NMSU: EH&S – Hazardous Waste Management Manual, Chpt 7 Waste Unknowns


Laboratory personnel must make every effort to provide an accurate description of all chemicals given to EH&S for handling and disposal. Unknown chemicals will be accepted by EH&S, but there will be a $50 charge for each unknown chemical turned in. Hazardous waste disposal companies will not accept unknowns without proper analysis, EH&S will complete a fingerprint analysis in attempt to identify the unknown. If further analysis is required, EH&S will notify the department. However; it is preferred that the generator (individual or department) to accurately identify all chemical unknowns in their laboratory, either by knowledge or analysis.


The process of identifying an unknown chemical can be tedious and paying for commercial analysis can be cost prohibitive. However, some activities can be done in the laboratory to help identify unknowns and also to prevent them from occurring in the first place.  The following guidelines are provided to assist with the problem of unknown chemicals:

  • Determine from other lab personnel any information that may help to identify the chemical.
  • Exercise caution in opening chemical containers without labels especially if the cap is corroded or disfigured in any way. If unsure, seek assistance.
  • Conduct simple chemical and physical tests to place the substance in some broad chemical category such as organic or inorganic. Consult with chemistry faculty or EH&S if necessary.


Like unknown chemicals, laboratory glassware containing reaction mixtures of an unknown nature and sometimes of unknown origin, can present difficult handling and disposal problems. Such materials occur frequently in research laboratories, particularly in those that have a high rate of personnel turnover.

Knowledge of the chemistry that was being conducted by the departed laboratory worker might provide a clue as to the identity of the mixture. The identification of such compounds can be achieved in primarily the same way as unknown chemicals.


EH&S offers the following suggestions to assist in reducing problems associated with unknown chemicals and orphan reaction mixtures:

  • Maintain labels on chemical containers. Replace defaced labels with new ones.
  • Institute a periodic review of chemical stock and rotate stock as new chemicals are purchased.
  • Maintain accurate records of chemicals in stock. This will help in the identification of any containers with missing labels.
  • Require all reaction mixtures stored in laboratory glassware to be labeled with the chemical composition, the date they were formed, the name of the laboratory worker responsible and a notebook reference. This procedure can provide the information necessary to facilitate the disposal of the mixture if the responsible laboratory worker is not available.
  • Use a check-out procedure that requires departing laboratory personnel to identify any remaining reaction mixtures and to provide information necessary for safe disposal. It may be necessary to require a financial deposit from incoming graduate students. This deposit would be refunded at the time of their departure once it has been determined that no orphaned mixtures have been left behind, all unknown chemicals have been identified and all waste chemicals have been properly removed from the laboratory.
  • Set a procedure that requires in-coming faculty, researchers, graduate students and others using laboratory space to check their new location prior to starting work for any orphan reaction mixtures or unknown chemicals that may be present.
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