Xylene is sold in two dimensions: isomer composition and purity grade. Most industrial buyers purchase mixed xylenes (CAS 1330-20-7), a blend of the ortho, meta, and para isomers. Above that sit purity grades — standard or production, ACS, USP, HPLC, and high purity — along with single-isomer material such as p-xylene, bought as a chemical intermediate rather than as a solvent.
Which one you need depends on whether xylene is doing work as a solvent, as a feedstock, or as an analytical reagent. This guide separates the isomers from the grades, gives the hard numbers for each, and lists what to check on a certificate of analysis.
What is xylene?
Xylene, also called dimethylbenzene or xylol, is an aromatic hydrocarbon with the molecular formula C8H10 and a molecular weight of 106.16 g/mol, per the PubChem record for o-xylene (CID 7237); the meta (CID 7929) and para (CID 7809) isomers share the same formula and weight. It is a colorless liquid with an aromatic odor, used as a solvent and thinner for coatings, printing inks, adhesives, and rubber processing, as a chemical intermediate, and in laboratory histology.
Three structural isomers exist, differing only in where the two methyl groups sit on the benzene ring. Those small structural differences produce meaningfully different boiling and freezing points, which is exactly why the grades below exist.
What are the xylene isomers and how do they differ?
All values below are from the NIOSH Pocket Guide to Chemical Hazards.
| Property | o-Xylene | m-Xylene | p-Xylene |
|---|---|---|---|
| Systematic name | 1,2-Dimethylbenzene | 1,3-Dimethylbenzene | 1,4-Dimethylbenzene |
| CAS number | 95-47-6 | 108-38-3 | 106-42-3 |
| Boiling point | 292°F | 282°F | 281°F |
| Freezing point | -13°F | -54°F | 56°F |
| Flash point | 90°F | 82°F | 81°F |
| Specific gravity | 0.88 | 0.86 | 0.86 |
| Vapor pressure | 7 mmHg | 9 mmHg | 9 mmHg |
| Molecular weight | 106.2 | 106.2 | 106.2 |
The freezing point of p-xylene is the number that surprises people. NIOSH notes that p-xylene is a solid below 56°F, so drums or totes of high-purity para material stored in an unheated warehouse over winter will solidify. Mixed xylenes do not have this problem, because the other isomers depress the freezing point.
What is mixed xylene?
Mixed xylenes (CAS 1330-20-7) is a blend of the ortho, meta, and para isomers, typically also containing ethylbenzene. It is the default commercial product and the form most solvent buyers mean when they say xylene. Because it is a blend, it distills over a range rather than at a single temperature, so specifications are written as a distillation range plus an aromatic content minimum rather than as a single-component purity.
If a formulation calls for a solvent with a specific evaporation rate, mixed xylene is usually the right and cheaper choice. If a process needs one isomer as a reactant, isomer-grade material is required and the price reflects the separation cost.
Which xylene grades can you buy?
| Grade | Typical use | What the spec controls |
|---|---|---|
| Standard / production | Coatings, thinners, degreasing, adhesives, printing | Distillation range, aromatic content, color, water |
| ACS reagent | Bench chemistry and general laboratory work | Purity plus limits on named impurities and residue |
| USP | Pharmaceutical and compendial applications | Compliance with the United States Pharmacopeia monograph |
| HPLC | Chromatography and instrumental analysis | UV absorbance, low residue after evaporation, water content |
| High purity | Electronics, semiconductor cleaning, critical synthesis | Trace metals, trace water, non-volatile residue |
| Histological | Clearing and deparaffinizing in pathology labs | Consistent clearing performance and low residue |
The same logic applies across analytical solvents generally — our explainer on ACS vs HPLC vs reagent grade covers how these designations are written and why HPLC grade costs more than ACS for the same nominal purity. Buyers comparing aromatic solvents often also weigh toluene, which is lighter and faster-evaporating than xylene.
What should you check on a xylene certificate of analysis?
- Identity and CAS. 1330-20-7 for mixed xylenes; 95-47-6, 108-38-3, or 106-42-3 for single isomers.
- Distillation range. For mixed xylenes this is the primary performance number.
- Isomer distribution and ethylbenzene content, when the process is sensitive to either.
- Water content, which matters for coatings and for any moisture-sensitive reaction.
- Non-volatile residue, the number that separates analytical grades from production grades.
- Color, usually reported on the platinum-cobalt scale.
See how to read a certificate of analysis for a section-by-section walkthrough.
Is xylene hazardous?
Yes. All three isomers carry an OSHA permissible exposure limit of 100 ppm as an 8-hour TWA and a NIOSH recommended exposure limit of 100 ppm TWA with a 150 ppm short-term limit, per the NIOSH Pocket Guide. The IDLH is 900 ppm. All three are Class IC flammable liquids, with flash points between 81°F and 90°F, and all three are incompatible with strong oxidizers and strong acids. Exposure routes include inhalation, skin absorption, ingestion, and skin or eye contact.
Always work from the current safety data sheet for the exact grade you received — see our guide to reading a safety data sheet, and pull current documents from the RightPath SDS library. For converting between volume and weight when sizing an order, use the RightPath conversion tools.
What grades and sizes do we stock?
RightPath Industries supplies mixed xylenes in Standard/Production, ACS, USP, HPLC, and High Purity grades, available in gallons, pails, drums, totes, and bulk, packed to your specification and lot-controlled on request. Xylene sits in our aromatics and solvents ranges, alongside toluene and the rest of a catalog of more than 8,000 chemicals shipped from our Pittsburgh headquarters.
How do you order xylene from RightPath?
Send the grade, the packaging size, the annual or per-shipment volume, and the destination. We will cross-reference your current specification exactly and return pricing with the SDS and documentation package. Request bulk pricing for same-day response.
Frequently asked questions
What is the difference between xylene and mixed xylene?
Xylene names the compound C8H10 in any of its three isomeric forms. Mixed xylene is the commercial product, CAS 1330-20-7, that blends the ortho, meta, and para isomers and usually contains ethylbenzene. Most industrial solvent purchases are mixed xylene.
What is the flash point of xylene?
NIOSH lists flash points of 90°F for o-xylene, 82°F for m-xylene, and 81°F for p-xylene. All three are classified as Class IC flammable liquids, meaning a flash point at or above 73°F and below 100°F.
What is the OSHA exposure limit for xylene?
The OSHA permissible exposure limit for o-, m-, and p-xylene is 100 ppm (435 mg/m3) as an 8-hour time-weighted average. The NIOSH recommended exposure limit is also 100 ppm TWA, with a 150 ppm short-term exposure limit, and the IDLH is 900 ppm.
Which xylene grade is used in histology labs?
Pathology laboratories use histological grade xylene for clearing and deparaffinizing tissue sections. It is specified for consistent clearing performance and low residue rather than for a single-isomer purity target.
Does xylene freeze in cold storage?
High-purity p-xylene does. NIOSH notes p-xylene is a solid below 56°F. