Abstract: A new method for the determination of traccs of arsenic is introduced. The arsenic in the sample solution was reduced to AsH₃with zinc and HCl Adisk of paper was impregnated with HAuCl₄The reaction of AsH₃with HAuCl₄give colored fleck (violet-blue), which has a fixed diameter of 8mm. The fleck is then measured with 721 spectrophotometer. Atrace amount of arsenic in water were determined, with C_min= 1×10^-8g/ml and the cofficient of variation is 4%.