The enthalpy increments △T 273∶15KH0m of Na2W2O7(s) and Na2W4O13(s) were measured in the temperature range 273-979 K by the drop method using a high temperature Calvet HT-1000 calorimeter. The results can be represented by the polynomial equations: △T 273.15KH0m(Na2W2O7)=-71, 006+211.12T+10.720×10-2T2+2.566×106T-1 △T273.15KH0m(Na2W4O13)-136, 568+388.97T+6.643×10-2T2+6.950×106T-1 The expressions of the heat capacity against temperature for these two compounds were obtained from the differentiation of the above equations. By combining these results with data from the literature, smoothed thermodynamic functions have been calculated for Na2W2O7.

The enthalpy of sodium paratungstate Na10H2W12O42 27H2O(s) dissolved in solution of 1.0mol dm-3 LiClO4 was measured at 298.15 K using a Calvet twin-vessel microcalorimeter. The standard enthalpy of formation of paratungstate B ion, H2W12O42 10-(aq), was calculated on the basis of the experimental results. Combining this with values from the literature led to DfH0m (H2W12O42 10-aq, 298.15 K)=-(11653.5