Knowing how to label lab solutions properly is a basic safety and accuracy practice that is easy to overlook when a bench is busy, but a mislabeled or unlabeled tube can invalidate an entire experiment or create a genuine safety hazard for anyone else working in the lab.
What Belongs on a Label
A complete lab solution label should include the name of the solute or reagent, its concentration, the solvent used, the date it was prepared, and the initials of the person who made it. Depending on the lab’s requirements, it may also need an expiration or “use by” date, storage conditions, and any relevant hazard information if the solution is corrosive, flammable, or otherwise dangerous.
Why Concentration Must Be on Every Label
A tube labeled only with a chemical name but no concentration is effectively unusable for any calculation, because every dilution performed afterward depends on knowing the starting concentration precisely. Writing the concentration directly on the label, rather than relying on memory or a separate notebook that might not be nearby, prevents a common source of downstream error when the solution is used in a C1V1 = C2V2 calculation weeks later.
Labeling a Dilution Series
When labeling tubes from a dilution series, include both the tube’s position in the series and its actual resulting concentration or dilution factor, not just a bare sequential number. A tube marked only with a position number, separated from its paperwork, becomes meaningless the moment it is moved to a different rack or handed to someone else in the lab.
Labeling Stock vs. Working Solutions
Clearly distinguishing a stock solution from a working solution on the label, for example by marking the stock as a concentrate, prevents someone from accidentally using a concentrated stock directly in an application designed for a much more dilute working solution, which can produce dramatically wrong results or, in some cases, a safety issue.
Handling Date and Stability Information
Many solutions degrade, evaporate, or lose potency over time, so including a preparation date allows anyone using the solution later to judge whether it is still within a reasonable usage window. For solutions with a known shelf life, writing an explicit expiration date is more reliable than expecting someone to calculate it from the preparation date every time.
A clearly labeled stock concentration also makes it far easier to use a Dilution Calculator correctly later, since the calculator’s output is only as accurate as the starting concentration entered into it.
Physical Labeling Practices
Use labels and markers that will not smear or fade when exposed to the conditions the tube will be stored in, such as a freezer, a water bath, or direct light. For small tubes where space is limited, a short code that corresponds to a full entry in a lab notebook or electronic log is acceptable, as long as that code is unique and the log is kept up to date and accessible to anyone who might need it.
Why This Matters for Reproducibility
Clear, consistent labeling is part of what makes an experiment reproducible, both by the original researcher returning to a solution weeks later and by anyone else in the lab who might need to use or continue the work. A small amount of extra care at the labeling step prevents much larger problems, including wasted reagent, repeated experiments, and in some cases genuine safety incidents.
Building a Labeling Habit Into the Workflow
The most reliable way to maintain good labeling practice is to label a tube before adding any liquid to it, rather than after, since a tube filled first and labeled later is far more likely to be set down, mixed up with a similar tube, or forgotten entirely before the label is written. Making label-first a standard step in every protocol, rather than an optional add-on at the end, removes most of the opportunity for mix-ups to occur in the first place.
Frequently Asked Questions
Is it acceptable to use a shorthand code instead of a full label?
Yes, as long as the code is unique and clearly linked to a complete entry in a lab notebook or log that records the full details, including concentration and preparation date.
What is the biggest risk of an unlabeled solution?
Beyond invalidating an experiment, an unlabeled solution can pose a direct safety risk if someone else in the lab handles it without knowing what it is or how concentrated it might be.
Should expiration dates be included even for stable solutions?
It is good practice to include some form of date, even an approximate one, since even relatively stable solutions can be affected by contamination, evaporation, or storage conditions over long periods.
