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Sodium chlorate (NaClO3) is an oxidizing agent. It is mostly used to produce chlorine dioxide for bleaching paper pulp, but is also used as a herbicide and to prepare other chlorates. Production in the United States is about 441,000 tons per year.
When pure, it is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 250 °C to release oxygen and leave sodium chloride. It is synthesised from the electrolysis of hot sodium chloride solution in a mixed electrode tank. It can also be synthesised by passing chlorine gas to a hot sodium hydroxide solution. It is then purified by crystallization.
Additional recommended knowledge
Sodium chlorate can be created for laboratory use in small quantities by performing electrolysis on a solution of sodium chloride and water. The following reaction occurs:
For industrial production other methods are used.
Sodium chlorate is used as a non-selective herbicide. It is considered phytotoxic to all green plant parts. It can also kill through root absorption. Sodium chlorate may be used to control morning glory, Canada thistle, johnson grass, bamboo, ragwort and St John's wort. The herbicide is mainly used on non-crop land for spot treatment and for total vegetation control on roadsides, fenceways, ditches and suchlike. Sodium chlorate is also used as a defoliant and desiccant for cotton, safflower, corn, flax, peppers, soybeans, grain sorghum, southern peas, dry beans, rice and sunflowers. If used in combination with atrazine, it increases the persistence of the effect. If used in combination with 2,4-D, it improves performance of the material. Sodium chlorate has a soil-sterilant effect. Mixing with other herbicides in aqueous solution is possible to some extent, so long as they are not susceptible to oxidation.
Sodium chlorate is used in some aircraft as a source of supplemental oxygen. Iron powder is mixed with sodium chlorate and ignited by a charge activated by pulling on the emergency mask. The reaction produces more oxygen than is required for combustion.
Sodium chlorate comes in dust, spray and granule formulations. There is a risk of fire and explosion in dry mixtures with other substances, especially organic materials, that is other herbicides, sulfur, phosphorus, powdered metals, strong acids. Particularly when mixed with sugar it has explosive properties. The ease of availability of these two ingredients make it a common choice for home made bombs. Marketed formulations contain a fire depressant, but this has little effect if deliberately ignited. Most commercially available chlorate weedkillers contain approximately 53% sodium chlorate with the balance being a fire depressant such as sodium metaborate or ammonium phosphates.
The active ingredient sodium chlorate is found in a variety of commercial herbicides. Some trade names for products containing sodium chlorate include Atlacide, Defol, De-Fol-Ate, Drop-Leaf, Fall, Harvest-Aid, Kusatol, Leafex, and Tumbleaf. The compound may be used in combination with other herbicides such as atrazine, 2,4-D, bromacil, diuron, and sodium metaborate. In the United Kingdom there are many brands of Sodium Chlorate Weedkillers. Two well known ones are Doff and Wilkinsons. In Italy it is found under the Zapi brand, sold as "Grasskiller Liquid".
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Sodium_chlorate". A list of authors is available in Wikipedia.|