Solid phase
Official name
Ammonium aluminium sulfate dodecahydrate (phase FE)
Secondary names
Ammonium alum; Ammonium aluminium sulphate dodecahydrate; Aluminium ammonium sulfate dodecahydrate; Aluminum ammonium disulfate dodecahydrate; Ammonium aluminum sulfate hydrate; ammonium alum dodecahydrate; Aluminum ammonium sulfate (1:1:2) dodecahydrate; Sulfuric acid, aluminum ammonium salt (2:1:1), dodecahydrate; Al(NH4)(SO4)2.12(H2O); AlH28NO20S2
CAS number
7784-26-1
Family
ionic solid
Class
normal salt
Compound type
sulfate
Formula
(NH+4)Al3+(SO24)212(H2O)
Chemical formula
(NH4)Al(SO4)2.12H2O
Elemental formula
(N+) H28 (Al3+) S2 O16 (O-)4
Isotope mixture type
terrestrial abundance
32.0
  Formula Name Family Number min-max Mole fraction Isotope mole fraction State Relevance
NH+4 Ammonium ion molecule 1 0.0625 1 constituent cation main
Al3+ Aluminium(III) cation element 1 0.0625 1 constituent cation main
SO24 Sulfate ion molecule 2 0.125 1 constituent anion main
H2O Water molecule 12 0.75 1 hydration main
Chemical functions
  Function Number
H4>∣N+ 2
(SO4)2 2
ROH 2
Chemical bonds
  Bond Number
>∣N+O 1
()Al3+O 3
N+H 4
SO 2
2
-O-H 2
\dddot - \dddot - \dddot - S \dddot - O^{-1/2} 4
Class
normal salts (07)
Type
hydrated simple normal salts (07.04)
Phase name
FE-NH4Al(SO4)2.12H2O
Phase type
crystalline
Crystal system
unknown
Crystal class
unknown
Crystal class symbol
unknown
Crystal spacegroup
unknown
Comments
paraelectric phase
Molar mass
453.33 g/mol
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-solid alpha-(NH4)Al(SO4)2.12H2O above -197°C (76 K)
Phase transitions comments
paraelectric-ferroelectric phase transition at 76K
Pure color
colorless
Color
colorless, white
Diaphaneity
transparent to translucent