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Reader task: a student or bench scientist who needs the boiling point of toluene, the other numbers that travel with it, and what they mean when heating, evaporating or storing it.
Short answer: toluene boils at about 110.6 °C
Toluene (C7H8, CAS 108-88-3) boils at about 110.6 °C (231.1 °F) at normal atmospheric pressure, 760 mmHg. That is the CRC Handbook value (95th edition) reported by PubChem. The NIST WebBook gives 383.8 ± 0.2 K, the same number in kelvin, averaged over 110 of 132 collected values. At room temperature toluene is a liquid, and it is flammable: its closed-cup flash point is about 4.4 °C.
Definition and scope
Toluene is an aromatic hydrocarbon with a molecular weight of 92.1384 g/mol (NIST WebBook). The numbers below are physical constants for the pure compound at stated conditions, not for a mixture, and they are not a substitute for the supplier’s safety data sheet for the container in front of you. For a comparable lab solvent reference, see our page on the boiling point of hexane.
Is toluene a solid, liquid or gas?
At ordinary laboratory temperatures toluene is a liquid. PubChem lists a melting point of -94.9 °C (CRC) and NIST gives a freezing point near 178.1 K (about -95.0 °C), so it stays liquid from roughly -95 °C to 110.6 °C at 1 atm. Its vapour is the practical concern: the vapour pressure is 28.4 mmHg at 25 °C (Daubert and Danner, via PubChem), so it evaporates readily at the bench.
How the boiling point is used at the bench
Why the number changes with pressure
A liquid boils when its vapour pressure equals the surrounding pressure. The 110.6 °C figure applies only at 760 mmHg. NIST publishes Antoine-equation parameters for toluene: log10(P) = A – B / (T + C), with P in bar and T in kelvin. For the range 308.52 to 384.66 K the parameters are A = 4.07827, B = 1343.943, C = -53.773 (Willingham et al., 1945).
Worked example: boiling point under reduced pressure
Rearranging gives T = B / (A – log10 P) – C. We calculated the following from the NIST parameters above; every result falls inside the stated temperature range of the fit.
| Pressure | Calculated boiling temperature |
|---|---|
| 1.01325 bar (760 mmHg) | 383.8 K, 110.6 °C |
| 0.5 bar | 360.7 K, 87.5 °C |
| 0.3 bar | 345.9 K, 72.7 °C |
| 0.2 bar | 335.1 K, 61.9 °C |
| 0.1 bar | 318.4 K, 45.3 °C |
This is why a rotary evaporator can remove toluene at a bath temperature far below 110 °C: lowering the pressure lowers the boiling temperature. Treat the table as a calculation from published parameters, not a measurement of any particular apparatus; real systems also depend on gauge accuracy and on what else is dissolved.
How to calculate boiling and melting points
For the boiling point at a given pressure, use the Antoine equation with the published parameters for that temperature range rather than a remembered rule of thumb. For the melting point, NIST reports the triple point at 178.15 K (Scott and Guthrie, 1962); at ordinary pressure the melting point is, for practical purposes, the same value. A teaching-lab boiling-point determination is a different exercise: it measures the value for your sample at your pressure.
Property reference card (sourced values)
| Property | Value | Condition | Source |
|---|---|---|---|
| Boiling point | 110.6 °C (231.1 °F) | 760 mmHg | CRC 95th ed. and NTP 1992 via PubChem; NIST 383.8 ± 0.2 K |
| Melting / freezing point | -94.9 °C | 1 atm | CRC 95th ed. via PubChem; NIST 178.1 ± 0.6 K |
| Density | 0.8623 g/cm³ | 20 °C | CRC 95th ed. via PubChem |
| Vapour pressure | 28.4 mmHg | 25 °C | Daubert and Danner 1989 via PubChem |
| Viscosity | 0.560 mPa·s | 25 °C | CRC via PubChem |
| Refractive index | 1.4967 | 20 °C, sodium D line | CRC via PubChem |
| Enthalpy of vaporization | 33.18 kJ/mol | at the boiling point | Majer and Svoboda 1985 via NIST |
| Flash point | 4.4 °C (40 °F) | closed cup | NTP / NFPA / Hawley via PubChem; one supplier SDS lists 4.0 °C |
| Water solubility | 526 mg/L | 25 °C | Sanemasa 1982 via PubChem |
| Miscibility | Miscible with alcohol, chloroform, ether, acetone, glacial acetic acid, carbon disulfide | – | Merck Index 15th ed. via PubChem |
The density at 20 °C is below that of water, so toluene floats on an aqueous layer; for comparison with other common solvents, see acetone density and ethyl acetate density. The low water solubility and the miscibility list are the figures behind its use as an organic phase in extractions; for the chromatography side, see running a TLC plate and calculating Rf.
