What Is Thallium Sulfate?
Thallium sulfate is the sulfate salt of thallium.
It is a colorless crystalline powder with no taste or odor. It is soluble in water and ethanol and is also used in liquid form.
Thallium sulfate is classified as a deleterious substance and must be stored and used with care. It has acute and chronic toxicity, affecting the gastrointestinal tract, nervous system, respiratory organs, and kidneys when ingested orally.
It has also been shown to be toxic for reproduction, and may affect the development of testes and fetuses. Because of these toxic effects, thallium sulfate was used as a rat poison, but is no longer used.
Uses of Thallium Sulfate
Thallium sulfate was once used as a rat poison. Because it is soluble in water, it is easy to prepare poison baits, and since rats eat it without avoiding it, poison baits were prepared by adding a solution of thallium sulfate to the food preferred by rats.
Thallium sulfate is not excreted but accumulates in the body of rats, so even if an individual does not eat a lethal dose at once, it will die by continuous ingestion of the poisoned food. In addition, its reproductive toxicity suppresses the reproduction of rats and keeps the population low over the long term.
Rodenticides containing thallium sulfate were previously registered as pesticides, but the registration was revoked due to its high toxicity and low distribution volume. Since the pesticide registration of thallium sulfate expired, other ingredients such as zinc phosphide, coumarin, and difethialol have been used in rodenticides.
Characteristics of Thallium Sulfate
Thallium sulfate is the sulfate salt of thallium, with the chemical formula Tl2SO4. Thallium sulfate is a colorless crystal that is stable at room temperature, and when dissolved in water, it ionizes into thallium (univalent) and sulfate ions.
The raw material thallium is a group 13 metallic element that is recovered as a byproduct of the refining process of copper, lead, and zinc. Thallium exists mainly as a monovalent ion, but when oxidized, trivalent ions may be produced to form thallium oxide, etc.
The basic properties of thallium sulfate (molecular weight, specific gravity, and solubility) are as follows:
- Molecular weight: 504.83
- Specific gravity: 6.77
- Solubility: Soluble in water (4.87 g/100 mL at 20°C)
Other Information on Thallium Sulfate
1. Toxicity to Humans
Thallium sulfate is toxic to humans. Ingestion due to accidents or incidents in the past has been reported to cause anorexia, vomiting, abdominal pain, bloody stools, etc., followed by abnormal limb perception, hallucinations, convulsions, tachycardia, hair loss, and other symptoms. In severe cases, death occurs due to kidney and central nervous system abnormalities and heart failure.
To prevent accidental ingestion, containers containing thallium sulfate must be clearly labeled with the name of the substance. Storing thallium sulfate in containers such as those used for food or handling it while eating or drinking increases the risk of accidental ingestion or ingestion and is very dangerous.
Since experiments on rats have confirmed that the original (unformulated pure product) of thallium sulfate is also percutaneous toxic, care must also be taken to avoid skin contact. Wear protective equipment such as nitrile gloves and protective glasses, and wash thoroughly with water if it adheres to the skin. If it gets into the eyes, rinse well under running water and seek medical attention.
2. Decomposition by Heating and Oxidation
When thallium sulfate is heated, it decomposes to produce fumes such as toxic thallium and sulfur oxides. Fumes are fine particles of evaporated or sublimated substances that condense in the air. Fumes are spread over a wide area as smoke or aerosols, so there is a risk of inhalation by workers. Thallium sulfate is also toxic in fumes, so if there is a risk that thallium sulfate may be heated in experiments, etc., measures such as handling it with ventilation in a draft are necessary.
Thallium sulfate reacts violently with oxidants to form oxides. The reaction heat during oxidation may produce toxic fumes, so care should be taken to store and use thallium sulfate in such a way that it does not come into contact with oxidants.
4. Environmental Impact
Thallium sulfate is toxic to wild birds and aquatic organisms, and must be prevented from leaking into the environment. When disposing of thallium sulfate, follow the standards set by the local government or outsource disposal to a specialized contractor.