Vapor phosgene

The enthalpy of vaporization of liquid phosgene measured calorimetrically at the normal boiling temperature has been found to be 24.402 0.003 kJ mol" [751]. It thus takes about one-ninth as much heat to vaporize phosgene as would be required to vaporize the equivalent quantity of water. The less reliable value of H,... 

For example, if CCI4 has been pumped in the presence of water vapor, phosgene (COCI2), a highly toxic chemical warfare agent, can be produced and accumulate in the pump oil. 

Health and Safety. Remover formulas that are nonflammable may be used in any area that provides adequate ventilation. Most manufacturers recommend a use environment of 50—100 parts per million (ppm) time weighted average (TWA). The environment can be monitored with passive detection badges or by active air sampling and charcoal absorption tube analysis. The vapor of methylene chloride produces hydrogen chloride and phosgene gas when burned. Methylene chloride-type removers should not be used in the presence of an open flame or other heat sources such as kerosene heaters (8). 

Chloroform slowly decomposes on prolonged exposure to sunlight in the presence or absence of air and in the dark in the presence of air. The products of oxidative breakdown include phosgene, hydrogen chloride, chlorine, carbon dioxide, and water. At 290°C, chloroform vapor is not attacked by oxygen. In contact with iron and water hydrogen peroxide is also produced, probably by the following reaction sequence (2) ... 

Carbon tetrachloride [56-23-5] (tetrachloromethane), CCl, at ordinary temperature and pressure is a heavy, colorless Hquid with a characteristic nonirritant odor it is nonflammable. Carbon tetrachloride contains 92 wt % chlorine. When in contact with a flame or very hot surface, the vapor decomposes to give toxic products, such as phosgene. It is the most toxic of the chloromethanes and the most unstable upon thermal oxidation. The commercial product frequendy contains added stabilizers. Carbon tetrachloride is miscible with many common organic Hquids and is a powerhil solvent for asphalt, benzyl resin (polymerized benzyl chloride), bitumens, chlorinated mbber, ethylceUulose, fats, gums, rosin, and waxes. 

Disaster hazard. Phosgene is highly dangerous. When heated to decompn, or on contact with w or steam, it wiii react to produce toxic and corrosive fumes (Ref 12). Powdered A1 burns in its vapor (Ref 3)... 

Mellor (Ref 5) reports that a mixt of K and phosgene explds when subjected to shock, and that vapors of Na and phosgene react with luminescence at about 260° (Ref 4), ... 

Vapors of all of the polychlorinated methyl chloroformates are toxic. Trichloromethyl chloroformate has a phosgene-like odor and is known to decompose to phosgene at elevated temperature or on contact with ferric oxide or charcoal. ... 

Trichloromethyl chloroformate is useful in synthesis as a substitute for phosgene, which, owing to its high volatility and toxicity, presents a severe hazard in the laboratory. Although trichloromethyl chloroformate is toxic, it is a dense and less volatile liquid, b.p. 128°, d l 1.65, having a vapor pressure of only 10 mm. at 20°. Consequently it is more easily handled in a safe manner than phosgene. 

Decomposition Toxic gases and vapors (such as oxides of nitrogen, phosgene, nitrosyl chloride, chlorine, and carbon monoxide) may be released when chloropicrin decomposes. 

Ct - vapor dosage, cutaneous - pertaining to the skin. CX - phosgene oxime, cyanosis - blueness of the skin owing to insufficient oxygen in the blood. 

For example, phosgene, COCl2, with an MW of 98.92, has a vapor density of 3.4x that of air. The calculation follows ... 

Phosgene is a colorless vapor with a boiling point of 46.8°F. Thus it is normally stored as a liquid in a container under pressure above its normal boiling point temperature. The TLV for phosgene is 0.1 ppm, and its odor threshold is 0.5-1 ppm, well above the TLV. 

In the process shown in Figure 10-9 the phosgene is fed from the container through a valve into a fritted glass bubbler in the reactor. The reflux condenser condenses aniline vapors and returns them to the reactor. A caustic scrubber is used to remove the phosgene and HC1 vapors from the exit vent stream. The complete process is contained in a hood. 

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