TERNARY CHLORIDES IN THE SYSTEMS ACL HOCL3 (A=CS, RB, K)(1)/

The phase diagrams of the pseudo-binary systems ACl/HoCl3 (A=Cs, Rb, K ) were investigated by DTA and XRT. The existence of compounds A(3)HoC l(6), Cs2HoCl5, Cs3Ho2Cl7 and AHo(2)Cl(7) could be confirmed. Addition ally, the 2:1-compounds Rb2HoCl5 (Cs2DyCl5- structure) and K2HoCl5 (K2 PrCl5-structure) were found. By solution enthalpy and e.m.f vs. T meas urements in galvanic chlorine cells for solid electrolytes, the thermo dynamic functions for the formation from ACl and HoCl3 and for the for mation from the compounds adjacent in the phase diagrams were measured . The compounds A(3)HoCl(6) could be prepared also from acetic acid so lutions. From aqueous solutions, the ternary halides Cs4HoCl7 and Cs3H oCl6 crystallizing in the space group Pbcm were prepared. Anhydrous Ho Cl3 can be obtained comfortably from holmium formiate at similar to 30 0 degrees C in an HCl gas stream. (C) 1997 Elsevier Science S.A.