Total vapor pressures of orpiment, As2S3, were measured by the torsion effusion method, and their dependence was found to fit the following equation: log(p/kPa) = (14.14+- 0.20) - (9160+-200)*(T/K) in the temperature range (501 to 583) K. The vapor molecular weight, evaluated at some temperatures in the covered range using the Knudsen equation on the vapor pressure measurements, was found to be equal to 250+-20 g*mol-1, which confirmed that, as reported in the literature, the primary sublimation processes of orpiment are As2S3(s) = As2S3- (g) and As2S3(s) =(1/2)As4S4(g) + (1/2)S2(g). Increasing the temperature does not change the importance of both reactions so that the second-law enthalpies associated with both reactions are comparable and equal to deltaH - (542 K) =175 +-4 kJ*mol-1.
Compounds
#
Formula
Name
1
As2S3
arsenic(III) sulfide
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.