.

External links

- [http://www.webelements.com/webelements/elements/text/Na/index.html WebElements.com – Sodium]
- [http://www.theodoregray.com/PeriodicTable/Elements/011/index.html The Wooden Periodic Table Table's Entry on Sodium]
- [http://www.americanheart.org/presenter.jhtml?identifier=4708 Dietary Sodium] Category:Chemical elements Category:Alkali metals ko:나트륨 ja:ナトリウム simple:Sodium th:โซเดียม

Salt

: This article is about the general chemical term salt. For the everyday meaning, see edible salt or its main ingredient, sodium chloride. For other meanings of the word salt, see salt (disambiguation). In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. These ions can be inorganic (Cl^-) as well as organic (CH₃-COO^-) and monoatomic (F^-) as well as polyatomic ions (SO₄^2-). Solutions of salts in water are called electrolytes. Electrolytes as well as molten salts conduct electricity. Zwitterions are salts that contain an anionic center and a cationic center in the same molecule, examples are the amino acids, many metabolites, peptides, and proteins. Mixtures of many different ions in solution like in the cytoplasm of cells, in blood, urine, plant saps, and mineral waters usually do not form defined salts after evaporation of the water. Therefore their salt content is given for the respective ions. Impure salt is a name for salt which has lost its saltiness. It can also refer to natron.

Appearance

Consistency

Salts are usually solid crystals with a relatively high melting point. However, there exist salts that are liquid at room temperature, so-called ionic liquids. Inorganic salts usually have a low hardness and a low compressibility, similar to edible salt.

Color

Salts can be clear and transparent (sodium chloride), opaque (titanium dioxide), and even metallic and lustrous (iron disulfide). Salts exist in all different colors, e.g. yellow (sodium chromate), orange (sodium dichromate), red (mercury sulfide), mauve (cobalt dichloride hexahydrate), blue (copper sulfate pentahydrate, ferric hexacyanoferrate), green (nickel oxide), colorless (magnesium sulfate), white (titanium dioxide), and black (manganese dioxide). Most minerals and inorganic pigments as well as many synthetic organic dyes are salts.

Taste

Different salts can elicit all five basic tastes, i.e. salty (sodium chloride), sweet (lead diacetate), sour (potassium bitartrate), bitter (magnesium sulfate), and umami or savory (monosodium glutamate).

Odor

Pure salts are odorless, while impure salts may smell after the acid (e.g. acetates like acetic acid (vinegar), cyanides like hydrogen cyanide (almonds)) or the base (e.g. ammonium salts like ammonia).

Nomenclature

The name of a salt starts with the name of the cation (e.g. sodium or ammonium) followed by the name of the anion (e.g. chloride or acetate). Salts are often referred to only by the name of the cation (e.g. sodium salt or ammonium salt) or by the name of the anion (e.g. chloride or acetate). Common salt-forming cations are:
- ammonium NH₄⁺
- calcium Ca²⁺
- iron Fe²⁺ and Fe³⁺
- magnesium Mg²⁺
- potassium K⁺
- pyridinium C₅H₅NH⁺
- quaternary ammonium NR₄⁺
- sodium Na⁺ Common salt-forming anions (and the name of the parent acids in parentheses) are:
- acetate CH₃-COO^- (acetic acid)
- carbonate CO₃^2- (carbonic acid)
- chloride Cl^- (hydrochloric acid)
- citrate HO-C(COO^-)(CH₂-COO^-)₂ (citric acid)
- cyanide C≡N^- (hydrogen cyanide)
- hydroxide OH^- (water)
- nitrate NO₃^- (nitric acid)
- nitrite NO₂^- (nitrous acid)
- oxide O^2- (water)
- phosphate PO₄^3- (phosphoric acid)
- sulfate SO₄^2- (sulfuric acid)

Formation

Salts are formed by a chemical reaction between:
- a base and an acid, e.g. NH₃ + HCl → NH_{4_Cl}
- a metal and an acid, e.g. Mg + H₂SO₄ → MgSO₄ + H₂ Salts can also form if solutions of different salts are mixed, their ions recombine, and the new salt is insoluble and precipitates (see: Solubility equilibrium).

