Lanthanide trihydroxide lattice constants

Lattice constants are reported for an isotypic series of hexagonal (P63/m)M(OH)₃ compounds where M = La, Sm, Eu, Gd, Tb, Dy, Ho, Y and Er. A stability field plot (V^1/3 vs. ionic radii) is linear, an indication of the internal consistency and accuracy of these constants. Plots of a and c vs. ionic radii are also linear and plots of a vs. c and a, c and V^1/3 vs. Z yield smooth regular curves contrary to several earlier investigations. The new results compare reasonably well with the recent results of Christensen [Acta Chem. Stand. (1966). 20, 896-899] and Christensen, Hazell & Nilsson [Acta Chem. Stand. (1967). 21,481-492] for Ce. Tb, Dy, Ho, Y, Er and Tm.