Bomb squads rushed to more than 40 schools in Yorkshire
Controlled explosions were carried out between October 21 and December 21, 2016 after schools were warned by the government advisory science servie CLEAPSS about old stocks of 2.4 dinitrophenylhydrazine (DNPH) in teaching labs.
The government’s science advisory service advised schools last autumn to check whether they had old supplies of the dangerous chemical.
The warning sparked an urgent number of calls to the Army over fears science labs across the country would explode.
Some schools received criticism from locals who had not been warned about the controlled blasts.
The Department for Education (DfE) said it worked with the Army to supports schools with "necessary disposals".
The chemical, also known as Brady’s reagent, is used to identify whether unknown compounds contain carbonyl compounds.
It is perfectly safe to be used in chemistry lessons where students add a few drops of aldehyde or ketone to 2.4 DNP.
In precipitate forms, students can then do melting points tests to identify the carbonyl compound.
However, it can be dangerous if stored incorrectly and therefore dries out.
The chemical is supposed to be stored in a labelled jar which is then kept inside an outer jar topped up with water as a precaution.
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