Ammonium dihydrogen phosphate (phase PE) | SSHADE

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Solid phase

Official name: Ammonium dihydrogen phosphate (phase PE)

Name and identifiers

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

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 and bonds

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)

Associated phases

Equivalent mineral: Biphosphammite

Crystallography

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

Physical properties

Molar mass: 115.025 $g/mol$
Density: 1.799 (calc.: 1.852 @155K) $g/cm^3$

Thermodynamical properties

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

Optical properties

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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