The structure of Li~2SO~4·20H~2O solution has been investigated with a θ-2θ type X-ray diffractometer. An empirical formula, r~x~- ~y=0.618λ/sinθ, has been applied to carry out qualitatively structural analysis of the diffraction curve, and another r~x~-~y=7. 766/s to calculate the interatomic distance of some strong peaks from the reduced intensity curve. The refinement results of structural models show that the dominant species in the solution are tetraquolithium and octaaquosulfate ion. the Li-H~2o distance is fixed at 0.20nm when the coordination number is 4. The vater-water distance at four vertexes in the tetrahedron is 0.321nm with n=6. The distance between lithium ion and water molecules on the second hydration shell was determined to be about 0.425nm, with n=12. the S- W distance of hydrated sulfate ion with 8 water molecules is estimated to be 0.386nm. Four interactions of oxygen atom O~s in sulfate ion and the water molecules have been expounded by a symmetric hydration model and the distances of O~s-W(1), O~s-W(2), O~s-W(3) and O~s-W(4) were refined to be 0.288, 0.316, 0.396 and 0.469nm respectively. No reliable enough evidence shows that there are the contact ion-pair and the solvent-shared ion-pair in the solution owing to very low scattering power of lithium.

Key words: LITHIUM SULFATE, WATER, X-RAY DIFFRACTION ANALYSIS