Gallium(III) sulfate

Gallium(III) sulfate refers to the chemical compound, a salt, with the formula Ga₂(SO₄)₃, or its hydrates Ga₂(SO₄)₃·xH₂O. Gallium metal dissolves in sulfuric acid to form solutions containing [Ga(OH₂)₆]³⁺ and SO₄²⁻ ions. The octadecahydrate Ga₂(SO₄)₃·18H₂O crystallises from these solutions at room temperature. This hydrate loses water in stages when heated, forming the anhydrate Ga₂(SO₄)₃ above 150 °C^[3] and completely above 310 °C.^[1] Anhydrous Ga₂(SO₄)₃ is isostructural with iron(III) sulfate, crystallizing in the rhombohedral space group R3.^[4]

Gallium(III) sulfate

Names
Other names Digallium trisulfate
Identifiers
CAS Number	(anhydrous): 13494-91-2 (sulfates are wrong in CAS) N (octadecahydrate): 13780-42-2
3D model (JSmol)	(anhydrous): Interactive image (monohydrate): Interactive image (octadecahydrate): Interactive image
ChemSpider	(anhydrous): 58307
EC Number	(anhydrous): 236-816-0
PubChem CID	(anhydrous): 64773 (monohydrate): 16213072 (hexahydrate): 129655091 (octadecahydrate): 91886266
CompTox Dashboard (EPA)	(anhydrous): DTXSID40890705
InChI InChI=1S/2Ga.3H2O4S/c;;3*1-5(2,3)4/h;;3*(H2,1,2,3,4)/q2*+3;;;/p-6 Key: UXLRWZBQRAWBQA-UHFFFAOYSA-H (octadecahydrate): InChI=1S/2Ga.3H2O4S.18H2O/c;;3*1-5(2,3)4;;;;;;;;;;;;;;;;;;/h;;3*(H2,1,2,3,4);18*1H2/q2*+3;;;;;;;;;;;;;;;;;;;;;/p-6 Key: RBIKSELZKJNPFC-UHFFFAOYSA-H
SMILES (anhydrous): [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Ga+3].[Ga+3] (monohydrate): O.[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Ga+3].[Ga+3] (octadecahydrate): O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Ga+3].[Ga+3]
Properties
Chemical formula	Ga2(SO4)3
Molar mass	445.7 g/mol
Appearance	White solid[1]
Density	3.86 g/cm3[2]
Melting point	680 °C (1,256 °F; 953 K)[1] (decomposes)
Solubility in water	Slightly soluble[2]
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P302+P352, P305+P351+P338
NFPA 704 (fire diamond)	0 0 1
Related compounds
Other cations	Aluminium sulfate, Indium(III) sulfate,
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Gallium(III) sulfate is prepared from the reaction of hydroxygallium diacetate and sulfuric acid. The two reactants were mixed at 90 °C and left for 2 days which produced the octadecahydrate. Then, it was dried in a vacuum for 2 hours which created the extremely hygroscopic anhydrous form. The overall reaction is below:

2 Ga(CH₃COO)₂OH + 3 H₂SO₄ → Ga₂(SO₄)₃ + 4 CH₃COOH + 2 H₂O

After the production, it was confirmed to be the simple salt, Ga₂(SO₄)₃, by x-ray diffraction.^[1]

Properties

When heated over 680 °C, gallium sulfate gives off sulfur trioxide, yielding gallium(III) oxide.^[1] A gallium sulfate solution in water mixed with zinc sulfate can precipitate ZnGa₂O₄.^[5]

Derivatives

Basic gallium sulfate is known with the formula (H₃O)Ga₃(SO₄)₂(OH)₆.^[6]

Double gallium sulfates are known with composition NaGa₃(SO₄)₂(OH)₆, KGa₃(SO₄)₂(OH)₆, RbGa₃(SO₄)₂(OH)₆, NH₄Ga₃(SO₄)₂(OH)₆. These compounds are isostructural with jarosite and alunite. Jarosite and alunite can contain a small amount of gallium substituted for iron or aluminium.^[6] Organic base double gallium sulfates can contain different core structures, these can be chains of [Ga(SO₄)₃]^3-, [Ga(OH)(SO₄)₂]^2- or [Ga(H₂O)₂(SO₄)₂]⁻ or sheets of [Ga(H₂O)₂(SO₄)₂]⁻ units.^[7]

	formula	mw	crystal system	space group	unit cell Å	volume	density	properties	reference
	(H3O)Ga3(SO4)2(OH)6			R3m	a=7.18 c=17.17 z=1.5	766			[8]
	Ga4(OH)10SO4								[9]
	NH4Ga3(SO4)2(OH)6								[7]
trisodium gallium sulfate	Na3Ga(SO4)3		tetragonal		a = 9.451 c = 7.097				[10]
	NaGa3(SO4)2(OH)6								[7]
	KGa3(SO4)2(OH)6								[7]
	RbGa3(SO4)2(OH)6								[7]
Caesium gallium sulfate dodecahydrate	CsGa(SO4)2•12H2O		cubic	Pa3	Z=4		2.127	refractive index=1.461	[11]
dimethylammonium gallium sulfate hexahydrate	(CH3)2NH2Ga(SO4)2·6H2O							ferroeelastic	[12][13]
guanidinium gallium sulfate	[C(NH2)3]Ga(SO4)2·6H2O		hexagonal	P31m	a=11.82 c=9.13			ferroelectric	[14]
Ethylenediammonium acid gallium sulfate	[C2H10N2][H3O][Ga(SO4)3]								[7]
Ethylenediammonium basic gallium sulfate	[C2H10N2][Ga(OH)(SO4)2]·H2O								[7]
Tetramethylenediammonium gallium sulfate	[C4H14N2][Ga(H2O)2(SO4)2]2								[7]
Hexamethylenediammonium gallium sulfate	[C6H18N2][Ga(H2O)2(SO4)2]2								[7]