Methyl mercaptan

  • Methanethiol
  • Mercaptomethane
  • Thiomethyl alcohol
  • Methyl sulfhydrate
Formula
CH3SH
Structure
Description
Water-white - colorless liquid. Garlic-like - unpleasant odor.

Registry Numbers and Inventories.
CAS
74-93-1
EC (EINECS/ELINCS)
200-822-1
EC Index Number
016-021-00-3
EC Class
Extremely flammable; Harmful; Dangerous for the Environment
RTECS
PB4375000
RTECS class
Mutagen
UN (DOT)
1064
Merck
12,6023
Beilstein/Gmelin
1696840
Beilstein Reference
4-01-00-01273
RCRA
U153
Swiss Giftliste 1
G-2513
Canada DSL/NDSL
DSL
US TSCA
Listed
Austrailia AICS
Listed
New Zealand
Listed
Japan ENCS (MITI)
Listed

Properties.
Formula
CH4S
Formula mass
48.11
Melting point, °C
-123.0
Boiling point, °C
5.9
Vapor pressure, mmHg
1900 (25 C)
Vapor density (air=1)
1.66
Odor Threshold Odor threshold 0.0021 ppm
Critical temperature
197
Critical pressure
71.40
Density
0.8948 g/cm3 (0 C)
Solubility in water
2.4 g/100 mL.
Surface tension
26.44 g/s2 (10 C)
pKa/pKb
10.54 (pKa)
Partition coefficient, pKow
0.72
Heat of fusion
5.9 kJ/mol
Heat of vaporization
23.8 kJ/mol
Heat of combustion
-1194 kJ/mol

Hazards and Protection.
Storage
Keep away from heat, sparks, and flame. Keep away from sources of ignition. Store in a cool, dry place. Keep container closed when not in use. Flammables-area.
Handling
Wash thoroughly after handling. Remove contaminated clothing and wash before reuse. Ground and bond containers when transferring material. Avoid contact with eyes, skin, and clothing. Empty containers retain product residue, (liquid and/or vapor), and can be dangerous. Avoid contact with heat, sparks and flame. Avoid ingestion and inhalation. Do not pressurize, cut, weld, braze, solder, drill, grind, or expose empty containers to heat, sparks or open flames.
Protection
Eyes: Wear chemical goggles. Wear appropriate protective eyeglasses or chemical safety goggles as described by OSHA's eye and face protection regulations in 29 CFR 1910.133 or European Standard EN166. Skin: Wear appropriate protective gloves to prevent skin exposure. Clothing: Wear appropriate protective clothing to minimize contact with skin.
Respirators
A respiratory protection program that meets OSHA's 29 CFR 1910.134 and ANSI Z88.2 requirements or European Standard EN 149 must be followed whenever workplace conditions warrant a respirator's use.
Small spills/leaks
Absorb spill with inert material, (e.g., dry sand or earth), then place into a chemical waste container. Avoid runoff into storm sewers and ditches which lead to waterways. Clean up spills immediately, using the appropriate protective equipment. Remove all sources of ignition. Use a spark-proof tool. A vapor suppressing foam may be used to reduce vapors. Rinse area for 10 minutes with a strong Sodium Hypochorite (bleach) solution, then reabsorb material.
Stability
Stable under normal temperatures and pressures.
Incompatibilities
Strong oxidizing agents, strong reducing agents, strong acids, strong bases, copper, copper alloys, halogenated agents, hydrazine, organic peroxides, zinc, ketones (e.g. acetone, acetophenone, MEK, MIBK), epoxides (e.g. butyl glycidyl ether), lead, moisture, organic materials.
Decomposition
Irritating and toxic fumes and gases, sulfur oxides (SOx), including sulfur oxide and sulfur dioxide.

Fire.
Flash Point,°C
-49
Fire fighting
Wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion. Use water spray to keep fire-exposed containers cool. Extremely flammable liquid. Containers may explode in the heat of a fire. Will be easily ignited by heat, sparks or flame. Extinguishing media: For small fires, use dry chemical, carbon dioxide, water spray or alcohol-resistant foam. For large fires, use water spray, fog, or alcohol-resistant foam. Use water spray to cool fire-exposed containers. Water may be ineffective. Use agent most appropriate to extinguish fire. Do NOT use straight streams of water.
Fire potential
Very flammable. Vapors may spread from spills. Avoid all ignition sources including static electric sparks.
Hazards
Combustion produces irritating sulfur dioxide. Flash back along vapor track may occur. Very dangerous when exposed to heat, flame, or oxidizers. On decomposition it emits highly toxic fumes of sulfur oxides. It will react with water, steam or acids to produce toxic and flammable vapors; and can react vigorously with oxidizing materials. Irritating sulfur dioxide is produced upon combustion. When heated to decomposition, it emits highly toxic fumes and flammable vapors. Incompatible with mercuric oxide and oxidizing materials. Avoid direct sunlight, and areas of high fire hazards.
Combustion products
Irritating sulfur dioxide is produced.
Health
4
 
Flammability
4
 
 
Reactivity
1
 

Health.
Exposure limit(s)
NIOSH REL: C 0.5 ppm (1 mg/m3) [15-minute] OSHA PEL: C 10 ppm (20 mg/m3) IDLH 150 ppm
Poison_Class
4
Exposure effects
May cause liver and kidney damage. Exposure to large doses may cause central nervous system depression.
   Ingestion
Causes gastrointestinal irritation with nausea, vomiting and diarrhea. May cause liver and kidney damage. May cause central nervous system depression. Mercaptans may cause nausea and headache. Exposure to high concentrations of mercaptans can produce unconsciousness with cyanosis, cold extremities and rapid pulse.
   Inhalation
Causes respiratory tract irritation. May cause liver and kidney damage. Exposure produces central nervous system depression. Vapors may cause dizziness or suffocation. Exposure may lead to delirium, convulsions, paralysis, and coma. Exposure to high concentrations of mercaptans can produce unconsciousness with cyanosis, cold extremities and rapid pulse. Mercaptans may cause nausea and headache. Harmful if inhaled.
   Skin
Causes skin irritation. May be absorbed through the skin.
   Eyes
Causes eye irritation.

First aid
 
   Ingestion
Do NOT induce vomiting. If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid immediately.
   Inhalation
Get medical aid immediately. Remove from exposure to fresh air immediately. If breathing is difficult, give oxygen. DO NOT use mouth-to-mouth respiration. If breathing has ceased apply artificial respiration using oxygen and a suitable mechanical device such as a bag and a mask.
   Skin
Get medical aid. Flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse.
   Eyes
Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid immediately. Do NOT allow victim to rub or keep eyes closed.

Transport.
UN number
1064
Response guide
Hazard class
2.3
PRTC
T
USCG CHRIS Code
MMC
 
Std. Transport #
4920355