Where it matters: bench safety
The properties that matter most for safe handling come from the NIOSH Pocket Guide to Chemical Hazards, read together with the numbers above:
- Ignition: the flash point (about 4 °C) is below normal room temperature, so vapour above the liquid can ignite at ordinary lab temperatures. NIOSH lists a lower explosive limit of 1.1% and an upper limit of 7.1% by volume in air.
- Exposure limits: OSHA PEL 200 ppm as an 8-hour TWA, 300 ppm ceiling and 500 ppm 10-minute peak; NIOSH REL 100 ppm TWA and 150 ppm STEL; IDLH 500 ppm.
- Routes of exposure: inhalation, skin absorption, ingestion and skin or eye contact.
- Incompatibility: strong oxidizers.
For handling, follow the safety data sheet and your institution’s chemical hygiene plan; see the acetone SDS guide for how a solvent safety data sheet is organised, and the green chemistry lab guide for solvent-selection considerations.
How is toluene made?
Toluene is mainly recovered from petroleum and other hydrocarbon streams rather than synthesised from scratch. According to the manufacturing-methods entry in PubChem, it is separated from petroleum reformates (the product of catalytic reforming), from the liquid products of steam cracking (pyrolysis gasoline), and from coal and lignite coking and gasification liquids. Pyrolysis products are first hydrogenated to remove unsaturated compounds and sulfur, nitrogen and oxygen compounds; reformates usually do not need that step. Toluene is then separated from the other components by fractionation, azeotropic distillation or extractive distillation. The same entry notes that toluene can also be synthesised, for example by alkylating benzene with methanol, but that recovery from petroleum streams is preferred for economic reasons. A 1985 monograph cited in the record attributes 87% of toluene production to catalytic reforming of petroleum, about 9% to steam-cracker pyrolysis gasoline, about 1% to coal-tar separation and up to 2% to styrene manufacture; treat those shares as historical, not current.
Common misunderstandings
- “Toluene boils at 110.6 °C everywhere.” Only at 760 mmHg; see the pressure table.
- “A high boiling point means low vapour hazard.” Toluene boils well above room temperature yet has a measurable vapour pressure of 28.4 mmHg at 25 °C and a flash point near 4 °C. Boiling point alone does not describe the vapour hazard.
- “Sources disagree on the boiling point.” They differ only in units and rounding: 383.8 K, 110.6 °C and 231.1 °F describe the same value.
- “Melting point and freezing point are different numbers.” For a pure substance they are the same temperature.
FAQ
What is the boiling point of toluene?
About 110.6 °C (231.1 °F, 383.8 K) at 760 mmHg.
What is the freezing point of toluene?
About -94.9 °C (CRC, via PubChem); NIST reports 178.1 ± 0.6 K.
What is the density of toluene?
0.8623 g/cm³ at 20 °C, so it is less dense than water.
What is the vapour pressure of toluene?
28.4 mmHg at 25 °C; use the Antoine parameters above for other temperatures within 308.52 to 384.66 K.
Is toluene miscible with water?
No. Water solubility is 526 mg/L at 25 °C. It is miscible with alcohol, chloroform, ether, acetone, glacial acetic acid and carbon disulfide.
How do I handle toluene safely?
Treat it as a flammable liquid with inhalation and skin-absorption hazards, keep it away from strong oxidizers, and work within the exposure limits listed above and the supplier’s safety data sheet.
How is toluene made?
Mainly by recovery from petroleum reformate and steam-cracker pyrolysis gasoline, plus coal-derived liquids, followed by distillation; synthesis such as benzene alkylation with methanol is also possible (PubChem manufacturing-methods entry).
Sources
- NIST Chemistry WebBook, Toluene (CAS 108-88-3): webbook.nist.gov, read 2026-11-07.
- PubChem, Toluene, experimental properties (CRC Handbook 95th ed., NTP, Merck Index 15th ed. and others): pubchem.ncbi.nlm.nih.gov, read 2026-11-07; the Methods of Manufacturing section was also read 2026-11-07.
- NIOSH Pocket Guide to Chemical Hazards, Toluene: cdc.gov/niosh/npg/npgd0619.html, read 2026-11-07.
