Temperature of nitrogen in a vessel of volume $2$ $m^3$ is $288$ $K$. A U-tube manometer connected to the vessel shows a reading of $70$ $cm$ of mercury (level higher in the end open to atmosphere). The universal gas constant is $8314$ $J$/$kmol$-$K$, atmospheric pressure is $1.01325$ $bar$, acceleration due to gravity is $9.81$ $m$/$s^2$ and density of mercury is $13600$ $kg$/$m^3$. The mass of nitrogen (in $kg$) in the vessel is _____________