Description
Monosodium methylarsonate is a herbicide that is not widely approved for use in the developed world due to its toxicity. As well as being highly toxic it is also a known skin, eye and inhalation irritant. It is highly soluble in water and considered to be persistent in soils. Monosodium methylarsonate is moderately toxic to fish, algae and honeybees and slightly less toxic to birds.
Chemical Properties
Colorless solid or colorless to red or green solution. Odorless. Specific Gravity: (DSMA) 1.0 @ 20C; (MSMA solutions) 1.4°1.6 @ 20°C (liquid);
Chemical Properties
White solid. Very solu-
ble in water.
Uses
Postemergence herbicide for grassy weeds.
Definition
The monosodiumsalt of methylarsonic acid.
Production Methods
Monosodium methylarsonate is commercially produced by reacting methylarsonic acid with sodium hydroxide. The process begins with the synthesis of methylarsonic acid, typically derived from the controlled oxidation of methylarsine or trimethylarsine oxide. This acid is then neutralised with sodium hydroxide to yield the monosodium salt. The reaction is conducted in aqueous solution under mild conditions, followed by concentration and crystallization to obtain the solid product.
General Description
Odorless colorless solid. Solution may be red or green. Solid may float or sink in water; solid and solution mix with water.
Air & Water Reactions
Water soluble.
Reactivity Profile
Sodium methylarsonate is decomposed by strong oxidizers and reducers.
Health Hazard
Subacute poisoning by arsenicals causes salty taste, burning in throat and stomach, and intestinal pain. Acute toxicity indicated by headache, vomiting, stupor, convulsions, paralysis. About 1 ounce to 1 pound must be taken to cause these symptoms.
Fire Hazard
Special Hazards of Combustion Products: Toxic gases may be generated in fires.
Trade name
WEED-BROOM® (DSMA+Bomacil+2,4-D); WEEDE-RAD®; WEED-S-RAD®; WEED HOE®
Mechanism of action
Selective, contact herbicide, phytotoxic
Safety Profile
Poison by unspecified
route. Moderately toxic by ingestion. A skin
and eye irritant. When heated to
decomposition it emits toxic fumes of As
and Na2O.
Potential Exposure
Those exposed to this organometallic, selective pesticide used for postemergence control of grasses, sedges, and weeds.
Shipping
UN2994 Arsenical pesticides, liquid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials. UN3280 Organoarsenic compound, liquid, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required, Potential Inhalation Hazard (Special Provision 5).
Incompatibilities
Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Incompatible with reducing agents
Waste Disposal
Disposal of unused product must be undertaken by qualified personnel who are knowledgeable in all applicable regulations and follow all pertinent safety precautions including the use of appropriate protective equipment. For proper handling and disposal, always comply with federal, state, and local regulations.
