Liquid Ethylene Density Calculator - Saturated C2H4 Density

A liquid ethylene density calculator returns the saturated liquid density of C2H4 from a single temperature input, drawing on the NIST WebBook saturation table to cover every subcooled liquid condition between the triple point at 104 K and the critical point at 282.34 K. The result panel reports density in kg/m^3, g/mL, lb/ft^3, and as specific gravity versus water, so the same number feeds cryogenic pipeline design, polymerization reactor sizing, and chemistry homework without a unit conversion.

• • Cryogenic pipeline and storage vessel sizing: Convert a mass flow requirement into a volumetric flow at the operating temperature of a liquefied ethylene line or bullet tank.
• • Low-density polyethylene (LDPE) reactor feed calculations: Pick the right pump displacement and compressor suction conditions for a polymerization reactor that runs on liquefied ethylene.
• • Physical chemistry and chemical engineering homework: Show students how saturated-liquid ethylene density drops between the boiling point and the critical temperature on a single chart.
• • LNG and ethylene vaporizer heat-balance work: Estimate the liquid mass leaving a vaporizer at a known supply temperature so the duty to vaporize it is correct.

Liquid ethylene density is not a fixed number. It moves sharply with temperature, dropping from 654 kg per cubic meter at the triple point to 214 kg per cubic meter at the critical point, which is why a single boiling-point value does not cover the practical operating range.

When you need the inverse calculation and want to recover pressure, volume, or moles from a known mass of ethylene vapor at the same temperature, the ideal gas calculator takes the same absolute temperature and molar-mass inputs and returns the ideal-gas side of the C2H4 equation.

The calculator converts the chosen temperature to Kelvin, locates the two NIST WebBook saturated-liquid table points that bracket that temperature, and linearly interpolates between them to return the density at saturation. The same calculation also produces the result in g/mL, lb/ft^3, and as a specific gravity versus water at 4 degrees C.

• T_K: Absolute temperature in Kelvin, converted from the user Celsius, Fahrenheit, or Kelvin input before the table lookup.
• rho_l: Saturated liquid ethylene density in kilograms per cubic meter, taken from the NIST WebBook C2H4 saturation table.
• rho_lower, rho_upper: Bracketing NIST WebBook table densities that sit immediately below and above the chosen temperature.
• T_lower, T_upper: Bracketing Kelvin temperatures from the NIST WebBook saturation table.

Linear interpolation works because the density drops monotonically with temperature and the table points are close enough together to stay within a fraction of a percent of the smooth NIST reference curve across the full subcritical range.

According to NIST WebBook Ethylene (C2H4), the saturated liquid density drops from about 654 kg per cubic meter at the triple point (104 K) to 214 kg per cubic meter at the critical point (282.34 K), with the normal boiling point at 169.45 K corresponding to a liquid density of about 565 kg per cubic meter.

For the companion calculation that connects ethylene pressure, volume, and temperature at fixed moles once the vapor leaves the saturated liquid, the gas laws calculator keeps the same combined-gas-law variables in one place.

Four ideas are enough to read every number this calculator returns.

These four definitions cover everything the result panel shows. They are also why the same calculator works in a cryogenic engineering class, an LDPE plant, and a physical-chemistry teaching lab: each community uses the same saturation curve and the same boiling-point reference.

To convert between the saturated liquid density result and a molar concentration of C2H4, the mole molar mass calculator takes the 28.05 g/mol molar mass of ethylene and returns moles from any mass or mass from any moles.

Five short steps move you from a temperature reading to a saturated-liquid ethylene answer in four units.

1. 1 Pick the temperature unit: Choose Celsius, Fahrenheit, or Kelvin in the second input. The calculator converts the value to Kelvin internally before the table lookup.
2. 2 Enter the temperature: Type the liquid ethylene temperature in the first input. Defaults to -103.15 degrees C, the nearest NIST WebBook table point to the 169.45 K normal boiling point.
3. 3 Read the saturated liquid density: The black result panel shows the density in kg/m^3 to one decimal place, which is the SI value used in cryogenic and process engineering calculations.
4. 4 Read the alternate units: Below the primary result, the panel lists g/mL for lab chemistry, lb/ft^3 for US vessel design, and specific gravity versus water at 4 degrees C.
5. 5 Check the temperature reference rows: The bottom two rows confirm the chosen temperature in Kelvin and the distance from the 169.45 K normal boiling point.

A lab technician monitoring an LDPE feed tank reads -50 degrees C on the tank thermocouple. The calculator returns 478.0 kg/m^3, 0.478 g/mL, 29.84 lb/ft^3, and a specific gravity of 0.478, which is the value entered into the volumetric flow calculation for the reactor feed pump.

When the same liquid ethylene stream is part of a mixed refrigerant blend or a polymerization solvent mixture, the mass percent calculator takes the mass of each component and returns the weight percent that combines with this density result to give the blend composition.

A dedicated liquid ethylene density calculator removes the unit-mixing errors that show up when the NIST WebBook table is read by hand.

• • Reads the NIST WebBook saturation table for you: Type one temperature and the calculator returns the density without manually cross-referencing a 16-row saturated-liquid table.
• • Reports density in four useful units: Process engineering uses kg/m^3, lab chemistry uses g/mL, US vessel design uses lb/ft^3, and quick comparisons use specific gravity. The result panel lists all four.
• • Shows the Kelvin temperature used internally: An auxiliary row repeats the chosen temperature in Kelvin so the user can confirm the value the table lookup used, especially after converting from Fahrenheit.
• • Flags the distance from the normal boiling point: An auxiliary row reports T minus 169.45 K, so the user can see whether the input sits below or above the boiling point reference.
• • Covers the full subcritical range: The table spans 104 K at the triple point to 282.34 K at the critical point, covering every subcooled liquid condition that exists for ethylene.

This calculator is best for single-point checks where one temperature produces one density value. For flow-rate work, the same result feeds into a Reynolds number calculation at the pipe operating temperature.

For the most common downstream use of a liquid ethylene density value, the Reynolds number calculator takes the density result from this calculator and combines it with velocity, characteristic length, and dynamic viscosity to classify the flow in a cryogenic pipeline as laminar, transitional, or turbulent.

Temperature dominates the answer, and three practical limits tell you when to expect the table to lose accuracy.

• • Above 260 K the curve steepens so much that the calculator one-decimal precision understates the physical uncertainty in that band.
• • The saturated-liquid density table assumes vapor-liquid equilibrium at the chosen temperature, so it does not apply to compressed liquid well above the saturation pressure.
• • Linear interpolation between adjacent table points can differ from a smooth NIST correlation by up to about 0.5 percent near the critical point.

According to Wikipedia Ethylene Data Page, the saturated liquid properties of C2H4 (including density, vapor pressure, and the triple and critical points) are tabulated from NIST WebBook and CRC Handbook values that the calculator uses to back the saturated-liquid density table.

According to PubChem Ethylene CID 6325, ethylene (C2H4) has a molar mass of 28.05 g/mol and a normal boiling point of -103.7 degrees C at 101.325 kPa, matching the value used by the NIST WebBook and confirming the saturated-liquid density that the calculator returns at that temperature.

To confirm the absolute temperature conversion before the table lookup, the Kelvin converter turns Celsius, Fahrenheit, Rankine, and Reaumur readings into Kelvin with the linear steps shown so the auxiliary Kelvin row on this page always matches.