Sodium Chloride (NaCl): Formula, Properties, Grades and Industrial Uses

The short answer

Sodium chloride is common salt. Formula NaCl, CAS 7647-14-5, formula weight 58.44 g/mol, melting point 801 °C. It is a neutral, non-hazardous ionic solid that dissolves readily in water and is one of the few chemicals that is mined, evaporated from the sea and manufactured, all at scale, in the same country.

The reason it matters industrially is not the salt itself but what comes out of it. Electrolysing brine gives chlorine, caustic soda and hydrogen. Reacting brine with ammonia and carbon dioxide gives soda ash. Between them those two routes stand behind PVC, bleach, glass, detergents, paper and a long tail of organic chemistry.

Formula, molecular weight and identifiers

In pharmacopoeial work it appears as Sodium Chloride IP, BP, USP or EP; in analytical work as Sodium Chloride AR or ACS. Those are the same compound held to different purity monographs, not different chemicals.

Physical properties

Pure sodium chloride crystals are transparent, not white. The white appearance of salt in a bag is the same optical effect that makes crushed glass white — light scattering at many small crystal faces.

Where the molecular weight 58.44 comes from

Add the two standard atomic weights: sodium 22.99 and chlorine 35.45, giving 58.44 g/mol. Two points worth noting because they come up constantly.

• NaCl has no molecules. The solid is a continuous lattice in which each Na⁺ is surrounded by six Cl⁻ and each Cl⁻ by six Na⁺. The correct term is formula weight, although almost everyone says molecular weight.
• The 35.45 for chlorine is an average. Natural chlorine is roughly 76 % chlorine-35 and 24 % chlorine-37, which is why the figure is not close to a whole number.

That six-fold coordination is also the reason for the 801 °C melting point. Melting salt means pulling apart a three-dimensional array of ionic bonds, not simply separating discrete molecules from one another.

Solubility and why it barely changes with temperature

Sodium chloride dissolves to about 36 g per 100 mL of water at 25 °C, and that figure hardly moves — roughly 35.7 g at 0 °C and about 39 g at 100 °C. Most salts become dramatically more soluble as water heats up. Sodium chloride does not, because the energy taken to break the lattice and the energy released when the ions hydrate very nearly cancel.

Two practical consequences follow. You cannot purify salt by recrystallisation from hot water the way you would with potassium nitrate, which is why refining goes through washing, brine treatment and controlled evaporation instead. And a saturated brine at about 26 % w/w stays saturated across the working temperature range, which makes it a stable, predictable process fluid.

The saturated solution freezes at about −21 °C, the eutectic that sets the practical limit of salt as a de-icer.

Solar, rock and vacuum salt

Three routes, three cost and purity profiles.

• Solar salt. Seawater or inland brine is evaporated in a series of shallow pans by sun and wind. India is one of the world's largest producers by this route, principally along the Gujarat coast. Cheapest, but it carries calcium and magnesium sulphates and insolubles unless washed.
• Rock salt. Halite is mined from ancient evaporite beds, crushed and screened. Purity depends on the deposit; typically used where dissolution is not required, such as de-icing.
• Vacuum salt. Purified brine is evaporated in multiple-effect vacuum evaporators. The most expensive route and the purest — fine, uniform, very low in calcium, magnesium and sulphate, and the normal basis for pharmacopoeial and high-end food grades.

A solar salt can be brought close to a vacuum salt specification by brine washing and recrystallisation, and most of the mid-range industrial grades on the market are exactly that.

Commercial grades and what separates them

Grades differ by impurity limits, particle size and moisture, not by chemistry. What follows is how the common ones are normally specified.

Scapex Exports supplies sodium chloride industrial grade, dyeing grade, detergent grade, softener tablets, pharma grade and AR grade.

What industrial salt is used for

• Chlor-alkali. Electrolysis of brine produces chlorine, caustic soda and hydrogen — the entry point to PVC, hypochlorite, and most industrial alkali chemistry.
• Soda ash. The Solvay process turns brine, ammonia and carbon dioxide into sodium carbonate for glass and detergents.
• Textile dyeing. Salt suppresses the negative charge repulsion between reactive dye and cellulose fibre, driving exhaustion. Dose rates of 30 to 80 g/L are ordinary, which is why a dye house buys salt by the tonne and cares intensely about its calcium content.
• Detergents. Sodium chloride is used as a filler and as a viscosity builder in liquid surfactant systems, where a small addition thickens the formulation sharply.
• Water treatment. Tablet and granular salt regenerate ion exchange resin in softeners and demineralisation plants.
• Food and pharmaceutical. Preservation, seasoning, curing, brines, saline and oral rehydration salts.
• Drilling and de-icing. Brine weighting in oilfield fluids, and road salt in cold climates.

Handling, packing and export documents

• Hazard. Not classified as a dangerous good. No UN number, no dangerous goods declaration, general cargo.
• Caking. Salt cakes when moisture migrates within the bag. Ask for the moisture limit in the specification and, where the grade allows, an anticaking agent; for grades that must remain additive-free, packing and storage discipline is the only control.
• Corrosion. Salt and moisture together corrode carbon steel aggressively. Brine systems use FRP, HDPE, rubber lining or suitable stainless grades, and even then chloride stress corrosion cracking limits which stainless steels are acceptable.
• Packing. 25 kg and 50 kg PP laminated bags, 1000 to 1250 kg jumbo bags, or bulk. Food and pharma grades take an inner liner.

An export consignment should carry a certificate of analysis stating assay, moisture, water-insoluble matter, calcium, magnesium, sulphate and iron; a 16-section GHS safety data sheet; commercial invoice and packing list; certificate of origin; and for food or pharmacopoeial grades the monograph reference together with any Halal, Kosher or food-contact declarations the destination requires.

Enquire with a specification

Sodium chloride is supplied by Scapex Exports as a manufacturer and supplier from qualified Indian producers, in industrial, dyeing, detergent, water treatment, food, pharmacopoeial and analytical grades, with certificate of analysis, safety data sheet and full export documentation.

Send the grade, assay, impurity limits that matter to your process, particle size, packing and destination port, and you will get a quotation written against that specification rather than a generic one.

Frequently asked questions