References

- Kurlansky, Mark (2002). Salt: A World History. Walker Publishing Company. ISBN: 0142001619
- silting is the natural deposit of salt from sea water

Ocean

:For other uses see Ocean (disambiguation) Ocean (disambiguation)] Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off Gibraltar, and assumed it was a great river); covers almost three quarters (71%) of the surface of the Earth, and nearly half of the world's marine waters are over 3000 m deep. This global, interconnected body of salt water, called the World Ocean, is divided by the continents and archipelagos into the following four bodies, from the largest to the smallest: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, and the Arctic Ocean, and, according to some authorities such as International Hydrographic Organization(IHO), a fifth ocean, the Southern Ocean. Some geographers and some governments but not the US, recognize the IHO as defining official water body names and boundaries. (The US authority is the United States Board on Geographic Names.) The IHO officially sanctioned the Southern Ocean name only in 2000, but its definition by a line of latitude (with IHO members widely disputing which line of latitude) has left its acceptance as a fifth ocean open to question. The National Geographic Society and some other leading geographers and cartographers continue to use "South Pacific", "South Atlantic", and "Indian" Ocean for the waters around Antarctica. A few Oceanographers recognize only four oceans also, treating the Arctic Ocean (or the Arctic Sea) as a part of the Atlantic Ocean. Smaller regions of the oceans are called seas, gulfs, straits and other names. Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt that covers the Earth's mantle where there are no continents. From this point of view, there are three "oceans" today: the World Ocean, and the Black and Caspian Seas that were formed by the collision of Cimmeria with Laurasia. The Mediterranean Sea is very nearly its own "ocean", being connected to the World Ocean through the Strait of Gibraltar, and indeed several times over the last few million years movement of the African Continent has closed the strait off entirely, making the Mediterranean a fourth "ocean". (The Black Sea is connected to the Mediterranean through the Bosporus, but this is in effect a natural canal, cut through continental rock some 7000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.) The area of the World Ocean is 361 million km², its volume is 1370 million km³, and its average depth is 3790 m. Nearly half of the world's marine waters are over 3000 m deep. This does not include seas not connected to the World Ocean, such as the Caspian Sea. The total mass of the hydrosphere is about 1.4 × 10²¹ kg, ca. 0.023 % of the Earth's total mass. See sea water for a detailed discussion of ocean water composition, most notably its salinity.

Origins

The Oceans of the world most likely originated by comets striking the Earth.

Exploration

salinity Travel on the surface of the ocean through the use of boats dates back to prehistoric times, but only in modern times has extensive underwater travel become possible. The deepest point in the ocean is the Mariana Trench located in the Pacific Ocean near the Northern Mariana Islands. It has a maximum depth of 10,923 m (35,838 ft) [http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html]. It was fully surveyed in 1951 by the British naval vessel, "Challenger II" which gave its name to the deepest part of the trench, the "Challenger Deep". Much of the bottom of the world's oceans is unexplored and unmapped. A global image of many underwater features larger than 10 km was created in 1995 based on gravitational distortions of the nearby sea surface.

Climate

One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where the system forms). Ocean currents greatly affect Earth's climate by transferring warm or cold air and precipitation to coastal regions, where they may be carried inland by winds. The Antarctic Circumpolar Current encircles that continent, influencing the area's climate and connecting currents in several oceans.

Ecology

The oceans are home to the majority of plant and animal life on Earth. These lifeforms include:
- fish
- cetacea such as whales, dolphins and porpoises,
- cephalopods such as the octopus
- crustaceans such as lobsters and shrimp
- marine worms
- plankton
- krill

Economy

The oceans are essential to transportation: a huge portion of the world's goods are moved by ship between the world's seaports. Important ship canals include the Saint Lawrence Seaway, Panama Canal, and Suez Canal.

Ancient oceans

Continental drift has reconfigured the Earth's oceans, joining and splitting ancient oceans to form the current oceans. Ancient oceans include:
- Panthalassa, the vast world ocean that surrounded the Pangaea supercontinent.
- Tethys Ocean, the ocean between the ancient continents of Gondwana and Laurasia.
- Iapetus Ocean, the southern hemisphere ocean between Baltica and Avalonia.

