Sodium chlorate is an inorganic chemical compound. It presents as a white to pale yellow crystalline solid that is odorless and highly soluble in water. It is classified primarily as a strong oxidizing agent, a characteristic that defines its various industrial and agricultural applications, as well as its inherent hazards.
Fundamental Chemical Properties
The core chemical nature of sodium chlorate stems from its high oxidizing potential. The chlorate ion readily accepts electrons from other substances, making it a reactive compound that can accelerate combustion and initiate fires. This powerful capability means the chemical is stable when pure but becomes highly dangerous upon contact with organic materials.
The compound is highly soluble in water, dissolving easily to form a clear, colorless liquid, which is why it is often used in liquid formulations. In its solid form, sodium chlorate is stable under normal storage temperatures, but it begins to decompose when heated above approximately \(250^\circ\text{C}\). This thermal decomposition releases a large volume of oxygen gas, simultaneously leaving behind sodium chloride. The oxygen release is particularly hazardous, as it can cause combustible materials to burn with explosive speed and intensity.
Primary Commercial and Industrial Applications
The largest industrial use of sodium chlorate is tied to the pulp and paper sector. It serves as the primary precursor for generating chlorine dioxide, which is then used in bleaching processes. This process effectively removes lignin from wood pulp to create high-brightness paper products.
The chemical’s strong oxidizing properties are also leveraged in the synthesis of other important chemicals. It serves as an intermediate in the production of other chlorate salts, such as potassium chlorate, and all perchlorate compounds. A specialized application involves its use in chemical oxygen generators, sometimes called “oxygen candles,” found in emergency oxygen systems on commercial aircraft and submarines. In these generators, the controlled thermal decomposition of sodium chlorate releases oxygen for breathing purposes.
Role in Agriculture and Environmental Persistence
Historically, sodium chlorate gained widespread attention as a non-selective, contact herbicide and defoliant. It is poisonous to virtually all green plant tissue and can be absorbed through both leaves and roots. Once inside the plant, the chlorate ion acts as a strong oxidant, disrupting metabolic pathways like photosynthesis, which leads to cell death.
The compound is also used as a desiccant, or drying agent, to prepare crops like cotton and soybeans for harvest. Its persistence in the environment is generally short-lived, particularly in moist soils high in organic matter. Soil microorganisms efficiently break down the chlorate ion, reducing it to the naturally occurring chloride ion. However, under dry conditions or in certain soil types, the compound may persist for several months, retaining its herbicidal activity.
Health Hazards and Toxicology
Ingestion represents the most serious route of exposure to sodium chlorate, as doses of only a few grams can be fatal in adults. The primary toxic mechanism involves the compound’s potent oxidative capacity, specifically targeting red blood cells and the kidneys. Sodium chlorate rapidly oxidizes the iron in hemoglobin, converting it into methemoglobin, a condition known as methemoglobinemia. Methemoglobin cannot effectively transport oxygen, leading to cyanosis and oxygen deprivation in tissues.
The compound also directly damages red blood cell membranes, causing massive intravascular hemolysis, or the destruction of red cells. The byproducts of this hemolysis overwhelm the body and are filtered by the kidneys. This buildup, combined with a direct toxic effect on the renal tubules, leads to acute kidney injury and potential renal failure. Symptoms of poisoning appear quickly and include severe gastrointestinal distress like nausea, vomiting, and abdominal pain, demanding immediate medical intervention.