| General | |
|---|---|
| Name | Sodium chloride |
| Chemical formula | NaCl |
| Appearance | White or clear solid |
| Physical | |
| Formula weight | 58.4 amu |
| Melting point | 1074 K (801 °C) |
| Boiling point | 1738 K (1465 °C) |
| Density | 2.2 ×103 kg/m3 |
| Crystal structure | f.c.c. |
| Solubility | 35.9 g in 100g water |
| Thermochemistry | |
| ΔfH0gas | -181.42 kJ/mol |
| ΔfH0liquid | -385.92 kJ/mol |
| ΔfH0solid | -411.12 kJ/mol |
| S0gas, 1 bar | 229.79 J/mol·K |
| S0liquid, 1 bar | 95.06 J/mol·K |
| S0solid | 72.11 J/mol·K |
| Safety | |
| Ingestion | Dangerous in large quantities |
| Inhalation | May cause irritation |
| Skin | May cause irritation |
| Eyes | May cause irritation |
| More info | Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/10/9918.html) |
| SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
Sodium chloride is essential for life. Humans are unusual among primates in secreting large amounts of salt by sweating.
0.9% sodium chloride in water is called a physiological solution because it is isoosmotic with blood plasma. This saline solution can be prepared by dissolving 0.85 gram of sodium chloride in 100 ml of distilled water. Physiological solution is the mainstay of fluid replacement[?] therapy that is widely used in medicine in prevention or treatment of dehydration.
Salt is produced by evaporation of seawater[?] or brine from other sources, such as brine wells and salt lakes[?], and by mining rock salt.
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.
Because of its importance for life, control over salt has often been used for social and political ends. In the Roman Empire, salt was sometimes used as a form of currency. The English word "salary" derives from the Latin word for "salt". The empire of Mali, in Africa, 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 was controlled in India as a means of generating enormous tax revenues.
Long a scarce commodity, industrialised production has made salt plentiful. About 51% of world output is now used by northern countries to de-ice roads in winter. This works because salt water has a lower freezing point than pure water: the ions prevent regular ice crystals from forming.
Salt is commonly used as a flavour enhancer for food and has been identified as one of the basic tastes. Ironically, 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.
Salty soil is generally unfit for agriculture, hence the practice of salting the earth in ancient times.
The CAS number of sodium chloride is 7647-14-5.