Hi, I'm looking at a question which asks how one can test for ammonia in [NH4]2Fe[SO4]2 The answer says that you add sodium hydroxide, and get [NH4]2Fe[SO4]2 + 2 NaOH -> [NH4]2Fe(OH)2 + 2 NaSO4 This is what I don't get: it then says you test the ammonia gas with litmus paper, or with HCL. In the former case, the litmus paper turns blue, and in the latter, you get white smoke. My two questions: I know ammonia is alkaline, but how is [NH4]2Fe(OH)2 a gas? Secondly, why do you get white smoke when you add HCL? Thanks for your input.