Chemical Properties
Phosgene (CG) is a colorless gas above 8.2C. Fog-like when concentrated. Colorless, fuming liquid below 8.2C. May have the appearance of a white cloud. Light yellow liquid when refrigerated or compressed. It is shipped as a liquefied compressed gas in steel cylinders. At low concentrations CG has a sweet (not pleasant) odor like newly mown hay, green corn, or moldy hay. In higher concentrations, it is poisonous with an odor that is suffocating, irritating, and pungent. The odor is only detectable for a short amount of time when CG is initially released and odor should not be regarded as a reliable indicator of overexposure. A fuming liquid below 8.3C/47F. Shipped as a liquefied compressed gas. The Odor Threshold is between 1.56 milligram per cubic meter. A choking agent, phosgene (CG) rapidly decompose in relative humidity over 70%.
Chemical Properties
Phosgene, COCL2, also known as carbonyl chloride and chlorofonnyl chloride, is a colorless,poisonous gas produced by the action of chlorine and carbon monoxide. It condenses at 0 °C (32 OF) to a fuming liquid. Phosgene was used as a war gas, but is now used in the production of metal chlorides, pharmaceuticals, isocyanate resins,and perfumes.
Definition
ChEBI: An acyl chloride obtained by substitution of both hydrogens of formaldehyde by chlorine.
Uses
For the preparation of many organic chemicals; as a war gas.
Reactivity Profile
PHOSGENE is water reactive. Incompatible with strong oxidizing agents, alcohols, amines, alkali. May react violently with aluminum, alkali metals (lithium, potassium, sodium), alcohols (isopropyl alcohol, 2,4-hexadiyn-1,6-diol), sodium azide [Bretherick, 5th ed., 1995, p. 134]. May react vigorously or explosively if mixed with diisopropyl ether or other ethers in the presence of trace amounts of metal salts [J. Haz. Mat., 1981, 4, 291]. Phosgene reacts with phosphate or silicate salts, yielding water-reactive and toxic POCl3 with phosphates (Dunlap, K.L. 2005. Phosgene. In Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc.).
Air & Water Reactions
Decomposes slowly in water or moist air (or when inhaled) to form very corrosive hydrogen chloride gas (hydrochloric acid) and carbon monoxide.
Health Hazard
Phosgene is a lung toxicant that causes damage to the capillaries, bronchioles and alveoli of the lungs, by decomposition to hydrochloric acid. There is little immediate irritant effect upon the respiratory tract, and the warning properties of the gas are therefore very slight. Pulmonary edema, bronchopneumonia and occasionally lung abscesses develop. Degenerative changes in the nerves have been reported as later developments. A concentration of 25 ppm is dangerous for exposures lasting 30-60 minutes and 50 ppm is rapidly fatal after even short exposure.
Potential Exposure
Phosgene can be deadly at a concentration as low as 2 ppm. Phosgene is used as an intermediate in the manufacture of many industrial chemicals, including dyes and plastics; in the making of dyestuffs based on triphenylmethane, coal tar, and urea. It is also used in the organic synthesis of isocyanates and their derivatives, carbonic acid esters (polycarbonates); and acid chlorides. Other applications include its utilization in metallurgy; and in the manufacture of some insecticides and pharmaceuticals. Exposure to phosgene may occur during arc welding and in fires involving vinyl chloride; released from household paint removers and degreasers when they are used in the presence of heat. Phosgene (CG) has been used as a military choking, pulmonary agent since WW I, and has become a staple of chemical arsenals in many countries
Fire Hazard
When heated to decomposition or on contact with water or steam, PHOSGENE will react to produce toxic and corrosive fumes. Reacts violently with aluminum; tert-butyl azido formate; 2,4-hexadiyn-1,6-diol; isopropyl alcohol; potassium; sodium; hexafluoro isopropylidene; amino lithium; lithium. Stable in steel containers if dry. Avoid moisture.
First aid
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately. If this chemical contacts the skin, flush with water immediately. If a person breathes in large amounts of this chemical, move the exposed person to fresh air at once and perform artificial respiration. When this chemical has been swallowed, get medical attention. Do not induce vomiting. Medical observation is recommended for 2448 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. If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them with water. In order to prevent further tissue damage, do NOT attempt to remove frozen clothing from frostbitten areas. If frostbite has NOT occurred, immediately and thoroughly wash contaminated skin with soap and water.
