Reacting an oxide or sulfide of this element with potassium cyanide yields 
Reacting an oxide or sulfide of this element with potassium cyanide yields the diatomic form of this element along with potassium cyanate in the Fresenius-von Babo method.  Reacting sulfuric acid and zinc, then reacting the resulting hydrogen with an oxide of this element and heating, produces the monatomic form of this element in a method named after (*) Marsh and Berzelius.  Robert Bunsen discovered that hydrated ferric oxide acts as an antidote to poisoning from this element.  Sahachiro Hata and Paul Ehrlich discovered that a compound Ehrlich had made by reacting this element with phenol was an effective treatment for syphilis.  For 10 points, name this major component of Salvarsan, a toxic metalloid with atomic number 33 that is often paired in semiconductors with gallium.
Reacting an oxide or sulfide of this element with potassium cyanide yields the diatomic form of this element along with potassium cyanate in the Fresenius-von Babo method.  
{arsenic} or {As} (1) [DW]