Incompatible Chemical Mixtures

When Mixing Chemicals Is Dangerous

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Some chemicals release toxic substances when mixed together. Doug Armand/Getty Images

Some chemicals shouldn't be mixed together. In fact, these chemicals shouldn't even be stored near each other on the chance that an accident could occur and the chemicals could react. Be sure to keep incompatibilities in mind when reusing containers to store other chemicals.

Key Takeaways: Incompatible Chemical Mixtures

  • It's dangerous to randomly mix chemicals together. Some chemicals react explosively, while other form toxic products.
  • In general, never mix bleach with any other chemical unless the other product states that it's safe to use with bleach.
  • Similarly, avoid mixing oxidizers, like peroxide, with other chemicals.

Here are some examples of mixtures to avoid:

  • Acids with cyanide salts or cyanide solution. Generates highly toxic hydrogen cyanide gas.
  • Acids with sulfide salts or sulfide solutions. Generates highly toxic hydrogen sulfide gas.
  • Acids with bleach. Generates highly toxic chlorine gas. An example of this would be mixing bleach and vinegar.
  • Ammonia with bleach. Releases toxic chloramine vapors.
  • Oxidizing acids (e.g., nitric acid, perchloric acid) with combustible materials (e.g., paper, alcohols, other common solvents). May result in a fire.​
  • Solid oxidizers (e.g., permanganates, iodates, nitrates) with combustible materials (e.g., paper, alcohols, other common solvents). May result in a fire.
  • Hydrides (e.g., sodium hydride) with water. May form flammable hydrogen gas.
  • Phosphides (e.g., sodium phosphide) with water. May form highly toxic phosphine gas.
  • Silver salts with ammonia in the presence of a strong base. May generate an explosively unstable solid.
  • Alkali metals (e.g., sodium, potassium) with water. May form flammable hydrogen gas.
  • Oxidizing agents (e.g., nitric acid) with reducing agents (e.g., hydrazine). May cause fires or explosions.
  • Unsaturated compounds (e.g., substances containing carbonyls or double bonds) in the presence of acids or bases. May polymerize violently.
  • Hydrogen peroxide/acetone mixtures when heated in the presence of an acid. May cause explosions.
  • Hydrogen peroxide/acetic acid mixtures. May explode upon heating.
  • Hydrogen peroxide/sulfuric acid mixtures. May spontaneously detonate.

Reading Labels

Products that react strongly with other chemicals or that produce toxins are labelled. It's important to read labels and heed warnings regarding storage and potentially dangerous reactions.

In a laboratory setting, chemical storage is a big deal. Special cabinets isolate reactive chemicals from one another. At home, most people put chemicals under the sink or in the garage. For the most part, this is reasonably safe, but it's worth keeping products that don't play nice together separate.

Always heed warnings about storage temperature conditions, too. Some chemicals decompose at high temperatures, so that even if the original chemical isn't hazardous, it turns into something reactive.

General Advice About Mixing Chemicals

While it may seem like chemistry is a good science to learn through experimentation, it's never a good idea to randomly mix together chemicals to see what you'll get. Household chemicals aren't any safer than lab chemicals. In particular, you should use care when dealing with cleaners and disinfectants, since these are common products that react with each other to yield nasty results.

It's a good rule of thumb to avoid mixing bleach or peroxide with any other chemical, unless you're following a documented procedure, are wearing protective gear, and are working under a fume hood or outdoors.

Note that many chemical mixtures produce toxic or flammable gases. Even in the home, it's important to have a fire extinguisher handy and work with ventilation. Use caution performing any chemical reaction near an open flame or heat source. In the lab, avoid mixing chemicals near burners. At home, avoid mixing chemicals near burners, heaters, and open flames. This includes pilot lights for ovens, fireplaces, and water heaters.

While it's common to label chemicals and store them separately in a lab, it's also good practice to do this in a home. For example, don't store muriatic acid (hydrochloric acid) with peroxide. Avoid storing household bleach together with peroxide and acetone.

Sources

  • Brown, Theodore L.; LeMay, H.; Bursten, Bruce E.; Murphy, Catherine; Woodward, Patrick; Stolzfus, Matthrew (2017). Chemistry: The Central Science (14th ed.). US: Pearson Education. ISBN 978-0134414232.
  • Gail, E.; Gos, S.; Kulzer, R.; Lorösch, J.; Rubo, A.; Sauer, M. "Cyano Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_159.pub2
  • Lawrence, Stephen A. (2004). Amines: Synthesis, Properties and Applications. Cambridge University Press. ISBN 9780521782845.
  • NSW Government. "Controlling chloramines in indoor swimming pools".
  • Odabasi, Mustafa (March 2008). "Halogenated Volatile Organic Compounds from the Use of Chlorine-Bleach-Containing Household Products". Environmental Science & Technology. 42 (5): 1445–1451. doi:10.1021/es702355u
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Helmenstine, Anne Marie, Ph.D. "Incompatible Chemical Mixtures." ThoughtCo, Jun. 2, 2021, thoughtco.com/dangerous-chemical-incompatibilities-602404. Helmenstine, Anne Marie, Ph.D. (2021, June 2). Incompatible Chemical Mixtures. Retrieved from https://www.thoughtco.com/dangerous-chemical-incompatibilities-602404 Helmenstine, Anne Marie, Ph.D. "Incompatible Chemical Mixtures." ThoughtCo. https://www.thoughtco.com/dangerous-chemical-incompatibilities-602404 (accessed June 15, 2021).