Speciation Diagram
Chart overview
Speciation diagrams display the mole fraction of each chemical species as a function of pH or total ligand concentration, derived from equilibrium constants and mass balance equations.
Key points
- Environmental chemists, biochemists, and pharmaceutical scientists use speciation diagrams to predict drug ionization states, metal bioavailability, and contaminant mobility across pH gradients.
- These calculations underpin pharmacokinetic pKa models and environmental fate assessments.
Python Tutorial
How to create a speciation diagram in Python
Use the full tutorial for implementation details, troubleshooting, and chart variations in matplotlib, seaborn, and plotly.
Complete Guide to Scientific Data VisualizationExample Visualization
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View example prompt
"Create a speciation diagram from my data. Plot pH on the x-axis and mole fraction (alpha, 0 to 1) on the y-axis for each chemical species. Calculate species fractions from pKa values and plot each as a smooth line in a distinct color with species names labeled at the fraction maximum. Add a vertical dashed line at physiological pH 7.4 if relevant. Ensure all fractions sum to 1 at every pH value. Use journal formatting with Arial font and no top or right spines."
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Python Code Example
Console Output
Figure saved: plotivy-speciation-diagram.png
Common Use Cases
- 1Predicting drug ionization state and membrane permeability across gastrointestinal pH environments
- 2Modeling heavy metal speciation and bioavailability in environmental soil and water systems
- 3Characterizing phosphate and carbonate buffer system speciation in physiological fluids
- 4Designing optimal pH conditions for metal chelation therapy and ligand coordination chemistry
Pro Tips
Solve the coupled equilibrium expressions analytically or numerically using scipy.optimize for complex systems
Label each species curve at the x-position of its fraction maximum to avoid overlapping legend clutter
Use a stacked area chart variant when showing speciation to visually confirm that fractions sum to unity
Add a secondary x-axis with H+ concentration for audiences more familiar with that scale
Long-tail keyword opportunities
High-intent chart variations
Library comparison for this chart
matplotlib
Best when you need full control over axis formatting, annotation placement, and journal-specific styling for speciation-diagram.
numpy
Useful in specialized workflows that complement core Python plotting libraries for speciation-diagram analysis tasks.
scipy
Useful in specialized workflows that complement core Python plotting libraries for speciation-diagram analysis tasks.
Scientific Chart Selection Cheat Sheet
Not sure whether to use a Violin Plot, Box Plot, or Ridge Plot? Download our single-page reference mapping the most-used scientific chart types, exactly when to use them, and the core Matplotlib/Seaborn functions.