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Short answer: the boiling point of xylene is about 138 to 144 °C (280 to 291 °F) at normal pressure, depending on the isomer: o-xylene 144 °C, m-xylene 139 °C, p-xylene 138 °C. That is well above water, but the liquid is still flammable at room temperature, with a closed-cup flash point of 25 to 30 °C. This datasheet-style page sets the three isomers side by side and explains what each number means at the bench.
Definition and scope
What is xylene solvent?
Xylene (dimethylbenzene) is an aromatic hydrocarbon with two methyl groups on a benzene ring. It exists as three isomers that differ only in where the methyl groups sit: ortho (o-, 1,2), meta (m-, 1,3) and para (p-, 1,4). Laboratory “xylene” is frequently a mixture of these isomers, so a single-isomer datasheet value will not exactly describe the bottle on the shelf; a supplier that lists a boiling range instead of a point is describing such a mixture.
Is xylene the same as acetone?
No. Xylene is an aromatic hydrocarbon; acetone is a ketone. They are different chemicals with different hazard profiles and are not interchangeable in a protocol, a waste stream or a glove-compatibility check. For histology workflows that replace xylene, see xylene substitutes.
Boiling point and key properties by isomer
The values below are from the International Chemical Safety Cards (ICSC) 0084, 0085 and 0086, read on 2026-11-07.
| Property | o-Xylene | m-Xylene | p-Xylene |
|---|---|---|---|
| CAS number | 95-47-6 | 108-38-3 | 106-42-3 |
| Boiling point | 144 °C | 139 °C | 138 °C |
| Melting (freezing) point | -25 °C | -48 °C | 13 °C |
| Relative density (water = 1) | 0.88 (20 °C) | 0.86 | 0.86 |
| Vapour pressure at 20 °C | 0.7 kPa | 0.8 kPa | 0.9 kPa |
| Flash point (closed cup) | 30 °C | 25 °C | 25 °C |
| Water solubility | 0.18 g/L (20 °C) | 0.174 g/L (25 °C) | 0.2 g/L (25 °C) |
| Log Pow (octanol/water) | 3.12 | 3.20 | 3.15 |
For p-xylene, the NIST Chemistry WebBook gives a boiling temperature of 411.4 ± 0.5 K (the average of 59 of 65 reported values), which converts to about 138.3 °C, and a fusion temperature of 286.3 ± 0.2 K (about 13.2 °C). NIST also lists Antoine equation parameters for p-xylene (A = 4.14553, B = 1474.403, C = -55.377, pressure in bar and temperature in K, valid from 286.43 to 452.38 K), which allow an estimate of boiling temperature at reduced pressure, for example on a rotary evaporator.
What is the density of o-xylene?
o-Xylene has a relative density of 0.88 at 20 °C, so it floats on water. m- and p-xylene are slightly lighter at 0.86 (ICSC 0085, 0086).
What is m-xylene?
m-Xylene is the meta isomer (CAS 108-38-3): boiling point 139 °C, melting point -48 °C, flash point 25 °C closed cup (ICSC 0085).
Xylene vapour pressure, miscibility and freezing point
At 20 °C the vapour pressure is 0.7 to 0.9 kPa depending on the isomer, so xylene evaporates readily at room temperature. Its water solubility is about 0.17 to 0.2 g/L, so it is practically immiscible with water and, with a density below 1, forms a layer on top. The lowest freezing point belongs to m-xylene (-48 °C); p-xylene freezes at 13 °C.
What the numbers mean at the bench
- Boiling point versus flash point. A boiling point near 140 °C does not make xylene a low-risk solvent. A flash point of 25 to 30 °C is within ordinary room temperature, and the vapour pressure shows meaningful vapour at 20 °C. ICSC 0084 lists explosive limits of 0.9 to 7.6 vol% for o-xylene. Treat it as a flammable liquid and keep ignition sources away.
- Separating isomers. The boiling points differ by only 1 °C (m- and p-) to 6 °C (o- and p-). This is an editorial reading of the table: such a narrow spread suggests simple distillation will not cleanly separate the isomers.
- Cold rooms. p-Xylene melts at 13 °C, so a bottle kept in a cold room or on a cold bench can solidify. o- and m-xylene melt far below that.
- Removing xylene by evaporation. With a boiling point well above water’s 100 °C, xylene is slow to remove by ordinary evaporation. The NIST Antoine parameters above give an estimate of the temperature for a given vacuum; make sure the vapour is captured or vented properly.
- Extractions. Low water solubility and a density below 1 mean a xylene layer sits above an aqueous layer.
- Handling. Check glove material against the specific chemical (see nitrile glove chemical resistance and the chemical resistance chart for plastics), label secondary containers (OSHA HazCom secondary container labeling) and send waste through your institution’s route (lab waste disposal).
Common misunderstandings
- “Xylene has one boiling point.” There are three isomer values (138, 139 and 144 °C), and a mixture boils over a range.
- “A high boiling point means low flammability.” Flammability follows flash point and vapour pressure, which for xylene sit near room temperature.
- “Freezing point and melting point are different.” For a pure compound they are the same temperature; datasheets use either term.
- “Xylene and acetone are interchangeable.” They belong to different chemical classes.
Frequently asked questions
What is the boiling point of xylene in Celsius?
138 °C for p-xylene, 139 °C for m-xylene and 144 °C for o-xylene (ICSC 0086, 0085, 0084).
What is the flash point of xylene?
30 °C closed cup for o-xylene and 25 °C for m- and p-xylene (ICSC).
What is the melting point of xylene?
-25 °C for o-xylene, -48 °C for m-xylene and 13 °C for p-xylene (ICSC).
What is the density of o-xylene?
Relative density 0.88 at 20 °C (ICSC 0084).
Sources
- International Chemical Safety Card 0084, o-xylene: inchem.org (read 2026-11-07).
- ICSC 0085, m-xylene: inchem.org (read 2026-11-07).
- ICSC 0086, p-xylene: inchem.org (read 2026-11-07).
- NIST Chemistry WebBook, p-xylene: webbook.nist.gov (read 2026-11-07).
General reference information for laboratory use, not safety or medical advice. Follow the supplier safety data sheet and your institution’s chemical hygiene plan.
