Solid phase
Official name
Ammonium dihydrogen phosphate (phase PE)
Secondary names
Ammonium biphosphate; azanium;dihydrogen phosphate; Phosphoric acid, monoammonium salt; Monoammonium phosphate; Ammonium monophosphate; Ammonium dihydrophosphate; NH4H2PO4; (NH4)H2PO4; PE-(NH4)H2PO4; (NH4+)(H2PO4)-; H6NO4P
CAS number
7722-76-1
Type
Family
ionic solid
Class
acid salt
Compound type
phosphate
Chemical composition
Formula
$(NH_4^+) \cdot H_2PO_4^-$
Chemical formula
(NH4)H2PO4
Elemental formula
(N+) H6 P O3 (O-)
Isotope mixture type
terrestrial abundance
4.0
  Formula Name Family Number min-max Mole fraction Isotope mole fraction State Relevance
$NH_4^+$ Ammonium ion molecule 1 0.5 1 constituent cation main
$H_2PO_4^-$ Dihydrogen phosphate ion molecule 1 0.5 1 constituent anion main
Chemical functions
  Function Number
$H_4 >\mid N^+$ 1
Chemical bonds
  Bond Number
$-O \dots H-$ 6
$\geq N^+-H$ 4
$=P-O^-$ 2
$=P-O-$ 2
$P=O$ 1
$-O-H$ 2
Class
acid salts (05)
Type
simple acid salts (05.01)
Group
phosphate (05.01.07)
Equivalent mineral
Biphosphammite
Phase name
PE-(NH4)H2PO4
Phase type
crystalline
Crystal system
tetragonal
Crystal class
scalenohedral
Crystal class symbol
-42m (D2d)
Crystal spacegroup
I-42d
Comments
H atoms are dynamically disordered between two equivalent sites about the bond center
Molar mass
115.025 $g/mol$
Density
1.799 (calc.: 1.852 @155K) $g/cm^3$
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-liquid liquid 190 °C (463.0 K)
solid-solid AFE-(NH4)H2PO4 -125°C (148 K)
Phase transitions comments
paraelectric - antiferroelectric phase transition
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.0462
Refraction index $n_{\alpha}$
1.5277 @532nm
Refraction index $n_{\beta}$
1.4815 @532nm
Pure color
colorless
Color
colorless, white
Diaphaneity
transparent to translucent
Luster
vitreous
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