For phosgene

The requirements of the US Armed Forces for phosgene are covered in specification Ml L-P-10455A (18 Apr 1951), which covers two grades Grade A - for use in munitions, max free chlorine 1.0%, and Grade B — for use in chemical manuf, max free chlorine 0.05%. Both grades are required to have a purity of 98.0% min, acidity (calcd as HC1) of 0.50% max, and residue on evaporation of 0.50%... 

A test of this relation is shown in Fig. 2, the seven points being those determined experimentally for phosgene and the six chloroethylenes. 

Fig. 2.—The relation between bond angle and carbon-chlorine distance for phosgene and the chloroethylenes.

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. 

An Existing Distributed Small-scale Plant for Phosgene Synthesis... 

Ajmera, S.K., Losey, M.W., Jensen, K.F., Schmidt, M.A. (2001) Microfabricated Packed-Bed Reactor for Phosgene Synthesis. AIChE Journal, 47, 1639-1647. 

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. 

Phosgene poisoning may cause respiratory and cardiovascular failure which results in low plasma volume, increased hemoglobin concentration, low blood pressure, and an accumulation of fluid in the lungs. There is no antidote for phosgene, and treatment consists of support of respiratory and cardiovascular functions. 

Inhalation is the most important route of exposure for phosgene. Because of phosgene s mild upper respiratory, eye, and skin irritancy and mildly pleasant odor, an exposed victim may not actively seek an avenue of escape before lower respiratory damage has occurred (Currie et al. 1987a Lipsett et al. 1994). Pulmonary edema is the cause of death after a clinical latency period of <24 hours (h) (Franch and Hatch 1986). 

TABLE 1-1 Summary of Proposed AEGL Values for Phosgene (ppm [mg/m3])... 

Rat and mouse lethality data from the well-conducted study of Zwart et al. (1990) also suggest that Haber s law is valid for phosgene. The study by ten Berge et al. (1986) has shown that the concentration-exposure-time relationship for many irritant and systemically acting vapors and gasses can be described by the relationship Cnxt=k. When the 10- to 60-min rat LC50 data are utilized in a linear regression analysis a value of the exponent, n, of 0.93 is obtained. The mouse 10- to 60-min lethality data yield a value of 1.3 for n. 

Thus, the fact that these empirically derived values for the exponent n approximate 1 is further support that Haber s law is valid for phosgene. 

Table 1-15 provides existing standards and guidelines for phosgene. 

IDLH (immediately dangerous to life and health) (NIOSH 1997) represents the maximum concentration from which one could escape within 30 min without any escapeimpairing symptoms or any irreversible health effects. The IDLH for phosgene is based on acute inhalation toxicity data in humans (Diller 1978). 

EPA (U.S. Environmental Protection Agency). 1986. Health Assessment Document for Phosgene. Office of Health and Environmental Assessment. EPA/600/8— 86/022A. Everett, E.D. and Overholt, E.L. 1968. Phosgene poisoning. JAMA. 205 243—245. 

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