Representation of the vapour pressures of sulfur

Standard values of fugacity for sulfur which are self-consistent with the low-pressure phase diagram

“…The critical pressure is in good agreement with that of Baker (20,670 kPa), but is larger than the 18,208 kPa calculated by Rau [20] and that used by Peng and Zhao [19]. Note that Ferreira and Lobo [1] also found a larger critical pressure (19,811 kPa) using a similar, but less constrained fit.…”

“…There are many low-pressure vapour pressure equations from which to choose [1,3,6,19,20] and not all of them will be discussed here. For a detailed review, see Peng and Zhao [19]. Vapour pressure correlations are complicated by the allotropic nature of the liquid and gaseous sulfur.…”

The low-pressure phase diagram of sulfur

“…15 and 374.15) K. Carrying out the necessary calculations, and taking into account the replacement of the subscript sm for sr, the coefficients in equation (11) Legend: s, reference [3]; j, reference [4]; r, reference [5]; +, reference [6]; Â, reference [7]; e, reference [9]; , reference [10]; È, reference [11]; I, reference [12]; Ç, reference [13]; N, triple points, this work; , normal boiling point, reference [14]; d, critical point, this work. Notice the different temperature scales.…”

“…The calculated critical pressure comes out as p c = 19 811 kPa. This is to be compared with p c = 18 208 kPa calculated by Rau et al [13], also selected in reference [15], and with p c = 20 670 kPa found by Baker [12]. The standard deviation of this fitting is r(p) = 0.027 kPa with a correlation coefficient r = 0.999.…”

“…The critical temperature has been taken from reference [13] as T c = 1313 K and p c has been treated as a fifth adjustable parameter. Having presented the wide range of the measured pressures, extending from p = (10 À3 to 10 4 ) kPa, and the large number of data points available, these were given weights proportional to 1/p 2 in this fitting as Peng and Zhao most certainly did in their work on the same subject [15]. The resulting parameters in equation (4) are a 1 = À7.1742; a 2 = À1.9154; a 3 = 8.4830; a 4 = À11.4867.…”