Tellurium Sulphates

By heating a mixture of powdered tellurium and concentrated sulphuric acid until a dry residue remained, Berzelius obtained a white, earthy mass, which after analysis he concluded to be a disulphate, TeO₂.2SO₃ or Te(SO₄)₂. The composition of the product, however, is somewhat uncertain; on heating it yields a more definite compound of composition 2TeO₂.SO₃, which can be regarded as a basic tellurium sulphate or as a pyrotelluryl sulphate. The latter compound is also obtained as rhombic crystals (a:b:c = 0.5265:1:0.7860) from a solution of tellurium dioxide in diluted sulphuric acid.