Incompatible Chemicals:  What We Have Learned by Lauren Kelly & Kevin McGhee

Be honest…at some point we have all made that innocent mistake of accidentally mixing two incompatible materials in a waste container. Sometimes mixing two chemicals results in nothing more than a more hazardous, but manageable solution such as a corrosive, toxic solution.  However, sometimes we may not be so lucky and may have accidentally created a potentially dangerous solution.  The best thing to do is call EH&S for guidance.  The two recent incidents illustrate the potential hazards of mixing incompatible chemicals.

In the first incident, methanol and nitric acid, a mixture which under certain conditions forms explosive methyl nitrate, were combined in the same hazardous waste container.  An alert laboratory worker, realizing the mistake, contacted University safety personnel.  Due to the potential danger of the mixture, the University’s chemical emergency response vendor was called in the early morning hours to assist.  The response team, dressed in full ballistics suits for protection, stabilized the container by adding methanol and water, diluting the mixture to a safe concentration, and ultimately disposed of the solution safely off-site. 

At the conclusion of the incident investigation, it was learned that although the container was labeled as hazardous waste and included all of the chemicals in the waste, the concentrations listed on the waste label were not accurate and that the waste stream could have - and should have - been separated into two containers. This minor error in handling and labeling the waste container prompted a building evacuation, but thankfully there were no injuries. 

In another recent incident involving the mismanagement of hazardous waste, an inexperienced student dumped a small amount of acetone waste into a waste container labeled for sulfuric acid. The resulting exothermic reaction caused the plastic waste container to partially melt, spilling much of its highly corrosive contents.  Thankfully, the student had the awareness to report the incident to EH&S.  A team of EH&S trained spill responders spent several hours cleaning up the spill..

Both of these incidents underpin several critical points:

  • Inexperienced lab personnel must be trained in all relevant safety topics before they begin handling hazardous materials or equipment and receive  hands-on instruction in all procedures from their supervisors or mentors, and should be closely supervised until they can demonstrate that they are able to carry out all necessary tasks safely.
  • Laboratories must properly  segregated chemical waste in terms of chemical compatibility and reactivity to avoid adverse reactions.  EH&S can assist in making these determinations if assistance is needed.
  • The concentrations and chemical components of all chemical waste streams must be clearly identified on hazardous waste labels.   This ensures that hazardous wastes are properly managed and handled safely.

If you are unsure as to the compatibility of different chemicals that you plan to combine in one container, contact EH&S in advance for guidance. 


Reactive chemical specialist stabilizing potentially explosive mixture

Oil Bath Déjà vu by Juliet Ogbonnaya

The incidents that occur on Columbia campuses, the lessons learned from them and subsequent recommendations made are often reported in the EH&S Safety Matters newsletter. The goal is to prevent recurrence, but unfortunately an incident that was reported in the Spring 2010 Newsletter recurred a month later.

Once again, a fire occurred in a fume hood when an oil bath was heated beyond its flashpoint. Most importantly, as in the prior incident, no one was injured; however both incidents could have been prevented if the basic principles stated in the original article were applied.

Safety Matters offers useful safety information and should be shared with all people that may benefit from it. It should be posted in visible locations (e.g. bulletin boards) and distributed to all staff.  Additionally, articles specific to your operation can also serve as useful teaching points during staff meetings, which should always include a few minutes for safety-related discussion.
For questions regarding the safe handling of oil baths, email or contact your Laboratory Safety Officer.  Previous editions of Safety Matters are archived at

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