Potassium chlorate from sodium chloride by electrolysis

Obtaining potassium chlorate from sodium chloride using electrolysis

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Potassium Chlorate Electrolysis

by ytmachx

Making KClO3 by Electrolysis

by mermaidkiller

Safety

Wear lab goggles and gloves. This experiment must be performed in a well-ventilated room or in a fume hood.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

NaCl + 3H2O →[DC]→ NaClO3 + 3H2

NaClO3 + KCl → KClO3 + NaCl

Step-by-step instruction

  1. Prepare a saturated solution of sodium chloride and a small amount of potassium dichromate in it (about 1.25 - 1.5 g per liter of solution).
  2. Fill an electrolysis cell with this solution. The anode in the cell should be made from an inert material (carbon, platinum, mixed metal oxides). The cathode may be made from a conductive material.
  3. Connect the electrolysis cell to a DC power supply (about 5V) and start the electrolysis process. The electrolysis process may take a few days.
  4. After this filter the solution to get rid of pieces of the carbon electrode.
  5. Heat the filtered solution to boiling.
  6. Prepare a saturated solution of potassium chloride and add it to the electrolyzed solution (about 250 ml of the former solution per 2 l of the latter one).
  7. Cool down the obtained solution. The crystals of potassium chlorate precipitate.
  8. Recrystallize potassium chlorate twice using common and distilled water.
  9. Dry obtained potassium chlorate.

Scientific background

During the electrolysis process oxidation reaction of Cl- ions takes place on the anode:

2 Cl- → Cl2 + 2 e-.

Reduction reaction of water takes place on the cathode:

2H2O +2 e- → 2 OH- + H2.

So, chlorine and hydroxide ions are presented together in the solution. They react forming hypochlorite ions

2 OH- + Cl2 → 2 ClO- + H2.

When the obtained solution heats up, hypochlorite turns to chloride and chlorate

3 ClO- → ClO-3 + Cl2.

Produced chlorine reacts with OH- ions again.

When the saturated solution of potassium chloride is added to the solution containing chlorate ions, potassium chlorate is formed. Because the solubility of potassium chlorate is relatively low in comparison with another salts presented in the solution, it is possible to purify potassium chlorate by recrystallization.

Danger:
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Published on 22 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst