I'm looking at the nutritional information on a pack of salt, as per the panel, 33.5g/100g is Sodium, everything else is in mg, totaling up to less than 1gm.

The Ingredients section lists Salt as the sole ingredient

However, atomic mass of Na = 23 , Cl = 35.5 (approx)

As per this, Na should be around 39% of the total, not 33.5%

Any idea what accounts for the difference?

2 Answers 2


Minerals, naturally found in salt whether it's mined or evaporated; and believe it or not, water. Infosa In the US, the FDA requires that salt must not contain more than 2.5% minerals other than NaCl and still call itself salt. That 2.5% does not include water. HowStuffWorks Your numbers for sodium content seem a bit low, but not extremely so, especially for a very unrefined, wet salt. The more refined the salt, the less trace minerals it will contain.

Outside the US, it's possible that your salt also contains added iodine, fluoride, folic acid and/or anti-caking agents, but in the US those would be listed among the ingredients, and would be included in that 2.5%. Only iodine and anti-caking agents are common in the US.

Plus, nutritional information labels have legal margins of error. If and when they can, they'll be slick. Lower sodium looks good on a nutritional label.


Table salt is often "fortified" with additional ingredients to address specific public health concerns as well as ingredients added to preserve the appearance and stability of granulated salt.

Health related additives include iodine (as potassium iodide, sodium iodide or sodium iodate), iron (as ferrous fumarate), and fluorine (more common in Europe than US). In addition iodized salts may contain traces of dextrose used to stabilize the iodine salts.

Most finely granulated salts will contain some sort of anti-caking chemical. These include tricalcium phosphate, calcium or magnesium carbonates, fatty acid salts (acid salts), magnesium oxide, silicon dioxide, calcium silicate, sodium aluminosilicate, or calcium aluminosilicate.

Additionally, there may be trace minerals, commonly small amounts of magnesium and calcium halides and sulphates.

  • Additives, like iodine or anti-caking agents should be listed with ingredients. For instance, my Morton Kosher Salt lists prussiate of soda (anti-caking agent). Incidentally, that salt claims 480mg of sodium in 1.2 grams. Exactly 40%.
    – Jolenealaska
    Sep 13, 2014 at 22:19
  • Oops...I should say that additives should be listed with ingredients in the US. I don't know about outside the US.
    – Jolenealaska
    Oct 22, 2014 at 9:07

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