About Salt Crystals

Salt isn't just for dinner, and never has been. These small cubes of sodium chloride have served an astoundingly powerful role in civilization: preserving food, funding kingdoms, or even prompting wars. And although these seemingly innocuous crystals have since abandoned their role as kingmakers, their impact can still be seen by anyone who looks.

Geography

The world's seas and oceans are about 3.5% salt (the Dead Sea, meanwhile, stands at 34%). Around the world, approximately 250 million metric tons of salt are produced per year. The United States has long been the foremost producer of salt, with giant salt beds centered around the Great Lakes, the Gulf of Mexico, and the Oklahoma Panhandle. Starting in 2005, however, salt production in China began to match, if not exceed, the United States. Germany, India, and Canada are also significant suppliers. In the 13th century, Poland opened the Wieliczeka Salt Mine, and used the site to fund what would become a vast Polish kingdom. As the longest-running salt mine in history (until 2007), it has since become a UNESCO World Heritage Site.

Features

Salt has a variety of properties that distinguish it from other elements. Salt crystals are cubic, as each ion is surrounded by six others in what is called "octahedral geometry." Salt can appear stark white when purified, although unrefined rock salts can range from gray to brown in color. Perhaps most importantly, salt possesses important hygroscopic properties - i.e. it draws out water molecules from the surrounding environment. This allows for the preservation of food.

Types

Depending on how it was produced, salt can be classified as evaporated salt, rock salt, solar salt, and salt in brine. Unrefined salts (also known as sea salt) are often too bitter for human consumption, and are often used instead in bath salts. Refined salt, which removes much of the magnesium and calcium, can serve a whole host of industrial purposes. Refined salt's most well-known variety is table salt, which exists as 99% sodium chloride. And iodised salt serves to battle iodine deficiencies, which can lead to thyroid gland problems such as goiters.

Function

Salt is widely used in manufacturing, for everything from paper to dye to soaps, while also serving as the raw material for the production of another essential chemical, chlorine. Over half of the world's salt production is used by northern industrial countries to de-ice roads in their freezing winters. And in the human body, sodium ions - a key electrolyte, which transmits electrical signals in the body - are essential for a person's health and well-being. A lack of electrolytes in the body can lead to muscle cramps, and in severe cases to swelling of the brain.

Significance

Salt's role in human history cannot be understated. Salt served as money, mummified pharaohs, and served as a religious symbol for purity. The phrase "not worth his salt" originates from the slave trade in ancient Greece, and "take it with a grain of salt" refers to a purported antidote for poison. Its ability to preserve food played a pivotal role in the development of agriculture, and allowed explorers to traverse vast distances. And in India, the British salt tax inspired Gandhi's non-violent Salt March - one of a series of powerful acts that challenged British rule.

Resources

• Salt Institute
• "Wieliczka" Salt Mine
• Dead Sea