The laser diffraction method was used to investigate bubble size and distribution for electrolytic-evolving H2 and O2. The electrolyte bubble size may change over a wide range, and a statistical law is given. The effects of c.d. and electrode material on the coalescing O2 bubble are more obvious than for the H2 bubble, which are almost noncoalesced. When the electrolyte changed from alkaline to acid as solution, not only the H2 bubble increases and O2 bubbles reduced greatly, but also the distributions of both are altered.

Key words: OXYGEN, HYDROGEN, ELECTRODE REACTION