Arsenic acid, with the chemical formula H3AsO4, is a chemical compound composed of arsenic (As) and oxygen (O) atoms. It is one of the oxoacids of arsenic and is a white or colorless crystalline solid that is highly soluble in water. Arsenic acid is a stronger acid compared to arsenous acid (H3AsO3).

Arsenic acid can be formed when arsenic trioxide (As2O3) reacts with water, and it can also be obtained through the reaction of other arsenic compounds with oxidizing agents.

Some key properties and uses of arsenic acid include:

1. Chemical Reagent: Arsenic acid is used as a chemical reagent in various chemical reactions and laboratory studies.
2. Glass and Ceramic Industry: It is used in the glass and ceramic industry as a fining agent and in the production of certain glass and ceramic materials.
3. Wood Preservative: Historically, arsenic acid was used as a wood preservative to protect against decay and insect infestation. However, its use in this application has been largely abandoned due to its high toxicity and environmental concerns.
4. Insecticide and Pesticide: In the past, arsenic acid and its derivatives were used as insecticides and pesticides. However, their use has been restricted or banned in many countries due to their high toxicity and environmental impact.
5. Medicinal Use: Arsenic acid and its compounds were used in traditional medicine for various purposes. However, their use in medicine has been largely discontinued due to their toxic effects and the availability of safer alternatives.

Due to its extreme toxicity, arsenic acid is considered a hazardous substance, and exposure to it should be avoided. Proper safety measures, such as good ventilation and the use of personal protective equipment, should be followed when working with arsenic acid or any arsenic-containing materials.

In modern times, arsenic acid is primarily used as a chemical reagent in laboratory studies and research. Its applications in wood preservation and insecticides have been replaced by safer alternatives due to health and environmental concerns.