Overview

Potassium arsenite is an inorganic salt commonly written with the empirical formula KAsO2. It contains potassium cations and arsenite anions derived from arsenous acid. As an arsenic(III) compound, it belongs to a class of chemicals noted for their toxicity and reactivity in biological systems.

Chemical characteristics

In solution, the arsenite component exists in reduced (As(III)) forms that are chemically distinct from arsenate (As(V)). Arsenite species are typically more soluble and more bioavailable under reducing conditions. They also tend to bind strongly to sulfhydryl groups in proteins, disrupting enzyme function.

History and uses

Compounds identified as potassium arsenite were used historically in small doses for medicinal preparations such as Fowler's solution and in certain traditional remedies. Industrially, arsenite salts have seen use in pesticides, wood preservation and other applications where arsenic's biocidal properties were valued. Most such uses have been curtailed or banned because of long-term health and environmental risks.

Health, environment, and regulation

Exposure to arsenite compounds is hazardous. Acute poisoning produces gastrointestinal distress and circulatory collapse, while chronic exposure elevates risks of skin lesions and cancers. Inorganic arsenic compounds, including arsenites, are classified as carcinogenic by major health agencies, and their manufacture, sale, and disposal are now tightly regulated in many jurisdictions.

Handling and distinctions

Laboratory and industrial handling of potassium arsenite requires appropriate personal protective equipment, fumehoods, and waste controls. It should be distinguished from arsenates (higher oxidation state) and from organic arsenic compounds (which have different toxicity profiles). For basic chemical information see potassium and for the arsenic oxyanion details see arsenite. Further reading and safety guidance are available from regulatory and public-health sources (references).

  • Key hazard: high acute and chronic toxicity.
  • Notable fact: more mobile and toxic in its reduced As(III) form than many As(V) species.
  • Current status: largely phased out for medicinal and many commercial uses.