{{distinguish|Copper arsenite}} {{chembox | Watchedfields = changed | verifiedrevid = 443420181 | ImageFile = Copper(II)-arsenate-constituent-ions-2D.png | ImageSize = | IUPACName = Copper(II) arsenate | OtherNames = {{ubl|Copper arsenate|Copper orthoarsenate|Cupric arsenate|Tricopper arsenate|Tricopper orthoarsenate}} |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 24279 | InChI = 1/2AsH3O4.3Cu/c2*2-1(3,4)5;;;/h2*(H3,2,3,4,5);;;/q;;3*+2/p-6 | InChIKey = RKYSWCFUYJGIQA-CYFPFDDLAM | SMILES = [Cu+2].[Cu+2].[Cu+2].[O-][As]([O-])(=O)[O-].[O-][As]([O-])([O-])=O | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/2AsH3O4.3Cu/c2*2-1(3,4)5;;;/h2*(H3,2,3,4,5);;;/q;;3*+2/p-6 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = RKYSWCFUYJGIQA-UHFFFAOYSA-H | CASNo = 7778-41-8 | CASNo_Ref = {{cascite|correct|??}} | UNII_Ref = {{fdacite|correct|FDA}} | UNII = EV78GZO3YS | PubChem = 26065 | RTECS = }} |Section2={{Chembox Properties | Formula = Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub> | MolarMass = 468.48 g/mol | Appearance = blue or bluish green solid | Density = 5.2 g/cm<sup>3</sup> | MeltingPtC = 1100 | BoilingPt = | Solubility = insoluble | SolubleOther = insoluble in alcohol<hr/>soluble in ammonia solution, dilute acids | SolubilityProduct = 7.95{{e|&minus;36}}<ref name="crc">{{cite book |author1=John Rumble |title=CRC Handbook of Chemistry and Physics |date=June 18, 2018 |publisher=CRC Press |isbn=978-1138561632 |pages=5–188|edition=99 |language=English}}</ref> }} | Section3 = {{Chembox Structure | Structure_ref = <ref name=Poulsen>{{Cite journal |last=Poulsen |first=Sandra J. |last2=Calvo |first2=C. |date=1968-03-15 |title=Crystal structure of Cu3(AsO4)2 |url=https://cdnsciencepub.com/doi/10.1139/v68-153 |journal=Canadian Journal of Chemistry |volume=46 |issue=6 |pages=917–927 |doi=10.1139/v68-153 |issn=0008-4042|url-access=subscription }}</ref> | CrystalStruct = monoclinic | SpaceGroup = ''P''2<sub>1</sub>/''c'' | PointGroup = | LattConst_a = 6.327 Å | LattConst_b = 8.642 Å | LattConst_c = 11.313 Å | LattConst_alpha = 92.04 | LattConst_beta = | LattConst_gamma = | UnitCellVolume = | UnitCellFormulas = 4 units per cell | Coordination = }} |Section7={{Chembox Hazards | FlashPt = | GHS_ref = <ref>{{Cite web |last=PubChem |title=Copper Arsenate |url=https://pubchem.ncbi.nlm.nih.gov/compound/26065 |access-date=2026-02-18 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> | GHSPictograms = {{GHS07}}{{GHS08}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|H319|H350|H361|H370|H372}} | PPhrases = {{P-phrases|P203|P260|P264|P264+P265|P270|P280|P305+P351+P338|P308+P316|P318|P319|P321|P337+P317|P405|P501}} | PEL = TWA 1 mg/m<sup>3</sup> (as Cu)<ref name=PGCH>{{PGCH|0150}}</ref> | REL = TWA 1 mg/m<sup>3</sup> (as Cu)<ref name=PGCH/> | IDLH = TWA 100 mg/m<sup>3</sup> (as Cu)<ref name=PGCH/> }} |Section8={{Chembox Related | OtherAnions = | OtherCations = }} }}

'''Copper arsenate''' is an inorganic compound with the chemical formula Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·nH<sub>2</sub>O (n=0,4). It is a blue or bluish-green solid, forming monoclinic crystals.

==Occurrence== Anhydrous copper arsenate (Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>) is found in nature as the mineral lammerite.<ref>{{ cite journal | first1 = F. C. | last1 = Hawthorne | journal = American Mineralogist | volume = 71 | year = 1986 | pages = 206–209 | title = Lammerite, Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>, a modulated close-packed structure | url = http://www.minsocam.org/ammin/AM71/AM71_206.pdf }}</ref> The tetrahydrate (Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O) occurs naturally as the mineral rollandite.<ref>{{ cite journal | title = Rollandite, Cu<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O, a new mineral | first1 = H. | last1 = Sarp | first2 = R. | last2 = Černý | journal = Eur. J. Mineral. | volume = 12 | year = 2000 | pages = 1045–1050 | doi = 10.1127/0935-1221/2000/0012-1045 | url = https://archive-ouverte.unige.ch/unige:86439 }}</ref>

== Preparation == Copper arsenate can be prepared by reacting disodium hydrogen arsenate and copper(II) chloride in aqueous solution.<ref name=Poulsen />

==Uses== {{Unreferenced|section|date=February 2026}} Copper arsenate is an insecticide used in agriculture. It is also used as a herbicide, fungicide, and a rodenticide. It is also used as a poison in slug baits.

==Related compounds== Basic copper arsenates with the formulas Cu<sub>2</sub>(OH)AsO<sub>4</sub> and Cu<sub>3</sub>(AsO<sub>4</sub>)(OH)<sub>3</sub> have been observed.<ref>{{Cite journal |last=Nelson |first=Hanna |last2=Shchukarev |first2=Andrey |last3=Sjöberg |first3=Staffan |last4=Lövgren |first4=Lars |date=2011-05-01 |title=Composition and solubility of precipitated copper(II) arsenates |url=https://www.sciencedirect.com/science/article/pii/S0883292711000291 |journal=Applied Geochemistry |volume=26 |issue=5 |pages=696–704 |doi=10.1016/j.apgeochem.2011.01.028 |issn=0883-2927|url-access=subscription }}</ref> The former is found naturally as the mineral olivenite.

==See also== *Calcium arsenate *Chromated copper arsenate *Lead arsenate *Paris Green (copper acetoarsenite) *Scheele's Green (copper arsenite)

==References== {{Reflist}}

==External links== {{Commons category}} *[https://web.archive.org/web/20080302034606/http://www.npi.gov.au/database/substance-info/profiles/27.html National Pollutant Inventory - Copper and compounds fact sheet]

{{Copper compounds}} {{Insecticides}}

Category:Arsenates Category:Copper(II) compounds Category:Inorganic insecticides Category:Arsenical herbicides Category:Rodenticides Category:Fungicides