Chemical Incompatibility Chart: What Not to Store Together
Ethanol, sulphuric acid, nitric acid, hydrogen peroxide and sodium hydroxide all appear on the list of laboratory chemicals commonly used in laboratories. Most behave well alone. Put the wrong two side by side, and a shelf becomes a hazard. A chemical incompatibility chart shows which pairs need distance, and this guide explains how to read one and turn it into a storage habit.
Table Of Contents:
Chemical Storage Compatibility Starts With Knowing What You Hold
Laboratory chemicals arrive as liquids, powders and gases, each with its own properties. That variety is why incompatible chemicals cause trouble. A liquid spreads when a container fails, a powder drifts as dust and a gas simply leaves. A cracked bottle, a loose cap or a shared tray can bring two substances together long before anyone plans a reaction.
A few basic rules already lower the risk. Keep chemicals away from heat sources such as steam pipes and laboratory ovens. Never leave them in direct sunlight. Date each container on arrival and again when opened, and add an expiry date for anything that degrades over time.
Those habits do not replace separation. They stop a good chart from being undermined by a warm shelf or an unlabelled bottle of unknown age.
Reading a Chemical Incompatibility Chart Without Guesswork
A chart lists hazard classes along both axes, such as acids, bases, oxidizers and flammable liquids. Each cell where two classes meet carries a colour or symbol. Some mean compatible, some mean cautious, and some mean keep apart. Colour coding varies between charts, so read the key before trusting a cell. Say sodium hydroxide sits in the base column and nitric acid in the acid column. The cell where they meet flags heat generation, which is the cue to separate them.
Two limits matter. A chart works at class level, so concentration, temperature and container condition can change the real outcome. It also cannot list every chemical, which is why the safety data sheet has the last word. Its storage and handling section and the stability and reactivity section name specific materials to avoid.
Free tools help too. NOAA’s CAMEO Chemicals lets you add the chemicals in your store to a list and see predicted hazards if they were mixed.
Four Pairings That Need Separate Shelves
The rows below show how a chemical incompatibility chart treats chemicals named on the Saffron Chemicals laboratory chemicals page. Outcomes depend on concentration and quantity, so treat the table as a starting point.
| Chemicals | What Can Go Wrong | Storage Response |
|---|---|---|
| Sulphuric acid and sodium hydroxide | Acid and base react fast and release heat, which can spatter corrosive liquid | Separate acid and base storage |
| Nitric acid and ethanol | An oxidizing acid meeting a flammable solvent can ignite or build pressure in a closed container | Keep nitric acid away from all organic solvents |
| Hydrogen peroxide and ethanol | The oxidizer feeds a flammable liquid and raises fire risk | Store oxidizers apart from flammables |
| Hydrogen peroxide and sodium hydroxide | Contamination and alkaline conditions speed decomposition, which releases oxygen | Give peroxide its own clean space |
Hazard Class Segregation in Daily Practice
Group chemicals by hazard, not by alphabet. Shelve those five names alphabetically, and ethanol lands beside hydrogen peroxide, so a flammable solvent ends up sharing a shelf with an oxidizer.
A workable layout is simple. Flammables go in a flammable cabinet. Acids sit apart from bases, and strong oxidizers stay away from organic materials such as solvents. Nitric acid is an oxidizing acid, so it often gets its own space. Liquids belong in secondary containment trays, and large bottles belong on low shelves. Good laboratory chemical storage also means a current inventory, so anyone can tell what is on the shelf and how old it is. Ventilated storage helps too, since vapours from a leaking bottle should not linger.
Who to Ask When the Chart Runs Out
Some chemicals fall into two groups, and different charts sometimes disagree. Take those cases to your safety officer before shelving anything. Supplier documents help as well. Saffron Chemicals states on its laboratory chemicals page that products come with data sheets and safety instructions and that its consultants assist with choosing chemicals and technical problems. Treat all of that as input to your own hazard assessment, since storage decisions remain the laboratory’s responsibility.
Final Thoughts
A chart is only as useful as the shelf plan behind it. Sort by hazard class, follow the data sheets, date every bottle and revisit the layout whenever new stock arrives. If two bottles swapped places tomorrow, would your current layout catch it?
FAQ
Think of it as a who-should-not-sit-together list for chemicals. It groups substances by hazard, such as acids, bases and oxidizers, and marks which groups react badly. Confirm every product on its safety data sheet.
No. Sulphuric acid and sodium hydroxide react fast and give off heat, so one leaking bottle can cause splashing. Use separate cabinets or trays.
A flammable cabinet, ideally. Keep it clear of nitric acid and hydrogen peroxide, and away from heat sources and direct sunlight, both flagged on the Saffron Chemicals lab page.
Every time new stock arrives, plus on a regular schedule. Date bottles on receipt and opening, watch expiry dates, and ask your safety officer how often a full inventory check is due.