Shipping
UN1076 Phosgene, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material, Inhalation, Hazard Zone A. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner. Military driver shall be given full and complete information regarding shipment and conditions in case of emergency.AR 50-6 deals specifically with the shipment of chemical agents. Shipments of agent will be escorted in accordance with AR 740-32
Incompatibilities
Moisture, alkalis, ammonia, alcohols, copper. Reacts slowly in water to form corrosive hydrogen chloride and carbon dioxide. Violent reaction with strong oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alcohols, alkaline materials, strong acids, strong bases, alcohols, ammonia, amines, aluminum, alkali metals. Attacks many metals in presence of water. Phosgene (CG) reacts violently with strong oxidants, amines, alkalis, and many metals. Above 300C, phosgene decomposes in the presence of moisture to form hydrochloric acid and carbon dioxide. In the presence of moisture, phosgene attacks plastic, rubber, coatings and many metals.
Waste Disposal
Principles and methods for destruction of chemical weapons: “Destruction of chemical weapons” means a process by which chemicals are converted in an essentially irreversible way to a form unsuitable for production of chemical weapons, and which in an irreversible manner renders munitions and other devices unusable as such. Each nation shall determine how it shall destroy chemical weapons, except that the following processes may not be used: dumping in any body of water, land burial or open-pit burning. It shall destroy chemical weapons only at specifically designated and appropriately designed and equipped facilities. Each nation shall ensure that its chemical weapons destruction facilities are constructed and operated in a manner to ensure the destruction of the chemical weapons; and that the destruction process can be verified under the provisions of this Convention (Organization for the Prohibition of Chemical Weapons; Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and Their Destruction). Return refillable compressed gas cylinders to supplier. Phosgene may be neutralized by covering it with sodium bicarbonate or an equal mixture of soda ash and slaked lime. After mixing, spray carefully with water. Transfer slowly to a larger container of water. Do not use water directly on spill. Pass controlled discharges of phosgene through 10% NaOH solution in a scrubbing tower . Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal.
Preparation
Phosgene is prepared by the reaction of carbon monoxide and chlorine. The mixture of these gases is passed over activated carbon:
CO + Cl2 → COCl2
Alternatively, phosgene can be made by reacting carbon monoxide with nitrosyl chloride, or by treating carbon tetrachloride with oleum.
Production Methods
Phosgene is manufactured in many facilities in the United States and in many other countries. Typical production processes involve the reaction of carbon monoxide with nitrosyl chloride, or the reaction of carbon tetrachloride with oleum.
Production Methods
Phosgene is produced commercially by the reaction of CO
and chlorine gas catalyzed by activated carbon. Estimated
worldwide production exceeds 5 billion pounds. Although a
gas at atmospheric temperature and pressure, phosgene is
often supplied to industry in liquid form in pressurized steel
cylinders or in limited quantities as a solid triphosgene.
It is used in the manufacture of a variety of organic chemicals,
including dyestuffs, isocyanates, carbonic acid esters (polycarbonates),
acid chlorides, insecticides, and pharmaceuticals
(293). In metallurgy, it is used to refine ores by
chlorination of metal oxides.
Suspected sources of atmospheric phosgene are fugitive
emissions. Phosgene can be generated by thermal decomposition
of chlorinated hydrocarbons (including carbon tetrachloride,
methylene chloride, trichloroethylene, or butyl
chloroformate) and photooxidation of chloroethylenes in
the ambient air. Occupational exposures have resulted
from heating paint removers, degreasers, and welding on
freshly degreased parts. Phosgene levels have
been measured in ambient air with an ambient concentration
median of 80 ng/m3. Chlorinated hydrocarbons,
such as chloroform, can also degrade spontaneously. One
example involved laboratory personnel who became ill when
working with 3-year-old chloroform. Subsequent analysis
found 15,000 ppm phosgene in the headspace of the bottle
and a 1.1% phosgene concentration in the bulk solution
(299, 300). Decomposition of chlorinated hydrocarbons
can produce other toxic chemicals, including hydrogen
chloride, chlorine, and dichloroacetyl chloride.
