[GaryHeld]

Can you help a frustrated dad trying to help his son with his science fair project?  Basically, we're using electrolysis to break water into hydrogen and oxygen w/ a 12volt, 1amp power supply.  The water is tap water with bicarbonate of soda added (about a teaspoon).

We see lots of hydrogen bubbles and _no_ oxygen bubbles.  I know oxygen has more of a tendency to dissolve back into the water, but I can't figure out why we're not collecting any oxygen.

If we were using table salt I'd expect chlorine gas instead of oxygen, but such is not the case.  Any ideas?

[AWK]

You see probably CO2 bubles. Add some H2SO4 or NaOH instead of bicarbonate

[kevins]

For electrolysis of water, I usually use dilute NaCl with stainless steel spoons as the electrodes, add few drops of phenolpthlein solution to the "cell". The bubbles of gases form on the electodes and also a pink colour will form near one of the electrode.

For electrolysis of Cl2, a conc NaCl solution with Pt electrodes are used.

Please try.

[TigerFX]

I tried this expierement, as well - with water from my well and NaCl. No oxygen bubbles.

Would distilled water help? I need to get some and try this again.

By the way - while we're on this subject... is there any reason my solution would turn yellow? After I ran my batteries through the wire for about a minute, the solution was clearly yellow - it looked like orange juice. I used ionized salt - do you think it's iodine?

I can check the exact contents of the salt if that would help. I think it was potassium iodine.

[Mitch]

Would distilled water help?

Think

[jdurg]

The yellow color is the result of chlorine gas that was formed and subsequently dissolved in the water.  Chlorine is fairly soluble in water, so as it's generated it will slowly turn the solution yellow.  Any KI in iodized salt would form some free iodine which has a brownish color when dissolved in water.  

[TigerFX]

The yellow color is the result of chlorine gas that was formed and subsequently dissolved in the water.  Chlorine is fairly soluble in water, so as it's generated it will slowly turn the solution yellow.  Any KI in iodized salt would form some free iodine which has a brownish color when dissolved in water.  

:S

You mean I actually isolated chlorine? Shouldn't I be dying or something? It was really yellow - it looked like orange juice. I thought chlorine was a toxic gas. Also, I didn't smell anything. Shouldn't it have smelled like a swimming pool?

I'll also point out that my solution that was salted from the salt shaker didn't turn yellow - it turned blue. I need to re-do these and keep good track of what I'm using and how much.

Think

Well, I suppose there could be another chemical in the water that's reacting with the oxygen before it has a chance to form a bubble. Any other ideas? My circut is making a connection - there's plenty of H2.

[limpet chicken]

Chlorine IS toxic, of course, it was used as the very first (modern) chemical warfare agent, thing was then of course, people were fighting in dirty trench-to-trench battles, one could not just up and run away from the oncoming gas cloud, and were forced to remain within it, using gas masks, and if they were not available, making do with breathing through wet rags even.

Chlorine gas, in a concentration enough to be severely immediately dangerous, HURTS, you won't stay in a lab that has been filled with an immediately dangerous conc of Cl2, you will cough, choke, tear, curse and swear your way to the nearest exit or gas mask, that is to say, Cl2 has excellent warning properties.

I have isolated it in my own lab (built in my garage) more times that I care to remember, and have had my fair share of whiffs and accidental inhalations, none of which have ever landed me with anything more than a slight cough, don't forget, the german commanders of WWII were using thousands of tons of chlorine in their gas attacks, common sense is all that is needed when working with Cl2.

Chlorine, in solution in water, forms an equilibrium between HOCl, hypochlorous acid, and HCl, hydrochloric, the solution is a lime-greeny-yellowish. HOCl is unstable, and cannot be isolated in a highly concentrated solution, so the equilibrium is more favoured to the long term existance of HCl.

The amount of iodine in iodised salt is absolutely miniscule, milligrams per kilogram, I strongly doubt it would prove enough to cause a stain.