Sodium and salt are two closely related chemicals that are important in health, nutrition, and cooking. But what is the difference between them? In short, sodium is a metallic element that reacts explosively with water, while salt is composed of sodium and chloride and is essential to life. Let’s explore their key differences in more detail.
What is Sodium?
Sodium is a soft, silvery-white metallic element that is highly reactive and corrodes rapidly when exposed to air. Its chemical symbol is Na, which comes from its Latin name natrium. Some key facts about sodium:
- Sodium is an alkali metal in group 1 of the periodic table.
- It has an atomic number of 11 and atomic weight of 22.99.
- Sodium has one valence electron in its outer electron shell, which it readily gives up to form compounds.
- In its pure form, sodium reacts vigorously when exposed to water or moist air, often resulting in an explosion.
- Sodium must be stored in mineral oil or an inert gas like argon to prevent reaction.
- Compounds of sodium have many uses, including in soaps, glass, paper, dyes, textiles, pharmaceuticals and food additives.
Sodium is the sixth most abundant element on Earth and makes up 2.6% of the Earth’s crust. It is found widely dispersed in minerals like rock salt, cryolite, amphibole and zeolite. Sodium is vital to animal and plant health and is an essential nutrient for animals. The human body contains around 100 grams of sodium.
What is Salt?
Salt is a crystalline compound formed when the caustic metal sodium reacts with the poisonous gas chlorine. The chemical name for salt is sodium chloride and its formula is NaCl. Some key facts about salt:
- Salt contains equal numbers of sodium cations (Na+) and chloride anions (Cl-).
- It forms cubic crystals with a typical halite structure.
- Salt is essential for animal life and is found widely in seawater and mineral deposits.
- Table salt used for cooking and seasoning is mainly sodium chloride, often with added iodine.
- Rock salt, halite or evaporated sea salt is relatively pure NaCl.
- Salt has been used extensively for thousands of years in cooking, food preservation and seasoning.
- The human body requires around 500mg of salt per day to maintain the correct sodium balance.
Salt deposits are found in vast beds of dried seabed sediment around the world. These can reach great thickness – up to 3.7 miles deep in some places. Major salt mines are found in Austria, Poland, Romania, Ukraine, Germany and Pakistan. Salt production is around 280 million tonnes per year globally.
Chemical Properties
Sodium and sodium chloride have very different chemical properties, despite sodium being one of the components of salt.
Sodium:
- Is a soft, low density, silvery metal.
- Has a melting point of 97.72°C and boiling point of 883°C.
- Reacts violently and sometimes explosively with water.
- Produces caustic sodium hydroxide on reaction with water.
- Readily forms ionic bonds and salts when reacted with non-metals.
- Is a powerful reducing agent, causing oxidation of other elements.
Sodium chloride:
- Is a crystalline solid, usually cubic structure.
- Has a high melting point of 801°C.
- Dissolves readily in water without violent reaction.
- Produces electrically neutral solutions when dissolved.
- Does not readily form compounds with other elements.
- Acts as a seasoning and preservative, without strong chemical reactivity.
Physical Properties
The physical properties of metallic sodium and ionic salt crystals are markedly different:
| Property | Sodium Metal | Sodium Chloride |
|---|---|---|
| State at room temperature | Soft silvery-white metal | Brittle transparent crystals |
| Density | 0.97 g/cm3 | 2.17 g/cm3 |
| Melting point | 97.72°C | 801°C |
| Boiling point | 883°C | 1413°C |
| Solubility | Reacts vigorously with water | Readily dissolves in water |
As the table highlights, sodium metal is soft, low density and reactive, while sodium chloride salt is a high density crystalline solid that dissolves easily in water.
Role in the Human Body
Both sodium and chloride ions play essential roles in human health as electrolytes. They have important but very different functions.
Sodium:
- Helps regulate blood volume and blood pressure.
- Allows transmission of nerve impulses.
- Assists in muscle contractions.
- Needed for absorbing nutrients like glucose and amino acids.
Chloride:
- Helps maintain blood pH and electrolyte balance.
- Aids in digestion by producing stomach acid.
- Allows fluid movement between cells.
