On Tue, 4 Mar 2008 14:47:54 -0800 (PST), Ricky
wrote in
:

hydrogen is a stronger lifting gas than helium.

The atmospheric displacement of hydrogen (H2 MW=2), with one fourth
the molecular weight of helium (He2 MW=8), should be a considerably
larger percentage of its mass. But because the hydrogen molecule is
physically smaller, containing it within the balloon envelope may be
an issue.

My 2¢