SODIUM CHLORATE

Sodium chlorate is highly soluble in water and acts as a strong oxidizing agent due to the presence of chlorine in a high oxidation state.
Sodium chlorate is produced industrially by the electrolysis of sodium chloride solutions, where chlorate ions are formed under controlled conditions.
Sodium chlorate exhibits good thermal stability on its own but can decompose at elevated temperatures, releasing oxygen and potentially accelerating combustion.

CAS Number: 7775-09-9

Synonyms: SODIUM CHLORATE, Chloric acid, sodium salt, Chloric acid, sodium salt (1:1), sodium;chlorate, Sodium chlorate (NaClO3), Sodium chlorate [ISO], Sodium chlorate [UN1495] [Oxidizer], NACLO3, ClNaO3, Chlorate salt of sodium, Soda chlorate, Weed Killer, United Chemical Defoliant No. 1, Ortho-C-1-Defoliant, Ortho C-1 defoliant & weed killer, Grain sorghum harvest-aid, Harvest-aid, Defol, De-Fol-Ate, Drexel defol, VAL-DROP, Drop-Leaf, Drop-Leaf, Dropleaf, Tumbleaf, Tumbleleaf, Shed-A-leaf, Shed-A-Leaf L, Leafex 2, Leafex 3, Leafex 2, Leafex 3, Asex, Atlacide, Agrosan, Desolet, Oxycil, Sodakem, Travex, Evau-super, Kusa-tohru, Kusatol, Kusa-tohru, Kusatol, Rasikal, Dervan, Fall, Granex O, B-Herbatox, Hibar C, Chlorax, Chlorate de sodium, Chlorate de sodium [ISO-French], Sodium(chlorate de) [French], Sodium (chlorate de) [French], Sodium(chlorate de), Sodium (chlorate de), Sodio (clorato di), Sodio (clorato di) [Italian], Natriumchlorat, Natriumchlorat [German], Natrium chlorat, Natrium chlorat [German], Chlorsaure, Chlorsaure [German], Natriumchloraat, Natriumchloraat [Dutch], Natrium chloraat, Natrium chloraat [Dutch], UN1495, UN2428, UNII-T95DR77GMR, T95DR77GMR, DTXSID7026025, DTXCID206025, CHEBI:65242, RefChem:6233, EINECS 231-887-4, EC 231-887-4, MFCD00003479, CCRIS 9185, HSDB 732, SODIUM CHLORATE [II], SODIUM CHLORATE [MI], SODIUM CHLORATE [HSDB], SODIUM CHLORATE [MART.], SODIUM CHLORATE [WHO-DD], CHEMBL1559268, HAA77509, NSC41881, NSC-41881, Tox21_202133, AKOS015843818, NCGC00091465-01, NCGC00259682-01, NS00075693, CAS-7775-09-9, 7775-09-9, 9011-70-5, EPA Pesticide Chemical Code 073301, Sodium chlorate, ACS reagent, >=99.0%, Sodium chlorate, ReagentPlus(R), >=99%, Sodium chlorate, p.a., ACS reagent, 99%, Sodium chlorate, SAJ first grade, >=98.0%, Sodium chlorate, puriss. p.a., >=99.0% (T), Sodium chlorate - metastable high temperature (255C) phase III, Caswell No. 753, 231-887-4, Q407446, C18765

Sodium chlorate is an inorganic compound with the chemical formula NaClO3. 
Sodium chlorate is a white crystalline powder that is readily soluble in water. 
Sodium chlorate is hygroscopic. 

Sodium chlorate decomposes above 300 °C to release oxygen and leaves sodium chloride. 
Several hundred million tons are produced annually, mainly for applications in bleaching pulp to produce high brightness paper.
Sodium chlorate is an inorganic salt composed of sodium cations and chlorate anions, and it appears as a white, crystalline, and odorless solid under normal conditions.

Because of this behavior, sodium chlorate must be handled with care in both industrial and laboratory environments.
Sodium chlorate has historically been used as a defoliant and non-selective herbicide because it disrupts plant metabolic processes.
This oxidizing nature makes it chemically reactive, especially when in contact with organic materials or reducing agents.

