Solvent intensity calculator.
Calculate the Solvent Intensity of any chemical process from the actual masses of solvents and auxiliaries used and the mass of product isolated. Results update live as you type — and every session stays in your browser, never on a server.
What is Solvent Intensity — and why does it matter?
Solvent Intensity (SI) is a direct experimental measure of how much solvent and auxiliary material a chemical process consumes per unit of desired product isolated. Expressed as grams of solvent per gram of product (g/g), SI isolates the solvent burden from the broader Process Mass Intensity (PMI) calculation, shining a direct light on Principle 5 of Green Chemistry — Safer Solvents and Auxiliaries.
The formula
| Symbol | Term | Units |
|---|---|---|
| \(\text{SI}\) | Solvent Intensity | g g−1; ideal value = 0 |
| \(m_{\text{solvent},i}\) | Mass of each solvent or auxiliary used (enter volume × density, or mass directly) | g |
| \(m_{\text{recovered},i}\) | Mass of solvent i recovered and recycled (credits recycling) | g |
| \(m_{\text{product}}\) | Mass of isolated desired product | g |
SI uses net solvent mass (used minus recovered) to reward recycling and recovery. All solvents and auxiliary substances — reaction solvents, extraction solvents, wash solvents, recrystallisation solvents, chromatography eluents, drying agents — should be included. A lower SI is always better; SI = 0 represents a fully solvent-free process.
Typical SI values by process type
| Process type | Typical SI (g/g) | Key driver |
|---|---|---|
| Industrial bulk chemicals (highly optimised) | < 5 | Minimal auxiliary solvent; continuous processing |
| Academic synthesis (simple, 1–2 solvents) | 5–20 | Reaction solvent + recrystallisation only |
| Pharmaceutical fine chemicals (multi-step) | 20–50 | Multiple solvent exchanges, workup, chromatography |
| Complex API synthesis or chiral resolution | > 50 | Many steps, large excess reagents, heavy purification |
Strengths and limitations
Strengths
- Directly targets Principle 5 — isolates solvent use from all other waste streams
- Simple to calculate from lab records; no molecular weights needed
- Rewards recovery and recycling — net solvent mass penalises waste, not reuse
- Identifies "hot spots" in multi-step processes (e.g. chromatography steps)
- Easy to communicate to non-chemists; units (g/g) are intuitive
Limitations
- Requires experimental data — cannot be calculated at the design stage
- Treats all solvents equally: 1 g of water = 1 g of dichloromethane (use solvent guides to complement)
- Does not capture hazard, toxicity, energy for evaporation, or life-cycle impacts
- SI alone does not distinguish between a process using 1 g of a carcinogen and 1 g of water
- Dependent on scale; lab-scale SI is often higher than pilot or manufacturing scale
SI in context: complementary green metrics
| Metric | What it measures | Stage |
|---|---|---|
| Solvent Intensity (SI) | Net solvent & auxiliary mass per unit product mass — the focus of this tool | Experimental |
| Atom Economy (AE) | Theoretical fraction of reactant mass in desired product (from balanced equation) | Design |
| % Yield | Fraction of theoretical product actually isolated | Experimental |
| E-factor | Total waste mass per unit product (includes all inputs: reagents, solvents, workup) | Experimental |
| PMI (Process Mass Intensity) | Total input mass per unit product; PMI = E-factor + 1; SI is a component of PMI | Experimental |
Experiment details
Solvents & auxiliaries
Enter every solvent and auxiliary substance used: reaction solvents, extraction solvents, wash solvents, recrystallisation solvents, chromatography eluents, drying agents, etc. Enter volume and density to auto-calculate mass, or enter mass directly. Enter any mass recovered to give credit for recycling — net mass = used − recovered.
| Solvent / auxiliary | Category | Vol. (mL) | Density (g/mL) | Mass used (g) | Recovered (g) | Net mass (g) |
|---|
Tip: Mass = Volume (mL) × Density (g/mL). Common densities: water 1.000, ethanol 0.789, ethyl acetate 0.902, DCM 1.325, acetone 0.791, toluene 0.867, hexane 0.659, THF 0.889, DMF 0.944.
Isolated product
Enter the mass of product actually isolated at the end of the process (after all workup and purification). This is the denominator of the SI calculation.
Results
Solvent mass contributions
Solvent burden vs. product
Detailed breakdown & interpretation
| Solvent / auxiliary | Category | Used (g) | Recovered (g) | Net (g) | % of Σ net | Visual |
|---|---|---|---|---|---|---|
| Enter solvents and product mass above to see breakdown. | ||||||
Interpretation
Save & load sessions
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Export
Export your Solvent Intensity calculation as a PDF report or CSV data file. PDF opens in a new tab and uses your browser's print function. CSV downloads directly.
Where can I read more?
References are sorted alphabetically by first author.
- P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, 1998. ISBN 978-0-19-850698-0. — Original statement of the 12 Principles; frames Principle 5 on solvents and auxiliaries.
- C. Capello, U. Fischer and K. Hungerbühler, "What is a green solvent? A comprehensive framework for the environmental assessment of solvents," Green Chem., 2007, 9, 927–934. DOI: 10.1039/B617536H. — Framework for evaluating solvent greenness beyond mass alone.
- D. J. C. Constable, C. Jiménez-González and R. K. Henderson, "Perspective on Solvent Use in the Pharmaceutical Industry," Org. Process Res. Dev., 2007, 11, 133–137. DOI: 10.1021/op060170h. — Industry data on solvent dominance in pharmaceutical process mass.
- R. K. Henderson et al., "Expanding GSK's solvent selection guide — embedding sustainability into solvent selection starting at medicinal chemistry," Green Chem., 2011, 13, 854–862. DOI: 10.1039/C0GC00918K. — GSK solvent selection guide; basis for comparing SI with solvent hazard.
- C. Jiménez-González et al., "Using the Right Green Yardstick: Why Process Mass Intensity Is Used in the Pharmaceutical Industry to Drive More Sustainable Processes," Org. Process Res. Dev., 2011, 15, 912–917. DOI: 10.1021/op200097d. — Introduces PMI; shows SI as a key PMI component.
- R. A. Sheldon, "The E-Factor 25 years on: the rise of green chemistry and sustainability," Green Chem., 2017, 19, 18–43. DOI: 10.1039/C6GC02157C. — Updated review of waste metrics including solvent intensity across sectors.
Contributors
Roles follow the CRediT taxonomy (Contributor Roles Taxonomy), adapted for educational software. Hover a contributor's name for a summary, or a column header for the definition of that role.
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