# What is the precipitate of aqueous copper (II) and polysulfides?

So if you heat up a piece of sodium engulfed in a large excess of sulfur, what you would get (from what I've read) is sodium polysulfide $$\ce{NaS_n}$$. But how large can $$n$$ get? If you left sodium polysulfide in molten sulfur, would you increase $$n$$?

If you tried to dissolve the sulfur-polysulfide mixture in water and filtered it, I assume you would get a basic aqueous hydrogen polysulfide solution. If you then poured in a solution of copper sulfate, besides $$\ce{Cu(OH)2}$$, would $$\ce{CuS_n}$$ also precipitate out with an arbitrarily large $$n$$, or would the larger polysulfides break up into elemental sulfur and lower polysulfides first and precipitate out $$\ce{CuS_n}$$ with a more discrete number $$n$$?

And if you acidified the polysulfide solution until you have only $$\ce{HS-}$$, $$\ce{H2S}$$ and suspended sulfur in the solution, from which you could get the precipitate $$\ce{CuS}$$, would you be able to calculate the initial mass of sodium used from the mass of copper sulfide?

• What $\ce{NaS_n}$ compounds would result from putting Na in sulfur is an interesting question. I'd guess that such a reaction would create a complicated mixture of compounds. There are probably certain configurations that would be quasi-stable, such a six-membered ring. – MaxW Apr 5 at 1:59
• Depending on the preparation, see pubs.acs.org/doi/abs/10.1021/ja00166a054, the 'n' may not be too arbitrary. – AJKOER Apr 5 at 3:00