Polyhalite

Formula : K2MgCa2(SO4)4:2H2O

Family: 
Sulfates
Space group: 
Triclinic Space Group: P 1,P1
Dana class: 
29.4.5.1VI- 29 Hydrated Acid and Sulfates ; 29.4 Hydrated Acid and Sulfates where (A+)2 Bn (XO4)p . x(H2O) ; 29.4.5

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
602.943 218.500 (Ref.: 63wyc) Wyckoff, R.W.G., 1963, Crystal Structures, Second edition, tome 4, Interscience Publishers, New York, p. 320-322. -5654734 (Ref.: 84har/mol) Harvie C.E., Moller N., and Weare J.H.. 1984, The prediction of mineral solubilities in natural waters: The Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2-H2O system to high ionic strengths at 25 C. Geochimica Cosmochimica Acta, 48, pp. 723-751.
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.
Reaction properties

Polyhalite ⇌ 2Ca+2 + 2K+ + Mg+2 + 4SO4-2 + 2H2O

298.15 K, 1 bar log10K: -13.74 ΔH°r: J·mol-1 (Ref.: )
T(°C) 0 25 60 100 150 200 250 300
log10K -13.74 -13.74 -13.74 -13.74 -13.74 -13.74 -13.74 -13.74
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-13.737968 0.000000 0.000000 0.000000 0.000000