Erbium(III) sulfate is an erbium compound with the chemical formula . It is a pink crystalline salt, readily absorbing water to form an octahydrate. It is used as a colorant in glass manufacturing and porcelain enamel glazes, as well as a dopant in the production of optical fiber.
Structure The anhydrous compound (Er2(SO4)4) forms orthorhombic crystals (space group: Pbcn (No. 60), a = 1269.5 pm, b = 915.0 pm, c = 923.7 pm, molar volume = 161.5 cm3/mol, formula units = 4 units per cell).
A dimorphic hydrogensulfate (Er(HSO4)3) exists: Form I: orthorhombic (space group: Pbca (No. 61), a = 1195.0 pm, b = 949.30 pm, c = 1644.3 pm, molar volume = 140.4 cm3/mol, formula units = 8 units per cell) Form II: monoclinic (space group: P21/n (No. 14), a = 520.00 pm, b = 1357.8 pm, c = 1233.4 pm, β = 92.13 °, molar volume = 131.0 cm3/mol, formula units = 4 units per cell)
A mixed sulfate-hydrogensulfate (Er(HSO4)(SO4)) forms monoclinic crystals (space group: P21/n (No. 14), a = 545.61 pm, b = 1075.6 pm, c = 1053.1 pm, β = 104.58 °, molar volume = 90.0 cm3/mol, formula units = 4 units per cell).
Synthesis Erbium sulfate can be prepared by dissolving erbium(III) oxide in sulfuric acid:
The rod shaped "Form I" of the hydrogensulfate crystallizes from concentrated sulfuric acid at 250 °C. In diluted sulfuric acid (85% with added Na2SO4), the brick shaped "Form II" crystallizes at 250 °C, while at 60 °C the mixed sulfate-hydrogensulfate is obtained.
The anhydrous compound cannot be prepared from solution but crystallizes from molten salt (with sodium impurities).
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