Sodium chloride, also known as common salt, table salt, or halite, is an ionic compound with the formula NaCl. The salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. It forms small, transparent, colorless to white cubic crystals. It is odorless but has a characteristic taste. As the major ingredient in edible salt, it is commonly used as a condiment and food preservative. It is soluble in water and very slightly soluble in ethanol; cubic; r.d. 2.17; m.p. 801°C; b.p. 1413°C. It occurs as the mineral halite (rock salt) and in natural brines and sea water. It has the interesting property of a solubility in water that changes very little with temperature. It is used industrially as the starting point for a range of sodium-based products (e.g. Solvay process for Na2CO3, Castner-Kellner process for NaOH), and is known universally as a preservative and seasoner of foods. It ihas a key role in biological systems in maintaining electrolyte balances.
Production and use
| Sodium chloride | |
|---|---|
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| IUPAC name | |
| Other names | Common salt; halite; table salt; rock salt |
| Identifiers | |
| CAS number | [] |
| PubChem | |
| RTECS number | VZ4725000 |
| ChemSpider ID | |
| Properties | |
| Molecular formula | NaCl |
| Molar mass | 58.443 g/mol |
| Appearance | Colorless/white crystalline solid |
| Odor | Odorless |
| Density | 2.165 g/cm3 |
| Melting point | 801 °C (1074 K) |
| Boiling point | 1465 °C (1738 K) |
| Solubility in water | 35.6 g/100 mL (0 °C) 35.9 g/100 mL (25 °C) 39.1 g/100 mL (100 °C) |
| Solubility | soluble in glycerol,
ethylene glycol, formic acid insoluble in HCl |
| Solubility in methanol | 1.49 g/100 mL |
| Solubility in ammonia | 2.15 g/100 mL |
| Refractive index (nD) | 1.5442 (589 nm) |
| Structure | |
| Crystal structure | Cubic (see text), cF8 |
| Space group | Fm3m, No. 225 |
| Coordination geometry |
Octahedral (Na+) Octahedral (Cl−) |
| Hazards | |
| EU Index | Not listed |
| NFPA 704 | |
| Flash point | Non-flammable |
| LD50 | 3000–8000 mg/kg (oral in rats, mice, rabbits) |
| Related compounds | |
| Other anions | Sodium fluoride Sodium bromide Sodium iodide |
| Other cations | Lithium chloride Potassium chloride Rubidium chloride Caesium chloride |
| Supplementary data page | |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
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 2002, world production was estimated at 210 million metric tonnes, the top five producers being the United States (40.3 million tonnes), China (32.9), Germany (17.7), India (14.5), and Canada (12.3).
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.
It 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. Even though more effective desiccants are available, few are safe for humans to ingest.
Synthetic uses
It iis also the raw material used to produce chlorine which itself is required for the production of many modern materials including PVC and pesticides. 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
-
2NaCl + 2H2O → Cl2 + H2 + 2NaOH
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.
Salt 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.
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 can also be used to detach leeches that have attached themselves to feed. It is also used to disinfect wounds.
Optical uses
Pure NaCl crystal is an optical compound with a wide transmission range from 200 nm to 20 um. It was often used in the infrared spectrum range and it is still used sometimes.
NaCl crystal is soft, hygroscopic and inexpensive. This limits its application to protected environment or for short term uses (prototyping). Exposed to free air NaCl optics will "rot".
Today tougher crystals like ZnSe are used instead of NaCl (for the IR spectral range).
Household uses
Since at least medieval times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of shampoo, and popularly to de-ice driveways and patches of ice. It is also used in tooth paste.
The Environment
Although NaCl is highly effective in reducing the build-up of snow and ice, a high concentration in the immediate area of its use can have a detrimental effect on plant life and smaller species. Some environmentalists prefer to use sand on icy surfaces.
Biological functions
In humans, a high-salt intake has long been known to generally raise blood pressure, especially in certain individuals. More recently, it was demonstrated to attenuate nitric oxide production. Nitric oxide (NO) contributes to vessel homeostasis by inhibiting vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the endothelium.
Road salt
While salt was once a scarce commodity in history, industrialized production has now made salt plentiful. Approximately 51% of world output is now used by cold countries to de-ice roads in winter, both in grit bins and spread by winter service vehicles. Calcium chloride is preferred over sodium chloride, since CaCl2 releases energy up on forming a solution with water, heating any ice or snow it is in contact with. It also lowers the freezing point, depending on the concentration. NaCl does not release heat upon solution; however, it does lower the freezing point. It is also more readily available and does not have any special handling or storage requirements, unlike calcium chloride.
Additives
Table salt sold for consumption today is not pure sodium chloride. 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, to reduce the incidence of simple goiter.
Salt for de-icing in the UK typically contains sodium hexacyanoferrate(II) at less than 100ppm as an anti-caking agent. In recent years this additive has also been used in table salt.
