Methamidophos

  • O,S-Dimethyl phosphoramidothioate
  • Phosphoramidothioic acid, O,S-dimethyl ester
Formula
C2H8NO2PS
Structure
Description
Crystalline solid, technical product is off-white with a pungent odor.
Uses
An acaracide and insecticide especially useful on brassica crops, cotton, head lettuce and potatoes.

Registry Numbers and Inventories.
CAS
10265-92-6
EC (EINECS/ELINCS)
233-606-0
EC Index Number
015-095-00-4
EC Class
Very toxic; Toxic; Irritant; Dangerous for the Environment
RTECS
TB4970000
RTECS class
Agricultural Chemical and Pesticide; Mutagen; Reproductive Effector; Human Data
UN (DOT)
2783
Merck
12,6014
Beilstein/Gmelin
1098870
EPA OPP
101201
Swiss Giftliste 1
G-5661
Austrailia AICS
Listed
New Zealand
Listed
Korea ECL
Listed

Properties.
Formula
C2H8NO2PS
Formula mass
141.13
Melting point, °C
44.4
Boiling point, °C
223
Vapor pressure, mmHg
0.0003
Density
1.31 g/cm3 (20 C)
Solubility in water
Very soluble
Refractive index
1.5092 (20 C)
Partition coefficient, pKow
-0.93

Hazards and Protection.
Storage
Do not store in mild steel containers. Stable at ambient temperatures.
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
(Non-Specific -- Organophosphorus Pesticide, n.o.s.) Stay upwind; keep out of low areas. Ventilate closed spaces before entering them. Do not touch spilled material; stop leak if you can do so without risk. Use water spray to reduce vapors. Small spills: absorb with sand or other noncombustible absorbent material and place into containers for later disposal. Small dry spills: with clean shovel place material into clean dry container and cover; move containers from spill area. Large spills: dike far ahead of spill for later disposal.
Stability
Stable at ambient temperature but 50% is decomposed in 140 hr at 40 C and ph2, in 120 hr at 37 C and pH 9. Stable at pH 3-8.Hydrolyzed in acids and alkalis, more rapidly at higher temperatures.
Incompatibilities
Incompatible with alkaline materials.

Fire.
Flash Point,°C
66 (EU A.9/ASTN-D56)
Fire fighting
(Non-Specific -- Organophosphorus Pesticide, n.o.s.) Stay upwind; keep out of low areas. Move containers from fire area if you can do it without risk. Fight fire from maximum distance. Dike fire control water for later disposal; do not scatter the material. Wear positive pressure breathing apparatus and special protective clothing.(Non-Specific -- Organophosphorus Pesticide, n.o.s.) This material may burn, but does not ignite readily. For small fires, use dry chemical, carbon dioxide, water spray, or foam. For large fires, use water spray, fog, or 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.
Poison_Class
2
Exposure effects
Reduced body temperature or elevated body temperature may occur. Low heart rate and abnormally low blood pressure may develop after moderate to severe poisoning. Rapid heart rate, elevated blood pressure, and changes in respiratory rate may also occur. Early giddiness, anxiety headache, and restlessness followed by ataxia, drowsiness, and confusion are common with moderate to severe exposures. Sporadic reports of human birth defects related to organophosphates have not been fully verified.
   Ingestion
Vomiting, hypersalivation, diarrhea, fecal incontinence and abdominal pain may occur.
   Inhalation
Dyspnea, rales, bronchorrhea, bronchospasm, or tachypnea may be noted. Noncardiogenic pulmonary edema may occur in severe cases. Chemical pneumonitis may be seen.
   Skin
Sweating is a consistent but not universal sign.
   Eyes
Constriction of the pupil, tearing, and blurred vision are common. Prolonged dialation of the pupils may occur in severe poisonings. Opsoclonus has been reported in one case. Salivation commonly occurs.

First aid
 
   Ingestion
Seek medical assistance.
   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
2783
Response guide
Hazard class
6.1
Packing Group
I; II; III
 
USCG CHRIS Code
MMD