  | |
| Names | |
|---|---|
| Other names Lead (II) monohydrogen arsenate | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.029.149 |
| EC Number |
|
| UNII | |
| UN number | 1617 |
| |
| |
| Properties | |
| PbHAsO4 | |
| Molar mass | 347.1 g·mol−1 |
| Appearance | white solid |
| Density | 5.943 g/cm3[1] |
| Melting point | Decomposes at 280°C[1] |
| Insoluble in water; soluble in nitric acid and alkalies[1] | |
| Hazards | |
| GHS labelling: | |
   | |
| Danger | |
| H301,H331,H350,H360Df,H373,H410 | |
| P201,P202,P260,P261,P264,P270,P271,P273,P281,P301+P310,P304+P340,P308+P313,P311,P314,P321,P330,P391,P403+P233,P405,P501 | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Lead hydrogen arsenate, also calledlead arsenate,acid lead arsenate orLA, chemical formula PbHAsO4, is an inorganicinsecticide formerly used to control pests includinggypsy moth,potato beetle andrats.[2]
Lead arsenate was the most extensively usedarsenical insecticide.[3] Two principal formulations of lead arsenate were marketed: basic lead arsenate (Pb5OH(AsO4)3, CASN: 1327-31-7) and acid lead arsenate (PbHAsO4).[3]
It is now banned for use as a pesticide in countries such as the US and UK as it is considered too toxic and persistent.
It is usually produced using the following reaction, which leads to formation of the desired product as a solid precipitate:
It has the same structure as the hydrogen phosphate PbHPO4. Like lead sulfate PbSO4, these salts are poorly soluble.[4]
As an insecticide, it was introduced in 1898 used against thegypsy moth inMassachusetts. It represented a less soluble and less toxic alternative to then-usedParis Green, which is about 10x more toxic.[5] It also adhered better to the surface of the plants, further enhancing and prolonging its insecticidal effect.
Lead arsenate was widely used in Australia, Canada, New Zealand, US, England, France, North Africa, and many other areas, principally against thecodling moth and snow-white linden moth.[6] It was used mainly onapples, but also on other fruit trees, garden crops, turfgrasses, and againstmosquitoes. In combination withammonium sulfate, it was used in southernCalifornia as a winter treatment on lawns to killcrab grass seed.[7]
The search for a substitute was commenced in 1919, when it was found that its residues remain in the products despite washing their surfaces. Alternatives were found to be less effective or more toxic to plants and animals, until 1947 whenDDT was found. US EPA banned use of lead arsenate on food crops in 1988.[8][9]
LD50 is 1050 mg/kg (rat, oral).[5]
Morel mushrooms growing in oldappleorchards that had been treated with lead arsenate mayaccumulate levels of toxiclead andarsenic that are unhealthy for human consumption.[10]
Lead arsenate was used as an insecticide in deciduous fruit trees from 1892[11] until around 1947 in Washington. Peryea et al. studied the distribution of Pb and As in these soils, concluding that these levels were above maximum tolerance levels. This indicates that these levels could be of environmental concern and potentially could be contaminating the groundwater in the area.[12]
EPA banned use of lead arsenate on food crops in 1988.