Purification Methods
Dry the gas with Linde 4A molecular sieves, de-gas it and distil it under vacuum at low temperature. This should be done in a closed system such as a vacuum line. It is hydrolysed by H2O but does not fume in moist air. It is available in cylinders and as a ~20% solution in toluene. It is HIGHLY TOXIC and should not be inhaled. If it is inhaled, the operator should lie still and, be made to breathe in ammonia vapour which reacts with phosgene to give urea. [Pope et al. J Chem Soc 117 1410 1920, Beilstein 3 IV 41.]
Hazard
Phosgene is a strong irritant to the eyes, is highly toxic by inhalation, and may be fatal if inhaled. The TLV is 0.1 ppm, and the IDLH is 2 ppm in air. The boiling point is 46°F, and it is noncombustible. When carbon tetrachloride comes in contact with a hot surface, phosgene gas is evolved, which is one of the main reasons that carbon tetrachloride fire extinguishers are no longer approved. The four-digit UN identification number is 1076. The NFPA 704 designation is health 4, flammability 0, and reactivity 1. It is shipped in steel cylinders, special tank cars, and tank trucks.
Flammability and Explosibility
Noncombustible.
Industrial uses
The common name for carbonyl chloride, COCl2, a colorless, poisonous gas made by the action of chlorine on carbon monoxide. It was used as a poison war gas. But it is now used in the manufacture of metal chlorides and anhydrides, pharmaceuticals, perfumes, isocyanate resins, and for blending in synthetic rubbers.
Because of its toxicity, most phosgene is produced and employed immediately in captive applications. The biggest use of the material is for toluene diisocyanate (TDI), which is then reacted into polyurethane resins for foams, elastomers, and coatings. Polycarbonate is used for making breakresistant housings, signs, glazings, and electrical tools. Phosgene also is a reactant for the isocyanates that are used in pesticides, and the di- and polyisocyanates are adhesives, coatings, and elastomers.
Materials Uses
Anhydrous phosgene in the liquid state is compatible with a variety of common metals, including aluminum (of 99.5 percent purity), copper, pure iron or cast iron, steel (including cast
steel and chrome-nickel steels), lead (up to
250°F or 121°q, nickel, and silver; it is also
compatible with platinum and platinum alloys in
instruments. Nonmetallic materials with which
liquid anhydrous phosgene is also compatible
include acid resistant linings (ceramic plates and
carbon blocks), enamel on cast iron or
glass-lined steel, Pyrex or Kimax, porcelain,
quartzware, granite or basalt natural stone,
stoneware, and Teflon.
In the presence of moisture, phosgene is not
compatible with copper, steel, or pure or cast
iron. Detailed data on the corrosion resistance
of various materials to phosgene under a range
of conditions are given in Corrosion Data Survey-Metals Section of the National Association
ofCorrosion Engineers.
For commercial (nonlaboratory) applications,
steel piping with seamless fittings is recommended for handling phosgene, and pipe no
smaller than 4-inch (l0.2-cm) nominal size
should be used to ensure rigidity and minimize
possible leaks. For pipe size up to 4 inches
(10.2 cm), Schedule 80 seamless (or alloy steel
to ASTM A333 GR3) piping is recommended;
6-inch (15.2-cm) diameter Schedule 40 seamless may be used as a larger pipe size.
Screwed or flanged joints should be kept to a
minimum, and cast iron or malleable iron fittings and valves should not be used; nonarmored porcelain valves must not be used, regardless of the pressure with either liquid or
gaseous phosgene. Only outside yoke or rising stem valves are recommended to reduce the
possibility of accident; nonindicating valves
should not be used. Monel is the material generally used in manually operated valves for the
disk, seat, and stem components.
A pipe joint compound of Teflon-based type
dope is usually used. Detailed recommendations
on these and other materials for various purposes in phosgene service may be obtained from
phosgene suppliers.
Physiological effects
Phosgene is a strong lung irritant and also attacks other parts of the respiratory system. Low
concentrations in air cause watering of the eyes
and coughing, which may result in a thin, frothy
expectoration. It will also result in upper respiratory tract irritation and bronchitis. High concentrations cause greater distress such as shortness of breath, choking, coughing, chest tightness, and painful breathing.
