Loading AI tools
Chemical compound From Wikipedia, the free encyclopedia
Calcium arsenate is the inorganic compound with the formula Ca3(AsO4)2. A colourless salt, it was originally used as a pesticide and as a germicide. It is highly soluble in water, in contrast to lead arsenate, which makes it more toxic. Two minerals are hydrates of calcium arsenate: rauenthalite Ca3(AsO4)2·10H2O and phaunouxite Ca3(AsO4)2·11H2O.[4] A related mineral is ferrarisite (Ca5H2(AsO4)4·9H2O.[5]
Names | |
---|---|
IUPAC name
Calcium arsorate | |
Other names
Calcium orthoarsenate Cucumber dust Tricalcium arsenate Tricalcium ortho-arsenate | |
Identifiers | |
3D model (JSmol) |
|
ChemSpider | |
ECHA InfoCard | 100.029.003 |
EC Number |
|
KEGG | |
PubChem CID |
|
RTECS number |
|
UNII | |
CompTox Dashboard (EPA) |
|
| |
| |
Properties | |
Ca3(AsO4)2 | |
Molar mass | 398.072 g/mol |
Appearance | white powder |
Odor | odorless |
Density | 3.62 g/cm3, solid |
Melting point | 1,455 °C (2,651 °F; 1,728 K) (decomposes) |
0.013 g/100 mL (25 °C)[1] | |
Solubility in Organic solvents | insoluble |
Solubility in acids | soluble |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards |
carcinogen[2] |
NFPA 704 (fire diamond) | |
Flash point | noncombustible[2] |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
20 mg/kg (rat, oral) 82 mg/kg (rat, oral) 74 mg/kg (mouse, oral) 50 mg/kg (rabbit, oral) 38 mg/kg (dog, oral)[3] |
NIOSH (US health exposure limits): | |
PEL (Permissible) |
TWA 0.010 mg/m3[2] |
REL (Recommended) |
Ca C 0.002 mg/m3 [15-minute][2] |
IDLH (Immediate danger) |
5 mg/m3 (as As)[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Calcium arsenate is commonly prepared from disodium hydrogen arsenate and calcium chloride:
In the 1920s, it was made in large vats by mixing calcium oxide and arsenic oxide.[6] In the United States, 1360 metric tons were produced in 1919, 4540 in 1920, and 7270 in 1922.[1] The composition of commercially available calcium arsenate varies from manufacturer to manufacturer. A typical composition is 80-85% of Ca3(AsO4)2 a basic arsenate probably with a composition of 4CaO.As2O5 together with calcium hydroxide and calcium carbonate.[citation needed]
It was once a common herbicide and insecticide. 38,000,000 kilograms were reported to be produced in 1942 alone, mainly for protection of cotton crops. Its high toxicity led the development of DDT.[7]
Calcium arsenate use is now banned in the UK, and its use is strictly regulated in the United States. It is currently the active ingredient in TURF-Cal manufactured by Mallinckrodt, it is one of the few herbicides – used mainly for the control of Poa annua and crabgrass- that hinders earthworm activity. Its label states that it will "reduce and inhibit earthworm activity and survival" and is only recommended against serious earthworm infestations in places such as golf course greens.[8]
Calcium arsenate is highly toxic, having both carcinogenic and systemic health effects.[9] The Occupational Safety and Health Administration has set a permissible exposure limit at 0.01 mg/m3 over an eight-hour time-weighted average, while the National Institute for Occupational Safety and Health recommends a limit five times less (0.002 mg/m3).[10]
It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[11]
Weilite is the monohydrogenated counterpart, Ca(HAsO4),[12] while švenekite – the dihydrogenated one, Ca(H2AsO4)2.[13] Hydrated analogues of weilite are haidingerite (monohydrate) and pharmacolite (dihydrate), with the latter name reflecting arsenic-related toxicity. Examples of more complex, hydrated Ca arsenates with some anions hydrogenated, are ferrarisite,[14] guérinite,[15] sainfeldite,[16] vladimirite,[17] and jeankempite.[18][19]
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.