Ocean rowing

Extraterrestrial oceans

Earth is the only known planet with liquid water on its surface, and is certainly the only such in our own solar system. However, liquid water is thought to be present under the surface of several natural satellites, particularly the Galilean moons of Europa, and, with less certainty, its fellows Callisto and Ganymede. Other icy moons may have once had internal oceans that have now frozen, such as Triton. The planets Uranus and Neptune may also possess large oceans of liquid water under their thick atmospheres, though their internal structure is not well understood at this time. There is currently much debate over whether Mars once had an ocean of water in its northern hemisphere, and over what happened to it if it did; recent findings by the Mars Exploration Rover mission indicate it had some long-term standing water in at least one location, but its extent is not known. Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than an "ocean". The distribution of these liquid regions will hopefully be better known after the full analysis of data from the Huygens probe of the Cassini-Huygens space mission, which dropped onto Titan's surface in January 2005. Titan is also thought likely to have a subterranean water ocean under the mix of ice and hydrocarbons that forms its outer crust.

Oceans in film

- In the movie Muppet Treasure Island, a non-specific ocean is featured, and referred to as the "Big Blue Wet Thing". Oceans have also been featured in many other movies such as Free Willy. To list more, click edit beside "Oceans on Film"

External links

- [http://www.oceanexplorer.noaa.gov/ Ocean Explorer] - An educational and reference resource from NOAA
- [http://news.bbc.co.uk/2/hi/science/nature/4033555.stm Science taps into ocean secrets]
- [http://www.palomar.edu/oceanography/salty_ocean.htm Why is the ocean salty?]
- [http://ioc.unesco.org/oceanteacher/resourcekit/M3/Formats/Geography/OceansSeas.htm Official IHO boundaries of Oceans and Seas]
- [http://www.thehydrogenexpedition.com The Hydrogen Expedition] The first circumnavigation of the globe in a hydrogen fuel cell powered boat
- [http://www.coreocean.org Coreocean]
- [http://www.nopp.org/ NOPP - The National Oceanographic Partnership Program] Category:Bodies of water Category:Oceanography zh-min-nan:Hái-iûⁿ ko:대양 ms:Lautan ja:大洋 simple:Ocean th:มหาสมุทร

Organism

In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered to represent two separate domains, called the Bacteria and Archaea, which are not closer to one another than to the eukaryotes. The gap between prokaryotes and eukaryotes is widely considered a major missing link in evolutionary history. Two eukaryotic organelles, namely mitochondria and chloroplasts, are generally considered to be derived from endosymbiotic bacteria. The phrase complex organism describes any organism with more than one cell.

Organizational terminology

Biological Organization

Viruses

Viruses are not typically considered to be organisms because they are not capable of independent reproduction or metabolism. However, according to the United States Code, they are considered to be microorganisms in the sense of biological weaponry and malicious use. This controversy is problematic, though, since some parasites and endosymbionts are incapable of independent life either. Although viruses do have enzymes and molecules characteristic of living organisms, they are incapable of surviving outside a host cell and most of their metabolic processes require a host and its 'genetic machinery'. The origin of such parasites is uncertain, but it appears most likely that they are derived from their host.

Life span

One of the basic parameters of organism is its life span. Some animals live as short as one day, while some plants can live thousands of years. Aging is important when determining life span of most organisms, bacterium, a virus or even a prion.

