This Standard Reference Material is intended for use as a primary calibration standard for the quantitative determination of the arsenic species arsenous acid (AsIII). This product can be used for quality assurance when assigning values to in-house control meaterials. A unit of NIST3037 consists of two 10mL sealed borosilicate glass ampoules of an acidified aqueous solution prepared gravimetrically to contain to contain a known mass fraction of arsenous acid.