7153. Perchloric Acid

Nomenclature

CAS number: 7601-90-3
ClHO4; mol wt 100.46.
Cl 35.29%, H 1.00%, O 63.70%.
HClO4.

Description and references

Prepd from potassium perchlorate and sulfuric acid: Schmeisser in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 318-320. Comprehensive monograph: J. C. Schumacher, Perchlorates (Reinhold, New York, 1960).

Properties

The anhydr acid is a colorless, volatile, very hygroscopic liquid. d22 1.768; bp11 19°. Oxidizer; corrosive. Dec when distilled at atmospheric pressure, sometimes with explosive violence. mp -112°. Combines vigorously with water with evolution of heat. Undergoes spontaneous and explosive decompn, hence it is marketed only in mixture with water contg 60-70% HClO4, density 1.5 and 1.6, respectively. The aq acid is very caustic and may deflagrate in contact with oxidizable substances. Density of aq solns at 15°: 1% = 1.0050; 10% = 1.0597; 20% = 1.1279; 30% = 1.2067; 40% = 1.2991; 50% = 1.4103; 60% = 1.5389; 70% = 1.6736. Density of aq solns at 25°: 65.0% = 1.597; 70.0% = 1.664; 75.0% = 1.731.

Caution

Corrosive to skin, mucous membranes.

Use

The acid in analytical chemistry as an oxidizer and for separation of potassium from sodium. Solvent for metals and ores. In nonaqueous titrimetry. In wet ashing. Its salts for explosives and for plating of metals.