External links

- [http://news.bbc.co.uk/1/hi/sci/tech/944790.stm BBCNews: 27 September, 2000, When slime is not so thick] Citat: "...It means that some of the lowliest creatures in the plant and animal kingdoms, such as slime and amoeba, may not be as primitive as once thought...."
- [http://www.spaceref.com/news/viewpr.html?pid=4742 SpaceRef.com, July 29, 1997: Scientists Discover Methane Ice Worms On Gulf Of Mexico Sea Floor]
- [http://www.science.psu.edu/iceworms/iceworms.html The Eberly College of Science: Methane Ice Worms discovered on Gulf of Mexico Sea Floor] download Publication quality photos
- [http://www.sb-roscoff.fr/Ecophy/PDF/00-Fisher-NatWis.pdf Artikel, 2000: Methane Ice Worms: Hesiocaeca methanicola. Colonizing Fossil Fuel Reserves]
- [http://www.spaceref.com/news/viewnews.html?id=339 SpaceRef.com, May 04, 2001: Redefining "Life as We Know it"] Hesiocaeca methanicola In 1997, Charles Fisher, professor of biology at Penn State, discovered this remarkable creature living on mounds of methane ice under half a mile of ocean on the floor of the Gulf of Mexico.
- [http://news.bbc.co.uk/1/hi/sci/tech/2585235.stm BBCNews, 18 December, 2002, 'Space bugs' grown in lab] Citat: "...Bacillus simplex and Staphylococcus pasteuri...Engyodontium album...The strains cultured by Dr Wainwright seemed to be resistant to the effects of UV - one quality required for survival in space...."
- [http://news.bbc.co.uk/1/hi/sci/tech/3003946.stm BBCNews, 19 June, 2003, Ancient organism challenges cell evolution] Citat: "..."It appears that this organelle has been conserved in evolution from prokaryotes to eukaryotes, since it is present in both,"..."
- [http://www.anselm.edu/homepage/jpitocch/genbios/bi04syllabsu03.html Interactive Syllabus for General Biology - BI 04, Saint Anselm College, Summer 2003]
- [http://www.personal.psu.edu/users/j/s/jsf165/Bio110.html Jacob Feldman: Stramenopila]
- [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Root NCBI Taxonomy entry: root] (rich)
- [http://www.anselm.edu/homepage/jpitocch/genbios/surveybi04.html Saint Anselm College: Survey of representatives of the major Kingdoms] Citat: "...Number of kingdoms has not been resolved...Bacteria present a problem with their diversity...Protista present a problem with their diversity...",
- [http://www.species2000.org/ Species 2000 Indexing the world's known species]. Species 2000 has the objective of enumerating all known species of plants, animals, fungi and microbes on Earth as the baseline dataset for studies of global biodiversity. It will also provide a simple access point enabling users to link from here to other data systems for all groups of organisms, using direct species-links.
- [http://www.abc.net.au/science/news/enviro/EnviroRepublish_828525.htm The largest organism in the world may be a fungus carpeting nearly 10 square kilometers of an Oregon forest, and may be as old as 8500 years.]
- [http://tolweb.org/tree/phylogeny.html The Tree of Life]. zh-min-nan:Seng-bu̍t ko:생물 ja:生物 th:สิ่งมีชีวิต

Condiment

A condiment is a substance applied to food, usually in the form of a sauce, powder, or spread, to enhance or improve the flavour. Condiments are typically smeared with knives, squirted, or sprinkled onto other foods. Commercially prepared condiments are usually packaged in glass or plastic containers. Plastic has displaced glass in a number of applications where plastic's squeezability is an advantage, such as for ketchup, mustard, mayonnaise, and other condiments with a paste-like consistency. Some commercial venues (especially packaged meals dispensed by airlines and in some cafeterias), condiments are packaged in single-serving packets. cafeterias cafeterias Examples of condiments include:
- Belacan
- Chili oil
- Chutneys
- Fish sauce
- Fry sauce
- Peanut Butter
- Hot sauces based on chili, including Tabasco sauce
- HP Sauce
- Ketchup
- Mayonnaise
- Mixed pickle
- Mustard
- Pepper
- raita
- Red pepper flakes
- Relish
- Remoulade
- salsa
- Salt
- Sauerkraut (sometimes seen as a condiment on sausages or hot dogs, occasionally seen as a side dish)
- Soy sauce
- Steak sauces such as A1 and Heinz 57
- Tabasco sauce
- Tartar sauce
- Trassi
- Wasabi
- Worcestershire sauce There is also a list of condiments.

