Variscite

Formula : AlPO4:2H2O

Family: 
Phosphates
Space group: 
Orthorhombic - Dipyramidal HM symbol (2/m 2/m 2/m) Space Group: Pcab
Dana class: 
40.4.1.1VII - 40 Hydrated Phosphates, etc ; 40.4 Hydrated Phosphates, etc where A+++ XO4 . x(H2O) ; 40.4.1

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
157.983 61.953 (Ref.: 63wyc) Wyckoff, R.W.G., 1963, Crystal Structures, Second edition, tome 4, Interscience Publishers, New York, p. 320-322. -2111400 (Ref.: 74nau/ryz) Naumov G.B., Ryzhenko B.N., and Khodakovsky I.L., 1974. Handbook of Thermodynamic Data. U.S. Geol. Surv.WRD 74 001, 328 pp. -2353410 (Ref.: Internal calculation) 134.500 (Ref.: 66ega/wak) Egan E.P., Wakefield Z.T., 1966, Low temperature, heat capacity and entropy of variscite, AlPO4.2H2O, 10 to 310K. J. Chem. Eng. Data, 11, 610-611 165.98 (Ref.: 74nau/ryz) Naumov G.B., Ryzhenko B.N., and Khodakovsky I.L., 1974. Handbook of Thermodynamic Data. U.S. Geol. Surv.WRD 74 001, 328 pp.
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.
165.98 0.00 0.00 (Ref.: 74nau/ryz) Naumov G.B., Ryzhenko B.N., and Khodakovsky I.L., 1974. Handbook of Thermodynamic Data. U.S. Geol. Surv.WRD 74 001, 328 pp.
Reaction properties

Variscite + 2H+ ⇌ Al+3 + H2PO4- + 2H2O

298.15 K, 1 bar log10K: -2.16 ΔH°r:-59250 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K -1.25 -2.16 -3.29 -4.43 -5.69 -6.88 -8.08 -9.41
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1069.095997 -0.173224 59751.042067 386.011849 -3287463.862916