Why are anticaking substances added to table salt?

Anticaking substances are added to table salt to ensure it remains free-flowing when exposed to the atmosphere. Because salt is a hygroscopic substance, it naturally attracts water from the air, which can cause it to clump together.1

To prevent this, manufacturers add small quantities of various agents, such as sodium aluminosilicate, tricalcium phosphate, magnesium silicate, calcium silicate, magnesium carbonate, or tricalcium silicate. In some countries, minute amounts of yellow prussiate of soda are also used for this purpose, subject to government regulation. These additives maintain the desired consistency of the salt, allowing it to pour easily for use as a seasoning.123