Bertoletov's salt

What is potassium chlorate?

The potassium salt of chloric acid (one of the four oxygen-containing acids formed by chlorine: hypochlorous - HClO, chloride - HClO2, chloric acid - HClO3 and chloric - HClO4) is commonly called potassium chlorate, its formula is KClO3. This salt in appearance is crystals (colorless), which are slightly soluble in water (at 20 ºC in 100 cm3 of water only 7.3 g of salt dissolves), but with increasing temperature the solubility increases. Another of its well-known names is Berthollet's salt. The molecular mass of the substance is 122.55 atomic mass units, density - 2.32 g / cm3. The salt melts at 356 ° C, decomposes at about 400 ° C.

Discovery of Berthollet Salt

For the first time (in 1786) potassium chlorate was obtained by French chemist Claude Berthollet. He passed chlorine through a concentrated hot potassium hydroxide solution. The reaction equation, by which the salt was obtained, is as follows: 3Cl2 + 6KOH → 5KCl + KClO3 + 3H2O. As a result of this reaction, potassium chlorate is precipitated as a white precipitate. Since it is slightly soluble in cold water, it is easily separated from the remaining salts when the solution is cooled. Since its discovery, the Berthollet salt has been the most common and useful product of all chlorates. Currently, KClO3 is produced commercially.

Chemical properties

Berthollet salt is a strong oxidizer. When it interacts with concentrated hydrochloric acid (HCl), free chlorine is released. This process is described by the chemical reaction equation: 6HCl + KClO3 → 3Cl ↑ + KCl + 3 H2O. Like all chlorates, this substance is highly poisonous. In molten form, KClO3 vigorously supports combustion. In a mixture with readily oxidizable substances (reducing agents), such as sulfur, phosphorus, sugar and other organic substances, potassium chlorate explodes from impact or friction. Sensitivity to these effects is enhanced in the presence of ammonium salts and bromates. With careful (heating to 60 ° C) oxidation of potassium chlorate with oxalic acid, chlorine dioxide is obtained, the process proceeds according to the reaction equation: 2KClO3 + H2C2O4 → K2CO3 + CO2 + H2O + 2ClO2. Chlorine oxide is used in the bleaching and sterilization of various materials (pulp, flour, etc.), and can also be used for dephenolation of sewage from chemical plants.

The use of potassium chlorate

Of all chlorates, bertholets salt is widely used. It is used in the production of dyes, matches (make the combustible substance of the match head, the raw material is moistened potassium chlorate according to TU 6-18-24-84), fireworks, disinfectants, chlorine dioxide. Because of the high danger of compounds with potassium chlorate, they are practically not used in the manufacture of explosives for industrial and military purposes. Very rarely, potassium chlorate is used as an initiating explosive. Sometimes it is used in pyrotechnics, as a result, they receive the color-flame compositions. Previously, salt was used in medicine: weak solutions of this substance (KClO3) were used for some time as an antiseptic for external gargling of the throat. Salt in the early 20th century was used to produce oxygen in the laboratory, but because of the danger of experiments, they were discontinued.

Obtaining potassium chlorate

One of the following methods: chlorination of potassium hydroxide, as a result of the exchange reaction of chlorates with other salts, electrochemical oxidation in aqueous solutions of metal chlorides - can be obtained bertholets salt. Its production on an industrial scale is more often carried out by the reaction of disproportionation of hypochlorites (hypochlorous acid salts). Technologically, the process is different. More often it is based on the reaction between calcium chlorate and potassium chloride: Ca (ClO3) 2 + 2KCl → 2KClO3 + CaCl2. Then the formed berthole salt from the mother liquor is isolated by the crystallization method. Potassium chlorate is also produced by the modified Berthollet method in the electrolysis of potassium chloride: the chlorine formed during electrolysis reacts with potassium hydroxide, the formed potassium hypochlorite KClO then disproportionates to potassium chlorate KClO3 and the initial potassium chloride KCl.

Decomposition of potassium chlorate

At a temperature of approximately 400 ° C, the decomposition of bertholets salt occurs. As a result, oxygen and potassium perchlorate are released: 4KClO3 → KCl + 3KClO4. The next stage of decomposition proceeds at a temperature from 550 to 620 ºС: KClO4 → 2O2 ↑ + KCl. On catalysts (they can be copper oxide CuO, iron (III) oxide Fe2O3 or manganese oxide (IV) MnO2), the decomposition proceeds at a lower temperature (from 150 to 300 ° C) and in one stage: 2KClO3 → 2KCl + 3O2.

Security measures

Berthollet salt is an unstable explosive chemical that can explode with stirring, storage (for example, next to reductants on one shelf in a laboratory or in a single storage room), grinding or other operations. As a result of the explosion, there may be a personal injury or even a fatal outcome. Therefore, when obtaining, using, storing or transporting potassium chlorate, the requirements of Federal Law 116. The facilities on which these processes are organized relate to hazardous production facilities.