Food

Food is any substance that can be consumed, including liquid drinks. Food is the main source of energy and of nutrition for animals, and is usually of animal or plant origin. The study of food is called food science. In English, the term food is often used metaphorically or figuratively, as in food for thought. Food can also be a system of communication, a collection of images, a protocol of usages, situations, and behavior. Food is what brings the memory of our past into our contemporary life.

Legal definition

Western food law defines four categories of object as food:
- any substance or product, whether processed, partially processed or unprocessed, intended to be, or reasonably expected to be ingested by humans whether of nutritional value or not;
- water and other drinks;
- chewing gum;
- articles and substances used as an ingredient or component in the preparation of food. Links to official legal definitions of food:
- [http://www.fda.gov/opacom/laws/fdcact/fdcact1.htm US federal definition of food]
- [http://www.legislation.hmso.gov.uk/acts/acts1990/Ukpga_19900016_en_2.htm#mdiv1 UK definition of food]
- [http://europa.eu.int/smartapi/cgi/sga_doc?smartapi!celexapi!prod!CELEXnumdoc&lg=EN&numdoc=32002R0178&model=guichett EU definition of food]

Human eating habits

Historical development

Humans are commonly believed to be omnivorous animals that can consume both plant and animal products. Evidence suggests that early Homo Sapiens employed Hunter-gatherer as their primary means of food collection. This involves combining stationary plant and fungal food sources (such as fruits, grains, roots, and mushrooms) with mobile animals which must be hunted and killed in order to be consumed. Additionally, it is believed that humans have used fire to prepare food prior to eating since their divergence from Homo erectus, possibly even earlier. At least ten thousand years ago, humans developed agriculture, which has Timeline of agriculture and food and altered the kind of food people eat. This has led to a variety of important historical consequences, such as increased [[population]], the development of [[cities, and the wider spread of infectious diseases. The types of food consumed, and the way in which they are prepared has varied widely by time, location, and culture.

Meals

A portion of food or the act of eating a portion of food is considered a meal. Often named and patterned, meals play a role in an important social occasion, such as the celebration of many key cultural and religious festivals. A meal can be used as means for feeding a single individual or shared and eaten simultaneously by two or more people. The number of meals consumed by individuals in a day, their size, composition, when and how they are prepared and eaten varies greatly around the world. This diversity can be attributed to a number of local factors, including climate, ecology, economy, cultural traditions and industrialisation. In societies where the availability of food has risen above subsistence levels and beyond staple foods, meals are also sold pre-prepared for immediate consumption in restaurants and other similar retail premises. Food eaten in smaller quantities between the culturally normative meals is regarded as snack food. :See also: Appetite, Buddhist cuisine, Eucharist, Fast food, Fasting, Gault Millau restaurant guide, Halaal, I-tal, Kashrut, Michelin restaurant guide, Muslim dietary laws, Potluck, Totemism.

Food production or acquisition

Food is traditionally obtained through farming, ranching, and fishing, with hunting, foraging and other methods of subsistence locally important for some populations, but minor for others. In the modern era in developed nations, food supply is increasingly dependent upon agriculture, industrial farming, aquaculture and fish farming techniques. These techniques aim to maximize the amount of food produced while minimizing the cost. The techniques include a reliance on mechanized tools, from the threshing machine and seed drill, to the tractor and combine. Developed tools have been combined with the use of pesticides to promote high crop yields and to combat insects or mammals which reduce yield. More recently, there has been a growing trend towards more Sustainable agricultural practices. This approach - which is partly fuelled by consumer demand - encourages biodiversity, local self-reliance and Organic farming methods. Major influences on food production are international policy, e.g. the World Trade Organization and Common Agricultural Policy, national government policy or law and war. Food for livestock is fodder and traditionally comprises hay or grain. :See also: mariculture, horticulture, agribusiness, gardening. gardening

