Editing Arsine (section)

===Gutzeit test===
A characteristic test for arsenic involves the reaction of AsH<sub>3</sub> with Ag<sup>+</sup>, called the Gutzeit test for arsenic.<ref name="King">King, E. J. (1959) ''Qualitative Analysis and Electrolytic Solutions'' Harcourt, Brace, and World; New York</ref> Although this test has become obsolete in [[analytical chemistry]], the underlying reactions further illustrate the affinity of AsH<sub>3</sub> for "soft" metal cations. In the Gutzeit test, AsH<sub>3</sub> is generated by reduction of aqueous arsenic compounds, typically [[arsenite]]s, with Zn in the presence of H<sub>2</sub>SO<sub>4</sub>. The evolved gaseous AsH<sub>3</sub> is then exposed to AgNO<sub>3</sub> either as powder or as a solution. With solid AgNO<sub>3</sub>, AsH<sub>3</sub> reacts to produce yellow Ag<sub>4</sub>AsNO<sub>3</sub>, whereas AsH<sub>3</sub> reacts with a solution of AgNO<sub>3</sub> to give black Ag<sub>3</sub>As.