INCIDENT ALERT
29 NOVEMBER, 2016
Incident Details
Sodium Amide Fire
A fire recently occurred in a laboratory sink after a researcher began cleaning glassware still containing unreacted
sodium amide (NaNH2). Water reacted with the remaining sodium amide causing a small fire in the bottom of the
sink that quickly spread and ignited a bottle of petroleum spirit left on the edge of the sink. The sodium amide
burned out quickly however the petroleum spirit fire had to be extinguished with a dry chemical fire extinguisher.
Contributing Factors
The small quantity of NaNH2 in the glassware had been left
overnight in the fume cupboard, but no actual process had
been undertaken to react the remaining NaNH2 in a controlled
manner (quenching), prior to washing with water.
Laboratory worker’s training with respect to hazards of water
reactive chemicals and the correct procedure for quenching
them appeared incomplete.
The sink was cluttered with a number of other chemical
containers and various glassware at the time of the incident
which contributed to the size of the fire and subsequent need for a fire extinguisher to be discharged.
Hazards of sodium amide
Fresh NaNH2 behaves like sodium and reacts violently with water to produce ammonia and sodium hydroxide and
will burn in air to give oxides of sodium and nitrogen. In the presence of limited quantities of air and moisture, such
as in a poorly closed container, explosive mixtures of peroxides may form. The formation of peroxides is
accompanied by a yellowing or browning of the solid. Residues of these colours should be considered an explosion
risk. It is essential that glassware used for reactions involving NaNH2 be appropriately quenched to avoid the
possibility of water or air reactions as well as the formation of peroxides.
Guidelines for Quenching Inorganic Hydrides
The principle of quenching is to treat the NaNH2 (either in an organic solvent or as a solid residue on glassware) with
a solvent that has less free hydroxide availability than water, thereby slowing the formation of the conjugate acid
and base products. This reagent can be quenched via slow and cautious addition of isopropanol or ethanol to the
sodium amide with stirring to avoid excessive heating of the mixture. This reaction is less exothermic than the
reaction with water. Alternatively, the reaction can be quenched by addition of small portions of sodium amide to
an excess of solid ammonium chloride.
Quenching Reactions:

NaNH2 + CH3(CH2)xOH  NH3 + CH3(CH2)xONa

NaNH2 + NH4Cl  NaCl + 2NH3
If excessive heating occurs during the treatment steps the mixture should be allowed to cool before the slow
addition of further alcohol. Perform the step reaction in a fume cupboard using an open reaction vessel only, as
enclosed or partially enclosed glassware may explode due to the formation of gaseous ammonia and heat. The
application of the above-mentioned treatment regime will vary depending on the quantity and form of the NaNH2
present and should be selected by risk assessment.
Recommendations

Laboratories using NaNH2 and other inorganic hydrides should review their handling procedures and ensure
workers are suitably trained to work safely with pyrophoric materials.

Sand or an appropriate extinguishing material should be kept close at hand when working with pyrophoric
chemicals to quickly extinguish small fires.

Work areas should be inspected immediately prior to use to ensure they’re free from clutter and
contamination.

An approved risk assessment should be in place prior to starting work with any hazardous chemicals and
consider both the physiochemical properties and health risks associated with use.

Housekeeping should be regularly reviewed in all laboratories and the build-up of chemical containers,
either empty or full, avoided on open benches and work spaces.
Contact for Additional Information
For further information, contact your local Work Health and Safety Manager/Coordinator, or the UQ OHS Division:
Phone:
+61 7 336-52365
Email:
[email protected]