A number of United States patents cover processes for
the manufacture of magnesium arsenates for use as
insecticides. The magnesium arsenates tested as insecticides
consisted generally of the dibasic magnesium arsenate,
MgHAsO4, the tribasic magnesium arsenate,
Mg3(AsO4)2, or the pyro-arsenate, Mg2As2O7, with varying amounts of water of crystallization and excess magnesium oxide or hydroxide. These magnesium arsenates
have been tested against a large number of insects
affecting fruits and vegetables and at one time were recommended
for the control of the Mexican Bean Beetle
but their use has declined due to the toxicity of As.
Various magnesium arsenates are available commercially
but it is the dibasic and tribasic salts that are
used in industry because of their relative stability.
