Table salt is sodium chloride, a compound made of two elements: sodium and chlorine. By weight, it’s 40% sodium and 60% chloride. But the salt sitting in your shaker isn’t pure sodium chloride alone. It typically contains a few minor additives, including iodine, a stabilizer, and an anti-caking agent, each serving a specific purpose.
Sodium and Chloride: The Core
At the atomic level, table salt is built from positively charged sodium ions and negatively charged chloride ions locked together in a repeating crystal lattice. Each sodium ion is surrounded by chloride ions, and vice versa, forming the cubic crystals you can see if you look at salt under a magnifying glass. This structure is what gives salt its characteristic crunch and clean dissolving properties in water.
The two elements contribute differently to your body. Sodium is the part that affects blood pressure and fluid balance. Since sodium makes up 40% of salt by weight, one teaspoon of table salt (about 6 grams) delivers roughly 2,300 milligrams of sodium, which is the commonly cited daily upper limit. Chloride, the other 60%, helps maintain acid-base balance and is a component of stomach acid.
Where Table Salt Comes From
Before any additives enter the picture, salt has to be harvested. There are three main methods. Rock salt mining extracts solid deposits left behind by ancient seas, typically using a room-and-pillar method where miners carve out chambers underground. Solution mining takes a different approach: a solvent is injected into underground salt beds to dissolve the mineral, and the resulting brine is pumped to the surface. Solar evaporation collects seawater or inland saltwater in shallow ponds and lets the sun do the work, gradually concentrating the brine until salt crystals form.
Raw salt from any of these sources contains impurities, primarily calcium, magnesium, potassium, sulfate, and bromide. To produce the fine, white, free-flowing product you buy at the store, manufacturers put the salt through a refining process.
How Raw Salt Becomes Table Salt
Refining starts by dissolving crude salt into brine. That brine is then treated with soda ash and caustic soda, which cause calcium to precipitate out as calcium carbonate and magnesium to drop out as magnesium hydroxide. These precipitates settle as sludge and are removed, leaving a purified brine behind.
The clean brine then enters a series of heated evaporators. The first operates near atmospheric pressure, while subsequent stages operate at progressively lower pressures, which lowers the boiling point and makes the process more energy-efficient. As water evaporates, salt crystals form in the supersaturated solution. Those crystals are collected, spun in a centrifuge to remove moisture, and dried in a fluid bed dryer. The result is sodium chloride with a purity above 99%, stripped of the trace minerals present in the raw material.
Iodine and Its Stabilizers
Most table salt in the United States is iodized, meaning a small amount of iodine has been added to prevent deficiency. The iodine typically comes from potassium iodide, which is about 76% iodine and 24% potassium by weight. Iodized salt contains roughly 0.007% iodine, or about 0.01% potassium iodide. That’s a tiny concentration, but it’s enough to support thyroid function when salt is used regularly in cooking and at the table.
Potassium iodide is chemically unstable on its own in salt. It can oxidize and lose its iodine content over time. To prevent that, manufacturers add two supporting ingredients. Dextrose, a simple sugar, acts as a reducing agent that protects the iodide from breaking down. Sodium bicarbonate (baking soda) creates a slightly alkaline environment that further stabilizes the iodide. Both are present in extremely small amounts, far too little to affect the taste or calorie content of the salt.
Anti-Caking Agents
Without an anti-caking agent, table salt would absorb moisture from the air and clump into a solid mass inside the container. To keep it free-flowing, manufacturers add one of several approved compounds. Calcium silicate works by physically separating salt particles and preventing them from bonding. Sodium aluminosilicate serves the same purpose by absorbing moisture before it can reach the salt crystals. You’ll find one of these listed on the ingredient label of most brands, usually as the last item, reflecting the very small quantity used.
What’s in a Typical Ingredient List
If you flip over a container of standard iodized table salt, you’ll generally see five ingredients:
- Salt (sodium chloride), making up the vast majority of the product
- Potassium iodide, the iodine source
- Dextrose, to stabilize the iodide
- Sodium bicarbonate, to further protect the iodide
- Calcium silicate or sodium aluminosilicate, to prevent clumping
Non-iodized table salt skips the potassium iodide, dextrose, and sodium bicarbonate but still includes an anti-caking agent. Specialty salts like sea salt flakes or pink Himalayan salt are less refined and retain trace amounts of the calcium, magnesium, and other minerals that standard refining removes. Those minerals account for the color differences and subtle flavor variations, but they’re present in such small quantities that they don’t meaningfully change the nutritional profile. The dominant component in every case is still sodium chloride.