Sodium chlorate interferes with photosynthesis and water regulation in plants, leading to rapid drying and leaf drop.
These properties led to its widespread agricultural and industrial use before concerns about safety and environmental impact reduced its application in many regions.
In addition to agricultural uses, sodium chlorate has been employed as a source of oxygen in chemical oxygen generators and emergency breathing devices.

Upon controlled thermal decomposition, it releases oxygen in a predictable manner.
This characteristic has made it useful in specialized safety and industrial systems.
From a chemical standpoint, sodium chlorate readily participates in redox reactions and can strongly enhance combustion of flammable substances.

It can react violently when mixed with fuels, sulfur, phosphorus, or finely divided organic matter.
This reactivity defines both its industrial value and its potential hazard.
In environmental and biological contexts, sodium chlorate is highly mobile in water due to its solubility and limited adsorption to soils.

If released, it can migrate into groundwater and surface water systems.
For this reason, its use and disposal are strictly regulated in many countries to limit environmental contamination and health risks.
Industrially, sodium chlorate is produced by the electrolysis of concentrated sodium chloride solutions. 

The sodium chlorate process is not to be confused with the chloralkali process, which is an industrial process for the electrolytic production of sodium hydroxide and chlorine gas.
Sodium chlorate has a well-defined ionic crystal structure that contributes to its high solubility and stability under dry storage conditions.
In aqueous solution, it dissociates completely into sodium and chlorate ions, which makes it highly conductive and chemically accessible.

This behavior is important for its industrial production and downstream chemical applications.
As a strong oxidizer, sodium chlorate readily supplies oxygen to chemical reactions without requiring atmospheric oxygen.
This property can significantly accelerate combustion and oxidation processes.

Because of this, it is incompatible with many combustible, organic, or sulfur-containing substances.
In industrial chemistry, sodium chlorate has been used as a precursor for the production of chlorine dioxide, which is an important bleaching agent.
This application has been especially relevant in pulp and paper processing.

Its ability to generate reactive chlorine-oxygen species under controlled conditions underpins this use.
Sodium chlorate does not occur naturally in significant amounts and is almost entirely of synthetic origin.
Its large-scale manufacture relies on carefully controlled electrochemical processes to ensure purity and safety.

Impurities or improper conditions can increase the risk of unwanted side reactions.
From a toxicological perspective, sodium chlorate can interfere with red blood cell function if ingested in sufficient quantities.
It can induce oxidative stress in biological systems due to its strong oxidizing capability.

These effects contribute to the strict handling and exposure limits associated with the substance.
In environmental systems, sodium chlorate is persistent because it does not readily degrade through biological or chemical pathways.
Its mobility in water allows it to spread beyond the point of release.

This persistence has led to increased regulatory attention and restrictions on its use in open environments.
The overall reaction can be simplified to the equation: NaCl + 3 H2O → NaClO3 + 3 H2
First, chloride is oxidised to form intermediate hypochlorite, ClO−, which undergoes further oxidation to chlorate along two competing reaction paths: Anodic chlorate formation at the boundary layer between the electrolyte and the anode, and Autoxidation of hypochlorite in the bulk electrolyte.

Under electrolysis hydrogen and sodium hydroxide are formed at the cathode and chloride ions are discharged at the anode (mixed metal oxide electrode is often used). 
The evolved chlorine does not escape as a gas but undergoes hydrolysis: Cl2 + H2O ⇋ HClO + H+ + Cl−
The hydrolysis of chlorine is considered to be fast. 

The formation of H+ ions should make the boundary layer at the anode strongly acidic and this is observed at low chloride concentrations. 
However, large concentrations of chloride, as they occur in industrial chlorate cells, shift the hydrolysis equilibrium to the left. 
At the boundary layer the concentration of H+ is not high enough to permit diffusion into the bulk electrolyte. 

Therefore hydrogen is transported away from the anode mostly as hypochlorous acid rather than H+. 
The hypochlorous acid dissociates in the bulk electrolyte where the pH is high and the hypochlorite ion diffuses back to the anode. 
More than two thirds of the hypochlorite is consumed by buffering before reaching the anode. 

