Pure sodium chloride (that is, pure salt) itself is eternal, but the shelf life of salt products occurs after food additives are added to it, which involves the food additive E536 (potassium ferric cyanate).

The fact is that pure minerals are not suitable for consumption by themselves. It contains too many impurities that may be harmful to humans. The rock salt is purified, dried and crushed. E536 gives natural salt a white and clean hue and prevents clumps from forming.

Of course, additives are toxic when added in large amounts. However, trace amounts of additives not exceeding 20 mg per kilogram of product are absolutely harmless. For example, E536 is also added to wine, sausages, cheese, and some types of cheese.

In most countries, including Russia, this additive is not banned and is actively used in food production. The shelf life of the additive is one year in paper bags and two years in polyethylene bags. If iodine is added to the salt, the product needs to be consumed within 6-9 months.

The origin of the name edible salt:

According to the explanation of the etymological dictionary S.I. Orzhegov, the words edible and cooking are synonyms. This is an outdated concept that was once used in food. For example, it is how table salt is distinguished from industrial salt, sea salt, and other types of salt.

However, the choice of the term "edible" may also indicate methods of handling and purifying the product. Until the end of the 19th century, salt was obtained by boiling it. They grind halite (aka rock salt from mineral deposits), filter it and dissolve it in the water.

In this way, craftsmen can remove metallic impurities from the rock salt. Then, to obtain pure salt, they would boil the water. The specialists responsible for the production of the condiment are called cooking craftsmen, and their products are called cooking salts.