Arsenate arsenite

An arsenate arsenite is a chemical compound or salt that contains arsenate and arsenite anions (AsO₃^3- and AsO₄^3-). These are mixed anion compounds or mixed valence compounds. Some have third anions. Most known substances are minerals, but a few artificial arsenate arsenite compounds have been made. Many of the minerals are in the Hematolite Group.

Yellow spherules of halilsarpite, an arsenate arsenite mineral, on orange-brown smolyaninovite

An arsenate arsenite compound may also be called an arsenite arsenate.

Properties

Some members of this group of materials like mcgovernite has an extremely high unit cell dimension of 204 Å.^[1]

Related

Mixed valence pnictide compounds related to the arsenate arsenites include the nitrite nitrates, and phosphate phosphites.

List

name	formula	ratio AsO4:AsO3	system	space group	unit cell Å	volume	density	properties	references
Arsenic dioxide	AsO2	1:1	orthorhomnic	Pnma	a=8.597 b=5.235 c=7.269 Z=8	327.1	4.382		[2]
Arsenic(III) Arsenic(V) Oxide Hydroxide	As3O5(OH)	1:2	monoclinic	P21/c	a = 12.504 b = 4.593 c = 10.976 β = 118.08° Z = 4	556.2	3.84		[3]
	H6As3+7As5+7O31	1:1	hexagonal	P63	a = 12.0525 c = 4.7344 Z = 2	595.6			[4]
Segerstromite	Ca3(As5+O4)2[As3+(OH)3]2	2:1	cubic	I213	a = 10.7627 Z = 4	1246.71	3.46	colourless; refract index: n = 1.731	[5]
Synadelphite	Mn2+9(As5+O4)2(As3+O3)(OH)9 · 2H2O	2:1	Orthorhombic	Pnma	a = 10.75 b = 18.86c = 9.88 Z=4	2005	3.58	red; Biaxial (+); refract index: nα = 1.750 - 1.870 nβ = 1.751 - 1.880 nγ = 1.761 - 1.930	[6]
Hematolite	(Mn,Mg,Al,Fe3+)15(As5+O4)2(As3+O3)(OH)23	2:1	trigonal	R3	a = 8.275 Å, c = 36.60 Å Z=3	2,170.4	3.49	deep red; Uniaxial (-) refractive index nω = 1.733 nε = 1.714; Birefringence: 0.019	[7][8]
Turtmannite	(Mn,Mg)22.5Mg3-3x((V5+,As5+)O4)3(As3+O3)x(SiO4)3O5-5x(OH)20+x		trigonal		a = 8.259 c = 204.3 Z=12	12,068	3.8	light yellow; Uniaxial (-); refractive index: nε = 1.787	[9]
Carlfrancisite	Mn2+3(Mn2+,Mg,Fe3+,Al)42[As3+O3]2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42		trigonal	R3c	a = 8.2238 c = 205.113 Z=6	12,013.5	3.620	yellow-orange; Uniaxial (+) refractive index: nω = 1.756(2) nε = 1.758 Birefringence: δ = 0.002	[10]
	K2Cu3(As2O6)2	1:1	monoclinic	C2m	a=10.359 b=5.388 c=11.234 β=110.48°			[As(V)As(III)O6]4−	[11]
Dixenite	CuMn2+14Fe2+(SiO4)2(As5+O4)(As3+O3)5(OH)6	1:5	trigonal	R3	a = 8.233 c = 37.499 Z=3	2201	4.35	deep red-brown; Uniaxial (+) refractive index nω = 1.970 nε = 1.730	[12]
Arakiite	(Zn,Mn2+)(Mn2+,Mg)12(Fe3+,Al)2(As5+O4)2(As3+O3)(OH)23	2:1	monoclinic	Cc	a = 14.248 b = 8.228 c = 24.23 β = 93.62° Z=4	2843	3.41	orange-red brown; Biaxial (-); refract index: nα = 1.723 nβ = 1.744 nγ = 1.750 Birefringence: 0.027	[13]
Kraisslite	Zn3(Mn,Mg)25(Fe3+,Al)(As3+O3)2[(Si,As5+)O4]10(OH)16	5:1	Orthorhombic	C2221	a = 8.1821 b = 14.1946 c = 43.9103 Z=4	5099.8	3.876	pale red; Uniaxial (+) Refractive index: nε = 1.805	[14]
Mcgovernite	Mn19Zn3(AsO4)3(AsO3)(SiO4)3(OH)21	3:1	trigonal	R3m or R3m	a = 8.22 c = 203.1 Z=6	11,887.52	3.719	brown; Uniaxial (+) Refractive index: nω = 1.757 nε = 1.760 Birefringence: δ = 0.003	[15]
Halilsarpite	[Mg(H2O)6][CaAs3+2(Fe3+2.67Mo6+0.33)(AsO4)2O7]		orthorhomnic	Imma	a = 26.489 b = 7.4205 c = 10.4378	2051.7		lemon yellow; Biaxial (-) refractive index: nα = 1.646 nβ = 1.765(5) nγ = 1.815(5) 2V: 62° Max Birefringence: δ = 0.169	[16]
Wiklundite	Pb2(Mn2+,Zn)3(Fe3+,Mn2+)2(Mn2+,Mg)19(As3+O3)2[(Si,As5+)O4]6(OH)18Cl6		hexagonal	? R3c	a = 8.257 c = 126.59 Z = 6	7474	4.072	dark reddish brown	[17]
	Bi8O6(AsO3)2(AsO4)2		monoclinic	I2/a	a=24.372 b=5.528 c=29.90 β=99.058 Z=8	3978	7.652	colourless	[18]
	Th(AsIII4AsV4O18)	1:1	monoclinic	C2/c	a=18.2148 b 5.19792 c=17.3588 β=99.1298 Z=4	1622.70	4.582	colourless	[19]