CHEMICAL IDENTITY
Ethylene oxide is both a manmade substance and a natural substance produced in the body via oxidation of absorbed or endogenously produced ethylene during normal oxidation processes.
Table 4-1 lists common synonyms, trade names, and other pertinent identification information for ethylene oxide.
| Characteristic | Information | Reference |
|---|---|---|
| Chemical name | Ethylene oxide | NLM 2021 |
| Synonym(s) and registered trade name(s) | Oxirane; dihydro-oxirane; dimethylene oxide; epoxyethane; ETO; Anprolene; Oxyfume; T-Gas; 1,2-epoxyethane; ethene oxide; diethylene oxide; E.O.; oxane; oxidoethane | NLM 2021; Parod 2014; WHO 2003 |
| Chemical formula | C2H4O | EPA 2017b |
| Chemical structure | ||
| CAS Registry Number | 75-21-8 | WHO 2003 |
PHYSICAL AND CHEMICAL PROPERTIES
Ethylene oxide is a colorless, flammable gas. It is highly soluble in water (1×106 mg/L at 20°C) and possesses a high vapor pressure (1.095×103 mm Hg at 20°C).
Table 4-2 lists important physical and chemical properties of ethylene oxide.
| Property | Information | Reference |
|---|---|---|
| Molecular weight | 44.05 g/mol | WHO 2003 |
| Color | Colorless | WHO 2003 |
| Physical state | Gas | NIOSH 2007 |
| Melting point | -111.7°C | NLM 2021 |
| Boiling point | 51°F (10.6°C) | NIOSH 2016 |
| Density at 10°C | 0.8824 | NLM 2021; Weast 1985 |
| Odor | Sweet, olefinic; ether-like | NIOSH 2007; Verschueren 1983 |
| Odor threshold: | ||
| Water | 140 mg/L | Amoore and Hautala 1983 |
| Air | 787 mg/m3 (432.85 ppm) | Amoore and Hautala 1983 |
| Solubility: | ||
| Water at 20°C | 1×106 mg/L | EPA 2017b |
| Organic solvents | Soluble in alcohol, ether, acetone, benzene | EPA 2017b |
| Partition coefficients: | ||
| Log Kow | -0.22 | EPA 2017b |
| Log Koc | 1.204 | WHO 2003 |
| Vapor pressure at 20°C | 1.095×103 mm Hg | EPA 2017b |
| Henry’s law constant at 25°C | 1.48×10-4 atm-m3/mol | NLM 2021 |
| Autoignition temperature | 429°C | NLM 2021 |
| Flashpoint | <-18°C (open cup) | NLM 2021 |
| Flammability limits | Lower: 3.0% Upper: 100% | NLM 2021 |
| Conversion factors at 20°C and 101.3 kPa | 1 ppm=1.83 mg/m3 1 mg/m3=0.55 ppm | WHO 2003 |
| Explosive limits | Lower: 3.0% Upper: 100% | NLM 2021 |