Liquid Ethylene Density Calculator
ChemistryCalculate the density of liquid ethylene (C₂H₄) at a given temperature using the NIST-based equation. Includes vapour pressure and saturated liquid density.
Density (kg/m³)
660
Specific Gravity (vs water)
0.66
Vapour Pressure (bar)
50.4
Phase
Saturated liquid (between normal boiling and critical point)
What is a Ethylene Density?
The Liquid Ethylene Density Calculator returns the saturated liquid density (kg/m³), specific gravity, and vapour pressure of ethylene (C₂H₄) at any temperature from the triple point (−169°C) to just below the critical temperature (+9.19°C). It uses a Rackett-type correlation fitted to NIST thermodynamic reference data.
Ethylene is stored and transported as a cryogenic liquid — understanding its density at operating temperatures is essential for vessel sizing, inventory calculations, flow metering, and safety system design. Liquid ethylene density varies from ~660 kg/m³ at the triple point to ~214 kg/m³ at the critical point, a 3× variation over the storage temperature range used in industry.
For gas-phase properties of ethylene, the Molar Mass of Gas Calculator computes ideal gas density and molar volume. For vapour pressure fundamentals applicable to any compound, the Vapor Pressure Calculator uses the Antoine equation. The STP Calculator gives ethylene vapour density at standard conditions.
How to use this Ethylene Density calculator
- Set the Temperature slider or enter a temperature (°C) between −169°C and +9°C.
- Read Density in kg/m³ for the saturated liquid at that temperature.
- Use Specific Gravity for quick comparison to water or other liquids.
- Check Vapour Pressure to determine vessel design pressure.
- For inventory: mass (kg) = vessel volume (m³) × density (kg/m³) × fill fraction.
Formula & Methodology
Saturated liquid density (Rackett-type correlation):T_r = T_K / T_c_K (reduced temperature, T_c = 282.34 K) ρ_L ≈ ρ_c × [f(1 - T_r)] (fitted to NIST data) ρ_c = 214 kg/m³ (critical density) Valid: T_triple (104 K) to T_critical (282.34 K)Vapour pressure (Antoine equation):log₁₀(P/bar) = 3.9468 − 656.0 / (256.0 + T_K)Worked example — ethylene storage sphere at −50°C: At T = −50°C: ρ ≈ 513 kg/m³; P_vap ≈ 8.8 bar. A 500 m³ sphere filled to 85% liquid volume: mass of ethylene = 0.85 × 500 × 513 = 217,800 kg ≈ 218 tonnes. Vapour space (15%) at 8.8 bar contains gaseous ethylene. The vessel must be rated for ≥ 8.8 bar (typically 12 bar design pressure with 1.5× safety factor). Indian pressure vessel certification under PESO requires inspection every 5 years for such storage equipment.
Frequently Asked Questions
Ethylene (C₂H₄, ethene) is the world's largest-volume industrial chemical — primarily used as a monomer for polyethylene (PE) production. It is stored and transported as a cryogenic liquid at its normal boiling point of −103.7°C and 1 atm, or as a pressurised liquid at ambient temperature. Liquid ethylene density (~570 kg/m³ at −103.7°C) is essential for sizing storage tanks, calculating fill ratios, designing relief valves, and computing mass flow in ethylene cracker units. India imports ethylene derivatives (polyethylene, ethylene oxide) and operates crackers at IPCL Vadodara, ONGC Petrochem, and GAIL Pata.
Ethylene physical constants: Molecular formula C₂H₄, M = 28.054 g/mol. Normal boiling point: −103.7°C (169.45 K) at 1 atm. Critical temperature: 9.19°C (282.34 K). Critical pressure: 50.4 bar. Critical density: 214 kg/m³. Triple point: −169.15°C (104.00 K) at 0.00122 bar. Ethylene must be stored below 9.19°C to remain liquid at any pressure. Above the critical temperature, it becomes supercritical — used in supercritical ethylene polymerisation processes (high-pressure LDPE production).
Ethylene saturated liquid density decreases from ~660 kg/m³ at the triple point (−169°C) to ~214 kg/m³ at the critical point (9.19°C). Representative values: −169°C: ≈657 kg/m³; −120°C: ≈612 kg/m³; −103.7°C (normal boiling point): ≈570 kg/m³; −50°C: ≈513 kg/m³; 0°C: ≈ 440 kg/m³; 9°C: ≈ 280 kg/m³. The density decreases rapidly as temperature approaches the critical point — a consequence of the diverging compressibility near the critical point.
Enter the Temperature (°C) using the slider (range: −169°C to 9°C, from triple point to near-critical). The calculator returns the saturated liquid density (kg/m³), specific gravity relative to water, vapour pressure at that temperature (bar), and phase description. The density is computed using a Rackett-type correlation fitted to NIST data. For temperatures outside this range (> 9°C), ethylene cannot be liquefied at any pressure.
Ethylene vapour pressure (approximate values from Antoine equation): −103.7°C (NBP): 1.013 bar (1 atm). −50°C: ≈8.8 bar. −25°C: ≈17.9 bar. 0°C: ≈36.3 bar. 9°C (critical): ≈50.4 bar. Storage at −25°C requires pressure vessels rated to at least 17.9 bar. Most industrial ethylene bullets (horizontal pressure vessels) store at −25°C to −50°C at 8–18 bar — a compromise between refrigeration cost and vessel pressure rating. LNG terminals in Dahej and Hazira also handle ethylene from associated gas streams.
Liquid ethylene hazards: (1) Cryogenic: contact with skin at −103°C causes immediate frostbite (cryogenic burns). (2) Asphyxiation: ethylene vapour is colourless and odourless — high concentrations displace oxygen, causing asphyxiation without warning. (3) Flammability: ethylene is highly flammable (LEL 2.7%, UEL 36% in air) — vapour-air mixtures near storage vessels present explosion risk. (4) Pressure: high-pressure storage vessels require regular inspection under PESO (Petroleum and Explosives Safety Organisation) regulations in India. Safe handling requires gas detectors, ATEX-rated equipment, and emergency relief systems.
Ethylene density is used for: (1) Inventory calculation: mass of ethylene in storage = volume × density at storage conditions. A 500 m³ ethylene sphere at −50°C and 8.8 bar contains ≈ 500 × 513 = 256,500 kg ≈ 257 tonnes of liquid ethylene. (2) Metering: mass flow meters (Coriolis type) measure mass flow directly; volumetric meters require density for mass conversion. (3) Relief valve sizing: ASME/API 521 procedures for emergency relief require density for flow calculations. (4) Compressor design: ethylene vapour density needed for power calculations. All Indian petrochemical plants use these calculations under OISD (Oil Industry Safety Directorate) standards.
Ethylene is polymerised to polyethylene (PE) in several processes: LDPE (Low Density PE): high-pressure process at 1500–3000 bar, 200–350°C — supercritical ethylene conditions. LLDPE/HDPE: Ziegler-Natta or metallocene catalyst in gas phase or slurry (liquid ethylene diluent). For slurry processes, liquid ethylene or isobutane is the solvent/diluent — density affects residence time and heat removal. India produces ~3.5 million tonnes/year of polyethylene (GAIL, Reliance, ONGC Petro, Haldia Petrochem) — one of the largest polymer markets in Asia, growing at >8% per year.
Yes — ethylene (common/trade name) and ethene (IUPAC systematic name) are identical: C₂H₄, the simplest alkene. The IUPAC name 'ethene' is preferred in academic chemistry; 'ethylene' is the industrial, regulatory, and everyday name. Similarly, propylene = propene, butylene = butene. The '-ylene' suffix for olefins (alkenes) is the older non-IUPAC convention still dominant in the chemical industry. Polyethylene is made from ethylene/ethene; polypropylene from propylene/propene. IUPAC 2013 recommendations allow both names as acceptable — India's BIS and CPCB standards use 'ethylene'.
Liquid ethylene sits between LNG (methane, boiling point −161.5°C) and liquid ammonia (boiling point −33.3°C) in terms of storage temperature. Related cryogens: LNG/methane: −161.5°C, 430 kg/m³ at NBP. Ethane: −88.6°C, 545 kg/m³ at NBP. Ethylene: −103.7°C, 570 kg/m³ at NBP. Propylene: −47.7°C, 613 kg/m³ at NBP. Propane: −42.1°C, 581 kg/m³ at NBP. LPG (propane/butane): −42 to 0°C (ambient pressure to modest pressure). Ethylene handling procedures are similar to LNG but require slightly higher containment pressures above −103.7°C. Indian cryogenic engineering standards fall under BIS IS:3196 for pressure vessels and IS:15663 for cryogenic piping.