WHAT IS MSMA?

General Information

MSMA, the monosodium salt of methanearsonic acid (MAA), is an herbicide used against a wide spectrum of grass and broad-leaf weeds. The chemical formula of MSMA is:

Pure MSMA is a white crystalline solid, its molecular weight is 162, its vapor pressure is 10-7 mm/Hg, and its melting point is 113-116ºC. MSMA is marketed and applied as water based formulations, containing 6-6.6 lbs/gal of the active ingredient. These formulations are clear, colorless to yellow/green/brown, and are odorless. The formulations are non-flammable, practically not corrosive, and easy to handle. MSMA has low toxicity -- the acute toxicity category of a typical MSMA product is III. This category requires labeling it with the signal word “CAUTION,” which is very common for many pesticides.