Monosodium methyl arsenate

Monosodium methyl arsenate (MSMA) is an arsenic-based herbicide and fungicide. It is an organic arsenate. Its CAS number is and its chemical formula is CH4AsNaO3. It is also known as monosodium methane arsonate and methyl arsonic acid monosodium salt (9CI).

Some of its trade names are Ansar 170, Ansar 170L, Ansar 529, Ansar 529 HC, Ansar 6.6, Asazol, Bueno, Bueno 6, CCRIS 4676, Caswell No. 582, Daconate, Daconate 6, Dal-E-Rad, Dal-E-Rad 120, Drexar, EPA Pesticide Chemical Code 013803, Gepiron, HSDB 754, Herb-All, Herban M, Merge, Merge 823, Mesamate, Mesamate H.C., Mesamate-400, Mesamate-600, and Sodium methylarsonate.

It is one of the most common herbicides used on golf courses. It is typically used for control of grassy weeds such as crabgrass.

It is a less toxic organic form of arsenic, which has replaced the lead hydrogen arsenate's role in agriculture.

See also:
 * Cacodylic acid.
 * Disodium methyl arsenate