Published online by Cambridge University Press: 10 January 2013
X-ray powder diffraction and single-crystal data are reported for a series of isomorphous compounds with the general chemical composition (Fe,Al)3(K,NH4,H3O)H14 (PO4)8·4H2O. The compounds are monoclinic with space group C2/c. Unit-cell parameters were determined on the mixed salt (Fe0.84,Al0.16)3KH14(PO4)8·4H2O, as obtained from sludge precipitated in commercial shipping-grade wet-process phosphoric acid. Single-crystal studies and refined powder diffraction data provided unit-cell parameters of a= 16.908(9) Å, b = 9.588(2) Å, c = 17.539(5) Å, and β = 91.06(4)°.