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TABLE 5–1 Physical and Chemical Properties for Hydrogen Chloride

Characteristic

Value

Synonyms

Muriatic acid, hydrochloric acid

CAS number

7647–01–1

Chemical formula

HCl

Molecular weight

36.47

Physical state

Colorless, fuming gas

Relative density

1.268 at 25°C

Boiling point/flash point

–85°C/nonflammable

Melting point

–114.22°C

Solubility

67.3 g per 100 g water at 30°C

Conversion factors in air (25°C, 1 atm)

1 mg/m3=0.67 ppm

1 ppm=1.49 mg/m3

Odor threshold

1–5 ppm

Abbreviation: CAS, Chemical Abstract Service.

Source: AIHA (1998); HDSB (2001); NRC (2000).

Hydrogen chloride can be produced from thermodegradation of chlorinated polymers (e.g., polyvinyl chloride (PVC) and chlorinated acrylics) (Coleman and Thomas 1954). When chlorinated polymers are heated to 300–900°C in air, more than 99.9% of the chlorine atoms are released as hydrogen chloride; the remaining chlorine atoms are released as carbonyl chloride. No chlorine gas is formed. Hydrogen chloride has been detected in fires involving the combustion of chlorinated polymers, most commonly PVC (Dyer and Esch 1976; Gold et al. 1978; Jankovic et al. 1991). Of hydrogen chloride released from PVC in fires, more than 2% was adsorbed to soot particles, and only about 0.8% reached the alveoli (Stone et al. 1973 as cited in the NRC 2000).

TOXICOKINETIC CONSIDERATIONS

Data on the absorption, distribution, metabolism, and excretion of hydrogen chloride are sparse. There are reports of severe nonlactic metabolic acidosis developing rapidly after ingestion of hydrochloric acid (suggesting systemic absorption from the gastrointestinal tract), but this effect has not been reported after dermal exposure to concentrated hydrochloric acid or after inhalation of hydrogen chloride vapor or aerosol. No studies were found on upper respiratory



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