Ammonium Chloride and Sodium Nitrite Reaction?

I have been trying to generate nitrogen by reacting ammonium chloride and sodium nitrite in aqueous solution. I was trying to collect the evolved nitrogen in a bottle over water. However, the reaction seemed to proceed extremely slowly. Even when I put the bottle (containing the reactants in aqueous solution) in a hot water bath, the gas still was produced at an extremely slow rate.

Is there some sort of catalyst or additive I can use to increase the reaction rate so that I can produce usable amounts of nitrogen in a reasonable time? I would appreciate any suggestions. Thanks!