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I was electroplating with a copper sulfate electrolyte, and now a yellow substance has settled at the bottom of the container, is it sulphur from the copper sulfate or something else from the screw I electroplated?

If it is sulphur, how can I safely remove it?

Thanks for any help you can give me.

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The yellow precipitate is probably cuprous oxide $\ce{Cu2O}$ which is insoluble, and which is produced in the electrolysis of $\ce{CuSO4}$if the solution is not acidic enough. Check by adding some acidic solution, like concentrated HCl. If the yellow precipitate is sulfur it will not be attacked by the acid. If it is $\ce{Cu2O}$, il will soon be dissolved and produce a colorless solution, due to : $$\ce{Cu2O + 4HCl ⟶ H2CuCl2 + H2O}$$

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  • $\begingroup$ I do not have hcl, would distilled white vinegar work? $\endgroup$
    – Taxolotl
    Commented Dec 7, 2022 at 14:57
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    $\begingroup$ Sulfur can never be formed by electrolytic reduction of copper sulfate. $\endgroup$
    – ACR
    Commented Dec 7, 2022 at 15:19
  • $\begingroup$ @UriahPowell acetic acid (vinegar) is not a strong enough acid to lower the pH sufficiently $\endgroup$
    – Waylander
    Commented Dec 7, 2022 at 15:56
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    $\begingroup$ @ Uriah Powell. Acetic acid is too weak an acid to redissolve $\ce{Cu2O}$. Why don't you make the same test with ammonia $\ce{NH3}$, or with ammonium chloride $\ce{NH4Cl}$. These substances should be able to dissolve $\ce{Cu2O}$ $\endgroup$
    – Maurice
    Commented Dec 7, 2022 at 16:00
  • $\begingroup$ I would also electrolyte the copper with some added sulfuric acid. This prevents Cu2O from forming. $\endgroup$
    – Oscar Lanzi
    Commented Dec 7, 2022 at 19:51

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