The molecular and crystal structures of a complex of echinochrome (2,3,5,6,8-pentahydroxy-7-ethyl-1,4-naphthoquinone) with dioxane are determined. The molecular complex 2(C12H10O7) · C4H8O2 crystallizes in the form of dark red transparent thin plates. The crystal data of the compound are as follows: a = 4.563(1) Å, b = 6.382(1) Å, c = 22.812(4) Å, α = 91.955(5)°, β = 90.408(5)°, γ = 104.801(4)°, space group \documentclass[12pt]{minimal}
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$$P\overline 1 $$
\end{document}, and Z = 2. The crystal structure is solved by direct methods and refined to R1 = 0.0656 and wR2 = 0.1196.