Chemical Properties
Benzidine is a white, grayish-yellow, or slightly reddish crystalline solid or powder. The
major use for benzidine is in the production of dyes, especially azo dyes in the leather, textile, and paper industries, as a synthetic precursor in the preparation and manufacture of
dyestuffs. It is also used in the manufacture of dyes and rubber, as a reagent, and as a stain
in microscopy. It is slightly soluble and slowly changes from a solid to a gas.
General Description
A grayish-yellow to grayish-red, crystalline solid. Toxic by ingestion, inhalation, and skin absorption. Combustion produces toxic oxides of nitrogen. Used to make other chemicals and in chemical and biological analysis.
Reactivity Profile
BENZIDINE(92-87-5) forms insoluble salts with sulfuric acid. Can be diazotized, acetylated and alkylated. Is hypergolic with red fuming nitric acid . Neutralizes acids in exothermic reactions to form salts plus water. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.
Air & Water Reactions
Darkens on exposure to air and light. Soluble in hot water.
Hazard
Highly toxic by ingestion, inhalation, and
skin absorption. Confirmed carcinogen.
Health Hazard
Exposure to benzidine causes irritation to the eyes. Laboratory animals exposed to benzidine at as low as 0.01% to 0.08% in food showed adverse health effects, such as organ
weight decrease in the liver, kidney, and body weight, and an increase in spleen weight,
swelling of the liver, and blood in the urine. Exposure may cause an increase in urination, blood in the urine, and urinary tract tumors. Benzidine is considered acutely toxic
to humans by ingestion, with an estimated oral lethal dose of between 50 and 500 mg/kg.
The symptoms of acute ingestion exposure include cyanosis, headache, mental confusion,
nausea, and vertigo. Dermal exposure may cause skin rashes and irritation. Prolonged
exposure to benzidine causes bladder injury in humans
Health Hazard
Poisonous if inhaled, swallowed or absorbed through skin. May cause contact dermatitis, irritation or sensitization. Ingestion may cause nausea and vomiting.
Potential Exposure
Benzidine is used primarily in the
manufacture of azo dyestuffs; there are over 250 of these
produced. Other uses, including some which may have
been discontinued, are in the rubber industry as a hardener;
in the manufacture of plastic films; for detection of
occult blood in feces, urine, and body fluids; in the detection
of H2O2 in milk; in the production of security paper;
and as a laboratory reagent in determining HCN, sulfate,
nicotine, and certain sugars. No substitute has been found
for its use in dyes. Free benzidine is present in the
benzidine-derived azo dyes. According to industry, quality
control specifications require that the level not exceed
20 ppm and in practice the level is usually below 10 ppm.
Regulations in the USA concerning this chemical define
strict procedures to avoid worker contact: mixture containing
0.1% or more must be maintained in isolated or closed
systems; employees must observe special personal hygiene
rules, and certain procedures must be followed in case of
emergencies. Some p-phenylenediamine compounds have
been used as rubber components, and DFG warns of danger
of skin sensitization. Benzidine and dyes metabolized to
benzidine: The following three benzidine-based dyes have
been tested and found to cause cancer in rodents after oral
exposure for 13 weeks (NCI 1978, IARC 1982): C.I. direct
black 38 (CAS 1937-37-7) caused liver cancer in rats and
mice, mammary-gland cancer in mice, and colon and
urinary-bladder cancer in rats. C.I. direct Blue 6 (CAS
2602-46-2) caused liver cancer in rats. C.I. direct brown 95
(CAS 16071-86-6) caused hepatocellular adenoma in the
liver and one malignant liver tumor in rats.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, including
resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medical
attention. Use gastric lavage if ingested followed by
saline catharsis. Medical observation is recommended for
24 to 48 hours after breathing overexposure, as pulmonary
edema may be delayed. As first aid for pulmonary edema,
a doctor or authorized paramedic may consider administering
a drug or other inhalation therapy.
Shipping
UN1885 Benzidine, Hazard Class: 6.1; Labels:
6.1—Poisonous materials. PGII.
Incompatibilities
Dust may form explosive mixture with
air. Incompatible with oxidizers (chlorates, nitrates, peroxides,
permanganates, perchlorates, chlorine, bromine, fluorine,
etc.); contact may cause fires or explosions. On
contact with strong reducing agents, such as hydrides may
form flammable gases. Keep away from alkaline materials,
strong bases, strong acids, oxoacids, epoxides. Contact with
red fuming nitric acid may cause fire. Oxidizes in air.
