Sodium methanearsonate

  • Ansar
  • Ansar 6.6
  • MSMA
  • Weed 108
  • Monosodium methylarsonate
  • Methanearsonic acid, monosodium salt
Formula
Na[AsO(OH)2(CH3)]
Structure
Description
Odorless colorless solid. Solution may be red or green.
Uses
herbicide

Registry Numbers and Inventories.
CAS
2163-80-6
EC (EINECS/ELINCS)
218-495-9
RTECS
PA2625000
RTECS class
Agricultural Chemical and Pesticide; Organometallic; Mutagen; Primary Irritant
Beilstein/Gmelin
3915729
Beilstein Reference
2-04-00-00996
RCRA
D004
EPA OPP
13803
Swiss Giftliste 1
G-2600
Austrailia AICS
Listed
New Zealand
Listed

Properties.
Formula
CH4AsO3.Na
Formula mass
161.95
Melting point, °C
113-116 (sesquihydrate);132- 139(hexahydrate)
Odor Threshold Odor threshold Odorless
Density
1.535 g/cm3 (25 C)
Solubility in water
1 kg/L @ 20 C
pKa/pKb
9.02 (pKa)
Partition coefficient, pKow
< 1

Hazards and Protection.
Storage
Solid formulations are somewhat hygroscopic and should be stored in dry place. Methanearsonic acid
Handling
All chemicals should be considered hazardous. Avoid direct physical contact. Use appropriate, approved safety equipment. Untrained individuals should not handle this chemical or its container. Handling should occur in a chemical fume hood.
Protection
Protective gloves rubber or neoprene, goggles, or face shield for eye protection, rubber apron. Long pants, long-sleeved shirt, impermeable gloves, boots for handling or applying. Mixer-loaders should wear an apron and full-face shield for handling, mixing concentrate. Flagmen should be fully protected during spray operations or use mechanical flagmen. Pilots and ground spray rig applicators should wear a mask or approved respirator.
Respirators
Use NIOSH/MSHA approved respirator appropriate for exposure of concern.
Small spills/leaks
If you spill this chemical, you should dampen the solid spill material with water, then transfer the dampened material to a suitable container. Use absorbent paper dampened with water to pick up any remaining material. Seal your contaminated clothing and the absorbent paper in a vapor-tight plastic bag for eventual disposal. Wash all contaminated surfaces with a strong soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.
Stability
Stable to hydrolysis.

Fire.
Fire fighting
Fires involving this compound should be controlled with a dry chemical, carbon dioxide or Halon extinguisher.
Fire potential
Non-flammable.
Combustion products
Toxic gases may be generated in fires.

Health.
Exposure limit(s)
OSHA: PEL (8 h TWA): 0.5 mg/m3.
Poison_Class
3
Exposure effects
Abnormally low blood pressure and rapid heart rate are common early signs. Fever and rapid breathing may occur. Elevated blood pressure has been associated with chronic environmental arsenic exposure. Altered mental status, seizures, toxic delirium, encephalopathy, and delayed peripheral neuropathy are complications of acute arsenic poisoning. Inorganic arsenic crosses the placenta and may result in spontaneous abortion or stillbirth with either acute or chronic poisoning.
   Ingestion
Acute toxicity results in early symptoms of abdominal pain, severe vomiting and diarrhea, as well as dryness of the oral and nasal cavities.
   Inhalation
Respiratory tract irritation may occur. Cardiogenic or noncardiogenic pulmonary edema and respiratory failure may develop in severe poisonings.
   Skin
Skin findings may include hyperpigmentation, keratoses, and epidermoid carcinomas. Mee's lines of the nails are common. Trivalent arsenic compounds are corrosive to the skin. Arsenic trioxide and pentoxide are sensitizers.
   Eyes
As(III) is corrosive to the eyes, mouth, and mucous membranes. Perforation of the nasal septum can occur.

First aid
 
   Ingestion
Seek medical attention. If individual is drowsy or unconscious, do not give anything by mouth; place individual on the left side with the head down. Contact a physician, medical facility, or poison control center for advice about whether to induce vomiting. If possible, do not leave individual unattended.
   Inhalation
IMMEDIATELY leave the contaminated area; take deep breaths of fresh air. IMMEDIATELY call a physician and be prepared to transport the victim to a hospital even if no symptoms (such as wheezing, coughing, shortness of breath, or burning in the mouth, throat, or chest) develop. Provide proper respiratory protection to rescuers entering an unknown atmosphere. Whenever possible, Self-Contained Breathing Apparatus (SCBA) should be used.
   Skin
IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water. If symptoms such as redness or irritation develop, IMMEDIATELY call a physician and be prepared to transport the victim to a hospital for treatment.
   Eyes
First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

Transport.
USCG CHRIS Code
MSA