| Sodium chlorate | |
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Sodium chlorate |
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Other names
Sodium chlorate(V) |
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| Identifiers | |
| CAS number | 7775-09-9 |
| PubChem | 24487 |
| ChemSpider | 22895 |
| UNII | T95DR77GMR |
| EC number | 231-887-4 |
| UN number | 1495, 2428 |
| KEGG | C18765 |
| MeSH | Sodium+chlorate |
| RTECS number | FO0525000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | NaClO3 |
| Molar mass | 106.44 g/mol |
| Appearance | white solid |
| Odor | odorless |
| Density | 2.5 g/cm3 |
| Melting point |
248 °C, 521 K, 478 °F |
| Boiling point |
~300 °C decomp. |
| Solubility in water | 101.0 g/100 mL (20 °C) |
| Refractive index (nD) | 1.572 |
| Hazards | |
| MSDS | ICSC 1117 |
| EU Index | 017-005-00-9 |
| EU classification | Oxidant (O) Harmful (Xn) Dangerous for the environment (N) |
| R-phrases | R9, R22, R51/53 |
| S-phrases | (S2), S13, S17, S46, S61 |
| NFPA 704 |
0
1
1
OX
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| Flash point | none |
| Related compounds | |
| Other anions | Sodium chloride; Sodium hypochlorite; Sodium chlorite; Sodium perchlorate; Sodium bromate; Sodium iodate |
| Other cations | Ammonium chlorate; Potassium chlorate; Barium chlorate |
| Related compounds | Chloric acid |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Sodium chlorate is a chemical compound with the chemical formula (NaClO3). 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. In September 2009, wholesale of sodium chlorate weedkiller was banned in all EU countries, but consumers were allowed to use and store the product until May 2010.
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Industrially, sodium chlorate is synthesized from the electrolysis of a hot sodium chloride solution in a mixed electrode tank:
It can also be synthesized by passing chlorine gas into a hot sodium hydroxide solution. It is then purified by crystallization.
The main commercial use for sodium chlorate is for making chlorine dioxide (ClO2). The largest application of ClO2, which accounts for about 95% of the use of chlorate, is in bleaching of pulp.
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 a variety of plants including:
The herbicide is mainly used on non-crop land for spot treatment and for total vegetation control on areas including roadsides, fenceways, and ditches.
Sodium chlorate is also used as a defoliant and desiccant for:
If used in combination with atrazine, it increases the persistence of the effect. If used in combination with 2,4-D, performance is improved. 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.
Chemical oxygen generators, such as those in commercial aircraft, provide emergency oxygen to passengers to protect them from drops in cabin pressure by catalytic decomposition of sodium chlorate. The catalyst is normally iron powder. Barium peroxide (BaO2) is used to absorb the chlorine which is a minor product in the decomposition.[1] Iron powder is mixed with sodium chlorate and ignited by a charge which is activated by pulling on the emergency mask. The reaction produces more oxygen than is required for combustion. Similarly, the Solidox welding system used pellets of sodium chlorate mixed with combustible fibers to generate oxygen.
Due to its oxidative nature, sodium chlorate can be very toxic if ingested. The oxidative effect on hemoglobin leads to methaemoglobin formation, which is followed by denaturation of the globin protein and a cross-linking of erythrocyte membrane proteins with resultant damage to the membrane enzymes. This leads to increased permeability of the membrane, and severe hemolysis. The denaturation of hemoglobin overwhelms the capacity of the G6PD metabolic pathway. In addition, this enzyme is directly denatured by chlorate reducing its activity.
Therapy with ascorbic acid and methylene blue are frequently used in the treatment of methemoglobinemia. However, since methylene blue requires the presence of NADPH that requires normal functioning of G6PD system, it is less effective than in other conditions characterized by hemoglobin oxidation.
Acute severe hemolysis results, with multi-organ failure, including DIC and renal failure. In addition there is a direct toxicity to the proximal renal tubule.[2] The treatment will consist of exchange transfusion, peritoneal dialysis or hemodialysis.[3]
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. If accidentally mixed with one of these substances it should not be stored in human dwellings.[4]
Marketed formulations contain a fire retardant, 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.
Sodium chlorate is the active ingredient 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.
Sodium chlorate was an extensively used weedkiller within the EU, up until 2009 when it was withdrawn after a decision made under terms of EU Regulations. Its use as an herbicide outside the EU remains unaffected, as does its use in other non-herbicidal applications, such as in the production of chlorine dioxide biocides and for pulp and paper bleaching
Historian James Watson of Massey University in New Zealand wrote a widely reported article, "The Significance of Mr. Richard Buckley's Exploding Trousers"[5][6] about accidents with sodium chlorate when used as an herbicide to control ragwort in the 1930s.[7] This later won him an Ig Nobel Prize in 2005,[8] and was the basis for the May 2006 "Exploding Pants" episode of MythBusters.