4-Hydroxy-3-nitrobenzenearsonic acid is an organic compound that is widely used agriculturally as a chicken-feed additive. The molecule is a derivative of phenylarsonic acid (C6H5As(O)(OH)2). This organoarsenic compound, usually under the tradename Roxarsone, has attracted attention as a source of arsenic contamination of the food chain. Approximately 1 million kilograms of this compound were produced in 2006 in the US. This compound was first reported in a 1923 British patent which describes the nitration and diazotization of arsanilic acid. When blended with calcite powder, it is widely used to make feed premixes in the poultry industry and is usually available in 5%, 20% and 50% concentrations.
In June 2011, Pfizer voluntarily discontinued selling this product; the FDA's findings indicated elevated (but 'very low') levels of arsenic in the livers of chickens consuming the arsonic acid.