Short-chain alcohols earn their place by evaporating on a useful schedule: long enough to wet a surface and dissolve what sits on it, short enough to leave nothing behind. The second half of that requirement is not a property of the molecule at all. It belongs to the finishing steps, which is why the same substance ships both as a bulk industrial solvent and as a filtered low-residue grade, and why only the certificate of analysis tells them apart.
Settle before you order: Water content and the method used to measure it, non-volatile residue, whether the grade carries a pharmacopoeial or cleanroom claim, and what the drum liner is made of.
Esters buy balanced solvency with a mild odour profile and a predictable evaporation curve, which is why coatings and printing inks are built around them. Their weakness is the same bond that makes them useful: it hydrolyses. Water and free acid in the drum are therefore not cosmetic specification lines. They are the leading indicators of how the material will behave three months from now, and they move in one direction only.
Settle before you order: Acid number together with its method, water content, and how long the material has already spent in a warehouse before it reaches you.
This family exists to couple things that do not want to mix and to control how a film dries. Two decisions matter more than the rest. The first is which series the material belongs to, because the regulatory histories of the ethylene and propylene series diverged decades ago and statements about one do not transfer to the other. The second is which isomer dominates, because the minor isomer follows a different oxidation pathway and is the one regulators look at.
Settle before you order: Series and isomer distribution stated on the certificate, peroxide handling in storage, and the compatibility of the whole package rather than the bottle alone: liner, gasket and closure.
With a solid, the specification that decides the process is almost never purity. It is particle size, bulk density, caking behaviour and how much dust the material throws when it is charged. Two lots at the same assay can behave completely differently in a hopper, and the difference shows up on the shop floor rather than in the laboratory, usually on the day nobody has time for it.
Settle before you order: Granulation, moisture with its method, packaging with net weight, and whether the lot was sieved or milled after drying.
Here the paperwork is part of the product. A supplier who quotes these without asking what you intend to do with them is telling you something about how the rest of their documentation is handled. Expect to state the end use, expect the licence to be checked, and expect the answer to take longer than for an ordinary solvent. That delay is the control working, not the supplier being slow.
Settle before you order: Your own licence status in the destination country, the end-use statement, and the transport classification for the exact concentration being bought rather than for the pure substance.
Everything that does not sit neatly in the families above: acids, anhydrides, carbonates, surfactant intermediates. These are bought against a named use rather than a general grade, so the most useful opening message is not a product name at all. It is a description of the reaction or the formulation the material has to survive.
Settle before you order: What the material must tolerate in your process, which impurities would be fatal to it, and which analytical method you will use to accept the lot.
