Solid phase
Official name
Sodium chloride dihydrate
Secondary names
Common salt, hydrated; Hydrohalite; Rock salt, hydrated; Sodium chloric dihydrate; NaCl dihydrate
CAS number
23724-87-0
Type
Family
ionic solid
Class
normal salt
Compound type
chloride
Comments
equivalent to mineral Hydrohalite
Chemical composition
Formula
$Na^+ \cdot Cl^- \bullet 2H_2O$
Chemical formula
NaCl•2H2O
Elemental formula
(Na+) (Cl-) H4 O2
Isotope mixture type
terrestrial abundance
8.0
  Formula Name Family Number min-max Mole fraction Isotope mole fraction State Relevance
$Na^+$ Sodium cation element 1 0.25 1 constituent cation main
$Cl^-$ Chloride anion element 1 0.25 1 constituent anion main
$H_2O$ Water molecule 2 0.5 1 hydration main
Chemical functions
  Function Number
$R-OH$ 2
Chemical bonds
  Bond Number
$Na^+ \cdot Cl^-$ 6
$-O \dots H-$ 4
$-O-H$ 2
Class
normal salts (07)
Type
hydrated simple normal salts (07.04)
Equivalent mineral
Hydrohalite
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
P2(1)/c
Molar mass
94.473 $g/mol$
Density
1.65 (calc.) $g/cm^3$
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-liquid liquid H2O -0.1°C (273.05 K)
Refringence type
biaxial
Refringence sign
unknown
Refraction index $n_{\alpha}$
unknown
Pure color
colorless
Color
colorless, white
Diaphaneity
transparent
Luster
vitreous
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