Help with my hydrolysis experiment?

The wires in the test tubes are powered by a 9-volt battery. The negative side is gathering gas, on the left. The positive side, on the right, is turning my silvery wire black, and generating no gas. The wire is falling apart. I suspect this is steel wire, as it’s only meant for gardening.

Am I getting oxidation of the iron atoms, and not generating any oxygen gas because of that? We tested the hydrogen gas tube, and it did pop.

Would copper wire not have the same kind of effect? I’m also going to try alligator clamps to graphite rods as electrodes.

I am no chemist, but if you are using an iron wire, I could imagine it’s scavenging the liberated oxygen and turning into an iron oxide. Iron (II) oxide is black. Dunno if that’d be the right one in that situation, rather than Iron (III) oxide (more common red rust).

When I did this experiment as a kid, I used copper wire and had no trouble liberating gaseous oxygen at the anode. But the idea of using a carbon electrode is good.

Slightly on-topic: my first attempt as a kid, using high-concentration table salt as the electrolyte, I accidentally liberated chlorine gas from the chloride ions rather than oxygen from the water. Your electrolyte choice is significant.

I think you have it.

I did this “experiment” quite a bit as a kid. I always used carbon rods (scavenged from old Carbon/Zinc dry cells) connected to the power source with copper wire. I made Oxygen and Hydrogen but it was slow. Adding a electrolyte speeds things up, considerably.

Yes, that’s exactly what’s happening. The usual method is to use graphite for the positive electrode. Copper will oxidize the same way.

I’m also informed that it’s “electrolysis”, so sorry.

How were people attaching the wire to the graphite posts? I’d rather not spend the money on the prices I’m seeing form 9-V alligator snaps/clips.

Anyone know the best electrolyte? We were using baking soda.

Just wrap the wire around the graphite a few times. You can use putty, gum, or tape to hold it together.

Table salt is a common eletrolyte, although some people get concerned about the small amount of chlorine gas that can be liberated (it’s no more than when you use a little bleach). A little vinegar also works if you want to avoid chlorine.

In my case, I used way too much salt; the predominant anode gas was definitely chlorine. And the battery got hot and ran flat very fast, meaning the electrolyte solution was probably almost a dead short.

ETA: Baking soda is what I used the second time around, when I actually succeeded in producing oxygen. I think it’s appropriate; its ions are less likely to be disrupted than the water itself, so the water will electrolyze instead of the soda.

Yeah, I just wrapped the wire around the carbon rods (I used one for each electrode). In High School, the chemistry teacher did the same thing, but she used platinum electrodes (I guess because she had them). Then she use sulfuric acid as the electrolyte (she really knew what she was doing; she knew her stuff and was a very good teacher). I never repeated the experiment, but if I was to, I think I might try Epsom salt.

black, iron II oxide, in hydroxide , red rust ( iron III oxide ) in neutral or acidic… the OH- are at this electrode and the H+'s at the other electrode… its basic where the rust is forming.