Methylarsonic acid

  • Methanearsonic acid
  • Monomethylarsinic acid
  • MAA
Formula
CH3AsO(OH)2
Structure
Description
Monoclinic, spear-shaped plates from absolute alcohol.
Uses
Substance is used as a herbicide.

Registry Numbers and Inventories.
CAS
124-58-3
EC (EINECS/ELINCS)
204-705-6
RTECS
PA1575000
RTECS class
Agricultural Chemical and Pesticide; Mutagen
UN (DOT)
1557
Merck
12,6020
Beilstein/Gmelin
1739373
Beilstein Reference
4-04-00-03682
RCRA
K031
EPA OPP
128876
Korea ECL
Listed

Properties.
Formula
CH5AsO3
Formula mass
139.97
Melting point, °C
161
Solubility in water
Very soluble
pKa/pKb
3.87 (pKa)

Hazards and Protection.
Storage
Solid formulations are somewhat hygroscopic and should be stored in dry place.
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
Wear appropriate protective gloves, clothing and goggles.
Respirators
Wear positive pressure self-contained breathing apparatus (SCBA).
Small spills/leaks
Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Cover with plastic sheet to prevent spreading. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS.
Stability
No data.
Incompatibilities
Hazardous when water soln is in contact with active metals, ie, iron, aluminum, zinc.
Decomposition
When heated to decomposition it is hazardous.

Fire.
Fire fighting
Small Fires: Dry chemical, carbon dioxide or water spray. Large Fires: Water spray, fog or regular foam.
Fire potential
Combustible material: may burn but does not ignite readily.
Hazards
Containers may explode when heated.
Combustion products
Fire may produce irritating, corrosive and/or toxic gases.

Health.
Exposure limit(s)
OSHA PEL: 1910.1018 TWA 0.010 mg/m3 NIOSH REL: Ca C 0.002 mg/m3 15-minute See Appendix A NIOSH IDLH: Potential occupational carcinogen 5 mg/m3 (as As)
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
Gastric decontamination - aggressive decontamination with gastric lavage is recommended. Activated charcoal: administer charcoal as a slurry (240 ml water/30 g charcoal). Usual dose: 25 to 100 g in adults/adolescents.
   Inhalation
Move victim to fresh air. Apply artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; induce artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult.
   Skin
Remove and isolate contaminated clothing and shoes. Immediately flush with running water for at least 20 minutes. For minor skin contact, avoid spreading material on unaffected skin.
   Eyes
Immediately flush with running water for at least 20 minutes.

Transport.
UN number
1557
Response guide
Hazard class
6.1
Packing Group
I; II; III