---
id: janaf
version: "1.4.0"
license: 0BSD
license_treatment: permissive
maintenance: active
---

# janaf — Python wrapper for NIST-JANAF Thermochemical Tables

License: permissive · Maintenance: active · Downloads: 531.8K/mo

## What it is and what it does

janaf is a Python wrapper around the NIST-JANAF Thermochemical Tables, a curated reference database of thermodynamic properties for chemical compounds. It lets you search for compounds by formula and retrieve their thermochemical data—heat capacity, entropy, Gibbs free energy, formation enthalpy, and more—across a temperature range, parsed directly into a polars DataFrame for analysis and calculation.

The package includes corrections for known data quality issues in the original NIST tables (missing signs, formatting gaps, stray comment lines) and exposes the underlying data as structured columns. It depends only on polars for data handling, making it lightweight to install. The bundled thermochemical data comes from NIST's official tables, though the wrapper itself is newly maintained.

Use it for:

- Look up standard formation enthalpies and Gibbs free energies for compounds at reference temperature (298.15 K) for equilibrium calculations.
- Retrieve heat capacity and entropy data across a temperature range for thermodynamic simulations or process design.
- Search for thermochemical properties of a specific compound by chemical formula to validate or supplement experimental measurements.
- Extract tabular thermodynamic data into a DataFrame for batch analysis or integration into a larger computational chemistry workflow.
- Verify compound identifiers and available temperature ranges before performing high-temperature thermodynamic calculations.

## Worth the install?

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

Searches and parses NIST-JANAF thermochemical tables into polars DataFrames, with corrections for common data quality issues in the source tables.

Yes, if you need reliable access to NIST-JANAF thermochemical reference data in Python. The package is actively maintained, has no known vulnerabilities, installs with minimal friction, and integrates cleanly with polars. The permissive license and low dependency count make it a straightforward addition to chemistry or materials science workflows. Not necessary if you already have direct access to NIST tables or use a different thermodynamic database.

## Install

pip install janaf
uv add janaf
poetry add janaf

## Installing janaf

Before you install: Low install friction with a single polars dependency. Active maintenance with a recent release (31 days ago) and current commits; supports Python 3.10 through 3.15.

License in practice: Licensed under 0BSD (permissive), allowing unrestricted use. Note that the bundled NIST-JANAF data itself carries a separate NIST disclaimer regarding accuracy and liability.

Quickstart:

pip install janaf

import janaf
table = janaf.search(formula="CO2$")
df = table.df
value = df.filter(pl.col("T(K)").is_close(298.15)).item(0, "delta-f H")

Requires polars to be installed; Python 3.10 or later.

Verify before relying:

- Scope of data corrections applied (missing signs, missing tabs, comment lines) and whether they affect all compounds or specific subsets
- Whether search supports compound names, formulas, or both; regex support indicated but full query syntax not detailed

## Package facts

- License: 0BSD (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 531.8K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

thermochemical data lookup, NIST JANAF tables, chemical compound thermodynamics, parse thermochemical tables, enthalpy entropy data, chemical property database, thermodynamic reference data, thermodynamics, chemistry-data, nist-reference

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