[en] Values of compressions of barium, yttrium, copper nitrate aqueous solutions (determination error is ±3·10^-5) are determined experimentally. Isothermal equations of states of nitrate aqueous solutions allowing to calculate specific volumes of solutions with error practically equal to error of their determination under atmospheric pressure, are plotted. Decrease of partial mole volume at pressure increase is determined for solutions of yttrium nitrates at 3.5 mole/kg and higher concentration, that is inversion of the sign of partial isothermal compressibility is detected