Every industrial chemical shipment should come with some form of test report or Certificate of Analysis (COA), but buyers new to procurement don't always know how to read one quickly. It's simpler than it looks once you know what the three core columns actually mean — which is exactly the format we use on every product page on this site.
The Three Columns: Characteristic, Specification, Result
Characteristic is which property was tested — Assay/Purity, Moisture, pH, Appearance, and so on. Specification is the agreed limit the batch is supposed to meet (a minimum, a maximum, or a range — e.g. "Min 98%" or "Max 0.5%"). Result is what this specific batch actually measured at when it was tested. A batch "passes" when its Result falls within the Specification's limit — nothing more complicated than that.
Characteristics You'll See Most Often
- Assay / Purity (%) — how concentrated the active chemical is; the single most important number for dosing calculations.
- Moisture / Loss on Drying — relevant for hygroscopic solids like caustic soda flakes or calcium chloride, where excess moisture effectively dilutes what you're paying for.
- pH (of a solution) — usually tested on a standard percentage solution, useful for confirming a batch behaves as expected in process.
- Insoluble Matter — impurities that won't dissolve or react; matters most for dosing systems with fine nozzles or filters.
- Appearance — a basic visual check (colour, form) that can flag contamination or degradation before anything else does.
Reading Min / Max Limits
A "Min" spec means the batch must be at or above that number — for an assay of "Min 98%", a result of 99.1% is a comfortable pass. A "Max" spec means the opposite — for moisture at "Max 0.5%", you want the result well under that ceiling, not right up against it. Watch for results that sit right at the edge of a limit; it's worth asking the supplier how consistent that number typically is batch to batch.
A Specification and a Result Aren't Always Both on File
Not every characteristic on a genuine test report will have both a Specification and a Result filled in — the two aren't mandatorily fixed together. Sometimes a lab only ever records a single value for a given characteristic: a stated limit ("Max 0.5%") with no separately logged measured result, or a one-off measured result with no formal spec agreed for it. Where that's the case, our own test reports show a dash (—) in the empty column rather than inventing a number to fill it. That's a sign of an honestly reported document, not a missing or failed test — if you specifically need the other half of that pair confirmed for your batch, just ask.
Why Results Vary Slightly Batch to Batch — and What to Do About It
Lab results shift a little from batch to batch even for a well-controlled product, which is exactly why a COA is tied to a specific batch or lot rather than being a one-time claim about the product in general. Always request a current test report with your order rather than relying on one from a previous shipment, and if a result ever comes back outside specification, the standard next step is to contact the supplier for a retest or replacement before the material goes into your process.