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chlorate (klōrˈāt, klôrˈ–) and perchlorate (pərklōrˈāt, –klôrˈ–), salts of chloric acid, HClO3, and perchloric acid, HClO4, respectively.

Chloric Acid and Its Salts

Chloric acid, HClO3·7H2O, is a colorless substance that occurs only in solution. It is a strong acid and a strong oxidizing agent that decomposes if heated above 40℃. Under certain conditions it forms oxygen, water, and the explosive gas chlorine dioxide, ClO2; under other conditions it forms perchloric acid and hydrochloric acid.

Formation of Chlorates

A chlorate may be formed (together with the corresponding chloride) by heating the hypochlorite; e.g., 3Ca(ClO)2→Ca(ClO3)2+2CaCl2. This reaction takes place when chlorine gas is passed into a hot aqueous solution of a metal hydroxide; the hypochlorite is formed and decomposes almost immediately. Commercially, a chlorate is derived when a hot aqueous metal chloride solution is decomposed by electrolysis, forming chlorine gas at the anode and metal hydroxide at the cathode (with evolution of hydrogen); the chlorine reacts with the hydroxide to form the hypochlorite, which decomposes to form the chlorate.

Commercial Uses of Chlorates

The most industrially important chlorate is potassium chlorate, or chlorate of potash, KClO3; sodium chlorate, or chlorate of soda, NaClO3, is also used. Potassium chlorate is a colorless crystalline substance that melts at 356℃ and decomposes violently at about 400℃. It is a powerful oxidizing agent and is used in making explosives and matches; a mixture of potassium chlorate with phosphorus, sulfur, or any of numerous organic compounds (e.g., charcoal or sugar) explodes upon friction or percussion. When a chlorate is heated, oxygen is evolved, often explosively, and the chloride is formed; e.g., 2KClO3→2KCl+3O2. The reaction proceeds controllably at lower temperatures if a catalyst, e.g., manganese dioxide, is used; this provides a convenient source of oxygen. If the chlorate is heated carefully at a lower temperature so that no oxygen is given off, the perchlorate and chloride are formed; e.g., 4KClO3→3KClO4+KCl.

Perchloric Acid and Its Salts

Perchloric acid, HClO4, is a volatile, unstable, colorless liquid that is a strong, corrosive acid and a powerful oxidizing agent, especially when hot. It explodes if heated to about 90℃ or on contact with combustible materials. The monohydrate, HClO4·H2O, is fairly stable and forms needlelike crystals that melt at 50℃. It explodes if heated to 110℃. The dihydrate, HClO4·2H2O, is a stable liquid that boils at 200℃.

Formation of Perchlorates

Perchloric anhydride, or chlorine heptoxide, Cl2O7, is a colorless, oily liquid that boils at 82℃ without exploding but that may be detonated by shock; it can be prepared by adding phosphorus pentoxide to cold perchloric acid. The perchlorate free radical (chlorine tetroxide, ClO4) can be prepared by adding bromine to silver perchlorate; it is extremely reactive and unstable.

Commercial Uses of Perchlorates

Perchlorates are safer to handle than chlorates; they are more stable when exposed to heat or shock. Potassium perchlorate, KClO4, is perhaps most widely used, e.g., in matches, fireworks, and explosives. It is a colorless crystalline substance that melts at about 610℃.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



any salt of perchloric acid (HClO4). A perchlorate is colorless if its cation is colorless. Perchlorates dissolve freely in water, except potassium perchlorate (KCIO4), whose slight solubility is only 1.3 g per 100 g H2 O at 25°C. They are stable when heated to temperatures between 300° and 600°C; at higher temperatures they decompose and release oxygen, as in the reaction KCIO4 = KCl + 2O2. Among the methods for obtaining perchlorates are heating of chlorates and electrolysis of chlorate solutions. Perchlorates are used to make safety explosives; for example, KCIO4 is a stronger oxidizing agent than potassium chlorate (KCIO3) and is suitable for storage, since it does not explode upon friction or impact.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(inorganic chemistry)
A salt of perchloric acid containing the ClO4- radical; for example, potassium perchlorate, KClO4.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
In order to see the effects of salt variation on the electrical and mechanical properties of the structural supercapacitor, three salts (lithium perchlorate, potassium perchlorate, and zinc chloride) were used.
While this suggests heating of perchlorate destroyed organic compounds and formed this molecule, there is no sure way to confirm this idea.
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"The Food and Drug Administration apparently didn't realize at the time how much perchlorate food can pick up as it rubs against the plastic," says Maffini.
Linear mixed-effects models (Proc Mixed in SAS) were used to evaluate associations of one time-point perchlorate, thiocyanate, and nitrate measures with repeated outcome anthropometric measurements (height, waist circumference, weight, and BMI) measured during 3-13 visits.
The case example of perchlorate, a rocket fuel component, attests to the pervasiveness of military chemical waste.
The statement also noted that iodine deficiency "increases vulnerability to the effects of certain environmental pollutants, such as nitrate, thiocyanate, and perchlorate."
EAST BROOKFIELD -- Town officials are breathing a sigh of relief after the latest test of the town's water supply revealed a significantly reduced level of the contaminant perchlorate, making it almost undetectable.
Environmental Protection Agency is developing standards for perchlorate in drinking water.
In particular, Part I looks at: (1) the challenges of regulating lead, a contaminant that is governed by the Safe Drinking Water Act (SDWA); (2) the health effects of perchlorate, a contaminant not currently regulated by the SDWA; and (3) the particular problems that simultaneous exposure to multiple contaminants can pose, when it is not clear which contaminants are causing what harm.