Sodium Chloride (7647-14-5) Physical and Chemical Properties
Sodium Chloride
High-purity inorganic sodium chloride supplied as a commodity process salt for bulk industrial, laboratory and formulation uses.
| CAS Number | 7647-14-5 |
| Family | Inorganic chloride salt |
| Typical Form | Powder or crystalline solid |
| Common Grades | BP, EP, JP, Reagent Grade, Technical Grade, USP |
Sodium chloride is an inorganic ionic halide belonging to the alkali metal–halide structural class; its stoichiometry is given as \(\ce{ClNa}\), representing a 1:1 lattice of sodium and chloride ions. Structurally it crystallizes in the rock-salt (NaCl) type lattice (face-centered cubic, coordination number 6) and is electronically characterized by complete charge separation into \(\ce{Na+}\) and \(\ce{Cl-}\) with strong electrostatic (Coulombic) lattice energy. In the solid state the ionic lattice produces a high lattice enthalpy and strong directional absence of covalent character; upon melting the ions become mobile and the molten phase is an ionic conductor.
In aqueous media sodium chloride behaves as a simple electrolyte: it is effectively the neutral salt of a strong acid (HCl) and a strong base (NaOH), therefore its aqueous solutions are essentially neutral (\(\mathrm{pH}\) close to 7) and do not hydrolyze. The compound is highly polar and hydrophilic, with pronounced solubility in water and negligible solubility in most organic solvents (very slight solubility in ethanol and methanol). Chemically it is resistant to oxidation and reduction under ambient conditions but will participate in electrochemical processes (e.g., chlor-alkali electrolysis) and can release corrosive or toxic gaseous species (hydrogen chloride, chlorine) under extreme thermal or electrochemical stress.
Industrial and clinical relevance is broad: bulk uses include chemical feedstock (chlor-alkali process), de-icing, water treatment, food seasoning and preservation, and brine/processing applications; in medicine, aqueous formulations (notably 0.9% isotonic saline) are principal parenteral fluids for hydration and electrolyte replacement. Common commercial grades reported for this substance include: BP, EP, JP, Reagent Grade, Technical Grade, USP.
Basic Physical Properties
Density
Reported solid density: 2.17 at 25 °C/4 °C (reported units: \(\mathrm{g}\,\mathrm{cm}^{-3}\)). Molten sodium chloride density at elevated temperature is also reported: \(\mathrm{1.549}\ \mathrm{g}\,\mathrm{cm}^{-3}\) at \(850\,^\circ\mathrm{C}\). Density is temperature-dependent and decreases on melting and further heating due to thermal expansion and increased ion mobility.
Melting or Decomposition Point
Melting point reported: \(800.7\,^\circ\mathrm{C}\). Boiling point reported: \(1465\,^\circ\mathrm{C}\). The solid–liquid transition corresponds to disruption of the ionic lattice; reported latent heat of fusion is 0.52 kJ g−1 and sodium chloride begins to volatilize somewhat above the melting point. At decomposition/very high temperatures, evolved species may include hydrogen chloride and sodium oxides.
Solubility in Water
Solubility in water at \(25\,^\circ\mathrm{C}\) is reported as 36.0 g per 100 g of water. Alternative presentation: one gram dissolves in 2.8 mL water at \(25\,^\circ\mathrm{C}\). A saturated aqueous solution density at \(25\,^\circ\mathrm{C}\) and other solution properties are temperature- and concentration-dependent; for example, a 23% (w/w) aqueous solution freezes at −20.5 °C. Solubility in common organic solvents is very low (e.g., 0.065 g/100 g ethanol at \(25\,^\circ\mathrm{C}\); 1.40 g/100 g methanol at \(25\,^\circ\mathrm{C}\)), consistent with the ionic character and strong solvation by water.
Solution pH (Qualitative Behavior)
Aqueous solutions of sodium chloride are essentially neutral: reported \(\mathrm{pH} = 6.7\) to \(7.3\). As the salt of a strong acid and a strong base, it does not impart significant acidity or basicity to dilute aqueous solutions; observed slight deviations from 7 reflect impurities or dissolved gases rather than intrinsic hydrolysis.
Chemical Properties
Acid–Base Behavior
Sodium chloride is the neutral salt product of hydrochloric acid and sodium hydroxide. It shows no appreciable acid–base reactivity in water (no hydrolysis), and solutions are effectively electrically neutral. In physiological contexts, isotonic formulations (e.g., 0.9% w/v) supply \(\ce{Na+}\) and \(\ce{Cl-}\) without altering acid–base balance when administered appropriately; 0.9% isotonic saline is equivalent (reported) to \(\ce{Na+}\) 154 \(\mathrm{mmol}\,\mathrm{L}^{-1}\) and \(\ce{Cl-}\) 154 \(\mathrm{mmol}\,\mathrm{L}^{-1}\).
Reactivity and Stability
Chemically stable under normal storage conditions and described as "stable under recommended storage conditions." Thermal decomposition at very high temperatures can produce hydrogen chloride and sodium oxides. Molten sodium chloride can be corrosive and is reactive toward strongly oxidizing fluorinating agents (e.g., bromine trifluoride) and certain reactive metals (e.g., burning lithium can form elemental sodium). Electrolysis of aqueous sodium chloride yields reactive chlorine species under appropriate conditions and, in the presence of nitrogenous compounds, can produce hazardous chlorinated nitrogen species. Aqueous solutions accelerate corrosion of base metals and require materials selection considerations for handling and piping.