ACGIH recommends a Threshold Limit
Value-Time-Weighted Average (TLV-TWA)
of 0.1 ppm (0.40 mg/m3) for phosgene. The
TLV- TWA is the time-weighted average concentration for a normal 8-hour workday and a
40-hour workweek, to which nearly all workers
may be repeatedly exposed, day after day, without adverse effect. In addition, ACGIH recommends a Threshold Limit Value-Ceiling (TLVq of 0.1 ppm (0.4 mg/m3) for phosgene. The
TLV-C is the concentration that should not be
exceeded during any part of the working exposure.
One serious difficulty with the treatment of
persons exposed to phosgene is that more serious symptoms may not appear until 2 to 24
hours after the exposure. These include bloody
sputum, increasing shortness of breath, pulmonary edema, and respiratory failure. The delayed action of phosgene can be particularly
injurious if the victim performs heavy exercise
after having been exposed. Persistent effects
after acute lung injury from phosgene can include bronchiolitis obliterans.
Phosgene is hydrolyzed to hydrogen chloride
and chlorine in the alveoli ofthe lungs, which in
turn causes irritation and results in pulmonary
edema and subsequently leads to respiratory and
cardiac failure.
All persons who have been exposed to phosgene must be examined by a physician as soon
as possible because serious symptoms may develop subsequently.
Environmental Fate
Phosgene’s widespread use may result in its release to the
environment through a variety of means. Historical publicized
releases of phosgene into the environment have been primarily
large scale, where storage tanks containing the gas have
ruptured. Effects have been varied, though largely temporary.
Phosgene is only slightly soluble in water; however, it rapidly
hydrolyzes to form carbon dioxide (CO2) and hydrochloric
acid (HCl); phosgene’s half-life when dissolved in aqueous
media is approximately 0.026 s.
In the air, phosgene is expected to degrade in much the
same way as in water – via hydrolysis to form carbon dioxide
and hydrochloric acid. Potential sources of atmospheric
phosgene follow from thermal decomposition of chlorinated
hydrocarbons, photooxidation of chloroethylenes, and other
emission sources. Phosgene exists as a gas in the ambient
atmosphere, and volatilization from contaminated soils is
expected to occur readily; the Henry’s Law constant of phosgene
is 1.7 × 10-2 atmm3 mol-1.
If deposited into the soil, phosgene is expected to maintain
high mobility with an estimated Koc of 2.2, although its
tendency to rapidly hydrolyze and volatilize likely prevents it
from persisting in soil or water for long. In the atmosphere,
phosgene is expected to degrade either by gas-phase hydrolysis
or by reaction with hydroxyl radicals that are produced
photochemically. The half-life for phosgene’s reaction
with hydroxyl radicals in air, however, is estimated at 44 years,
and the hydrolysis pathway in air is sluggish, resulting in
the potential for phosgene to persist in the atmosphere. Due
to its persistence in the air, it is possible for long-range
transport to be an issue until degradation or some form of
deposition allows phosgene to become degraded by a more
expedient route.
Although it is capable of persisting in the air, phosgene is
not expected to bioaccumulate due to its hydrolytic lability in
aqueous environments.
storage
In particular,
work with phosgene should be conducted in a fume hood to prevent exposure by
inhalation, and splash goggles and impermeable gloves should be worn at all times
to prevent eye and skin contact. Containers of phosgene solutions should be stored in
secondary containers, and phosgene cylinders should be stored in a cool, wellventilated
area separate from incompatible materials.
Toxicity evaluation
Acute irritations of the airway as well as associated mucous
membranes (primarily of the nose, throat, and eyes) occur due
to the rapid formation of hydrochloric acid upon degradation
of phosgene. Irritation or more lasting effects may result from
the ability of phosgene to participate in other reactions,
including acylation with amino (–NH2), hydroxyl (–OH), and
sulfhydryl (–SH) groups. Further, phosgene is capable of
reacting with macromolecules such as proteins, enzymes, and
phospholipids to form covalent adducts that are not native to
cellular environments. Depletion of these nucleophiles, especially
glutathione in the lung, is an important component of
phosgene’s toxicity, as restoration of glutathione has been
shown to protect individuals from additional injury from
phosgene.
In the lung, these secondary reactions may result in fluid
leakage into the pulmonary interstitium, and potential for fluid
levels to reach the alveoli and peripheral airways, leading to
dyspnea and pulmonary edema.
GRADES AVAILABLE
Phosgene is available for commercial and industrial use from various suppliers at a typical
minimum purity of99 mole percent.
