The published Grade I and Grade II table
BIS revised the standard as IS 797:2023. Its consumer summary and implementation circular identify the current two-grade framework; the Salt Commissioner Organisation page supplies the numerical Grade I and Grade II table. Buyers should cite the current edition in new contracts.
| Characteristic | Grade I | Grade II |
|---|---|---|
| NaCl, minimum | 99.5% | 98.5% |
| Water-insoluble matter, maximum | 0.05% | 0.20% |
| Calcium as Ca, maximum | 0.03% | 0.20% |
| Magnesium as Mg, maximum | 0.01% | 0.10% |
| Sulphate as SO₄, maximum | 0.20% | 0.60% |
| Iron as Fe, maximum | 10 ppm | 20 ppm |
| Moisture, maximum | 1% | 4% |
What each parameter can signal
NaCl is the primary active material, while moisture affects delivered dry-salt value and flow. Insolubles can create residue and filtration load. Calcium and magnesium are hardness-forming constituents that can matter in brine systems. Sulphate and iron may be important to particular downstream processes.
These explanations are general. Only the buyer’s process owner can decide the economic or operating effect of a limit. A requirement tighter than the reference should be written explicitly and priced as such.
Avoid three common contracting mistakes
First, do not write only ‘IS 797’ if the grade and applicable revision are not clear. Second, do not accept a generic brochure as lot evidence. Third, do not leave the sampling and test method undefined, because two results can differ when samples are drawn or prepared differently.
A strong order names the grade, parameter limits, basis of measurement, sampling rule, test method, certificate issuer, lot identity and dispute procedure.
Worked RFQ language for a grade-based purchase
A stronger line than 'industrial salt as per IS 797' is: common salt for chemical industries, IS 797:2023 Grade I, followed by the complete agreed parameter table, unit, basis and method. Add packing, quantity, sampling, certificate and rejection terms in separate clauses. If the process needs a tighter value than Grade I, show the tighter contractual limit explicitly rather than expecting the supplier to infer it.
Before issuing the order, make the supplier return a line-by-line compliance statement. 'Complied' should point to an offered value and evidence, not merely repeat the buyer's text. Preserve that response, the approved sample and the purchase specification under the same revision number.
- Name the 2023 edition and grade
- Repeat every numerical limit
- State wet or dry basis
- Name the sampling and test method
- Link the COA to the offered lot
Buyer questions
Frequently asked questions
Is Grade I always better than Grade II?
Grade I has tighter published limits, but ‘better’ depends on the process and total cost. A buyer should specify the grade that safely meets the application rather than over- or under-specifying by habit.
Does 99.5% NaCl alone prove Grade I?
No. Grade I also has limits for insolubles, calcium, magnesium, sulphate, iron and moisture in the published table.
Should every delivery be tested?
Testing frequency should reflect process criticality, supplier performance, lot variability and the contract. Define it before purchase.
Primary references
Official sources used on this page
Standards and regulations can change. Follow the linked authority and verify the current requirement for the actual contract.
- Consumer-friendly summary of IS 797:2023 common salt for chemical industriesBureau of Indian Standards
- Implementation circular for revised IS 797:2023Bureau of Indian Standards
- Industrial-grade salt numerical reference tableSalt Commissioner Organisation, Government of India