Cover Image

PAPERBACK
$45.52



View/Hide Left Panel

PHYSICAL AND CHEMICAL PROPERTIES

PG is a colorless, practically odorless, and rather viscous liquid. Unlike EG, it has no taste. Its physical and chemical properties are shown in Table 6-1.

OCCURRENCE AND USE

PG is commonly used as a food additive, in cosmetics, and in medicinal agents. It is thought to have low toxicity and is used as a vehicle for intravenous (IV) and topical medications, as well as for cosmetics. Some medications in which notable amounts of PG are present are lorazepam (Ativan), etomidate (Amidate), diazepam, esmolol, nitroglycerin (Tridil), pentobarbital, phenytoin, phenobarbital, and trimethoprim/sulfmethoxazole (Bactrim). The percentage of PG in many injectable forms generally ranges from 40% to 80% in single-dose units. For example, each single dose of a lorazepam solution of 2 millig rams per milliliter (mg/mL) contains 0.8 mL of PG (of a 1-mL dose) as the drug vehicle, whereas phenytoin (Dilantin) contains 40% PG (see Zar et al. 2007b). The Food and Drug Administration considers PG safe for use in medication and cosmetics. It is also antibacterial, which makes it useful as a preservative and disinfectant. PG is the principal component of aircraft deicing and anti-icing fluids and of motor vehicle antifreeze. As the general weight of evidence in the toxicology literature supports the conclusion that PG-based fluids are preferable to EG-based fluids, the ISS program prefers to use PG rather than EG as a coolant.

TABLE 6-1 Physical and Chemical Properties of Propylene Glycol

Chemical formula

CH3CHOHCH2OH or C3H8O2

Chemical name

Propylene glycol

Synonyms

1,2-propanediol, 1,2-dihydroxypropane, methyl glycol

Molecular weight

78

CAS number

57-55-6

Water solubility

100 g/100 g of H2O at 25°C

Specific gravity

1.04

Melting point

−60°C

Boiling point

187°C

Vapor pressure

0.07 mm Hg at 20°C; 0.13 mm Hg at 25°C

Concentration in air at saturation

170 ppm at 25°C (calculated from vapor pressure at that temperature)

Conversion factor

1 ppm = 3.2 mg/m3, 1 mg/m3 = 0.31 ppm



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement