Hydroquinone

  • p-Benzenediol
  • Quinol
  • 1,4-Dihydroxybenzene
  • p-Dihydroxybenzene
Formula
C6H4(OH)2
Structure
Description
White or colorless, odorless, crystalline solid when pure. Commercial grades are typically white, off-white, light tan or light grey crystalline solids.
Uses
As photographic reducer & developer, as reagent in determination of small quantities of phosphate, as antioxidant.

Registry Numbers and Inventories.
CAS
123-31-9
EC (EINECS/ELINCS)
204-617-8
EC Index Number
604-005-00-4
EC Class
Carcinogenic Category 3; Mutagenic Category 3; Harmful; Irritant; Sensitising; Dangerous for the Environment
R 22 40 41 43 50 68
S 26 36/37/39 61
RTECS
MX3500000
RTECS class
Tumorigen; Mutagen; Reproductive Effector; Human Data; Primary Irritant
UN (DOT)
2662
Merck
13,4833
Beilstein/Gmelin
605970
Beilstein Reference
4-06-00-05712
Swiss Giftliste 1
G-1691
Canada DSL/NDSL
DSL
US TSCA
Listed
Austrailia AICS
Listed
New Zealand
Listed
Japan ENCS (MITI)
Listed
Korea ECL
Listed

Properties.
Formula
C6H6O2
Formula mass
110.11
Melting point, °C
172
Boiling point, °C
285
Vapor pressure, mmHg
0.01 (60 C)
Vapor density (air=1)
3.81
Saturation Concentration
0.024 ppm at 25 C (calculated)
Density
1.328 g/cm3 (25 C)
Solubility in water
70 g/L
Refractive index
1.632 (25 C)
pKa/pKb
9.96 (pKa)
Partition coefficient, pKow
0.59
Heat of fusion
27.2 kJ/mol
Heat of vaporization
94.13 kJ/mol
Heat of combustion
-2848 kJ/mol

Hazards and Protection.
Storage
Store in a cool, dry place. Do not store in direct sunlight.
D1B D2B
Handling
Wash thoroughly after handling. Use only in a well ventilated area. Minimize dust generation and accumulation. Avoid contact with eyes, skin, and clothing. Avoid ingestion and inhalation.
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
Follow the OSHA respirator regulations found in 29CFR 1910.134 or European Standard EN 149. Always use a NIOSH or European Standard EN 149 approved respirator when necessary.
Small spills/leaks
Sweep up or absorb material, then place into a suitable clean, dry, closed container for disposal. Avoid generating dusty conditions.
Stability
Stable under normal temperatures and pressures. Substance undergoes color change upon exposure to light and air.
Incompatibilities
Strong oxidizers, alkalies. Undergoes violent reaction with sodium hydroxide.
Decomposition
Carbon monoxide, carbon dioxide, quinone.

Fire.
Flash Point,°C
165
Autoignition, °C
515
Upper exp. limit, %
15.3
Lower exp. limit, %
1.6
Fire fighting
Wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. Dusts at sufficient concentrations can form explosive mixtures with air. Extinguishing media: Use foam, dry chemical, or carbon dioxide.
Fire potential
Slightly flammable. Combustible but must be preheated for ignition.
Hazards
Dust cloud may explode if ignited in an enclosed area. It can react with oxidizing materials and is rapidly oxidized in the presence of alkaline materials. Oxidizes in air.
Combustion products
Fire may produce irritating, corrosive and/or toxic gases.
Health
2
 
Flammability
1
 
 
Reactivity
0
 

Health.
Exposure limit(s)
TLV: ppm; 2 mg/m3 (ACGIH 1992-1993). OSHA PEL: TWA 2 mg/m3 NIOSH REL: C 2 mg/m3 15-minute NIOSH IDLH: 50 mg/m3
Poison_Class
3
Exposure effects
Prolonged or repeated skin contact may cause sensitization dermatitis and possible destruction and/or ulceration.
   Ingestion
May cause severe irritation of the digestive tract. May be harmful if swallowed. May caues dizziness nausea, sense of suffocation, increased respiratory rate, vomitting, pallor, muscle twitching, cyanosis, delerium, collapse. May cause green or brownish green urine which continues to darken upon standing.
   Inhalation
May cause respiratory tract irritation. Causes narcotic effects including headache, dizziness, weakness, unconsciousness, and possible death. Vapors may cause dizziness or suffocation. Inhalation of dust may cause respiratory tract irritation. Exposure to high concentration of vapor may caues irritation, photophobia, lacrimation, and corneal ulceration.
   Skin
Causes severe skin irritation. May cause skin sensitization, an allergic reaction, which becomes evident upon re-exposure to this material. May cause dermatitis. Repeated exposure may cause hyperpigmentation of fair skin and depigmentation of dark skin.
   Eyes
May cause eye irritation. Repeated exposure may cause corneal abnormalities including structural changes and brownish discoloration which can lead to decreased visual acuity and blindness.

First aid
 
   Ingestion
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
Remove from exposure to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical aid.
   Skin
Get medical aid. Immediately flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes.
   Eyes
Immediately 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
2662
Response guide
Hazard class
6.1
Packing Group
III
 
USCG CHRIS Code
HDQ
 
HS Code
2907 22 10
 
Std. Transport #
4925129