Orpiment

Formula : As2S3

Family: 
Arsenide
Space group: 
Monoclinic - Prismatic HM symbol (2/m) Space Group: P 21/n
Dana class: 
2.11.1.1II- 2 Sulfide Minerals ; 2.11 Sulfides - Including Selenides and Tellurides where Am Bn Xp, with (m+n):p=2:3 ; 2.11.1

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
246.041 70.500 (Ref.: 96pok/gou) Pokrovski G., Gout R., Schott J., Zotov A. and Harrichoury J.C., 1996. Thermodynamic properties and stoichiometry of As (III) hydroxide complexes at hydrothermal conditions. Geochimica et Cosmochimica Acta, 60, 737-749 -85981 (Ref.: 96pok/gou) Pokrovski G., Gout R., Schott J., Zotov A. and Harrichoury J.C., 1996. Thermodynamic properties and stoichiometry of As (III) hydroxide complexes at hydrothermal conditions. Geochimica et Cosmochimica Acta, 60, 737-749 -87158 (Ref.: Internal calculation) 163.594 (Ref.: 96pok/gou) Pokrovski G., Gout R., Schott J., Zotov A. and Harrichoury J.C., 1996. Thermodynamic properties and stoichiometry of As (III) hydroxide complexes at hydrothermal conditions. Geochimica et Cosmochimica Acta, 60, 737-749 115.19 (Ref.: 96pok/gou) Pokrovski G., Gout R., Schott J., Zotov A. and Harrichoury J.C., 1996. Thermodynamic properties and stoichiometry of As (III) hydroxide complexes at hydrothermal conditions. Geochimica et Cosmochimica Acta, 60, 737-749
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
95.10 57.82 2.53 (Ref.: 96pok/gou) Pokrovski G., Gout R., Schott J., Zotov A. and Harrichoury J.C., 1996. Thermodynamic properties and stoichiometry of As (III) hydroxide complexes at hydrothermal conditions. Geochimica et Cosmochimica Acta, 60, 737-749
Reaction properties

Orpiment + 6H2O ⇌ 2H2AsO3- + 3HS- + 5H+

298.15 K, 1 bar log10K: -65.11 ΔH°r:334975 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K -70.58 -65.11 -59.08 -53.89 -49.20 -46.01 -44.03 -43.31
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2559.977199 -0.422680 119887.838597 933.288221 -8051705.700979