Arsenic ( n. ) One of the elements, a solid substance resembling a metal in its physical properties, but in its chemical relations ranking with the nonmetals. It is of a steel-gray color and brilliant luster, though usually dull from tarnish. It is very brittle, and sublimes at 356! Fahrenheit. It is sometimes found native, but usually combined with silver, cobalt, nickel, iron, antimony, or sulphur. Orpiment and realgar are two of its sulphur compounds, the first of which is the true arsenic> Arsenic ( n. ) Arsenious oxide or arsenious anhydride; -- called also arsenious acid, white arsenic, and ratsbane.