What is formed when calomel $(Hg_2Cl_2)$ reacts with $NH_4OH$?

Compound $X$ is tested and the results are shown in the table.

Test	Result
Aqueous $NaOH$ is added, then heated gently.	Gas given off which turns damp red litmus paper blue.
Dilute $HCl$ is added.	Effervescence, gas given off which turns lime water milky and acidified $K_2Cr_2O_7$ paper green.

Which ions are present in compound $X$?

$A$ black sulphide is formed by the action of $H_2S$ on

Salt $X$ is:
$X \text{ (Colourless salt)}$ $\xrightarrow[\Delta]{NaOH} Y$ $\xrightarrow{HCl} \text{White fumes}$
$X \text{ (Colourless salt)}$ $\xrightarrow{CaCl_2} Z \text{ (White ppts.)}$ $\xrightarrow{KMnO_4} \text{Colourless solution}$

$A$ salt on treatment with dil. $HCl$ gives a pungent smelling gas and a yellow precipitate. The salt gives a green flame when tested. The salt solution gives a yellow precipitate with potassium chromate. The salt is:

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