How to label lab reagents

The regulatory floor

In the United States, a workplace container of a hazardous chemical that is not in its original packaging must carry a label under 29 CFR 1910.1200(f)(6). The employer may use the full GHS elements — product identifier, signal word, hazard statements, pictograms, precautionary statements — or the alternative the rule explicitly allows: the product identifier plus words, pictures, symbols or a combination that convey at least general information about the hazards.

That alternative is what makes in-house labelling practical. It means a bottle of 1 M NaOH can carry “1 M NaOH — corrosive” with a corrosion pictogram rather than the whole label from the supplier's drum, provided the full hazard information is available to workers through the safety data sheet and the written hazard communication programme.

There is a genuine exemption for portable containers: a chemical transferred from a labelled container into a portable one for the immediate use of the employee who performs the transfer, during that work shift, does not need a label. It is narrower than most people assume — it does not cover anything left on a bench overnight, and it does not cover anything another person might pick up.

Outside the US the equivalents differ in detail. The EU's CLP Regulation governs supply labelling rather than workplace containers, with workplace requirements coming from the Chemical Agents Directive as implemented nationally; the practical content of a good in-house label is much the same everywhere.

A standard that survives contact with a real lab

Identity that distinguishes

Enough to tell this bottle from the one next to it. Salt form, concentration, pH where relevant. “Tris” fails this test; “Tris-HCl 1 M pH 8.0” passes.

Date prepared

One date, and make it the preparation date. Expiries that were guessed get ignored, and the habit of ignoring dates spreads.

Initials

Two or three characters. This is the field that makes every other question answerable.

Hazard, where there is one

Signal word plus pictograms. Skip it entirely on genuinely non-hazardous materials — a label where everything is marked hazardous conveys nothing.

Storage, only when surprising

Write it when someone would otherwise get it wrong, not as a matter of routine.

Make the label outlive the project

Reagent bottles routinely outlast the person who made them. That is the real argument for printed labels over marker: not neatness, but that a printed label is still legible after two years of ethanol wipes and a handwritten one is not.

It is also the argument for putting the year in the date. A label reading “14/03” is ambiguous in two ways at once, and a bottle found at the back of a shelf is exactly where that ambiguity bites. ISO-style dates — 2026-03-14 — sort correctly, read the same in every country, and cost three characters.

What to do about secondary containers people fill daily

Wash bottles, solvent squeeze bottles and the ethanol decanted into a beaker are where labelling standards break down. The portable-container exemption covers some of it and not the rest, and in practice the distinction is invisible to whoever picks the bottle up.

The workable answer is a permanent label on the container rather than a label per fill: a wash bottle labelled “70% ethanol” once, refilled from a labelled stock, is both compliant and honest. What is not acceptable is an unlabelled bottle of clear liquid, however briefly it was intended to exist.