Download Nitric Acid Fact Sheet

Caution! Nitric Acid !
A FACT SHEET ON NITRIC ACID USE.
Nitric acid is a fairly common reagent in the laboratory but it is a highly reactive reagent that
has led to serious accidents in the School.
Why is nitric acid so dangerous?
Reason 1:- When nitric acid is used to oxidise materials nitrogen oxide gases are produced
along with carbon dioxide. The sudden release of gases can cause frothing, pressurisation of
glassware and rupture. Nitric acid will oxidise virtually all organic solvents.
Case History: A researcher was washing glassware coated with small amounts of copper metal with
approx 40% nitric acid. The mixture fizzed and the after a few minutes the researcher poured the
residues into a bottle and put the stopper on. A violent reaction continued and the bottle broke
splashing the researcher with acid. Fortunately there was no permanent injury.
Reason 2:- Nitric acid can nitrate materials and create explosive compounds. Reaction of
nitric acid with alcohols can produce alkyl nitrates which can explode spontaneously. The
combination of nitric acid and methanol was considered too dangerous to use as rocket fuel!
Combinations of heavy metals (eg mercury or silver) with nitric acid and alcohols can produce
highly explosive metal fulminates. Fulminates were used in munitions as detonators.
Case History: A researcher was washing glassware coated with iron with conc nitric acid. After it had
been cleaned the residues were poured into an old methanol bottle. One hour later the bottle
exploded causing major damage to the fume hood. Fortunately there was no one in the lab.
Left: The fume cupboard
after the explosion- the sash
has completely shattered.
Right: the brown material in
the centre is all that
remained of the waste
Winchester.
What do you need to know?
1. Nitric acid is not just another acid, it is a very powerful oxidising agent and can form
explosive substances.
2. All uses of nitric acid even for simple glassware washing must be fully risk assessed and
approved by your supervisor. Both the incidents above occurred during cleaning operations.
3. If there is no alternative to the use of nitric acid then always use the most dilute solution of
possible.
4. After use immediately dilute the waste solution as much as possible. If possible, dispose of
the nitric acid residues immediately by dilution with large quantities of water. If this is not
possible (e.g. due to other contaminants) dilute the nitric acid below 10% concentration
before storage. . Any waste bottles should have the lids only loosely attached until final
disposal.
5. Further information on nitric acid is available in Brethericks's Reactive Chemical Hazards
which is kept on the bench in the downstairs library.