From plants

- Seeds
- Cereals from grasses, including barley, maize, oats, rice, rye, and wheat
- Cereals from non-grasses, including buckwheat, amaranth, and quinoa
- Legumes, including beans, peas, and lentils
- Nuts, including coconuts, almonds, and pine nuts
- Oilseeds, including sesame, sunflower, and hemp
- Vegetables (see also list of vegetables)
- Root vegetables, including potatoes, cassava, and turnips
- Leaf vegetables, including amaranth, spinach, and kale
- Sea vegetables, including dulse, kombu, and dabberlocks
- Stem vegetables, including bamboo shoots, nopales, and asparagus
- inflorescence vegetables, including globe artichokes, broccoli, and daylilies
- Fruit vegetables, including pumpkin, okra, and eggplant
- Fruits (see also list of fruits)
- Herbs and spices (see also list of herbs and spices) list of herbs and spices

From animals

- Dairy products, including milk
- Eggs, including roe and caviar
- Insects, including honey
- Meat, including beef, frogs' legs, goat, horse, kangaroo, lamb, mutton, pork, veal, rodents, human (i.e. cannibalism)
- Offal, including blood
- Poultry, including chicken, turkey, duck, goose, pigeon or dove, ostrich, emu, guinea fowl, pheasant, quail
- Seafood, including finfish such as salmon and tilapia, and shellfish such as mollusks and crustaceans
- Snails
- Game, this includes all animals hunted for food.

From neither animals or plants

- Salt
- Mushrooms, which are a type of fungi
- Seaweed, which is a protist
- Water, including mineral water and spring (water)

Food preparation

spring (water) While some food can be eaten without preparation, many foods undergo some form of preparation for reasons of safety, palatability, or flavor. At the simplest level this may involve washing, cutting, trimming or adding other foods or ingredients, such as spices. It may also involve mixing, heating or cooling, pressure cooking, fermentation, or combination with other food. Most food preparation takes place in a kitchen. The preparation of animal-based food will usually involve slaughter, evisceration, hanging, portioning and rendering. :See also: Barbecue, Eating utensils, Frankfurt kitchen, Hangi, Oven, Microwave oven, Refrigeration, Food preparation utensils.

Food manufacture

Early food processing techniques were limited by the available food preservation, packaging and transportation. Early food processing mainly involved salting, curing, curdling, drying, pickling and smoking. An early processed food product was cheese. During the industrialisation era in the 19th century, food manufacturing arose. This development took advantage of new mass markets and emerging new technology, such as milling, preservation, packaging and labelling and transportation. It brought the advantages of pre-prepared time saving food to the bulk of ordinary people who did not employ domestic servants. At the start of the 21st century, a two-tier structure has arisen, with a few international food processing giants controlling a wide range of well known food brands; with a populous number of small local or national food processing companies. :See also: Best before, Canning, Coloring, Food quality, Snap freezing, Additives, Flavoring, Enzymes, Genetically modified food, Pasteurization, Shelf-life, Ultra-high temperature processing.

Types of manufactured food

- Drinks: beer, juice, soft drink, squash, wine.
- Bread is a staple food for many nations, being made of risen dough of wheat or other cereals.
- Cakes and cookies
- Cheese is a curdled milk product, of which many varieties exist.
- Dessert is a course, usually sweet, and generally served after the main course, e.g. Ice cream.
- French fries, Chips
- Functional food
- Jam and Jelly
- Pasta
- Pie
- Pizza
- Processed meats
- Sandwiches
- Salad
- Sauce
- Sausage

Food trade

Food is now traded on a global basis. The variety and availability of food is no longer restricted by the diversity of locally grown food or the limitations of the local growing season. Between 1961 and 1999 there has been a 400% increase in worldwide food exports. Some countries are now economically dependent on food exports, which in some cases account for over 80% of all exports. In 1994 trade liberalisation began when over 100 countries became signatories to the Uruguay Round of the General Agreement on Tariffs and Trade which included an agreement to reduce subsidies paid to farmers. This is underpinned by the WTO enforcement of agricultural subsidy, tariffs, import quotas and settlement of trade disputes that cannot be bilaterally resolved. Where trade barriers are raised on the disputed grounds of public health and safety, the WTO refer the dispute to the Codex Alimentarius Commission, which was founded in 1962 by the United Nations Food and Agriculture Organization and the World Health Organization.

