Lead hydrogen arsenate

It is usually produced using the following reaction, which leads to formation of the desired product as a solid precipitate: :Pb(NO3)2 + H3AsO4 → PbHAsO4 +2 HNO3 It has the same structure as the hydrogen phosphate PbHPO4. Like lead sulfate PbSO4, these salts are poorly soluble. ==Uses==

As an insecticide, it was introduced in 1898 used against the gypsy moth in Massachusetts. It represented a less soluble and less toxic alternative to then-used Paris Green, which is about 10x more toxic. 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 the codling moth and snow-white linden moth. It was used mainly on apples, but also on other fruit trees, garden crops, turfgrasses, and against mosquitoes. In combination with ammonium sulfate, it was used in southern California as a winter treatment on lawns to kill crab grass seed. 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 when DDT was found. US EPA banned use of lead arsenate on food crops in 1988. ==Safety==

LD50 is 1050 mg/kg (rat, oral). 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. pesticides from the 1911 Door County Democrat. Today, about 3.9% of the land in the county is classified as "impaired" by the local government due to persistent contamination of the soil and groundwater. ==See also==