# How can I clean up from electrolysis?

So, I was doing a little experimental electrolysis in my basement. I used 2 (presumably) galvanized steel screws as my electrodes and ran 5A through tap water with a lot of NaCl dissolved in it (to decrease resistance). It worked great: I got a lot of bubbles from the - side. Problem is, my cup started filling up with this black crud.

Now, I have a little plastic disposable cup with really salt water, 2 screws (black with what I presume is some corrosion), and a lot of black and red insoluble crud. How do I get rid of it?

Also, what it that crud (most likely)?

EDIT: I figured out that putting NaCl in an electrolytic cell means that I was actually generating chlorine gas instead of oxygen gas. That means that I have a bunch of iron and zinc chlorides in that water. It's also probably pretty basic (I saw no bubbling at that electrode). Any disposal problems?

• most likely iron oxides, pretty safe to dispose. – permeakra May 26 '16 at 21:12
• @permeakra I update the question to reflect my current research: it turns out that I was generating Cl2 which reacted with electrodes (I think). – dpdt May 26 '16 at 21:17

The black one is probably $\ce{ZnFe2O4}$; insoluble compound of very weakly toxic metal ions, or $\ce{Fe3O4}$. The red one is $\ce{Fe2O3}$ In terms of disposal all above counts as non-toxic mineral materials, similar to sand.