# Compound formed from concentrated sulfuric acid and sulfur

In the reaction below, I know what A and B are, but I'm not sure what compound C is.

All I know about it is the following:

• Deep yellow solid
• Dication contains only sulfur
• Raman and infra-red spectra of the dication show no common features

I think that the dication might be $\ce{[S4]^{2+}}$ since I think that this would be square planar and therefore have $D_{\mathrm{4h}}$ symmetry, which has no irreps that are both Raman and IR active, but I don't know what the anion would be.

The other likely options for the sulfur dication would be $\ce{[S8]^{2+}}$ or $\ce{[S19]^{2+}}$ but I think the fact that it's yellow would make it $\ce{[S4]^{2+}}$.

$$\ce{S + 2H2SO4 → 3SO2 + 2H2O}$$
$\ce{[S4]^2+}$, $\ce{[S8]^2+}$ or $\ce{[S19]^2+}$ is formed when sulfur is dissolved in oleum. The following is a paraphrase of an inorganic textbook.