What is Sodium Chloride?

by Lucy Bell-Young

Sodium chloride (NaCl), more popularly known as table salt, is one of the most common and important minerals on earth with culinary, commercial, and industrial value. This ionic compound is also essential to life. Many biological organisms would be unable to function properly without sodium chloride as an electrolyte component of cells, tissues, and systems.

Sodium chloride is also crucial to our oceans. Approximately 77.76% of all salts in ocean water are composed of sodium chloride. This salinity of seawater affects the ocean current, as well as heat retention and the overall behaviour of the climate. Salinity also determines the type of life and ecology that can be sustained in a particular area. For example, the Dead Sea contains no macroscopic life (e.g. fish) because of its high concentration of salt, which is almost ten times the salinity of ocean water.

What Does Sodium Chloride Do?

NaCl is a simple mineral with ionic bonds organised into crystalline structures. Salt’s abundance, its ionic bonds, and its crystalline molecular structure make it important in several ways. Here are six examples of the many things sodium chloride can do.

  1. Desiccant

Its strong affinity with water makes this compound an excellent desiccant, or a substance which absorbs moisture and can maintain dryness. Sodium chloride can easily absorb moisture due to its ionic bonds, which attract the polar molecules of water. This makes it very useful as a preservative of organic materials and is why humans have used salt to preserve spoilable food like meat and fish over millennia.

Together with sodium carbonate and sodium bicarbonate, sodium chloride has also been used as a desiccant in preserving bodies of royalties, like Egyptian pharaohs.

In fact, salt makes such a good desiccant that it can actually be used as a DIY dehumidifier. To do this, you first need a bucket or similar container with small holes along the sides and bottom. You then fill this with rock salt, place it in the area you want to dehumidify (like the kitchen or bathroom), and let it do its thing. When used in this way, salt can even help prevent mould forming in your home.

NaCl written in spilled salt on table
  1. Electrolyte

When you sweat or urinate, you lose electrolytes. Sodium and chlorine ions from salt are important electrolytes that need to be regularly replenished, so incorporating salt into your diet is actually very important (in the right quantities, of course). In fact, despite its role as a desiccant, salt helps keep the body hydrated by allowing it to hold onto water.

As an electrolyte in the body, sodium chloride ions have crucial roles in absorbing and transporting nutrients in the cells. These ions regulate blood pressure and maintain the right balance of fluid through osmosis. They’re also crucial in transmitting nerve signals that allow our muscles to work properly.

  1. Climate Regulator

On average, seawater is about 3% salt, but the range varies from 1% in polar regions to 5% in enclosed seas, like the Red Sea. In terms of proportion, sodium chloride is about 77.76% of all the salts dissolved in seawater. The other types of salts found here include:

  • Magnesium chloride (10.88%)
  • Magnesium sulphate (4.74%)
  • Calcium sulphate (3.60%)
  • Potassium chloride (2.46%)
  • Magnesium bromide (0.22%)
  • Calcium carbonate (0.34%)

All of these salts contribute to the overall density of seawater, which fluctuates and has gradients depending on the area. For example, near polar regions, seawater is a bit more diluted because of the melting ice caps.

As the most abundant salt in the ocean, sodium chloride has a direct effect on the climate. It regulates the oceans’ temperature and drives the ocean currents. Consequently, it also has a role in the formation of hurricanes. Small changes in the concentrations of sodium chloride in seawater can spell the difference between La Niña and El Niño.

  1. Chemical Manufacturing

About 250 metric tonnes of NaCl is produced or harvested each year for large-scale chemical processes. It can either be used as a precursor, reactant, or product of large-scale chemical manufacturing. For example, it’s used at the starting point of the chlor alkali industrial process of producing chlorine and sodium hydroxide through large-scale electrolysis. See the balanced chemical equation below:

2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

  1. Water Softening 

Another major application of sodium chloride is in water softening. Potable water sources contain minerals, such as calcium and magnesium compounds, that are dissolved as ions. These ions can build up and become a film of mineral deposits (scale) in household or industrial pipes. Sodium chloride is used to generate ion-exchange resins that remove the ions of other minerals in hard water.

  1. De-icing 

NaCl also plays an important role in the de-icing of roads and pavements. Salt is able to melt ice and prevent the formation of ice crystals because it reduces the freezing point of water. In the UK, the main source of salt for de-icing is a single salt mine in Winsford, Cheshire.

What is the Formula for Sodium Chloride?

Sodium chloride is a simple compound with only two elements: sodium (Na) and chloride, which is the negatively charged ionic form of chlorine (Cl). This is why its chemical formula is NaCl. This compound has a molar mass of 58.443 g/mol.

The ionic bonds of a molecule of salt are so strong that it takes extremely high energy to break them. For instance, the melting point of salt is 800.7°C. The ionic bonds form strong lattice crystalline structures that have lattice energy of 787.3 kJ/mol. Nonetheless, its solubility is 360g/1000g of water at 25°C, making it highly soluble in water.

Below is a tabulated summary of the lattice energies of alkali metals and halides in kJ/mol:

A tabulated summary of the lattice energies of alkali metals and halides


Is Sodium Chloride Safe?

Sodium chloride is an essential electrolyte that our bodies need to function normally. Therefore, it’s not only safe, but necessary. However, just like other substances that the body needs, it also has a toxic effect when taken excessively.

For example, the estimated lethal dose concentration of salt is between 0.75-3 g per kilogram of body weight. For an adult weighing around 75kg, this would mean consuming 56-225 g of salt in one sitting could be fatal. Luckily, it’s very unlikely that you would ever consume this much salt at once.

Similarly, the concentration of salt in seawater makes it undrinkable for humans. If taken in excess of the daily dietary recommendation, sodium chloride can cause several health problems, such as kidney disease, high blood pressure, water retention, and heart disease.

What Foods Are High in Sodium Chloride?

Sodium chloride is virtually ubiquitous in the food that we eat. Processed foods are particularly rich in salt, where it acts as both a preservative and a seasoning. Additionally, almost all dairy products contain salt, with some cheese brands having particularly high salt content. Here are some examples of food items that are high in sodium chloride:

  • Shrimp: A serving of 85g of non-breaded frozen shrimp may contain as much as 800 mg of sodium, which is 35% of the recommended daily intake (RDI)
  • Ham: A serving of 85g of roasted ham has an average sodium content of 1,117 mg, or 48% of the RDI
  • Cottage cheese: A mere 113g serving of cottage cheese has an average of 350 mg of sodium (15% of the RDI)
  • Pizza: A 140g slice of frozen pizza on average has 765 mg of sodium, or about 33% of the RDI
  • Hot dogs: A hot dog may contain 578 mg of sodium (about 25% of the RDI)
  • Biscuits: Just one biscuit made may contain 528 mg of sodium, which is 23% of the RDI


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