Heat capacity values of Se6 g at

All values of the heat capacity of See(g) at 298.15 K are based on estimated quantities and are summarised in Table V-14. The heat capacity value attributed to [84PUP/RUS] was calculated by the review from the estimated molecular parameters reported in the paper. Similarly, the heat capacity expression C° ,(Se6, g, (298.15 -1500) K) = (132.511 -H 0.7288 X 10 T - 0.2731 x 10 6.36682 x 10 T ) 

J K -mor was obtained by fitting the expression to heat capacity values calculated from the molecular parameters reported in [84PUP/RUS], The difference between the heat capacity calculated from this expression and that calculated from the expression in [74M1L] amounts to 0.05 J K. mor in the temperature range 1000 to 1500 K and reaches a maximum of 0.7 J K mor at 298.15 K. The derived heat capacity expression was employed by the review in all recalculations and evaluations wherever the thermodynamic properties of Sc6(g) were required at other temperatures than the standard temperature. The heat capacity at 298.15 K calculated from the expression is C° , (Se6, g, 298.15 K) = (125.5 +2.0) J-K -mor. No value of the heat capacity is selected because all tentative values are based on estimated quantities only. 

The heat capacities calculated from the expressions in [74MIL] and [84PUP/RUS] differ by less than 0.6 J K -mol in the whole temperature range 298.15 to 1500 K. 

The enthalpy of formation of See(g) has been determined from mass spectro-metric investigations of selenium vapour using Knudsen cells. The measurements can be separated into the approximate temperature ranges 420 to 494 K for equilibria with 

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