Liquid Ethylene Density Calculator (saturated liquid C₂H₄, 105–275 K)

Understanding the liquid ethylene density calculator — concept and principle

This calculator gives the density of saturated liquid ethylene (C₂H₄) between 105 K and 275 K, in kg/m³, g/cm³, lb/ft³ and mol/L, together with its specific volume and the mass of a given liquid volume. It is used in cryogenic storage, LNG and petrochemical work and in thermodynamics courses.

How it is calculated

Molar density c is interpolated linearly in a published table of saturated-liquid values (5 K steps from 105 to 275 K)

Density ρ (kg/m³) = c (mol/L) × 28.054 g/mol

Specific volume = 1,000 ÷ ρ (L/kg); mass = ρ × volume

• Temperature can be entered in K, °C or °F and is converted to kelvin.

The principle

Liquid ethylene exists between its triple point (about 104 K) and its critical point (282.34 K, 5.039 MPa). Along the saturation curve, where liquid and vapour coexist, the liquid expands as it warms because molecules move more and sit further apart. Close to the critical point the difference between liquid and vapour disappears and density falls ever faster. Rather than an equation, the page uses tabulated reference data from the US National Bureau of Standards and multiplies molar density by the molar mass.

Worked example

Default inputs: 170 K, volume 1,000 L.

1. 170 K is a table point: c = 20.208 mol/L.
2. ρ = 20.208 × 28.054 = 566.9 kg/m³ = 0.5669 g/cm³ = 35.391 lb/ft³.
3. Specific volume = 1,000 ÷ 566.9 = 1.7639 L/kg.
4. Mass of 1,000 L = 566.9 × 1 m³ = 566.9 kg.

How to read the result

Liquid ethylene is a little more than half as dense as water at these temperatures. Between 105 K and 275 K its density drops by roughly half, so the same tank holds much less mass when the liquid is warm. Near 270–275 K the density changes very quickly, so small temperature errors give larger density errors.

Common mistakes

• Using saturated-liquid density for subcooled, pressurised liquid, which is slightly denser.
• Entering °C when the field is set to K.
• Using the table outside 105–275 K.

Frequently asked questions

What is saturated liquid?

Liquid in equilibrium with its own vapour, at its vapour pressure for that temperature.

Why does density fall so fast near 282 K?

That is near the critical point, where liquid and vapour become indistinguishable.

What is the molar mass of ethylene?

28.054 g/mol.

Can I use this for ethane?

No. Ethane has different properties; use data for that substance.

Sources: P. M. Holland, B. E. Eaton and H. J. M. Hanley, J. Phys. Chem. Ref. Data 12, 917 (1983), Tables 4 and 7