So I am talking about any gas. I anm going to doubt that the air really has some weight. What is the simplest expeiment that could prove that the air does have weight? May be baloons on a balance, when one of them is blown up, the weight on that pan decreases. I suppose that the gas molcules have no weight. The air has weight only due to the dust paricles and the water droplets/? solved in it which give the impession that the air has weight. What expeimental setup would give purely the weight of the gas molecules excluding any of the entities solved in air?