The remainder is discharged at the anode to form chlorate and oxygen: 3 ClO− + 1.5 H2O → ClO3− + 3 H+ + 2 Cl− + 0.75 O2
The autoxidation of hypochlorous acid in the bulk electrolyte proceeds according to the simplified overall equation: 3 HClO → ClO3− + 2 Cl− + 3 H+
It is preceded by the dissociation of a part of the hypochlorous acid involved: HClO → ClO− + H+

The reaction requires a certain distance from the anode to occur to a significant degree, where the electrolyte is sufficiently buffered by the hydroxyl formed at the cathode. 
The hypochlorite then reacts with the rest of the acid: 2 HClO + ClO− → ClO3− + 2 Cl− + 2 H+
In addition to anode distance the autoxidation also depends on temperature and pH. 

A typical cell operates at temperatures between 80 °C and 90 °C and at a pH of 6.1–6.4.
Independent of the reaction route the discharge of 6 mol of chloride is required to yield 1 mol of chlorate. 
However, the anodic oxidation route requires 50% additional electric energy. 

Therefore, industrial cells are optimised to favour autoxidation. 
Chlorate formation at the anode is treated as a loss reaction and is minimised by design.
Other loss reactions also decrease the current efficiency and must be suppressed in industrial systems. 

The main loss occurs by the back reduction of hypochlorite at the cathode. 
The reaction is suppressed by the addition of a small amount of dichromate (1–5 g/L) to the electrolyte. 
A porous film of chromium hydroxide is formed by cathodic deposition. 

The film impedes the diffusion of anions to the cathode, whereas the access of cations and their reduction is facilitated. 
The film stops growing on its own after it reaches a certain thickness.
Chemical oxygen generators, such as those in commercial aircraft, provide emergency oxygen to passengers to protect them from drops in cabin pressure. 

Oxygen is generated by high-temperature decomposition of sodium chlorate: 2 NaClO3 → 2 NaCl + 3 O2
Heat required to initiate this reaction is generated by oxidation of a small amount of iron powder mixed with the sodium chlorate, and the reaction consumes less oxygen than is produced. 
Barium peroxide (BaO2) is used to absorb the chlorine that is a minor product in the decomposition.

An ignitor charge is activated by pulling on the emergency mask. 
Similarly, the Solidox welding system used pellets of sodium chlorate mixed with combustible fibers to generate oxygen.
Sodium chlorate can be mixed with sucrose sugar to make a highly energetic fuel, similar to that of gunpowder, that burns in airtight spaces. 

This is the reaction: 8 NaClO3 + C12H22O11 → 8 NaCl + 12 CO2 + 11 H2O
However this sodium chlorate is mostly replaced by potassium chlorate.
Sodium chlorate can be used with hydrochloric acid (or also sulfuric acid and sodium chloride, the reaction of which generates HCl) to chlorinate aromatic compounds without the use of organic solvents. 

In this case its function is to oxidize the HCl to obtain either HOCl or Cl2 (depending upon the pH) in-situ which are the active chlorinating agents.
When combined with a vanadium pentoxide catalyst, it serves as an oxidant for a variety of organic compounds. 
Examples include the oxidation of hydroquinone to quinone, and of furfural to a mixture of maleic and fumaric acid.

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. 
Sodium chlorate 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 weed killer within the EU, until 2009 when it was withdrawn after a decision made under terms of EU Regulations. 
Its use as a 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.

Uses:
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. 
All other, less important chlorates are derived from sodium chlorate, usually by salt metathesis with the corresponding chloride. 

All perchlorate compounds are produced industrially by the oxidation of solutions of sodium chlorate by electrolysis.
Sodium chlorate is used as a non-selective herbicide. 
It is considered phytotoxic to all green plant parts. 

Sodium chlorate can also kill through root absorption.
Sodium chlorate may be used to control a variety of plants including morning glory, canada thistle, johnson grass, bamboo, ragwort, and St John's wort.
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.

The sale of sodium chlorate as a weedkiller was banned in the European Union in 2009 citing health dangers, with existing stocks to be used within the following year.
Sodium chlorate has been widely used as a non-selective herbicide and defoliant to control unwanted vegetation by causing rapid dehydration and leaf drop in plants.
It acts by disrupting plant metabolic and photosynthetic processes, leading to complete plant desiccation.

