[en] Solubility of solid phases in the ternary systems ytterbium nitrate - diethylamine nitrate - water (1) and ytterbium nitrate - tetraethylammonium nitrate - water (2) is studied at 25 and 50 deg C. Isotherms of the system 1 are stated to comprise two branches complying with solid phases by tetraaqueous ytterbium nitrate and diethylamine nitrate. Homogeneous phases take place in the quasibinary cross section Yb(NO₃)₃x4H₂O-(C₂H₅)₂NHxHNO₃. Congruently soluble compound of Yb(NO₃)₃x2{[(C₂H₅)₄N]NO₃}x4H₂O composition is formed in the system 2 besides solid phases of the initial salts. Composition of the compound is specified by the analytical method. IR spectra are studied, X-ray phase and thermogravimetric analyses of the new solid phase are carried out