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Potassium perchlorate in crystal form. Potassium perchlorate is prepared industrially by treating an aqueous solution of sodium perchlorate with potassium chloride.This single precipitation reaction exploits the low solubility of KClO 4, which is about 1/100 as much as the solubility of NaClO 4 (209.6 g/100 mL at 25 °C).
The stoichiometric ratio is 34.2% aluminum and 65.8% perchlorate by mass. A ratio of seven parts potassium perchlorate to three parts dark pyro aluminium is the composition used by most pyrotechnicians. For best results, the aluminium powder should be "Dark Pyro" grade, with a flake particle shape, and a particle size of fewer than 10 micrometres.
Perchlorate concentration was the highest in Chilean nitrate, ranging from 3.3 to 3.98%. [51] Perchlorate in the solid fertilizer ranged from 0.7 to 2.0 mg g −1, variation of less than a factor of 3 and it is estimated that sodium nitrate fertilizers derived from Chilean caliche contain approximately 0.5–2 mg g −1 of perchlorate anion. [74]
With further heating, potassium perchlorate decomposes to potassium chloride and oxygen: KClO 4 → KCl + 2 O 2. The safe performance of this reaction requires very pure reagents and careful temperature control. Molten potassium chlorate is an extremely powerful oxidizer and spontaneously reacts with many common materials such as sugar.
Common oxidizers used are potassium perchlorate and potassium nitrate. Common fuels used are titanium, titanium(II) hydride, zirconium, zirconium hydride, and boron. The size of the fuel particles is determined to produce hot particles with the required burning time. More exotic materials can be used, e.g. carboranes. [1]
Potassium and lithium chlorate, and sodium, potassium and lithium perchlorates can also be used in oxygen candles. In the Vika oxygen generator used on some spacecraft, lithium perchlorate is the source of oxygen. At 400 °C (750 °F), it releases 60% of its weight as oxygen: [9] LiClO 4 → LiCl + 2 O 2
It is desired that the pyrotechnic source be gasless. The standard heat source typically consist of mixtures of iron powder and potassium perchlorate in weight ratios of typically 88/12, 86/14, and 84/16. The higher the potassium perchlorate level, the higher the heat output (nominally 200, 259, and 297 calories/gram, respectively).
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