A number of gaseous oxyacid salts have been identified by Knudsen effusion mass spectrometry by vaporizing Ga(2)O(3) from molybdenum and tungsten cells. The stability of gaseous molecules Ga(2)MoO(4), Ga(2)WO(4), Ga(2)Mo(2)O(7), and Ga(2)W(2)O(7) was deduced from the measurements. The structures and molecular parameters of all salts investigated were obtained using quantum chemical calculations. On the basis of equilibrium constants measured for gas-phase reactions, the standard formation enthalpies were determined to be -827 +/- 26, -843 +/- 26, -1578 +/- 32, and -1525 +/- 34 kJ.mol(-1) for Ga(2)MoO(4), Ga(2)WO(4), Ga(2)Mo(2)O(7), and Ga(2)W(2)O(7), respectively.