Re: Electrolysis of Water - Nonproduction of oxygen

The key to your problem seems to be solubility because as far as I know, 
water cannot
dissociate to form hydrogen without at the same time generating oxygen.

With a potential difference of only 6 V, water dissociates slowly and the 
oxygen that
forms initially dissolves in water, so you're under the impression that it 
isn't there.
Hydrogen, meanwhile is less soluble than oxygen, quickly saturating the 
water and
then displacing it, as you observed. One part of oxygen dissolves in 32 
parts of water
at 20 C ( Merck 12th edition ), whereas for hydrogen only one part in 50 
dissolves 
close to the freezing mark. For warmer temperatures the solubility is even 
lower, though I don't
have the exact numbers.

The key to a successful and quick electrolysis is to boost the 
concentration of acid in the water. 

Also when testing for oxygen, remeber to hold the open end of the test tube 
upwards, since oxygen is slightly more dense than air.