When $H_2S$ gas is passed through a hot acidic aqueous solution containing $Al^{3+}$,$Cu^{2+}$,$Pb^{2+}$ and $Ni^{2+}$,a precipitate is formed,which consists of

Which of the following can be used instead of $NH_4Cl$ in the analysis of group $III$ radicals?

What color does lead acetate give with $H_2S$?

In which of the following is $NH_{3}$ not used?

Which ion is not precipitated by both $HCl$ and $H_2S$?

$A$ solution of a metal ion,when treated with $KI$,gives a red precipitate which dissolves in excess $KI$ to give a colourless solution. Moreover,the solution of the metal ion,on treatment with a solution of cobalt$(II)$ thiocyanate,gives rise to a deep blue crystalline precipitate. The metal ion is: