Mixed Xylene Boiling Point, Density & Key Physical Properties
Mixed xylene (CAS 1330-20-7) boils in the range of approximately 137–140°C, with some commercial specifications listing a slightly wider range of up to 138–144°C depending on isomer ratio and ethylbenzene content.
Two other specifications buyers commonly check alongside boiling point: density, generally 0.86–0.88 g/cm³ at 20–25°C, and flash point (closed cup), typically reported in the 25–29°C range though some sources cite a broader range depending on grade and test method - placing mixed xylene in UN 1307, Class 3, Packing Group III for transport. These figures are the specifications buyers most often cross-check between a supplier's Technical Data Sheet (TDS) and a shipment's Certificate of Analysis (COA) before confirming an order.
This article breaks down what these properties mean, why mixed xylene doesn't have a single fixed boiling point, and how the numbers translate into practical decisions around storage, transport, and quality verification.
What Is the Boiling Point of Mixed Xylene?
Mixed xylene (CAS 1330-20-7, EINECS 215-535-7) is not a single compound - it's a blend of three xylene isomers (ortho-, meta-, para-xylene) plus a variable amount of ethylbenzene. Because of this, suppliers report a boiling range rather than one fixed temperature.
Commonly cited literature values place the boiling range at 137–140°C, while some commercial specifications extend this to 138–144°C to account for higher ethylbenzene or o-xylene content. Neither figure is "more correct" - the actual range depends on the specific grade and isomer composition of the batch, which is why the boiling point on a generic reference sheet can differ slightly from the value on an actual production lot's COA.
For procurement purposes: always confirm the boiling range stated on the specific product's TDS rather than relying solely on general reference data, since blending ratios vary by producer and by grade (e.g., industrial-grade vs. high-purity mixed xylene).
Why Mixed Xylene Has a Boiling Range Instead of a Single Point
Typical Boiling Points of the Individual Isomers
Each component of mixed xylene has its own distinct boiling point:
| Component | Approximate Boiling Point |
|---|---|
| Ethylbenzene | ~136°C |
| p-Xylene | ~138°C |
| m-Xylene | ~139°C |
| o-Xylene | ~144°C |
(These are widely documented literature values for the pure isomers; they are provided for reference and should not be substituted for a supplier's batch-specific data.)
Because these boiling points sit close together, separating the isomers by simple distillation is difficult - most commercial mixed xylene is sold and used as a blend rather than as individually isolated isomers.
How Isomer Ratio Affects the Overall Range
The proportion of each isomer - and how much ethylbenzene remains in the blend - shifts where the overall boiling range falls. A batch with a higher o-xylene fraction will trend toward the upper end of the range; a batch with more ethylbenzene or p-xylene will trend lower. This is a normal characteristic of mixed xylene as a commercial product, not a sign of inconsistent quality, but it's the reason two suppliers' TDS documents can list slightly different ranges for what is functionally the same product grade.
Density and Specific Gravity of Mixed Xylene
Density at Standard Conditions
Mixed xylene has a density of approximately 0.86 g/mL at 25°C, with commercial specification sheets commonly listing a broader typical range of 0.86–0.88 g/cm³ at 20–25°C. This makes it noticeably less dense than water (1.00 g/cm³), which is directly relevant to its behavior in storage and spill scenarios - mixed xylene will float on water rather than mix into it.
Density vs. Temperature - What Buyers Should Know
Like most liquid hydrocarbons, mixed xylene's density decreases slightly as temperature rises. For day-to-day procurement, this matters most when converting between volume (liters/gallons) and weight (kg/metric tons) for shipping documentation, tank calibration, or invoicing. Suppliers state the specific reference temperature used for their density figure on the TDS - this can vary by supplier - so buyers should always match the conversion factor to that stated temperature rather than assuming a standard condition, to avoid discrepancies between ordered volume and invoiced weight.
Other Key Physical and Chemical Properties
Flash Point and Flammability Classification
Mixed xylene's flash point (closed cup) is commonly reported in the 25–29°C range, though published values vary somewhat by grade, isomer ratio, and test method - some reference sources list figures spanning roughly 11–34°C for different xylene grades and mixtures. Buyers should treat the flash point stated on the specific product's TDS/SDS as authoritative rather than any single figure cited in general reference material. Because this range sits at or below typical ambient warehouse temperatures in many regions, mixed xylene is classified for transport as UN 1307, Class 3 (Flammable Liquid), Packing Group III, and warmer climates warrant extra attention to tank and warehouse ventilation planning.
Vapor Pressure and Evaporation Rate
For reagent-grade mixed xylene, vapor pressure is reported at approximately 18 mmHg at 37.7°C, with a vapor density around 3.7 times that of air . Commercial/industrial-grade material may differ slightly depending on composition, so this figure should be treated as indicative rather than a specification value - request the exact figure from your supplier's TDS if it's relevant to your ventilation or vapor-recovery calculations. In general terms, xylene vapor is heavier than air and can accumulate at low points in poorly ventilated storage areas - a factor relevant to both safety planning and evaporation losses during transfer and decanting operations.
Appearance, Odor & Basic Characteristics
Mixed xylene is a clear, colorless to light-colored liquid with a characteristic aromatic (sweet, hydrocarbon) odor. It is insoluble in water and miscible with most organic solvents, including alcohols and ethers - a topic covered in more depth in our dedicated article on mixed xylene solubility.
Why These Properties Matter for Storage, Transport & Handling
Boiling Point & Flash Point Implications for Storage Tank Selection
Because mixed xylene's flash point sits close to or below ambient temperature in many climates, storage tanks and drums should be selected and sited with flammable-liquid handling requirements in mind - including grounding/bonding during transfer, adequate ventilation, and separation from ignition sources. The boiling range also informs headspace and venting design, since any localized heating (e.g., tanks exposed to direct sun) can increase vapor generation.
Density's Role in Shipping Weight & Container Loading Calculations
Density is the figure logistics teams use to convert between the volume ordered and the weight declared on shipping documents - a routine but important calculation for ISO tank containers, tank trucks, and drummed shipments. Since density varies slightly with temperature and isomer ratio, buyers reconciling a bill of lading against a purchase order should confirm which density value (and reference temperature) the supplier used for the conversion.
How to Verify Mixed Xylene Physical Properties Before Purchase
Reading Boiling Point & Density on a TDS
A supplier's Technical Data Sheet should list boiling range, density (with reference temperature), and flash point as standard specification items, typically alongside purity (% xylenes), water content, and color (Pt-Co scale). When comparing quotes from multiple suppliers, checking these fields side by side is a fast way to confirm you're comparing equivalent grades. The physical-property data on the TDS should also be read alongside the Safety Data Sheet (SDS), which covers hazard classification, handling precautions, and regulatory information (including REACH registration status for shipments into the EU) - the TDS confirms what the product is, the SDS confirms how it must be handled and shipped.
Why COA Batch Data May Vary Slightly From Published Reference Ranges
A Certificate of Analysis reflects the actual test results for a specific production lot, not a generic literature value. Minor variation between a batch's COA and general reference data (such as the ranges cited in this article) is normal and expected - what matters for procurement is that the COA figures fall within the tolerance stated on the agreed TDS or purchase specification. If a batch falls outside the agreed range, that's the basis for a quality claim, not the reference literature value itself.
What to Request Alongside Physical Property Data
Boiling point, density, and flash point are only part of a complete quality and logistics picture. Before placing an order, buyers typically also confirm:
- TDS and SDS for the specific grade being quoted
- COA for the actual production batch or shipment
- Packaging options (e.g., drums, IBCs, flexitanks, ISO tank containers) and their compatibility with the product's flash point/flammability class
- MOQ (minimum order quantity) and available pack sizes
- Shipping and Incoterms - mixed xylene's Class 3 flammable liquid classification affects freight options, documentation, and lead times
Speak with our technical sales team to confirm current TDS/SDS/COA documentation, packaging options, and MOQ for your required grade.
Key Takeaways
Mixed xylene (CAS 1330-20-7) has a boiling range of approximately 137–140°C, sometimes specified up to 144°C depending on grade and isomer ratio - it does not have one fixed boiling point because it is a blend, not a single compound.
Density is generally 0.86–0.88 g/cm³ at 20–25°C.
Flash point (closed cup) is typically 25–29°C, which is why mixed xylene is classified as a UN 1307, Class 3, Packing Group III flammable liquid for transport.
Always confirm boiling range, density, and flash point against the current TDS, SDS, and COA for the specific grade and batch being purchased - published reference values are a starting point, not a substitute for supplier documentation.
FAQ
Does the boiling point of mixed xylene vary between suppliers or production batches?
Yes, slightly. Because mixed xylene is a blend of isomers and ethylbenzene rather than a single compound, small differences in composition between production batches or suppliers can shift the boiling range by a few degrees. This is normal and is why specifications are given as a range rather than a fixed point - the relevant benchmark is the range stated on the agreed TDS, not a generic reference figure.
Is mixed xylene's boiling point affected by the isomer ratio (o-/m-/p-xylene)?
Yes. A batch containing a higher proportion of o-xylene will trend toward the upper end of the boiling range, while a batch with more ethylbenzene or p-xylene will trend lower. This is a normal characteristic of the product and does not by itself indicate a quality issue.
How does boiling point affect the evaporation rate of mixed xylene in paint and coating formulations?
Boiling range is one of several factors influencing evaporation rate; in general, a solvent within this boiling range provides a moderate evaporation rate compared to faster-evaporating solvents like acetone or toluene, which is one reason mixed xylene is widely used to control drying/flash-off time in coatings and inks. Formulators should still verify actual evaporation performance for their specific formulation and application conditions rather than relying on boiling point alone.
What's the difference between mixed xylene's boiling point and its flash point?
Boiling point is the temperature at which the liquid turns to vapor at atmospheric pressure; flash point is the much lower temperature at which the liquid's vapor can ignite in the presence of an ignition source. For mixed xylene, the flash point (~25–29°C) is well below the boiling range (~137–144°C) - the flash point is the more critical figure for storage and handling safety, while the boiling range is more relevant to processing and evaporation behavior.
Where can I find the exact boiling point and density values for a specific mixed xylene batch?
These figures are listed on the product's Technical Data Sheet (typical specification range) and Certificate of Analysis (actual tested values for that lot). Buyers should request both documents from their supplier before finalizing an order, particularly when the application has tight tolerance requirements.