A CAS Registry Number is a unique numeric identifier assigned to every distinct chemical substance by the Chemical Abstracts Service — and it's the single most reliable way to confirm two suppliers are actually quoting on the same chemical.
Why Product Names Alone Aren't Reliable
The same chemical can be sold under multiple trade names, and confusingly, similar-sounding names sometimes refer to genuinely different compounds or concentrations. "Caustic soda," "soda ash" and "washing soda," for instance, are three different compounds despite the overlapping "soda" naming. A CAS number cuts through this ambiguity — it identifies the exact substance, independent of what any particular supplier chooses to call it.
How to Use It Practically
When comparing quotes from different suppliers for what's supposed to be the same chemical, check that the CAS number matches before comparing price or specification — a mismatch means you're not actually comparing like for like. Every product page on this site lists the CAS number (where one applies) alongside the product name for exactly this reason.
When There's No CAS Number
Some products genuinely don't have a single CAS number — proprietary blends, mixtures, and some polymer products are identified by composition or trade designation instead, since they aren't a single registered substance. Where that's the case on our own product pages, we note it rather than inventing a number, and can share compositional information on request where it isn't commercially confidential.