Perchloric Acid

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perchloric acid

[pər′klȯr·ik ′as·əd]
(inorganic chemistry)
HClO4 Strongly oxidizing, corrosive, colorless, hygroscopic liquid, boiling at 16°C (8 mmHg, or 1067 pascals); soluble in water; unstable in pure form, but stable when diluted in water; used in medicine, electrolytic baths, electropolishing, explosives, and analytical chemistry, and as a chemical intermediate. Also known as Fraude's reagent.

Perchloric Acid


HClO4 a monobasic acid in which the chlorine has an oxidation number of + 7. Anhydrous perchloric acid is a colorless mobile liquid, which fumes in the air; it has a density of 1.761 g/cm3 at 20°C, a melting point of – 102°C, and a boiling point of 110°C. Perchloric acid is one of the strongest inorganic acids; its corresponding salts are the perchlorates (seePERCHLORATE). Anhydrous perchloric acid is very reactive and unstable. With water it forms a series of hydrates HClO4 · nH2O, where n = 0.25 to 4. Aqueous solutions of perchloric acid are stable and have a low oxidizing capability. With water, perchloric acid forms an azeotropic mixture, which boils at 203°C and contains 72 percent HClO4.

Aqueous solutions of perchloric acid are produced by the electrochemical oxidation of hydrochloric acid or chlorine dissolved in strong perchloric acid or by the exchange decomposition of sodium perchlorate or potassium perchlorate by strong inorganic acids. Concentrated aqueous solutions of perchloric acid are widely used in analytical chemistry, as well as in the production of perchlorates.

Anhydrous perchloric acid is produced by the interaction of sodium perchlorate or potassium perchlorate with strong sulfuric acid or by the interaction of aqueous solutions of perchloric acid with oleum (fuming sulfuric acid). It cannot be stored for long periods or transported long distances, since it decomposes slowly under ordinary conditions, becomes colored by the chlorine oxides formed during its decomposition, and may explode spontaneously.

Perchloric acid is used in the separation of complex ores and the analysis of minerals; it is also used as a catalyst.


Rosolovskii, V. la. Khimiia bezvodnoi khlornoi kisloty. Moscow, 1966.
Iakimenko, L. M. Proizvodstvo khlora, kausticheskoi sody i neorganicheskikh khlorproduktov. Moscow, 1974.
Iakimenko, L. M., and M. I. Pasmanik. Spravochnik po proizvodstvu khlora, kausticheskoi sody i osnovnykh khlorproduktov, 2nd ed. Moscow, 1976.


References in periodicals archive ?
On the other hand, using a 4:1 v/v nitric to perchloric acid ratio, rather than 2 or 3:1 v/v, could be more advantageous due to the lower cost of nitric acid when compared to perchloric acid.
1979, "Kinetics and mechanism of oxidation of some aldoses by Vanadium (V) in perchloric acid medium" Carbohydrate Research, 72, 139-149.
Determination of total phosphorus in soils: A rapid perchloric acid digestion procedure.
On the other hand for amine-groups determinations, the titration solution, a mixture of perchloric acid with methanol, was added properly in the polyamide solutions at room temperature.
8 g, 210 mL of ethanol and 50 mL of 60% perchloric acid were dissolved in 3 L of double-distilled water.
70% perchloric acid AR/GR grade in 500ml bottle each of MERCK make
The erythrocytes were washed with cold saline by centrifuging at 2000g for 5 min, precipitated by adding 6% of cold perchloric acid (3mL), and centrifuged again at 2000g for 10 min.