Molecular and Ionic Parameters
Formula and Molecular Weight
Empirical/molecular formula (as reported): \(\ce{ClNa}\). Molecular weight (reported): \(58.44\) (units: \(\mathrm{g}\,\mathrm{mol}^{-1}\)). Exact/monoisotopic mass (reported): \(57.9586220\).
SMILES, InChI, InChIKey (structural identifiers):
- SMILES: [Na+].[Cl-]
- InChI: InChI=1S/ClH.Na/h1H;/q;+1/p-1
- InChIKey: FAPWRFPIFSIZLT-UHFFFAOYSA-M
(Hydration state, isotopic labels, and other variants are described in specific product specifications.)
Constituent Ions
Primary ionic constituents in both solid and solution phases are \(\ce{Na+}\) and \(\ce{Cl-}\). In the crystalline rock-salt type lattice each ion is octahedrally coordinated by six counter-ions; multiple reported crystallographic datasets list space group symmetries (e.g., F m -3 m, space group number 225) with lattice parameter values reported in the literature such as \(a = 5.6035\), \(5.6393\), and \(5.6635\) (unit convention: Å for cell edge parameters). These parameters reflect experimentally measured unit-cell dimensions for different samples and measurement conditions.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS: 7647-14-5
- EC / EINECS identifiers reported (examples): 231-598-3; 617-042-6
- UNII: 451W47IQ8X
- ChEBI: CHEBI:26710
- KEGG: D02056 / C13563
- Other industry and catalog identifiers (e.g., NSC, RXCUI) exist in supplier and regulatory registries.
Also available: SMILES [Na+].[Cl-], InChI InChI=1S/ClH.Na/h1H;/q;+1/p-1, InChIKey FAPWRFPIFSIZLT-UHFFFAOYSA-M.
Synonyms and Common Names
Common names and synonyms appearing in technical use: table salt; common salt; halite; rock salt; NaCl; saline; sea salt; Natrium muriaticum (various traditional/homeopathic names). These names are used in food, industrial, and medical contexts to denote the same chemical entity or its formulations.
Industrial and Commercial Applications
Functional Roles and Use Sectors
Sodium chloride serves multiple high-volume roles: primary feedstock for chlor-alkali manufacturing (chlorine and caustic soda production), de-icing and road-salt applications, food seasoning and preservation, water-softening and conditioning (brine regeneration for ion-exchange resins), chemical processing (PVC and other commodity chemicals), leather tanning, and various industrial process aids. In pharmaceuticals and clinical practice it is the principal electrolyte in isotonic and hypertonic aqueous formulations used for rehydration, irrigation, and drug dilution.
Typical Application Examples
- Parenteral fluids: isotonic saline (0.9% w/v) for intravenous hydration and electrolyte replacement; hypertonic solutions (e.g., 3%, 5%) for specific clinical interventions.
- Industrial feedstock: brine for chlor-alkali electrolysis and soda-ash production pathways.
- De-icing: bulk rock salt or brine applied for ice control on highways.
- Food and consumer products: seasoning, curing, preservation, and as a processing aid in many food-manufacturing operations.
- Water treatment and softening: regeneration salt for ion-exchange resins and process brines. If a concise application summary is required for a particular sector or formulation, selection is made on the basis of the physical form, grade and purity appropriate to that use (see specifications and grades listed above).
Safety and Handling Overview
Health and Environmental Hazards
Sodium chloride is of low acute hazard at typical exposure levels but ingestion of large amounts can produce severe hypernatremia with neurologic and systemic consequences; reported approximate fatal dose range is 0.75 to 3.00 g kg−1. Reported LD50 for rat (oral) is 3000 mg kg−1 (reported values vary with route and species). Solid or concentrated solutions are eye irritants; certain occupational notifications classify eye-damage/irritation potential (examples of hazard statements reported include eye-damage and aquatic toxicity codes). Chronic excess dietary sodium is linked to cardiovascular effects in population health contexts.
Ecologically, elevated chloride concentrations in freshwaters can be toxic to many aquatic invertebrates and fish; acute and chronic effects are concentration-, exposure-duration-, and species-dependent. Road-salt run-off and discharges can elevate salinity locally and affect sensitive freshwater ecosystems.
For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
Storage and Handling Considerations
Sodium chloride is stable under normal ambient storage conditions; recommended storage practices include keeping containers tightly closed, dry, and in a well-ventilated area to avoid caking and moisture uptake. Some parenteral (bacteriostatic) formulations must be protected from freezing. Avoid dust generation during handling; where dust is present, local exhaust ventilation and dust-control measures are recommended. Use appropriate personal protective equipment (PPE): chemical-resistant gloves for prolonged contact, eye protection that meets relevant standards. Respiratory protection is generally not required for typical handling, but nuisance-dust masks (e.g., N95) may be used where dust control is inadequate.
Molten sodium chloride or contact of molten salt with water can be hazardous (violent reaction, release of hot corrosive vapors); do not introduce water to molten salt. Aqueous salt solutions are corrosive to base metals and appropriate material compatibility should be considered for storage and process equipment. For disposal and spill response, contain and collect granules or saturated solution and manage per applicable waste regulations; prevent entry to drains and natural waters.
