Calcium arsenate
chemical compound
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. A related mineral is ferrarisite (Ca5H2(AsO4)4·9H2O.
Preparation
Calcium arsenate is commonly prepared from disodium hydrogen arsenate and calcium chloride:
2 Na2H[AsO4] + 3 CaCl2 → 4 NaCl + Ca3[AsO4]2 + 2 HCl
In the 1920s, it was made in large vats by mixing calcium oxide and arsenic oxide. In the United States, 1360 metric tons were produced in 1919, 4540 in 1920, and 7270 in 1922.
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.
Use as a herbicide
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.
Regulation
Calcium arsenate use is now banned in the UK, and its use is strictly regulated in the United States.
The public source identifies “Calcium arsenate” as chemical compound. This brief keeps that definition visible, then builds a research path around Calcium, arsenate and chemical.
Why this record matters
A short description can identify a subject without explaining its stakes. For “Calcium arsenate”, the useful work is to connect “chemical compound” to the records capable of establishing context and consequence.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Nov 10, 2024. The linked authority identifier is Q412645. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1360, 1919, 1920 and 1922.
A general summary may omit uncertainty, sample limits or methodological disagreement that is explicit in the technical record. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Check terminology, classification and the date of the cited evidence. Scientific names and technical consensus can change while older records retain historical value.
- Current terminology
- Classification context
- Finding cited technical literature
Primary datasets, specimen catalogues, standards bodies and the most recent peer-reviewed literature.
Three-step research path
- Establish the record: confirm the title “Calcium arsenate”, its source revision and the description used here.
- Expand the search: follow Calcium arsenate primary sources, Calcium arsenate archive and Calcium research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Calcium arsenate”?
- Has classification or technical consensus changed since the cited source?
- Which observation, specimen, dataset or publication supports the account?
Search terms from this dossier
This entry incorporates text from “Calcium arsenate” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.