• Demeton-s methyl sulfoxide
  • O,O-dimethyl S-(2-(ethylsufinyl)ethyl) thiophosphate
  • O,O-Dimethyl S-(2-(ethylsulfinyl)ethyl) monothiophosphate
  • O,O-Dimethyl S-(2-(ethylsulfinyl)ethyl) phosphorothioate
  • Phosphorothioic acid, s-(2-(ethylsulfinyl)ethyl) O,O-dimethyl ester
Clear amber liquid.
Systemic insecticide, acaricide, effective control by contact & systemic action of many destructive pests that attack certain vegetable, fruit & field crops. Primarily for aphids, mites, thrips, leafhoppers, and other sucking pests.

Registry Numbers and Inventories.
EC Index Number
EC Class
Toxic; Dangerous for the Environment
RTECS class
Agricultural Chemical and Pesticide; Mutagen; Reproductive Effector
Beilstein Reference
Swiss Giftliste 1

Formula mass
Melting point, °C
Boiling point, °C
Vapor pressure, mmHg
1.5E-5 (25 C)
1.289 g/cm3 (20 C)
Solubility in water
Refractive index
1.5151 (20 C)
Partition coefficient, pKow
Heat of vaporization
60.1 kJ/mol

Hazards and Protection.
Keep in a cool, dry, dark location in a tightly sealed container or cylinder. Keep away from incompatible materials, ignition sources and untrained individuals. Secure and label area. Protect containers/cylinders from physical damage.
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.
If Tyvek-type disposable protective clothing is not worn during handling of this chemical, wear disposable Tyvek-type sleeves taped to your gloves.
Wear a NIOSH-approved half face respirator equipped with a combination filter cartridge, i.e. organic vapor/acid gas/HEPA (specific for organic vapors, HCl, acid gas, SO2 and a high efficiency particulate filter).
Small spills/leaks
If you spill this chemical, use absorbent paper to pick up all liquid spill material. Your contaminated clothing and absorbent paper should be sealed in a vapor-tight plastic bag for eventual disposal. Solvent wash all contaminated surfaces with alcohol followed by washing 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.
Subject to hydrolysis and the rate is fairly rapidly in alkaline media, oxidizes to sulfone, decompes at elevated temperatures. Its volatility is 0.09 Mgcu m @ 20 C, 0.3 Mgcu m @ 30 C.

Flash Point,°C
Fire fighting
Fires involving this material can be controlled with a dry chemical, carbon dioxide or Halon extinguisher.
Fire potential
This chemical is flammable.

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.
Nausea, vomiting, abdominal cramps, and diarrhea are common muscarinic effects. Both painless and frank clinical pancreatitis have been reported.
Increased bronchial secretions, bronchospasm and dyspnea occur in moderate to severe exposures. Respiratory failure and non-cardiogenic pulmonary edema may occur with severe poisonings. Acute respiratory insufficiency is the main cause of death in acute poisonings. The hydrocarbon vehicle may cause chemical pneumonitis.
Profuse sweating is common. Pallor may be noted. Dermal sensitization has been reported.
Constriction of the pupil, tearing, and blurred vision are common. Prolonged dialation of the pupils may occur. Salivation commonly occurs.

First aid
CHOLINESTERASE INHIBITORS ARE EXTREMELY TOXIC AND FAST-ACTING POISONS. IMMEDIATELY call a hospital of poison control center and transport the victim to a hospital. Atropine is an antidote for cholinesterase inhibitors but should only be administered by properly trained personnel. In the absence of this option and if the victim is conscious and not convulsing, it may be worth considering the risk of inducing vomiting, even though the induction of vomiting is not usually recommended outside of a physician's care. Ipecac syrup or salt water may be used to induce vomiting in such an emergency. If the victim is convulsing or unconscious, do not give anything by mouth, assure that the victim's airway is open and lay the victim on his/her side with the head lower than the body. DO NOT INDUCE VOMITING. IMMEDIATELY transport the victim to a hospital.
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.
IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water. IMMEDIATELY call a hospital or poison control center even if no symptoms (such as redness or irritation) develop. IMMEDIATELY transport the victim to a hospital for treatment after washing the affected areas.
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.