---
id: chemicals
version: "1.5.2"
license: MIT
license_treatment: permissive
maintenance: active
---

# chemicals — Chemical properties component of Chemical Engineering Design Library (ChEDL)

License: permissive · Maintenance: active · Downloads: 434.0K/mo

## What it is and what it does

Chemicals is a reference library for chemical and thermodynamic data, providing lookup functions and calculation methods for over 20,000 substances. It wraps extensive databanks (critical properties, vapor pressure, heat capacity, transport properties) and makes them available on-demand, so you only load the data you need. The library is built around SI units and accessed primarily by CAS Registry Number, returning None when data is unavailable rather than guessing.

It serves engineers, scientists, and process modelers who need reliable chemical constants and property correlations. The package integrates with NumPy for vectorized operations, Numba for JIT compilation, and Pint for unit tracking. It is a core dependency of BioSTEAM and similar process simulation frameworks. Data comes from cited, openly published sources—not an exhaustive recommended-value repository, but a practical collection of working correlations and coefficients.

Use it for:

- Look up molecular weight, critical temperature, or heat of formation for a chemical by name or CAS number.
- Calculate vapor pressure or heat capacity at a given temperature using Antoine or other correlation methods.
- Solve flash calculations or vapor-liquid equilibrium problems in process simulation.
- Retrieve safety and toxicity information for a chemical in a batch workflow.
- Accelerate thermodynamic calculations using Numba-compiled functions in performance-critical code.
- Track units of measure in chemical property calculations using Pint Quantity objects.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Retrieves and calculates chemical properties and constants for over 20,000 chemicals, including molecular weight, boiling/melting points, vapor pressure, heat capacity, viscosity, and thermodynamic phase equilibrium solutions.

Yes. Chemicals is actively maintained, has no known vulnerabilities, installs cleanly, and is the standard reference library for chemical data in Python process engineering. Install it if you need reliable chemical constants, property correlations, or thermodynamic phase equilibrium routines. The MIT license poses no barrier. Skip it only if your use case requires proprietary or specialized data not in its databanks.

## Install

pip install chemicals
uv add chemicals
poetry add chemicals

## Installing chemicals

Before you install: Low friction installation with a pure Python wheel. Actively maintained with a recent release (68 days ago) and steady repository activity. Depends on scipy, numpy, pandas, and fluids—all well-established scientific libraries.

License in practice: MIT license is permissive; you can use this package freely in commercial and private projects with minimal restrictions.

Quickstart:

pip install chemicals

from chemicals import CAS_from_any, MW, Tb
CAS_water = CAS_from_any('Water')
molecular_weight = MW(CAS_water)  # Returns 18.01528 g/mol
boiling_point = Tb(CAS_water)     # Returns 373.124 K

Requires Python 3.9 or later.

Verify before relying:

- Whether the on-demand databank loading actually reduces memory footprint in typical workflows.
- Performance characteristics when querying properties for large numbers of chemicals sequentially.
- Completeness and accuracy of data for chemicals outside common industrial compounds.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 434.0K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

chemical properties database, thermodynamic calculations, vapor pressure estimation, chemical constants lookup, phase equilibrium solver, molecular weight retrieval, heat capacity methods, chemical engineering data, thermodynamics, chemical-data, process-simulation

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