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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Figure 6 indicates the CVs of 1.0x[10.sup.-3] M caffeine in perchloric acid solution (0.1 M, pH 0.56) at a scan rate ranging between 20 and 500 mV[s.sup.-1].
The effect [Cl.sup.-], [Br.sup.-], and [I.sup.-] ions on the anodic behaviour of nickel in perchloric acid solution was examined in the concentration interval of anions from [10.sup.-5] to [10.sup.-3] M.
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Reaction mixture containing an excess of oxidant [BPSDC] over DPSO in the presence of perchloric acid were kept at room temperature for the sufficient length of time.
Phosphorus was analysed by digestion with nitric acid and perchloric acid (2:1) for a minimum of 12 h, and determined in 7.5 ml of vanadomolybdenum-phosphorus complex by photometry at 470 nm.
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[1] These authors found that sulfuric acid and perchloric acid in solution in anhydrous acetic acid were able to protonate a variety of weak bases such as ketones and other carbonyl compounds that do not form salts in aqueous solutions of the same acids.
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