Tachyhydrite

Formula : Mg₂CaCl₆:12H₂O

Family:

Space group:

Trigonal - Rhombohedral or Pyramidal HM symbol (3 or -3) Space Group: P 3

Dana class:

11.5.5.1IV- 11 Halide Complexes; Alumino-fluorides ; 11.5 Halide Complexes; Alumino-fluorides where(?)m B(?)6 ; 11.5.3

Dernière mise à jour le 25.01.2021

Individual properties (298.15 K)

M g·mol^-1	V° cm³·mol^-1	ΔGº_f J·mol^-1	ΔHº_f J·mol^-1	Sº J·mol^-1·k^-1	C_P J·mol^-1·K^-1
517.586	311.807 (Ref.: 63wyc) Wyckoff, R.W.G., 1963, Crystal Structures, Second edition, tome 4, Interscience Publishers, New York, p. 320-322.	-4997345 (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.

C_P(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

Tachyhydrite ⇌ Ca⁺² + 6Cl^- + 2Mg⁺² + 12H₂O

298.15 K, 1 bar log₁₀K: 17.39 ΔH°_r: J·mol^-1

T(°C)	0	25	60	100	150	200	250	300
log₁₀K	17.39	17.39	17.39	17.39	17.39	17.39	17.39	17.39

log₁₀K(T) = A + B·T + C·T^-1 + D·log₁₀(T) + E·T⁻² (T in Kelvin)

A	B	C	D	E
17.392193	0.000000	0.000000	0.000000	0.000000