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In the decomposition of potassium chlorate by heat, potassium perchlorate, KClO4, is formed: 4.KClO3 = 3KClO4 + KCl. This may also be prepared by fusing potassium chlorate with barium peroxide, extracting with hot water, and crystallising:
KClO3 + BaO2 = KClO4 + BaO.
The salt was discovered by Stadion in 1815. The orthorhombic crystalline form of the perchlorate
 | Fig: Crystal of potassium perchlorate |
differs from the form of the chlorate.
Potassium perchlorate gives the following reactions:
- It decomposes at a higher temperature than the chlorate:
KClO4 = KCl + 2O2. - It does not bleach indigo in presence of sulphites.
- With concentrated sulphuric acid it does not give a yellow ex plosive gas, but dense white fumes of perchloric acid, HClO4.
- It is not acted upon by hydrochloric acid.
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