A Problem on Salt Analysis!

A colourless salt $(A)$,soluble in water,gives a mixture of three gases $(B),(C),(D)$ along with water vapours.$(C)$ is not oxidisable. $(B)$ turns red litmus blue,$(C)$ turns blue litmus red and gas$(D)$ is neutral towards litmus paper. Gas $(B)$ is also obtained when $(A)$ is heated with $\ce{NaOH}$ and gives brown ppt with $\ce{{K}_{2}Hg{I}_{4}}$. Solution thus obtained gives white ppt $(E)$ with $\ce{Ca{Cl}_{2}}$ solution in presence of $\ce{C{H}_{3}COOH }$. $(E)$ decolourises $\ce{{Mn{O}_{4}}^{-}/{H}^{+}}$. Gas $(C)$ turns lime water milky while gas $(D)$ burns with blue flame and is fatal when inhaled. Find the molecular mass of salt $(A)$.

Two more problems on Salt Analysis are as follows:

1. A Problem on Salt Analysis! 2

2. A Problem on Salt Analysis! 3