Food retailing

World Health Organization The sale of surplus food traditionally took place once a week when farmers took their wares on market day, into the local village market place. Here food was sold to grocers for sale in their local shops for purchase by local people. With the onset of industrialisation, and the development of the food processing industry, a wider range of food could be sold and distributed in distant locations. Typically early grocery shops would be counter-based shops, in which purchasers told the shop-keeper what they wanted, so that the shop-keeper could get it for them. In the 20th century supermarkets were born. Supermarkets brought with them a self-service approach to shopping using shopping carts (or Trollies in Commonwealth English) and were able to offer quality food at lower cost, through economies of scale and reduced staffing costs. This was sometimes known as 'pile it high' In the latter part of the 20th century, this has been further revolutionised by the development of vast warehouse sized out-of-town supermarkets, selling an extraordinarily wide range of food from around the world. Unlike food processors, food retailing is a two-tier market in which a small number of very large companies control a large proportion of supermarkets. The supermarket giants wield great purchasing power over farmers and processors, and strong influence over consumers. Nevertheless, in 2000 only 19% of all US consumer expenditure spent on food went to farmers. Recent technological innovations such as point of sale technology - barcodes. This allows ordering of goods and food to be driven by actual sales.

Food sufficiency

Food deprivation leads to malnutrition and ultimately starvation. This is often connected with famine, which involves the absence of food in entire communities. This can have a devastating and widespread effect on human health and mortality. In 2003 it was estimated that each year, 40 million people die of hunger worldwide. Rationing is sometimes used to distribute food in times of shortage, most notably during times of war. Food deprivation is regarded as a deficit need in Maslow's hierarchy of needs and is measured using famine scales.

Food aid

Food aid can benefit people suffering from a shortage of food. Conversely, badly managed food aid can cause problems by disrupting local markets, depressing crop prices and discouraging food production. Its provision, or threatened withdrawal, is sometimes used as a political tool to influence the politics of the destination country. International efforts to distribute food to the neediest countries are co-ordinated by the World Food Programme. :See also: Fair trade, food security.

Food safety

Foodborne illness, commonly called "food poisoning," is caused by bacteria, toxins, viruses and prions. Food poisoning has been recognised as a disease of man since as early as Hippocrates. Murder by food poisoning was used during the Roman Empire. In the Middle Ages all Royal Courts had food tasters. The sale of rancid, contaminated or adulterated food was commonplace until introduction of hygiene, refrigeration, and vermin controls in the 19th century. Discovery of techniques for killing bacteria using heat and other microbiological studies by scientists such as Louis Pasteur contributed to the modern sanitation standards that we enjoy today. This was further underpinned by the work of Justus von Liebig whose work led to the development of modern food storage and food preservation methods. The two most common factors leading to cases of bacterial foodborne illness are cross-contamination of ready-to-eat food from other uncooked foods and improper temperature control. Less commonly, acute adverse reactions can also occur if chemical contamination of food occurs, for example from improper storage, or use of non-food grade soaps and disinfectants. Food can also be adulterated by a very wide range of articles (known as 'foreign bodies') during farming, manufacture, cooking, packaging, distribution or sale. For example, pests (or their feces), hairs, cigarette butts, wood chips, metal shards, plasters etc. It is possible for certain types of food to become contaminated if stored or presented in an unsafe container, such as a ceramic pot with lead-based glaze. Understanding of the causes of food-borne-illnesses and more systematic techniques for their elimination has led to the development of commercial systems such as HACCP which can, if properly implemented, identify and eliminate many, but not all, possible risks. HACCP is well suited to identifying and controlling these potential food safety risks.

