Acopper-arsenic unknown solution, when treated with an
excessof (nh4)2s, yielded a dark brown precipitate, a, and a pale
yellowsolution, b. precipitate a, when treated with a mixture of
hno3 andhcl, dissolved to give a clear, colorless solution and a
residue ofsulfur. the colorless solution was first boiled with 6m
hcl untilalll hno3 was destroyed; it was then treated with an
excess of(nh4)2s. a yellow pale precipitate and a pale yellow
solutionformed; this yellow solution gave a yellow precipitate when
treatedwith 2m hcl.
the pale yellow solution, b, when treated dropwise with
12mhcl, formed a precipitate; this precipitate dissolved completely
inexcess 12m hcl to form a solution, c. when a piece of tin
wasplaced in solution c, the only sign of reaction was the
evolutionof hydrogen gas bubbles on the surface of the tin.
indicate which of the two cu-as group ions are present.