How Graham's Law can be used to predict the ring of gases that will occur in the glas tube.
Draw a tube, say 1 meter long.
distance traveled by lower molar mass cmpd = x = say NH3
distance traveled by higher molar mass cmpd = 1-x = say HCl
(x/1-x) = sqrt(mol mass HCl/molar mass NH3)
|-----------------------| tube
|..............|........|<<1 meter
|<------x-----> <..1-x..>