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 arsenicum of the ancients. The element and its compounds are
   active poisons. Specific gravity from 5.7 to 5.9. Atomic weight 75.
   Symbol As.