Common chemicals
Chemicals used in de-icing salts are mostly found to be sodium chloride (NaCl) or calcium chloride (CaCl2). Both are similar and are effective in de-icing roads. When these chemicals are produced, they are mined/made, crushed to fine granules, then treated with an anti-caking agent. Adding salt lowers the freezing point of the water, which allows the liquid to be stable at lower temperatures and allows the ice to melt. Alternative de-icing chemicals have also been used. Chemicals such as calcium magnesium acetate and potassium formate are being produced. These chemicals have few of the negative chemical effects on the environment commonly associated with NaCl and CaCl2.
Bacteriostatic Sodium Chloride - Clinical Pharmacology
Sodium chloride in water dissociates to provide sodium (Na+) and chloride (Cl−) ions. These ions are normal constituents of the body fluids (principally extracellular) and are essential for maintaining electrolyte balance.
The distribution and excretion of sodium (Na+) and chloride (Cl−) are largely under the control of the kidney which maintains a balance between intake and output.
The small volume of fluid and amount of sodium chloride provided by Bacteriostatic 0.9% Sodium Chloride Injection, USP, when used only as a vehicle for parenteral injection of drugs, is unlikely to exert a significant effect on fluid and electrolyte balance except possibly in neonates and very small infants.
Water is an essential constituent of all body tissues and accounts for approximately 70% of total body weight. Average normal adult daily requirement ranges from two to three liters (1.0 to 1.5 liters each for insensible water loss by perspiration and urine production).
Water balance is maintained by various regulatory mechanisms. Water distribution depends primarily on the concentration of electrolytes in the body compartments and sodium (Na+) plays a major role in maintaining physiologic equilibrium.
Indications and Usage for Bacteriostatic Sodium Chloride
This parenteral preparation is indicated only for diluting or dissolving drugs for intravenous, intramuscular or subcutaneous injection, according to instructions of the manufacturer of the drug to be administered.
Contraindications
Due to the potential toxicity of benzyl alcohol in neonates, solutions containing benzyl alcohol must not be used in this patient population.
Parenteral preparations with benzyl alcohol should not be used for fluid or NaCl replacement.
Parenteral preparations containing benzyl alcohol should not be used in epidural or spinal anesthetic procedures.
Warnings
Benzyl alcohol, a preservative in Bacteriostatic NaCl Injection, USP has been associated with toxicity in neonates. Data are unavailable on the toxicity of other preservatives in this age group. Preservative-free NaCl Injection should be used for flushing intravascular catheters. Where a sodium chloride solution is required for preparing or diluting medications for use in neonates, only preservative-free NaCl Injection should be used.
Precautions
Consult the manufacturer’s instructions for choice of vehicle, appropriate dilution or volume for dissolving the drugs to be injected, including the route and rate of injection.
Inspect reconstituted (diluted or dissolved) drugs for clarity (if soluble) and freedom from unexpected precipitation or discoloration prior to administration.
Pregnancy Category C.
Animal reproduction studies have not been conducted with Bacteriostatic 0.9% Sodium Chloride Injection, USP. It is also not known whether Bacteriostatic 0.9% NaCl Injection containing additives can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Bacteriostatic 0.9% NaCl Injection containing additives should be given to a pregnant woman only if clearly needed.
Pediatric Use
The safety and effectiveness in the pediatric population are based on the similarity of the clinical conditions of the pediatric and adult populations. However, due to potential toxicity of benzyl alcohol in neonates, solutions containing benzyl alcohol are contraindicated in this patient population.
Drug Interactions
Some drugs for injection may be incompatible in a given vehicle, or when combined in the same vehicle or in a vehicle containing benzyl alcohol. Consult with pharmacist, if available.
Use aseptic technique for single or multiple entry and withdrawal from all containers.
When diluting or dissolving drugs, mix thoroughly and use promptly.
Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.
Adverse Reactions
Reactions which may occur because of this solution, added drugs or the technique of reconstitution or administration include febrile response, local tenderness, abscess, tissue necrosis or infection at the site of injection, venous thrombosis or phlebitis extending from the site of injection and extravasation.
If an adverse reaction does occur, discontinue the infusion, evaluate the patient, institute appropriate countermeasures, and if possible, retrieve and save the remainder of the unused vehicle for examination.
Although adverse reactions to intravenous, intramuscular or subcutaneous injection of 0.9% benzyl alcohol are not known to occur in man, experimental studies of small volume parenteral preparations containing 0.9% benzyl alcohol in several species of animals have indicated that an estimated intravenous dose up to 30 mL may be safely given to an adult without toxic effects. Administration of an estimated 9 mL to a 6 kg neonate or infant is potentially capable of producing blood pressure changes.
Overdosage
Use only as a diluent or solvent. This parenteral preparation is unlikely to pose a threat of sodium chloride or fluid overload except possibly in neonates and very small infants. In the event these should occur, re-evaluate the patient and institute appropriate corrective measures. See PRECAUTIONS and ADVERSE REACTIONS.
Bacteriostatic Sodium Chloride Dosage and Administration
The volume of the preparation to be used for diluting or dissolving any drug for injection, is dependent on the vehicle concentration, dose and route of administration as recommended by the manufacturer.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. See PRECAUTIONS.
