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Short answer: diethyl ether (CAS 60-29-7) has a density of about 0.713 g/mL at 20 °C, so it is much less dense than water and floats on it. Its boiling point is about 34.6 °C and its vapour pressure about 58.6 kPa at 20 °C, which is why it evaporates fast and is treated as an extremely flammable, peroxide-forming solvent.
This page is a sourced solvent datasheet for lab staff. It sets out the values reported by several reference sources side by side, explains why they differ slightly, and says what each number implies at the bench. It is general reference information, not a substitute for the supplier safety data sheet or your institution’s chemical hygiene plan.
What is denser, water or ether?
Water is denser. NOAA CAMEO Chemicals lists diethyl ether at 0.714 at 68 °F and notes it is less dense than water and will float. HSDB gives 0.7134 at 20 °C relative to water at 4 °C, and the ILO/WHO International Chemical Safety Card (ICSC 0355, April 2024) gives 0.7 g/cm³ at 20 °C. Water is about 1.0 g/mL, so in a separatory funnel an ether layer sits on top of an aqueous layer, unless something dense is dissolved in it.
Diethyl ether physical properties compared across sources
Values quoted by PubChem (compound 3283) from the original sources named in the table, read 2026-11-07. Small differences come from temperature, units and measurement method, not from different substances.
| Property | Reported value | Source named |
|---|---|---|
| Density | 0.714 at 68 °F (about 20 °C) | NOAA CAMEO Chemicals (USCG, 1999) |
| Density | 0.7134 at 20 °C/4 °C | HSDB |
| Density | 0.7 g/cm³ at 20 °C | ICSC 0355 |
| Boiling point | 34.6 °C at 760 mm Hg; 17.9 °C at 400 mm Hg; 2.2 °C at 200 mm Hg | Merck Index (13th ed.) |
| Boiling point | 94.3 °F at 760 mmHg; 35 °C | CAMEO; ICSC |
| Melting/freezing point | -116.3 °C (stable crystals); -123.3 °C (metastable form); -116 °C | Merck Index; ICSC |
| Vapour pressure | 58.6 kPa at 20 °C | ICSC 0355 |
| Vapour pressure | 538 mm Hg at 25 °C | HSDB (Daubert and Danner, 1989) |
| Vapour pressure | 440 mmHg | NIOSH/OSHA |
| Flash point | -49 °F; -45 °C (closed cup) | CAMEO; ICSC; HSDB |
| Water solubility | 6.9 g/100 mL at 20 °C; 6.04×10⁴ mg/L at 25 °C; 8% | ICSC; HSDB (Riddick, 1985); NIOSH |
| Viscosity | 0.2448 cP at 20 °C | Merck Index |
| Dielectric constant | 4.197 at 26.9 °C, 85.8 kHz | Merck Index |
Why the vapour pressure rows differ: 58.6 kPa converts to about 440 mmHg, in line with the NIOSH/OSHA figure, while HSDB’s 538 mm Hg is quoted at 25 °C. Vapour pressure rises with temperature, so the same solvent reads higher at a warmer temperature. Compare values at the same temperature and in the same units before treating two sources as disagreeing.
Diethyl ether boiling point, vapour pressure and freezing point
Boiling point
About 34.6 °C at atmospheric pressure (Merck Index). The same source gives 17.9 °C at 400 mm Hg and 2.2 °C at 200 mm Hg, showing how strongly reduced pressure lowers it. For comparison, see the sibling datasheets for hexane and toluene.
Vapour pressure
At 58.6 kPa (20 °C) the vapour pressure is more than half of standard atmospheric pressure (101.3 kPa). CAMEO notes the vapour is heavier than air and can travel to an ignition source and flash back, and ICSC specifies closed systems, ventilation and explosion-proof electrical equipment.
Freezing point
Around -116 °C (Merck Index, ICSC); the Merck Index also lists a metastable form at -123.3 °C.
How soluble is diethyl ether in water?
Only slightly. ICSC reports 6.9 g/100 mL at 20 °C, HSDB 6.04×10⁴ mg/L at 25 °C (Riddick, 1985) and NIOSH about 8%. Polarity index, pKa and miscibility with organic solvents are tabulated differently by different solvent charts, so take those from the chart or supplier datasheet you work from rather than from a single number.
What the numbers imply at the bench
- Layer position: density 0.713 g/mL against water at about 1.0 g/mL puts ether on top in an aqueous extraction. Compare ethyl acetate density and acetone density.
- Volatility: a boiling point near 35 °C and a vapour pressure of 58.6 kPa at 20 °C mean it evaporates rapidly at ordinary lab temperatures.
- Ignition control: a flash point of about -45 °C means the vapour can ignite far below room temperature. ICSC lists no open flames, no sparks, grounding to prevent static build-up, non-sparking tools and no compressed air for filling or discharging.
Is diethyl ether hazardous?
Yes. ICSC 0355 describes it as extremely flammable, with explosive vapour/air mixtures, and lists inhalation symptoms including drowsiness, dizziness and unconsciousness. CAMEO Chemicals classes it as peroxidizable: in contact with air it can form unstable peroxides that may explode, and ICSC advises checking for peroxides before distillation. Follow your supplier’s safety data sheet and your institution’s rules. For the wider hazard class, see peroxide-forming chemicals and shock-sensitive chemicals in the laboratory.
Common misunderstandings
- Different sources, different density: 0.714, 0.7134 and 0.7 are the same property at slightly different rounding or temperature basis.
- Ether only boils at 35 °C, so it is safe below that: the high vapour pressure at 20 °C means significant vapour is present well below the boiling point.
- The vapour disperses upward: CAMEO states the vapour is heavier than air.
FAQ
What is denser, water or ether?
Water. Diethyl ether is about 0.713 g/mL at 20 °C and floats on water.
Is ether a drug?
Diethyl ether has been used medically as an anaesthetic, but this page treats it only as a laboratory solvent and is not medical advice. ICSC 0355 lists drowsiness, dizziness and unconsciousness among the effects of inhaling it, which is why lab use calls for ventilation and controlled handling.
How soluble is diethyl ether in water?
About 6.9 g/100 mL at 20 °C (ICSC), so slightly soluble.
Is diethyl ether hazardous?
Yes: extremely flammable, vapour heavier than air, and peroxide-forming on exposure to air.
Sources
- PubChem compound 3283, Diethyl ether (aggregating CAMEO, HSDB, ICSC, Merck Index, NIOSH, OSHA): pubchem.ncbi.nlm.nih.gov/compound/3283, read 2026-11-07.
- NOAA CAMEO Chemicals, Diethyl ether: cameochemicals.noaa.gov/chemical/696, read 2026-11-07.
- ILO/WHO International Chemical Safety Card ICSC 0355, Diethyl ether (April 2024): inchem.org, read 2026-11-07.