Food allergies

Some people have food allergies or sensitivities to foods which are otherwise wholesome to the majority of people. The amount of the food substance required to provoke a reaction in a susceptible individual can be minute. For instance, tiny amounts of food in the air, too minute to be smelled, have been known to provoke lethal reactions in sufficiently sensitive individuals. In theory, any food may provoke a reaction, however, this most commonly involves gluten, corn, shellfish (mollusks), peanuts, and soy. Most patients present with diarrhea after ingesting certain foodstuffs, skin symptoms (rashes), bloating, vomiting and regurgitation. The digestive complaints usually develop within half an hour of ingesting the allergen. Rarely, food allergy can lead to anaphylactic shock: hypotension (low blood pressure) and loss of consciousness. This is a medical emergency. An allergen associated with this type of reaction is peanut, although latex products can induce similar reactions. Initial treatment is with epinephrine (adrenaline), often carried by known patients in the form of an Epi-pen. Food allergy is thought to develop easier in patients with the atopic syndrome, a very common combination of diseases: allergic rhinitis and conjunctivitis, eczema and asthma. The syndrome has a strong inherited component; a family history of these diseases can be indicative of the atopic syndrome.

Dietary habits

Dietary habits play a significant role in the health and mortality of all humans. For example:
- Eating disorders are a group of mental disorders that interfere with normal food consumption. They often affect people with a negative body image;
- 13% of the world's population suffer from Iodine deficiency;
- In 2003 it was estimated that vitamin A deficiency causes blindness in up to 500,000 children each year;
- Vitamin C deficiency results in scurvy;
- Calcium, Vitamin D and Phosphorus are inter-related. The consumption of each may affect the absorption of the others.
- Kwashiorkor and marasmus are childhood disorders caused by lack of dietary protein.
- Obesity, a serious problem in the western world, leads to higher chances of developing heart disease, diabetes, and many other diseases. Concerns about foodborne illness have long influenced diet. Traditionally humans have learned to avoid foods that induce acute illness. Some believe that this is the underlying rationale behind some traditional religious dietary requirements. Additionally, many people choose to forgo food from animal sources to varying degrees; see vegetarianism, veganism, fruitarianism, living foods diet, and raw foodism. The nutrient content of diets in industrialised countries contain more animal fat, sugar, energy, alcohol and less dietary fiber, carbohydrates and antioxidants. Contemporary changes to work, family and exercise patterns, together with concerns about the effect of nutrition and overeating on human health and mortality are all having an effect on traditional eating habits. Physicians and alternative medicine practitioners may recommend changes to diet as part of their recommendations for treatment. More recently, dietary habits have been influenced by the concerns that some people have about the chronic impact on health that arise through the consumption of genetically modified food. Further concerns about the impact of industrial farming on animal welfare, human health and the environment are also having an effect on contemporary human dietary habits. This has led to the emergence of a counterculture with a preference for organic and local food. :See also: Food faddism, Health claims on food labels, list of diets, Slow Food.

Nutrients in food

- Calcium
- Carbohydrate
- Essential amino acids
- Fat
- Iron
- Minerals
- Phytochemicals, including anti-oxidants, enzymes, bio-flavinoids
- Potassium
- Protein
- Sodium
- Starch
- Vitamins
- Water Category:Nutrition Category:Biology

Crystal

:This article is about the form of solid matter. For other uses of this word, see Crystal (disambiguation). Crystal (disambiguation) A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. Generally, fluid substances form crystals when they undergo a process of solidification. Under ideal conditions, the result may be a single crystal, where all of the atoms in the solid fit into the same lattice or crystal structure but, generally, many crystals form simultaneously during solidification, leading to a polycrystalline solid. For example, most metals encountered in everyday life are polycrystals. Crystals are often symmetrically intergrown to form crystal twins. Which crystal structure the fluid will form depends on the chemistry of the fluid, the conditions under which it is being solidified, and also on the ambient pressure. The process of forming a crystalline structure is often referred to as crystallization. pressure While the process of cooling usually results in the generation of a crystalline material, under certain conditions the fluid may be frozen in a noncrystalline state. In most cases, this involves cooling the fluid so rapidly that atoms cannot travel to their lattice sites before they lose mobility. A noncrystalline material, which has no long-range order, is called an amorphous, vitreous, or glassy material. It is also often referred to as an amorphous solid, although there are distinct differences between solids and glasses: most notably, the process of forming a glass does not release the latent heat of fusion. For this reason, many scientists consider glassy materials to be viscous liquids rather than solids, although this is a controversial topic; see the entry on glass for more details. glass Crystalline structures occur in all classes of materials, with all types of chemical bonds. Almo