On Wed, 19 Sep 2007 04:35:51 +0000, Larry wrote:

Apparently hydrogen being the lightest
molecule will leak right through most metal tanks.


Hmm...great point, Bruce! I suppose it's the same as the lighest elements
of gasoline leaking right through those cheapassed polyethelene gas tanks
they put in expensive boats...leaving the shellac behind.

Bruce was almost right. Hydrogen is the smallest molecule and it
leaks through normal joints like a sieve. Helium being the next
smallest is commonly used for leak testing high vacuum equipment as a
result. With the proper detection apparatus you could leak test with
hydrogen but it has an unfortunate tendency to release energy in a
rather violent kind of way.