Product Identification

Product Name

Mercaptoacetic acid

Synonyms

2-Mercaptoacetic acid
2-Sulfanylacetic acid
2-Thioglycolic acid
Acetyl mercaptan
Mercaptoacetate
Mercaptoacetic acid

CAS

68-11-1

Formula

C2H4O2S

Molecular Weight

92.11

EINECS

200-677-4

RTECS

AI5950000

RTECS Class

Agricultural Chemical and Pesticide; Primary Irritant

Merck

12,9472

Beilstein/Gmelin

506166

Beilstein Reference

4-03-00-00600

EC Index Number

607-090-00-6

EC Class

Toxic; Corrosive

Physical and Chemical Properties

Appearance

Colorless liquid with a characteristic strong unpleasant odor, lachrymator.

Solubility in water

Miscible

Melting Point

-16.5

Boiling Point

96

Vapor Pressure

0.03 (25 C)

Density

1.326 g/cm3 (17 C)

pKa/pKb

3.73 (pKa)

Partition Coefficient

.09

Heat Of Vaporization

50.9 kJ/mol

Heat Of Combustion

-1450 kJ/mol

Usage

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.

Vapor Density

3.18

Saturation Concentration

13200 ppm (1.3%) at 18 C (calc.)

Refractive Index

1.503 (20 C)

First Aid Measures

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).

Handling and Storage

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.

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.

Hazards Identification

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.

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.

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.

EC Risk Phrase

R 23/24/25 34

EC Safety Phrase

S 25 27 28 45

UN (DOT)

1940

Exposure Controls/Personal Protection

Personal 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.

Exposure Effects

CNS depression, seizures, and paralysis were seen in animal experiments, but not in human exposures.

Exposure limit(s)

NIOSH REL: TWA 1 ppm (4 mg/m3) [skin]

Poison Class

3

Fire Fighting Measures

Flash Point

132

Autoignition

350

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.

Lower exp. limit

5.9

Fire Potential

May burn but does not ignite readily.

Accidental Release Measures

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 and Reactivity

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.

Combustion Products

Fire may produce irritating, corrosive and/or toxic gases.

Transport Information

UN Number

1940

Hazard Class

8

Packing Group

II

HS Code

2930 90 70