•White or yellow phosphorous – (Class 4.1) will ignite in air and must be stored under water. Red phosphorous will not ignite.
• Diethyl ether – (Class 3) extremely flammable and will form organic peroxides if stored in clear glass. Must not be stored in a fridge unless it is intrinsically safe. Store with copper gauze or ferrous sulphate.
• Formic acid concentrated – (Class 8) forms Carbon monoxide in long term storage with enough pressure to blow bottle top off or cause bottle to explode. Caps should be vented or pressure released on a monthly basis.
• Nitric acid – (Class 8/5.1) strong acid and oxidiser even when diluted. It is the most common cause of industrial accidents involving oxidising agents.
• Aluminium powder – (Class 4.1) will ignite when wet or mixed with many common chemicals including sulphur.
• Zinc powder – (Class 4.1) as above.
• Ammonium nitrate – (Class 5.1) has caused many explosions and fires through being incorrectly stored or mixed with incompatible chemicals.
• Ammonium dichromate – (Class 5.1) explosive risk when dry and cold.
• Calcium hypochlorite – (Class 5.1) will emit chlorine gas if acidified and is a powerful oxidiser that will ignite oil and organic solvents.
• Hydrogen peroxide – (Class 5.1) emits oxygen as it ages and can build pressure in the container. Should have a vented cap or pressure released on a monthly basis. If stored in a fridge it must not contain flammable liquids.
• Sodium or potassium cyanide – (Class 6, Schedule 7 poison) 0.2 gram is enough to kill a healthy 75 kg adult.
• tert-Butyl Lithium – (Class 3) reacts violently with water, air, acids, halogens and amines.
• Picric acid/picrates – (Class 1 when dry) contact or friction explosive when dry. Must be stored in water.
• Carbon disulphide – (Class 3) extremely flammable, flashpoint -30 degC, has ignited when warmed on water bath.
• Sodium and potassium metal – (Class 4.3) explosive reactions with water. Store under paraffin.

The Dirty Dozen

Inappropriate mixing or handling of certain compounds can lead to volatile reactions causing fires, explosions or producing toxic gases. Certain chemicals and reactions have over time become recognised as being responsible for more than their share of accidents. In some laboratories these are known as the "Dirty Dozen", as detailed in the table below.