Thioglycolic acid

  • Mercaptoacetic acid
  • Acetyl mercaptan
  • Mercaptoacetate
  • 2-Thioglycolic acid
  • 2-Mercaptoacetic acid
Formula
HSCH2COOH
Structure
Description
Colorless liquid with a characteristic strong unpleasant odor, lachrymator.
Uses
Chemical intermediate for thioglycolates (eg, calcium thioglycolate), ingredient of depilatories, permanent hair wave solutions and biological media for microorganism growth, reagent for detection of iron and other metal ions, chelating agent.

Registry Numbers and Inventories.
CAS
68-11-1
EC (EINECS/ELINCS)
200-677-4
EC Index Number
607-090-00-6
EC Class
Toxic; Corrosive
R 23/24/25 34
S 25 27 28 45
RTECS
AI5950000
RTECS class
Agricultural Chemical and Pesticide; Primary Irritant
UN (DOT)
1940
Merck
12,9472
Beilstein/Gmelin
506166
Beilstein Reference
4-03-00-00600
Swiss Giftliste 1
G-2940
Canada DSL/NDSL
DSL
US TSCA
Listed
Austrailia AICS
Listed
New Zealand
Listed
Japan ENCS (MITI)
Listed
Korea ECL
Listed

Properties.
Formula
C2H4O2S
Formula mass
92.11
Melting point, °C
-16.5
Boiling point, °C
96
Vapor pressure, mmHg
0.03 (25 C)
Vapor density (air=1)
3.18
Saturation Concentration
13200 ppm (1.3%) at 18 C (calc.)
Density
1.326 g/cm3 (17 C)
Solubility in water
Miscible
Viscosity
6.55 cp (=cp) @ 20C
Refractive index
1.503 (20 C)
pKa/pKb
3.73 (pKa)
Partition coefficient, pKow
0.09
Heat of vaporization
50.9 kJ/mol
Heat of combustion
-1450 kJ/mol

Hazards and Protection.
Storage
Keep away from heat and flame. Do not store near combustible materials. Store in a cool, dry place. Keep container closed when not in use. Keep away from metals. Corrosives area. Do not store in metal containers.
D1B E
Handling
Wash thoroughly after handling. Use with adequate ventilation. Do not allow water to get into the container because of violent reaction. Do not reuse this container. Empty containers retain product residue, (liquid and/or vapor), and can be dangerous. Do not get on skin or in eyes. Do not ingest or inhale. Keep away from clothing and other combustible materials. Discard contaminated shoes. Do not pressurize, cut, weld, braze, solder, drill, grind, or expose empty containers to heat, sparks or open flames.
Protection
Eyes: 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 prevent skin exposure.
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. Provide ventilation. Do not get water inside containers.
Stability
Stable at room temperature in closed containers under normal storage and handling conditions. Oxidizes when exposed to air.
Incompatibilities
Strong oxidizing agents and strong bases. Reacts with group 1 and 2 metals (Sodium, Potassium, Magnesium, ...) to produce hydrogen gas. Corrosive to steel, stainless steel, nickel base alloys, and aluminum.
Decomposition
Carbon monoxide, irritating and toxic fumes and gases, carbon dioxide, sulfur oxides (SOx), including sulfur oxide and sulfur dioxide.

Fire.
Flash Point,°C
132
Autoignition, °C
350
Lower exp. limit, %
5.9
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. Reacts with most metals to form highly flammable hydrogen gas which can form explosive mixtures with air. Reacts violently with water. May polymerize explosively when involved in a fire. Containers may explode when heated. Extinguishing media: Do NOT get water inside containers. For small fires, use dry chemical, carbon dioxide, or water spray. For large fires, use dry chemical, carbon dioxide, alcohol-resistant foam, or water spray. Cool containers with flooding quantities of water until well after fire is out.
Fire potential
May burn but does not ignite readily.
Hazards
When heated, vapors may form explosive mixtures with air: indoors, outdoors, and sewers explosion hazards. May polymerize explosively when heated or involved in a fire. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated. Runoff may pollute waterways. Substance may be transported in a molten form.
Combustion products
Fire may produce irritating, corrosive and/or toxic gases.
Health
3
 
Flammability
0
 
 
Reactivity
2
 

Health.
Exposure limit(s)
NIOSH REL: TWA 1 ppm (4 mg/m3) [skin]
Poison_Class
3
Exposure effects
CNS depression, seizures, and paralysis were seen in animal experiments, but not in human exposures.
   Ingestion
Harmful if swallowed. Causes gastrointestinal tract burns. Mercaptans may cause nausea and headache. Exposure to high concentrations of mercaptans can produce unconsciousness with cyanosis, cold extremities and rapid pulse.
   Inhalation
May cause severe irritation of the respiratory tract with sore throat, coughing, shortness of breath and delayed lung edema. Olfactory fatigue may occur. Exposure to high concentrations of mercaptans can produce unconsciousness with cyanosis, cold extremities and rapid pulse. Mercaptans may cause nausea and headache.
   Skin
May be fatal if absorbed through the skin. Causes skin burns. Strong irritant of the skin.
   Eyes
Causes severe eye burns. May cause irreversible eye injury.

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 not breathing, give artificial respiration. If breathing is difficult, give oxygen. DO NOT use mouth-to-mouth respiration.
   Skin
Get medical aid immediately. Flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. Destroy contaminated shoes.
   Eyes
Get medical aid immediately. Do NOT allow victim to rub or keep eyes closed. Extensive irrigation is required (at least 30 minutes).

Transport.
UN number
1940
Response guide
Hazard class
8
Packing Group
II
 
HS Code
2930 90 70
 
Std. Transport #
4931460