The composition of the basic nitrate salt of Y3+ has been investigated by Gran plots, ion chromatography (IC), atomic absorption spectroscopy (AAS) and X-ray diffraction (XRD). The salt seems to be stoichiometric with formula Y2(OH)5NO3 . 1.5H2O. The decomposition is studied using TG-FTIR (heating rate, 10-degrees-C min-1). The product decomposes between 200 and 600-degrees-C. The solid residue is Y2O3 and the gases evolved stepwise during decomposition are H2O, NO2 and O2.