Perchloric acid
Strong mineral acid and oxidizer used in rocket propellant.
Perchloric acid is a mineral acid with the formula HClO4, classified as an oxoacid of chlorine. It is a colorless compound usually found as an aqueous solution and is a stronger acid than sulfuric acid, nitric acid, and hydrochloric acid. It is a powerful oxidizer when hot, though aqueous solutions up to approximately 70% by weight at room temperature are generally safe, showing only strong acid features. Perchloric acid is useful for preparing perchlorate salts, especially ammonium perchlorate, an important rocket fuel component, but is dangerously corrosive and readily forms potentially explosive mixtures.
- chemical_formula
- HClO4
- first_synthesized
- mid-1810s
- first_synthesized_by
- Friedrich von Stadion
- classification
- mineral acid, oxoacid of chlorine
- key_property
- stronger acid than sulfuric, nitric, and hydrochloric acid
- common_use
- precursor to ammonium perchlorate for rocket propellant
Lore & Background
Perchloric acid was first synthesized by Austrian chemist Friedrich von Stadion, together with potassium perchlorate, in the mid-1810s, and was initially called 'oxygenated chloric acid.' French pharmacist Georges-Simon Serullas introduced the modern designation and discovered its solid monohydrate, which he mistook for an anhydride. Berzelius produced dilute perchloric acid by electrolysis of chloric acid, and in the late 1800s, German and Swedish workers commercialized the electrolysis process.
Reader's Guide
Perchloric acid is mainly produced as a precursor to ammonium perchlorate, which is used in rocket propellant, and the growth in rocketry has led to increased production, with several million kilograms produced annually. It is one of the most proven materials for etching liquid-crystal displays and critical electronics applications, as well as ore extraction, and has unique properties in analytical chemistry. As a superacid with a pKa lower than −9, it provides strong acidity with minimal interference because perchlorate is weakly nucleophilic. Despite hazards associated with the explosiveness of its salts, the acid is often preferred in certain syntheses and is a useful eluent in ion-exchange chromatography. In geochemistry, it aids in the digestion of silicate mineral samples and complete digestion of organic matter. Safety is a major concern due to its strong oxidizing properties; it can react violently with metals and flammable substances, and work must be conducted in fume hoods with wash-down capability.
Did You Know?
- Perchloric acid is a stronger acid than sulfuric acid, nitric acid, and hydrochloric acid.
- It forms an azeotrope with water consisting of about 72.5% perchloric acid, which is stable indefinitely.
- Anhydrous perchloric acid is an unstable oily liquid at room temperature.
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