Potassium tin(II) sulphate and related tin apatites: Mössbauer and X-ray studies

Abstract

Isolation of solid phases containing potassium, tin(II), and sulphate has been attempted from aqueous K–Sn^II–SO₄ and K–Sn^II–SO₄–X (X = F, Cl, Br, I, or NO₃) systems. The only phases isolated were potassium tin(II) sulphate of composition ranging from K₂Sn(SO₄)₂ to K₂Sn₂(SO₄)₃, and potassium tin(II) chloride- and bromide-sulphates, K₃Sn₂(SO₄)₃X. Single-crystal X-ray studies show the former to be essentially similar to the well known K₂Pb(SO₄)₂, except for a marked tendency to form solid solutions with the simple Sn^II sulphate. The chloro- and bromo-compounds are shown to be closely similar to chlorapatites, with SO₄^2– replacing PO₄^3–. Mössbauer spectra of these phases are discussed in relation to the proposed structures.