- Assists in nerve impulse transmission.
The kidneys, adrenal glands and circulatory system closely regulate sodium levels in the human body. Sodium chloride (salt) is essential to good health, but excess sodium can contribute to high blood pressure.
Uses of Sodium vs Salt
Metallic sodium has some specialized applications, while sodium chloride salt is ubiquitous:
Sodium uses:
- Reducing agent in chemical production of metals like titanium and zirconium.
- Coolant in fast-breeder nuclear reactors.
- Component of sodium-vapor lamps for street lighting.
- Used in certain types of batteries.
Salt uses:
- Seasoning for food like vegetables, eggs, fish and meat.
- Preservation of meat and fish products.
- Flavor enhancement and food texture control.
- De-icing of roads and sidewalks.
- Component of saline solution used for medical purposes.
Salt’s versatility for cooking, preservation, cleaning, and medicine has made it an essential commodity for thousands of years. Sodium metal has some important but niche industrial applications.
Occurrence and Production
Sodium and salt deposits have different natural origins and methods of production:
Sodium occurrence:
- Sodium makes up 2.6% of the Earth’s crust.
- It is the 6th most abundant element.
- Found dispersed in many minerals like feldspars and rock salt.
- Produced commercially by electrolysis of molten sodium chloride.
Salt occurrence:
- Halite (rock salt) deposits often underground or in dried lake beds.
- Salt lakes and seawater – high in dissolved sodium chloride.
- Ancient trapped seas like the Dead Sea are very saline.
- Salt produced by solar evaporation of seawater or brine wells.
- Rock salt mining via shafts, drilling or controlled explosions.
Sodium is obtained from electrolysis of molten salt. Common table salt is mined from geological deposits or produced by evaporating brine solutions.
Cost Comparison
Due to their very different chemical properties and applications, sodium and salt have big differences in cost:
- Sodium metal is relatively expensive at around $1,500 per tonne.
- It requires large energy input for production via electrolysis.
- Handling sodium metal requires safety precautions.
- Common table salt is extremely cheap at around $100 per ton.
- Abundant sea salt and rock salt deposits make it inexpensive.
- Easy handling and distribution mean low production costs.
Salt is one of the world’s cheapest and most plentiful commodities. Metallic sodium is a specialty product with more limited demand and complex production requirements.
Toxicity
Sodium and salt have very different toxicity and safety profiles:
Sodium metal:
- Highly reactive, flammable in air and explosive in water.
- Contact with skin can cause burns.
- Reacts to produce corrosive sodium hydroxide.
- Requires careful handling to avoid accidents.
Sodium chloride:
- Low toxicity makes it safe to eat in normal amounts.
- Essential nutrient for humans and animals.
- Excessive intake linked to high blood pressure.
- Easy and safe to handle as a powder or crystals.
Metallic sodium requires great care in handling and storage. Salt is non-toxic and safe at normal dietary levels, although too much can be harmful.
Environmental Effects
Sodium and salt also differ in their environmental impact:
Sodium metal:
- Reactive sodium can contaminate waterways.
- Releases corrosive and caustic byproducts.
- Na+ ion can affect soil function and aquatic life at high levels.
Sodium chloride:
- Widespread use means it enters environment readily.
- Moderate water contaminant that increases salinity.
- Excess salt can inhibit plant growth and affect osmoregulation in organisms.
- Chloride contamination of water also a concern.
Both sodium and chloride ions can have detrimental effects on ecosystems when present at elevated concentrations. Sodium metal further poses risks from its caustic chemical reactivity.
Conclusion
In summary, sodium and salt have the following key differences:
- Sodium is a reactive, soft silvery metal, while salt is a crystalline ionic compound.
- Sodium reacts explosively with water, whereas salt readily dissolves.
- Sodium has niche uses in chemical production and nuclear reactors, whereas table salt has widespread culinary applications.
- Sodium metal is hazardous and toxic, but dietary salt is mostly safe.
- Sodium is rare and costly to produce, but salt is hugely abundant and cheap.
So in essence, sodium is a pure metallic element suitable for specialized industrial uses, while common salt is sodium chloride, an ionic compound essential for human nutrition and flavoring.
