| Abstract: Fifteen solid complexes of rare earth (except Sc,Pm) isothiocyanates with N,N-dimcthylacetamide (DMA) were synthesized. They were characterized by chemical analysis,infrared spectra,X-ray diffraction,differential thermal and thermogravimetric analyses.Both integral heats of solution of RE(NCS)3·mDMA(for RE=La,Ce,Pr,Nd,m=5; for RE=Sm,Eu,Gd,Dy,Ho,Yb,Y,m=4) in water and those of RE(NCS)3·nH2O(for RE=La,Ce,Pr,Nd,n=7;for RE=Sm,Eu,Gd,Dy,Ho,Yb,Y,n=6) in aqueous DMA solution have been measured calorimetrically at 298.15K. By means of the thermochcmical cycle suggested in this paper,using the data measured and picked from references [4-7],the standard enthalpies of formation for eleven RE(NCS)3·mDMA as stated above were calculated. Furthermore,corresponding data for other four RE(NCS)3· mDMA(RE=Tb,Er,Tm,Lu,m=4) were estimated. Plot-ΔHffo RE(NCS)3·mDMA against the atomic numbers of theelements in Ln-scrics,"double peak" are observed at the positions of Eu and Yb. The lattice energies of RE(NCS)3·mDMAwere also calculated. |
