Tools · Fluids & Thermodynamics

Solid–Liquid Equilibrium / Eutectic Diagram

The liquidus curves and eutectic point of a binary organic mixture, or a solute's solubility against temperature, for crystallization and formulation work.

Updated October 1, 2026

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This tool computes solid–liquid equilibrium for a two-component organic system: where each component starts to crystallize as the mixture cools, the eutectic point where both do, and how a solute's solubility changes with temperature. Use it for crystallization, purification, and formulation decisions. It runs on CPU.

How it works

For each component crystallizing as a pure solid, the solubility equation relates its liquid-phase mole fraction x and activity coefficient γ to its melting point T_m, enthalpy of fusion ΔH_fus, and (optionally) the heat-capacity difference ΔC_p between liquid and solid:

ln(x·γ) = −(ΔH_fus/R)(1/T − 1/T_m) + (ΔC_p/R)[(T_m/T − 1) − ln(T_m/T)]

Simple eutectic: the solids are taken as pure and immiscible; solid solutions, cocrystals, and polymorphs aren't modeled.
Liquid non-ideality (activity_model): ideal (γ = 1, the default), nrtl (published parameters, or your own fitted pair from VLE Parameter Regression), or unifac (predicted from structure).
Melting data: your tm_k and hfus_j_mol are used when given; otherwise they are looked up in the open chemicals database. The source of each value is recorded.

Modes

`mode`	You get
`diagram` (default)	Both liquidus branches across composition (`grid_points`, default 51), the stable liquidus, and the eutectic
`solubility`	The solubility of the first component in the second from `temperature_min_k` to `temperature_max_k`, with the ideal solubility alongside for comparison

Inputs

components: exactly two rows, each with a name (or SMILES) and, optionally, tm_k, hfus_j_mol, and dcp_j_mol_k. The properties table from Group-Contribution Properties also works, though its estimated melting data are rough.

Outputs

File	Mode	Contents
`liquidus.csv`	diagram	The liquidus temperature at each composition, which solid forms first, and both branches
`eutectic.csv`	diagram	The eutectic composition and temperature
`solubility.csv`	solubility	Solubility (mole fraction), ideal solubility, and activity coefficient at each temperature
`result.json`	both	Model, assumptions, melting data and their sources, and warnings

Each row has a status. A failed point where x·γ exceeds 1 near the melting point can mean the liquids separate into two phases, which this model doesn't handle.

VLE / Flash for vapor–liquid equilibrium, Hansen Solubility Parameters for solvent screening, and PHREEQC Aqueous Speciation for minerals in water.

Run it from the API

Submit with Submit a job and the job_type below. Price it first with Estimate job reservation cost: submitting reserves that amount from your wallet, and the charge settles at the actual runtime.