Alunite(Na)

Formula : NaAl3(SO4)2(OH)6

Family: 
Alunite
Space group: 
Trigonal Space Group: R 3m, R 3m
Dana class: 
30.2.4.1 (30)Anhydrous Sulfates Containing Hydroxyl or Halogen (30.2)where (A B)2 XO4 Zq (30.2.4) Alunite Group (Alunite Subgroup)
High temperature: 
Newly formed at a temperature less than 300C.
Geological context: 
Hydrothermal and supergene mineral, high sulfidation epithermal deposits

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
398.106 -4622400 (Ref.: 90sto/cyg) Stoffregen R. E., Cygan G.L. (1990). An experimental study of Na-K exchange between alunite and aqueous sulfate solutions. Am. Min., 75:209-220 -5131441 (Ref.: Internal calculation) 321.080 (Ref.: 90sto/cyg) Stoffregen R. E., Cygan G.L. (1990). An experimental study of Na-K exchange between alunite and aqueous sulfate solutions. Am. Min., 75:209-220 375.78 (Ref.: 90sto/cyg) Stoffregen R. E., Cygan G.L. (1990). An experimental study of Na-K exchange between alunite and aqueous sulfate solutions. Am. Min., 75:209-220
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.
641.50 -7.87 -234.12 (Ref.: 90sto/cyg) Stoffregen R. E., Cygan G.L. (1990). An experimental study of Na-K exchange between alunite and aqueous sulfate solutions. Am. Min., 75:209-220
Reaction properties

Alunite(Na) + 6H+ ⇌ 3Al+3 + Na+ + 2SO4-2 + 6H2O

298.15 K, 1 bar log10K: 2.34 ΔH°r:-257759 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 6.29 2.34 -2.62 -7.60 -13.14 -18.34 -23.56 -29.30
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-4329.182619 -0.705398 244147.061036 1565.946798 -13500184.387678