I know that Arsenic is a semi-metallic poisonous element. Used in the past as rat poison, and is commonly found in insecticides and other pesticides. Element 33 Symbol As, Atomic mass 75.
It's popularly used as an assassination poison in literature and other fictitious works.
It conducts electricity, is used to harden lead. Was discovered in 1250 by Albertus Magnus. Is naturally a gray brittle flaky mineral. Appears in yellow, black and gray forms. Gray Arsenic is the most common form, it melts at 817 C, at 28 times Atmospheric pressure. It sublimes at 613 C under normal atmospheric pressure.