77
Potassium chlorate(V) & chlorate(VII) and sodium chlorate(V)
Do NOT make mixtures of potassium chlorate(V) or sodium chlorate (V) with sulfur and/or phosphorus.
Potassium chlorate(V)
Potassium chlorate(VII)
Sodium chlorate(V)
Oxidising
O
Harmful
Store: Ox
H
KClO3
KClO4
NaClO3
R9: Explosive when mixed with combustible material. R20/22: Harmful by inhalation
and if swallowed. R51/53: Toxic to aquatic organisms, may cause long-term adverse
effects in the aquatic environment.
Dangerous with: AMMONIA and AMMONIUM SALTS. Unstable, explosive salts form
even when mixed dry.
METAL POWDERS, MANGANESE(VI) OXIDE, SULFIDES, THIOSULFATES,
CARBON, SUGARS, HYDROCARBONS. Unstable & dangerous mixtures are formed.
CONCENTRATED SULFURIC(VI) ACID and PHOSPHORIC(V) ACID. Explosive
chlorine oxides or chloric acids are produced.
COMBUSTIBLE MATERIALS: SUGAR, WOOD, CLOTHES etc, impregnated with
solutions, ignite easily and burn very vigorously when dry. These reactions may be
carried using special risk assessments (eg, the howling jelly-baby demonstration).
Emergencies: see standard procedures on Hazcard E, BUT ALSO:
If spilt in the laboratory: It is essential to ensure that no significant impregnation of
wood, cloth or other combustible matter occurs. Never use fabric gloves to handle
these substances.
Disposal: W1, Wspec
-3
Wspec:
Dilute to, or prepare, a 0.1 mol dm solution. Add about 10 g of sodium or
3
potassium metabisulfite to 100 cm of this solution. Leave for 1 hour in a
fume cupboard. Pour the solution down a foul-water drain.
Potassium perchlorate
Potassium chlorate(V) and sodium chlorate(V) should not be available in the laboratory at the same time as concentrated
sulfuric(VI) acid. Do not confuse sodium chlorate(V) (NaClO3), a commercial weed killer, usually found as a solid, with sodium
chlorate(I) (NaClO), a disinfectant, which is only found as a solution. Where chlorates are required by a scheme of work,
potassium chlorate(V) usually satisfies the requirements and there is little need to keep sodium chlorate(V).
For emergencies, see Hazcard E as well as more detailed information which may be on this Hazcard.
© CLEAPSS 2009
77
Potassium chlorate(V) & chlorate(VII) and sodium chlorate(V) Model risk assessments
Activity
Solubility
investigations
using
potassium
chlorate(V)
User
Y9
Control measures
Wear eye protection.
Take care not to allow the
solution to impregnate wood
or clothing.
Redox
reactions
Action of heat
Y12
Wear eye protection.
Y12
Wear goggles.
Do not add manganese(IV)
oxide to catalyse the
reaction.
Catalysis of
the decomposition of
potassium
chlorate(V)
TT
Wear goggles or a face
shield.
Preparation of
oxygen using
chlorates
Howling
jelly-baby
demonstration
TT
There are better ways of
producing oxygen. Do not
use this method.
Wear goggles or a face
shield.
Use safety screens.
TT
Experimental points
3
The solubility changes from 7.1 g to 57 g per 100 cm of water
in the temperature range 20 to 100 °C, making this an ideal
chemical to investigate solubility changes with temperature.
Collect all solutions at the end for disposal. Some courses suggest this activity for younger pupils and, with well-motivated
pupils, this may be possible. Aluminium potassium sulfate(VI)
and sodium tetraborate (anhydrous) are safer alternatives.
-3
Work on a test-tube scale. Use 0.1 mol dm solutions to oxidise
iron(II) or iodide ions.
Use 1-2 g in a dry, borosilicate test tube. Place a mineral-wool
plug in the neck of the test tube; this stops the student allowing
the glowing splint to touch the molten salt.
Under careful conditions, potassium chlorate(VII) can be made
and isolated. These crystals should not be stored but immediately disposed of after isolation and weighing.
‘Oxygen mixture’, ie, potassium chlorate(V) and manganese(IV)
oxide, should not be stored nor used for the preparation of
oxygen (see below). A mixture can be made to demonstrate the
catalytic activity of oxides using about 0.3 g of potassium
chlorate(V) and a pinch of manganese(IV) oxide or copper(II)
oxide in an ignition tube. Zinc oxide or magnesium oxide could
be used to show that they have no effect.
Numerous accidents have been reported with the traditional
method of heating potassium chlorate(V) with manganese(IV)
oxide. See Hazcard 69 for the preparation of oxygen.
The supplementary risk assessment for this demonstration is
available on the CLEAPSS members-only web site and Science
Publications CD-ROM.
For emergencies, see Hazcard E as well as more detailed information which may be on this Hazcard.
© CLEAPSS 2007