Ethylene is the most produced organic chemical in the world – well over 150 million tonnes a year – and the starting material for polyethylene, ethylene oxide, ethylene glycol and PVC. At atmospheric pressure it boils at −103.7 °C, so it is shipped and stored as a refrigerated liquid in insulated tanks and gas carriers, or under pressure at higher temperatures. Its critical point is 9.2 °C and 50.4 bar: above 9.2 °C it cannot be liquefied however hard you press.
Liquid ethylene is light – about 568 kg/m³ at its normal boiling point, a little more than half the density of water – and its density changes strongly with temperature: from about 654 kg/m³ at the triple point (−169.2 °C) to roughly 214 kg/m³ at the critical point. Pressure has a much smaller effect, a few tenths of a percent per 10 bar well below the critical temperature. Accurate density is needed for custody transfer, tank gauging and the design of pumps and pipelines.
This calculator uses the DIPPR equations published in Perry’s Chemical Engineers’ Handbook for the saturated-liquid density and the vapour pressure, and the Thomson–Brobst–Hankinson (COSTALD-type) correlation to add the effect of pressure above saturation. Checked against reference data, they reproduce the triple-point and normal-boiling-point densities to within about 0.2% and are typically within about 1% up to roughly −20 °C.
How to use the Liquid Ethylene Density Calculator
- Calculate from
- Mass of liquid ethylene
- Volume
- Temperature
- Pressure (absolute)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
In the first mode the density is simply mass divided by volume. In the second the calculator checks the phase: below the triple point ethylene is solid, below the vapour pressure it is a gas and above the critical temperature it is supercritical. For a liquid it computes the saturated density at that temperature and increases it for the extra pressure with the Thomson–Brobst–Hankinson equation (Tc = 282.34 K, pc = 50.41 bar, ω = 0.087).
Worked example
Find the density of liquid ethylene at −110 °C (163.15 K) and 10 bar. The vapour pressure from the DIPPR equation is exp(53.963 − 2443/163.15 − 5.5643 ln 163.15 + 1.9079 × 10⁻⁵ × 163.15²) = 0.6947 bar, so at 10 bar ethylene is a compressed liquid. The saturated density is 2.0961 / 0.27657^(1 + (1 − 163.15/282.34)^0.29147) = 20.594 kmol/m³ × 28.053 kg/kmol = 577.7 kg/m³. The Thomson–Brobst–Hankinson correction (B = 495 bar, C = 0.0891) raises this by 0.17% to 578.7 kg/m³.
In the mass-and-volume mode, 1 kg of liquid ethylene filling 1.75 L has a density of 1,000 g / 1.75 L = 571.4 kg/m³ – close to the value at the normal boiling point.
Liquid ethylene density table
| T (°C) | T (K) | Vapour pressure (bar) | Saturated liquid density (kg/m³) | Density at 10 bar (kg/m³) |
|---|---|---|---|---|
| -168.15 | 105 | 0.0015 | 653.2 | 653.8 |
| -153.15 | 120 | 0.0139 | 634.8 | 635.5 |
| -133.15 | 140 | 0.120 | 609.2 | 610.0 |
| -113.15 | 160 | 0.566 | 582.1 | 583.1 |
| -103.75 | 169.4 | 1.019 | 568.8 | 569.8 |
| -93.15 | 180 | 1.824 | 553.2 | 554.2 |
| -73.15 | 200 | 4.558 | 521.6 | 522.6 |
| -53.15 | 220 | 9.556 | 486.4 | 486.5 |
| -33.15 | 240 | 17.707 | 445.3 | (vapour at 10 bar) |
| -13.15 | 260 | 30.035 | 392.7 | (vapour at 10 bar) |
Values computed with the same equations as the calculator. At 169.4 K the vapour pressure is 1.013 bar – the normal boiling point.
Tips
- Count halogens like hydrogens and ignore oxygen and sulfur in degree-of-unsaturation formulas.
- Balance combustion with O₂ last – it is the easiest to adjust.
- Use dry mass for combustion analysis and protein content.
- Everything is calculated in your browser.
Common mistakes to avoid
- Counting nitrogen like a hydrogen in degree of unsaturation (it subtracts one H).