This use was common in agriculture and land management before being restricted in many regions due to safety and environmental concerns.
In industrial chemistry, sodium chlorate is an important raw material for the production of chlorine dioxide.
Chlorine dioxide derived from sodium chlorate is extensively used as a bleaching agent in the pulp and paper industry.

This application relies on the strong oxidizing properties of sodium chlorate under controlled reaction conditions.
Sodium chlorate is also used as an oxygen-releasing compound in chemical oxygen generators.
When thermally decomposed in a controlled system, it releases oxygen that can support breathing in emergency or enclosed environments.

Such systems have been used in aircraft, submarines, and industrial safety equipment.
In pyrotechnic and match manufacturing industries, sodium chlorate has been used as an oxidizing component.
Sodium chlorate enhances combustion by supplying oxygen directly to the reaction mixture.

Because of its high reactivity, its use in these applications requires strict formulation and safety controls.
Sodium chlorate has been applied in certain mining and metallurgical processes where strong oxidizing conditions are required.
Sodium chlorate can assist in oxidative treatments of ores or residues to improve processing efficiency.

These uses are typically limited to controlled industrial settings due to its hazardous nature.
In laboratory and research environments, sodium chlorate is sometimes used as a reagent in oxidation reactions and analytical chemistry.
Its predictable redox behavior makes it useful for studying oxidative mechanisms.

Such use is generally small-scale and subject to strict safety protocols.
Sodium chlorate has been used in controlled industrial environments for the chemical removal of vegetation along railways, roadsides, and industrial sites.
Its non-selective action allows it to eliminate deep-rooted and persistent plant growth.

This application requires careful handling due to the risk of fire and environmental contamination.
In the pulp and paper industry, sodium chlorate plays a critical role in on-site chlorine dioxide generation systems.
The chlorine dioxide produced is valued for its strong bleaching efficiency with reduced damage to cellulose fibers.

This improves paper brightness while maintaining mechanical strength.
Sodium chlorate has also been applied in oxygen candles and emergency oxygen supply systems designed for enclosed or low-oxygen environments.
When heated in a controlled device, it decomposes to release oxygen steadily over time.

This function is essential in safety equipment used in aviation, mining, and confined industrial spaces.
In chemical manufacturing, sodium chlorate is sometimes used as an oxidizing agent in specialty synthesis processes.
It enables oxidation reactions that require strong and consistent oxygen availability.

These applications are typically limited to well-controlled reactors due to safety considerations.
Sodium chlorate has been employed in experimental and pilot-scale processes for waste treatment and chemical remediation.

Sodium chlorates oxidizing power can assist in breaking down certain resistant organic compounds.
Such uses are carefully regulated to prevent secondary environmental impacts.

Safety Profile:
Sodium chlorate is a strong oxidizing agent and can greatly increase the risk of fire when it comes into contact with combustible or organic materials.
Mixtures with fuels, sulfur, phosphorus, finely divided metals, or organic substances may ignite or explode due to rapid oxidation.
Even small amounts can intensify combustion, making strict separation from flammable materials essential.

Direct contact with sodium chlorate may cause irritation to the skin and eyes.
Dust or splashes can lead to redness, burning sensations, or discomfort.
Protective gloves, eye protection, and appropriate clothing are necessary during handling.

Inhalation of sodium chlorate dust can irritate the respiratory tract.
Exposure may cause coughing, throat irritation, or breathing discomfort, especially in poorly ventilated areas.
Adequate ventilation and dust control measures are required in occupational settings.

Ingestion of sodium chlorate is hazardous and can lead to serious health effects.
Sodium chlorate may cause nausea, vomiting, abdominal pain, and damage to red blood cells by inducing oxidative stress.
Severe poisoning can result in kidney failure, circulatory problems, or life-threatening conditions.

From an environmental perspective, sodium chlorate is highly soluble in water and can easily contaminate soil and groundwater.
Sodium chlorate is toxic to plants and aquatic organisms at elevated concentrations.
Spills must be contained promptly, and disposal must follow strict regulatory guidelines to prevent long-term environmental damage.