Brushite

Formula : CaHPO4:2H2O

Family: 
Phosphates
Space group: 
Monoclinic - Prismatic HM symbol (2/m) Space Group: I2/a
Dana class: 
39.1.1.1VII - 39 Hydrated Acid Phosphates, etc ; 39.1 Hydrated Acid Phosphates, etc A+ [HXO4] . x(H2O) ; 39.1.1
High temperature: 
Stable at room temperature
Geological context: 
Occurs as the most common cave minerals, in guano deposits, and in phosphorites, formed at low pH by reaction of phosphate-rich solutions with calcite and clay.

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
172.088 73.920 (Ref.: 84nri) Nriagu J.O., 1984, Formation and stability of base metal phosphates in soils and sediments, Chap. 10. In: Phosphate Minerals, J.O. Nriagu and P.B. Moore (Eds), Springer-Verlag, ISBN 3-540-12757-7, 318-329 -2160814 (Ref.: 84nan) Nancollas G.H., 1984, The nucleation and growth of phosphate minerals, Chap. 2. In: Phosphate Minerals, J.O. Nriagu and P.B. Moore (Eds), Springer-Verlag, ISBN 3-540-12757-7, 318-329 -2409885 (Ref.: Internal calculation) 189.450 (Ref.: 84nan) Nancollas G.H., 1984, The nucleation and growth of phosphate minerals, Chap. 2. In: Phosphate Minerals, J.O. Nriagu and P.B. Moore (Eds), Springer-Verlag, ISBN 3-540-12757-7, 318-329 200.45 (Ref.: 70gre/mor, after 64aega/wak and bega/wak)
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.
31.72 569.44 -0.93 (Ref.: 70gre/mor, after 64aega/wak and bega/wak)
Reaction properties

Brushite + H+ ⇌ Ca+2 + H2PO4- + 2H2O

298.15 K, 1 bar log10K: 0.60 ΔH°r:-7375 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 0.70 0.60 0.43 0.21 -0.14 -0.59 -1.16 -1.95
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-900.250696 -0.151024 47493.594956 329.939902 -2651561.188912