How to read a chemical specification sheet, why the CAS number matters more than the trade name, and the specification traps that cost buyers money.
Two suppliers quote what appears to be the same product at prices 30% apart. Before assuming one is overcharging, read both specifications properly.
Start with the CAS number
A CAS Registry Number uniquely identifies a chemical substance regardless of trade name, language or supplier. Caustic soda, sodium hydroxide, lye and NaOH all share CAS 1310-73-2. When comparing quotes, match on CAS number first — trade names mislead, CAS numbers do not.
Note that CAS numbers identify the substance, not the hydrate form or concentration. Citric acid anhydrous (77-92-9) and citric acid monohydrate (5949-29-1) carry different numbers, and buying the wrong one changes your dosing arithmetic by about 8%.
Assay is the headline, impurities are the story
Assay tells you how much of the substance is present. The impurity profile tells you what else you are buying. For water treatment, iron content matters because it causes colour. For electronics cleaning, chloride matters because it causes corrosion. For food, heavy metals matter because they are regulated. A cheaper product with a loose impurity specification is often the more expensive choice once you account for the consequences.
Concentration and basis
A quote for hydrochloric acid at "33%" should specify whether that is w/w or w/v, and whether the price is per tonne of solution or per tonne of contained HCl. Suppliers who quote on the solution basis for a weaker product appear cheaper until you calculate cost per unit of active chemical.
Physical form affects your process
Caustic soda flakes dissolve faster than pearls; dense soda ash dusts less than light. Titanium dioxide particle size determines opacity. These attributes rarely appear in a headline price comparison, but they determine whether the material works in your plant.
What a complete specification includes
A specification worth trusting states appearance, assay with a tolerance, named impurity limits with numeric values, physical properties such as bulk density or specific gravity, packaging, and the test methods used. Vague entries like "high purity" or "meets industry standard" are marketing, not specification.
Ask for a batch COA before you commit
A specification sheet describes what the supplier intends to deliver. A Certificate of Analysis describes what was actually in a specific batch. Request a recent COA alongside any new quotation, and check it against the specification line by line.
