Magnesium chloride · MgCl2

What the numbers tell you

At 20 wt% and 20 °C, aqueous magnesium chloride has a density of about 1175 kg/m³ (1.175 g/cm³) — roughly 1.18× the density of water. It also has a specific heat of about 3.11 kJ/kg·K, about 74% of water’s 4.18 kJ/kg·K. Those differences carry straight into volume-to-mass conversions, pump and pipe sizing, and the heat needed to change its temperature.

How low it protects

Freezing point of the aqueous solution against strength, computed from the same correlation and checked against an independently cited value. A 20 wt% magnesium chloride solution freezes at about −28.7 °C.

Freeze check: 5 wt% computed −3.0 °C against a cited −3.0 °C (tolerance ±1.5 °C). CRC Handbook of Chemistry and Physics - Concentrative Properties of Aqueous Solutions. CRC Handbook of Chemistry and Physics, Concentrative Properties of Aqueous Solutions, Magnesium chloride (MgCl2) table: 5.0 mass % at 20 degC, freezing point depression = 3.01 degC (freezing point about -3.0 degC); the CRC depression column for MgCl2 is tabulated to 5 mass %. The Melinder freeze curve underlying CoolProp's INCOMP::MMG matches it to within 0.1 degC here.

Before you use these numbers

• ▸CoolProp's incompressible aqueous magnesium chloride correlation (INCOMP::MMG), built on Melinder (2010). Tabulated for 5-20 wt% MgCl2 over -25 to 40 degC. Magnesium chloride brine is used for deicing, dust suppression and secondary cooling; the Melinder incompressible path is used (over the Laliberte electrolyte correlation) because it carries the freezing line. Each cell sits above the solution's freezing line; cells below it are left blank and the explorer will not interpolate across them. The 20 wt% ceiling stays near the eutectic (about 21 wt%) and below saturation. Density and freezing points are tabulated; viscosity is not, because the correlation's viscosity term for MgCl2 deviates about 10% from independent CRC measured data, and an unreliable property is omitted rather than published with a caveat. Concentrations are anhydrous MgCl2; the commercial hexahydrate (MgCl2.6H2O) is 47% MgCl2 by mass. Values are for preliminary design; verify against vendor data for critical service.
• ▸Values are tabulated only inside the 5–20 wt% and -25–40 °C ranges shown; the correlation is not extrapolated beyond them here.
• ▸Figures are for a pure magnesium chloride–water system. Commercial grades contain impurities (for example chloride in some caustic grades) that shift density and viscosity; check the supplier's data sheet for a specific product.
• ▸Use for preliminary design; verify for critical service.