Sodium Chloride

Topics: Sodium chloride, Sodium, Chlorine Pages: 6 (1718 words) Published: November 10, 2010
Sodium chloride, also known as salt, common salt, table salt, or halite, is an ionic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. As the major ingredient in edible salt, it is commonly used as a condiment and food preservative. [edit] Properties

Thermal conductivity of pure NaCl as a function of temperature has a maximum of 2.03 W/(cm K) at 8 K and decreases to 0.069 at 314 K (41 °C). It also decreases with doping.[3] [edit] Production and use

Modern rock salt mine near Mount Morris, New York, United States Salt is currently mass-produced by evaporation of seawater or brine from other sources, such as brine wells and salt lakes, and by mining rock salt, called halite. In 2009, world production was estimated at 260 million metric tons, the top five producers (in million tonnes) being China (60.0), United States (46.0), Germany (16.5), India (15.8) and Canada (14.0).[4] As well as the familiar uses of salt in cooking, salt is used in many applications, from manufacturing pulp and paper, to setting dyes in textiles and fabric, to producing soaps, detergents, and other bath products. It is the major source of industrial chlorine and sodium hydroxide, and used in almost every industry. Sodium chloride is sometimes used as a cheap and safe desiccant because it appears to have hygroscopic properties, making salting an effective method of food preservation historically; the salt draws water out of bacteria through osmotic pressure, keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest. Solubility of NaCl in various solvents

(g NaCl / 1 kg of solvent at 25 °C)[5]|
H2O| 360|
Liquid ammonia| 30.2|
glycerin| 83|
propylene glycol| 71|
Methanol| 14|
Ethanol| 0.65|
1-propanol| 0.124|
2-propanol| 0.03|
1-butanol| 0.05|
1-pentanol| 0.018|
Sulfolane| 0.05|
Formic acid| 52|
Acetone| 0.00042|
Formamide| 94|
Acetonitrile| 0.003|
Dimethylformamide| 0.4|
[edit] Synthetic uses
Uses of chlorine include PVC, pesticides and epoxy resins. Industrially, elemental chlorine is usually produced by the electrolysis of sodium chloride dissolved in water. Along with chlorine, this chloralkali process yields hydrogen gas and sodium hydroxide, according to the chemical equation 2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

Sodium metal is produced commercially through the electrolysis of liquid sodium chloride. This is now done in a Down's cell in which sodium chloride 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. Sodium chloride is used in other chemical processes for the large-scale production of compounds containing sodium or chlorine. In the Solvay process, sodium chloride is used for producing sodium carbonate and calcium chloride. In the Mannheim process and in the Hargreaves process, it is used for the production of sodium sulfate and hydrochloric acid. [edit] Biological uses

Many micro organisms 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 can also be used to detach leeches that have attached themselves to feed. It is also used to disinfect wounds. [edit] Optical uses

Pure NaCl crystal is an optical compound with a wide transmission range from 200 nm to 20 µm. It was often used in the infrared spectrum range and it is still used sometimes. While inexpensive, NaCl crystal is soft and hygroscopic. When exposed to free air, NaCl optics gradually covers with "frost". This limits application of NaCl to protected environments or for short-term...
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