Industrial salt 99% means the sodium chloride content is at least 99%, normally measured on a dry basis. That one figure is only the start. Salt for chlor alkali is judged mainly on the impurities that upset brine purification, while de-icing salt is judged on particle size, flow and what it is treated with.
Always ask whether the 99% is quoted on a dry or as-shipped basis, because moisture alone can move the number.
What does a chlor-alkali plant need from salt?
A chlor-alkali plant dissolves the salt into brine and then electrolyses it. Anything that does not belong in the brine has to be removed first, so the impurity limits matter more than the headline purity. The ones a plant will ask about are:
- Calcium and magnesium, which form scale and foul the purification step and, in membrane cell plants, damage the membrane.
- Sulphate, which builds up in the circulating brine and has to be bled off or removed.
- Insoluble matter, which loads the clarifiers and filters.
- Moisture, which affects handling and the true sodium chloride you are paying for.
- Heavy metals and iron, which some cell technologies limit tightly.
Where do the limits come from?
Plants differ, so the limits come from your own process. Give your supplier the full list rather than just the 99%. Our note on what purity industrial salt should have explains how purity is tested.
What does de-icing salt need?
For salt for de icing, sodium chloride content is usually a lower priority than physical form. Road authorities and municipalities normally specify a particle size range, a limit on fines and a limit on insoluble matter so the spreader works and the residue is acceptable. Many refer to a national or ASTM gradation standard; check which one your tender names.
Two other points matter. First, anti-caking agents are sometimes added so the salt does not set hard in stockpiles, and some destination markets restrict certain agents or ask for a declaration. Second, moisture must be low and stable, because wet salt clumps in storage and blocks spreaders.
Because de-icing demand is seasonal, buyers often order well ahead of winter. Plan lead time and shipping with that in mind, and read how salt is shipped in bulk, bags or jumbo bags.
How to write the specification
State the application first, then the numbers. For chlor-alkali, list sodium chloride on a dry basis, calcium, magnesium, sulphate, insolubles and moisture, each with a maximum and a test method. For de-icing, list the gradation limits, fines, moisture, insolubles and any additive.
Salt types and grades differ by use. If you are unsure which category you need, start with industrial, edible and de-icing salt grades. Do not accept a general industrial grade for a chlor-alkali plant without the impurity analysis.
Check it before it ships
Ask for a certificate of analysis from each lot and a retained sample. Better, have the lot sampled at loading by an independent party and tested against your specification. In Gujarat, salt is produced in large quantity from solar evaporation, but quality varies by pan, washing and storage, so the supplier matters.
Next step
We find salt producers that can meet your impurity or gradation limits, have lots tested, and supervise loading. To have that done for your tender or plant, book a free sourcing review.