The gas liberated at electrode in dry cell is removed in the form a complex.The formula of the complex formed is 

Gas liberated at anode is NH₃, and is removed in the form a complex with Zn⁺²

formed at anode as follows

${\mathrm{Zn}}^{+2}+4{\mathrm{NH}}_3\to {\left[\mathrm{Zn}{\left({\mathrm{NH}}_3\right)}_4\right]}^{+2}$