Summary. The SPC data sheet for disodium EDTA dihydrate, technical grade (SPC-TDS-PWD-006), lists assay, chelation value, pH, loss on drying, chloride, iron and heavy metals. A batch Certificate of Analysis should be read line by line against those limits. This guide explains what each line tells a buyer. The TDS values are specification limits, not batch results; the meanings of the parameters are general knowledge, not an SPC specification.
Why read the document before the first order
EDTA is sold in several forms and the paperwork is where the forms are told apart. A buyer who asks only for EDTA may be quoted the free acid, the disodium salt or the tetrasodium salt, and the three behave differently in a bath or a formulation. Reading the TDS and the batch Certificate of Analysis catches a wrong salt or an out-of-limit lot before it reaches your process.
Supreme Petro Chemicals is a Chennai importer and bulk distributor, not a manufacturer. The TDS and SDS are on the EDTA product page. A batch Certificate of Analysis is supplied with every delivery.
Step one: check the salt and CAS
Start with identity, because everything else depends on it. The TDS covers disodium EDTA dihydrate, CAS 6381-92-6. The free acid is CAS 60-00-4 and tetrasodium EDTA is CAS 64-02-8. If the document says only EDTA, ask which salt. The TDS also states HSN 2922 49 90; treat that as the code on the document and confirm duty with your customs advisor.
The parameters, one by one
| Parameter | TDS limit | What it tells you (general knowledge) |
|---|---|---|
| Assay (EDTA-2Na, dried basis) | 99.0 - 101.0 % | Content of the active salt once water is removed from the calculation |
| Chelation value (as CaCO3) | 272 mg/g min | How much calcium carbonate one gram can bind; a direct measure of metal-binding capacity |
| pH, 1% solution | 4.0 - 6.0 | Confirms the disodium salt; tetrasodium reads far higher, the free acid far lower |
| Loss on drying | 10.0 - 11.5 % | Water of crystallisation; explains why assay is quoted on a dried basis |
| Heavy metals (as Pb) | 10 ppm max | Trace metal contamination of the powder |
| Iron (Fe) | 10 ppm max | Residual iron, relevant where colour or staining matters |
| Chloride (Cl) | 0.1 % max | Residual salt; matters where chloride affects corrosion or process |
| 1% solution | Clear and colourless | A quick visual check for insolubles and colour |
| Limits from SPC TDS SPC-TDS-PWD-006 (manufacturer published specification, BP/commercial basis). Right-hand column is general knowledge, not an SPC specification. |
Assay and loss on drying go together
The assay is stated on a dried basis, while the product itself is the dihydrate and carries water. That is why the TDS also gives a loss on drying range. If you compare two documents, make sure both quote assay on the same basis; a figure on an as-received basis will look lower without the product being worse.
Chelation value is the performance number
Assay tells you about the salt; chelation value tells you how much metal a gram can bind. It is the figure to compare when two lots look alike on assay. A lot that meets assay but reports a chelation value below 272 mg/g deserves a question before use.
pH is an identity check
A 1% disodium solution should sit at pH 4.0 to 6.0. A pH far outside that range suggests a different salt or a problem lot.
Chloride, iron and heavy metals are impurity limits
These are maximums. Where your process is sensitive to chloride, iron staining or trace metals, check these lines first.
The three salts side by side (SDS values)
The SDS figures show why the salt name matters. Free acid (CAS 60-00-4): pH about 2.0 to 3.5 for a 1% suspension, water solubility about 0.5 g/L at 25 C, classified Eye Irrit. 2 (H319), signal word Warning. Disodium dihydrate (CAS 6381-92-6): pH about 4 to 6, solubility about 100 g/L at 20 C, Eye Irrit. 2 (H319), Warning. Tetrasodium (CAS 64-02-8): pH about 10.5 to 12.0 for a 1% solution, solubility about 400 g/L at 20 C, Acute Tox. 4 (H302) and Eye Dam. 1 (H318), signal word Danger. The TDS covers the disodium only, so the pH, assay and chelation limits above must not be applied to the other two.
Comparing a Certificate of Analysis with the TDS
- Match identity. Salt name, CAS and product name on the Certificate of Analysis should match the TDS.
- Check each limit. Assay, chelation value, pH, loss on drying, chloride, iron and heavy metals should each sit inside the TDS limit.
- Check the basis. Confirm assay is stated on a dried basis.
- Match lot to pack. The lot number on the Certificate of Analysis should match the bags received.
- Keep the pair. File the Certificate of Analysis with the TDS and SDS for your quality records.
A worked comparison
Take the chelation value line. The TDS says 272 mg/g minimum. If a Certificate of Analysis reports a number lower than 272, the lot is outside the limit and you should raise it before use. If it reports 272 or higher, the line passes. The same logic applies to every other row: a minimum is a floor, a maximum is a ceiling, and a range such as pH 4.0 to 6.0 must be met at both ends. Write the TDS limit and the reported value next to each other for every line, and mark each as inside or outside.
What if the certificate only says pass
Some certificates show the word pass or conforms instead of a number. A pass tells you the supplier judged the lot to be inside the limit, but it gives you nothing to trend between lots. For critical lines such as chelation value, chloride and iron, ask whether the measured figure is available, and keep it on file so you can see drift over time.
What the TDS does not tell you
- Batch results. The TDS lists limits. Only the Certificate of Analysis gives lot values, and we do not publish batch values on the product page.
- Other salts. There is a TDS for disodium only. The free acid and tetrasodium have safety data sheets but no data sheet, so ask for the document you need.
- Grade for food or pharma. The published grade is technical. It is not food grade or pharma grade, and the BP/commercial wording is the specification basis of the manufacturer, not a pharmacopoeial claim.
- Hazards. Read the SDS for your salt. Tetrasodium is classified for serious eye damage (H318) and harmful if swallowed (H302); disodium and the free acid are eye irritants (H319).
Common mistakes to avoid
- Ordering by the name EDTA alone without naming the salt and CAS.
- Comparing assay figures that are on different bases.
- Treating the TDS as a batch result.
- Assuming a disodium TDS applies to tetrasodium or the free acid.
Choosing between chelants
If you are weighing EDTA against sodium gluconate or citrate, see the general-knowledge comparison in sodium gluconate versus EDTA, gluconic acid and citrate. For grades and uses, see EDTA supplier in Chennai: grades and uses, and for reading safety documents, how to read an SDS.
How to enquire
Supreme Petro Chemicals, with its head office at Periyamet and warehouse at Redhills, Chennai, publishes the TDS for technical-grade disodium EDTA dihydrate in 25 kg bags and dispatches across South India. Send the salt, quantity, application and delivery location through the EDTA product page enquiry form, and we quote in 4 working hours. Grade and pack for the free acid and tetrasodium are confirmed on enquiry.