Neutralizes acids in exothermic reactions to form salts plus
water. May be incompatible with isocyanates, halogenated
organics, peroxides, phenols (acidic), epoxides, anhydrides,
and acid halides.
Waste Disposal
Incineration; oxides of nitrogen
are removed from the effluent gas by scrubber, catalytic
or thermal device. Package spill residues and
sorbent media in 17 hour epoxy-lined drums and move to
an EPA-approved disposal site. Treatment may include
destruction by potassium permanganate oxidation, hightemperature
incineration, or microwave plasma methods.
398 Benzidine
Encapsulation by organic polyester resin or silicate fixation.
These disposal procedures should be confirmed with
responsible environmental engineering and regulatory
officials.
Physical properties
Grayish-yellow to pale reddish powder or crystals. Darkens on exposure to air or light. Odorless.
Definition
ChEBI: A member of the class of biphenyls that is 1,1'-biphenyl in which the hydrogen at the para-position of each phenyl group has been replaced by an amino group.
Preparation
1-Nitrobenzene restore 1,2-Diphenylhydrazine?turn with acid rearrangement.
Production Methods
Benzidine production is now exclusively for captive consumption and must be carried out in closed systems under stringent workplace controls. Benzidine is used in the synthesisofdyesanddyeintermediates,asahardenerforrubber, and as a laboratory reagent. The ?rst successful synthetic direct dye was Congo Red, a diazo derivative prepared from benzidinebyBoettigerin1884.Nearlyalldirectdyesareazo products. Congo Red is used in humans intravenously for the medical diagnosis of amyloidosis. The basis for its use is an unexplained af?nity for amyloid, which rapidly removes the dye from the blood. It is used medically for the management of profuse capillary hemorrhage such as the one occurring in septicemias and in the terminal phases of leukemia.
Carcinogenicity
Benzidine is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans.
Source
Benzidine can enter the environment by transport, use, and disposal, or by dyes and
pigments containing the compound. A photodegradation product of 3,3′-dichlorobenzidine.
Based on laboratory analysis of 7 coal tar samples, benzidine was ND (EPRI, 1990).
Environmental Fate
Biological. In activated sludge, <0.1% mineralized to carbon dioxide after 5 d (Freitag et al.,
1985). Kincannon and Lin (1985) reported a half-life of 76 d when benzidine in sludge was
applied to a sandy loam soil.
Soil. Benzidine was added to different soils and incubated in the dark at 23 °C under a carbon
dioxide-free atmosphere. After 1 yr, 8.3 to 11.6% of the added benzidine degraded to carbon
dioxide primarily by microbial metabolism and partially by hydrolysis (Graveel et al., 1986).
Tentatively identified biooxidation compounds using GC/MS include hydroxybenzidine, 3-
hydroxybenzidine, 4-amino-4′-nitrobiphenyl, N,N′-dihydroxybenzidine, 3,3′-dihydroxybenzidine
and 4,4′-dinitrobiphenyl (Baird et al., 1977). Under aerobic conditions, the half-life was estimated
to be 2 to 8 d (Lu et al., 1977).
Chemical/Physical. Benzidine is not subject to hydrolysis (Kollig, 1993). Reacts with HCl
forming a salt (C12H12N2?2HCl) that is very soluble in water (61.7 mg/L at 25 °C) (Bowman et al.,
1976).
Properties and Applications
white or pink micro crystalline powder. Melting point 125 ℃, boiling point 400 ℃, relative density 1.250 (20 ℃). Soluble in ethanol, rare hydrochloric acid and acetic acid boiling, slightly soluble in ethyl ether, slightly soluble in water, very slightly soluble in cold water. In the air and light color line darker. This product is the dye and organic pigments intermediate.
Purification Methods
Its solution in *benzene is decolorized by percolating through two 2-cm columns of activated alumina, then concentrated until benzidine crystallises on cooling. Recrystallise alternately from EtOH and *benzene to constant absorption spectrum [Carlin et al. J Am Chem Soc 73 1002 1951]. It has also been crystallised from hot water (charcoal) and from diethyl ether. Dry it under vacuum in an Abderhalden pistol. Store it in the dark in a stoppered container. CARCINOGENIC. [Beilstein 13 IV 364.]
Toxicity evaluation
Industries release benzidine into the environment in the form
of liquid waste and sludges. Benzidine may also be released
into the environment due to spillage during transport. In air,
benzidine is found bound to suspended particles or as a vapor,
which may be brought back to the earth’s surface by rain or
gravity.