- Forgetting that one mole of CO₂ contains one mole of C.
- Using the wrong Kjeldahl factor (6.25 is generic).
Inputs explained
| Field | What to enter |
|---|---|
| Calculate from | Choose one: Mass and volume, Temperature and pressure (liquid property lookup) |
| Mass of liquid ethylene | Units: kg, g, lb, t (tonne) |
| Volume | Units: L, mL, µL, m³, dm³, cm³ … |
| Temperature | Units: °C, K, °F |
| Pressure (absolute) | Units: bar, kPa, MPa, atm, psi, Pa |
What each result means
- Vapour pressure (boiling pressure) at this temperature = [Vapour pressure]
- Specific volume = 1000÷[Density of liquid ethylene]
- Molar volume = 28.0532÷[Density of liquid ethylene]×1000
- Density relative to water at 4 °C = ([Density of liquid ethylene]÷999.97)×100
- Amount of ethylene = [Mass of liquid ethylene]÷28.0532
Formula
ρ = m ÷ V · ρ_sat (kmol/m³) = 2.0961 ÷ 0.27657^(1 + (1 − T/282.34)^0.29147) · ln p_sat (Pa) = 53.963 − 2443/T − 5.5643 ln T + 1.9079×10⁻⁵ T² · ρ = ρ_sat ÷ [1 − C·ln((B + p)/(B + p_sat))]Worked example
Inputs — Calculate from: Temperature and pressure (liquid property lookup); Temperature: -110 °C; Pressure (absolute): 10 bar.
Results — Density of liquid ethylene = 578.68422 kg/m³; Phase at these conditions = Liquid; Vapour pressure (boiling pressure) at this temperature = 0.69468 bar; Saturated liquid density at this temperature = 577.724 kg/m³; Specific volume = 1.72806 L/kg; Molar volume = 48.47756 cm³/mol; Density relative to water at 4 °C = 57.87 %.
Key terms
- Saturated liquid
- Liquid in equilibrium with its own vapour – at its boiling point for the given pressure.
- Compressed (subcooled) liquid
- Liquid at a pressure above its vapour pressure.
- Vapour pressure
- Pressure at which liquid and vapour coexist at a given temperature.
- Critical point
- Temperature and pressure above which liquid and gas can no longer be told apart (282.35 K, 50.4 bar for ethylene).
- Acentric factor (ω)
- Parameter describing the shape of a molecule's vapour pressure curve; 0.087 for ethylene.
Frequently asked questions
What is the density of liquid ethylene?
About 568 kg/m³ (0.568 g/cm³) at its normal boiling point of −103.7 °C and 1 atm. It rises to about 654 kg/m³ near the triple point and falls towards 214 kg/m³ at the critical point (9.2 °C).
At what temperature is ethylene a liquid at atmospheric pressure?
Between its melting point, −169.2 °C, and its boiling point, −103.7 °C. Above −103.7 °C it can only stay liquid under pressure – for example about 19 bar at −30 °C.
Can ethylene be liquid at room temperature?
No. Its critical temperature is 9.2 °C (282.35 K); above it ethylene is a supercritical fluid at any pressure.
How much does pressure change the density?
Little. At −110 °C going from saturation (0.7 bar) to 10 bar raises the density by about 0.17%, and to 100 bar by about 1.7%. Close to the critical point the liquid becomes much more compressible.
What correlation does the calculator use?
The DIPPR 105 equation for saturated liquid density and the DIPPR 101 equation for vapour pressure (coefficients from Perry's Chemical Engineers' Handbook), plus the Thomson–Brobst–Hankinson compressed-liquid correction. Above −5 °C (Tr > 0.95) no result is given because the correction breaks down near the critical point.
How is liquid ethylene stored and shipped?
Fully refrigerated at about −104 °C and near atmospheric pressure in large insulated tanks and ships, or semi-refrigerated at higher temperatures under a few bar of pressure in smaller pressurised tanks.
How do I convert a tank volume to mass?
Multiply the liquid volume by the density at the tank temperature: 1,000 m³ at −104 °C holds about 568 t of ethylene.