Table salt is sodium chloride (NaCl), a mineral compound fundamental to human life. It serves a biological function and is widely used as a seasoning and food preservative. Although the grocery store version contains other compounds, table salt is typically 97% to 99.5% sodium chloride by mass.
The Chemistry of Sodium Chloride
Sodium chloride is an ionic compound formed by the electrostatic attraction between two oppositely charged ions. It consists of a positively charged sodium ion (Na+) and a negatively charged chloride ion (Cl-) in a 1:1 ratio. These ions organize into a highly ordered, three-dimensional crystal lattice, giving salt its characteristic cubic structure. Salt is sourced from two primary natural sources: the mineral halite (rock salt) mined from ancient underground deposits, and the evaporation of seawater. The purification process refines the raw material, often by heating, to remove impurities, yielding the clean, white granules known as table salt.
Mandatory Additives in Table Salt
The refined product sold as table salt is differentiated from pure sodium chloride by intentional additives included for consumer benefit. One primary additive is a form of iodine, such as potassium iodide, added for public health purposes. Since the 1920s, iodization has been used to prevent iodine deficiency disorders, such as goiter, which affect thyroid function. Anti-caking agents, such as calcium silicate, are also included to prevent the fine grains from clumping together. These agents absorb moisture, allowing the salt to flow freely from a shaker.
Distinguishing Different Culinary Salts
A variety of culinary salts are available, and all are predominantly sodium chloride. The differences between table salt, Kosher salt, sea salt, and Himalayan pink salt lie in their crystal size, texture, and trace mineral content. Sea salt is harvested from evaporated seawater and retains trace elements like magnesium and potassium, which subtly affect its flavor. Himalayan pink salt, a rock salt, gets its rosy hue from minute amounts of iron oxide. Kosher salt is distinguished by its large, flat, flaky crystal structure, making it a favorite for seasoning because it adheres evenly to food.
The Role of Sodium in Diet
The sodium component of sodium chloride plays a significant role in human physiology as an electrolyte. The sodium ion (Na+) maintains the body’s fluid balance, working closely with potassium to regulate water movement across cell membranes. It is also necessary for nervous system function, enabling the transmission of electrical impulses for nerve signaling. Sodium is directly involved in muscle contraction, including the rhythmic beating of the heart. However, excessive sodium intake, primarily from processed foods, is a contributor to hypertension, a risk factor for cardiovascular disease.