Nessler's reagent is

Which of the following is sparingly soluble in cold water and fairly soluble in hot water?

Which reagent can be used to identify nickel ion $(Ni^{2+})$?

An aqueous solution of an inorganic salt on treatment with $HCl$ gives a white precipitate. This solution contains

$A$ 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:

$A$ colourless crystalline salt $X$ is soluble in dilute $HCl$. On adding $NaOH$ solution,it gives a white precipitate which is insoluble in excess of $NaOH$. $X$ is