arsenic

[Formed from the substantive, but distinguished from it by being accented on the second syllable instead of the first. In Fr. arsenique, Port. arseniaco.] arsenic oxide, As2O5, called in the hydrated state arsenic acid . This compound is prepared by oxidising arsenious oxide with nitric acid, also by pa ing chlorine into aqueous arsenious acid. Arsenic oxide forms three hydrates analogous to phosphoric acid -mon hydrate (HASO3), dihydrate (H1AS207), and trihydrate (H3AsO4); the last forms salts isomorphous with the phosphates. Arsenic oxide, when strongly heated, is decomposed into arsenious oxide and oxygen, and is reduced to metallic arsenic by charcoal or cyanide of pota ium at red heat. Sulphurous anhydride, SO2, reduces As O5 to A5203. Hydrosulphuric acid, H2S, pa ed through a warım solution, acidified with hydrochloric acid, of arsenic acid or of an arsenate, gives a precipitate of As2S3+82. Arsenic oxide is used in dyeing and in preparing aniline colours. The salts of arsenic acid are called arsenates or arseniates . The salt of magnesium and ammonium is a white crystalline salt like the corresponding phosphate. Nitrate of silver gives a brick-red precipitate, and with basic acetate of lead a white precipitate, which is reduced by heating with charcoal with evolution of arsenic, recognised by the garlic-like smell.