Most problems with buying caustic soda surface not during the price negotiation but after the consignment arrives: material that has caked, a figure that does not match last time, bags that got damp in the store. These ten points are checked before the order goes in, and they remove almost all of it.
1. Define your requirement in active material
“Twenty tonnes of caustic a month” is an ambiguous sentence. What your process consumes is pure sodium hydroxide, not bag weight. Write the monthly requirement as pure NaOH and derive the purchase quantity by dividing it by the product purity.
2. Know which impurity your process is sensitive to
Chloride, iron and carbonate are the three main impurities, and every industry is more sensitive to one of them. Dyeing and textiles to iron, resin regeneration to chloride, catalytic processes to carbonate. Until you know this, you cannot say which product suits you.
3. Ask for the certificate of analysis for that batch
This is the most important item on the list. The certificate must belong to the consignment being sent to you, with its batch number on it — not a sample sheet issued last year. A supplier who is evasive about this has told you what you need to know.
4. Ask about variation between consignments
For a line whose formulation is set against a number, consistency matters more than higher purity. Ask what the last three consignments returned and how far apart those figures were.
5. Compare price per kilogram of active material
Price per tonne of product is a misleading number. Work out the price per kilogram of pure NaOH delivered into your own plant, freight, unloading and storage included. Sometimes the dearer product lands cheaper.
6. Specify the packaging
State the bag weight, the inner liner and the pallet pattern in the order. A moisture barrier is not a luxury on a hygroscopic material. Ask too whether pallets are shrink-wrapped.
7. Get the safety data sheet before the material arrives
Not afterwards. The sheet must be in the hands of your HSE department before the material enters the plant, so that working instructions and store layout can be prepared. It should follow the standard sixteen-section format and carry a current revision date.
8. Check the store is ready
Before the consignment arrives, these must be in place:
- A dry, covered space, with pallets to keep bags off the floor
- Separation from any acid storage
- Removal of every aluminium vessel, funnel or tool from the handling path
- A working, accessible emergency shower and eyewash
- Personal protective equipment for the operators
9. Settle the delivery terms
Who loads, who unloads, and does the weighbridge at origin or at destination govern? For an export order the agreed Incoterm must be written down explicitly. None of this is negotiable once the truck is at your gate.
10. Agree the document list in advance
The minimum that should arrive with, or before, the goods:
- Certificate of analysis for that batch
- Safety data sheet
- Certificate of conformity to the relevant standard
- Transport documents for a corrosive substance
- Invoice stating purity and net weight
One last point
Before committing to a large order, take a sample and run it on your own line. No certificate of analysis substitutes for that, because how the material behaves in your process depends on variables no supplier’s laboratory reproduces.
Our flake caustic soda is supplied at 98 to 99 per cent purity to the Iranian national standard ISIRI 364, in 25 kg bags, and the certificate of analysis for each batch travels with that consignment. Contact our commercial department to request a trial sample.
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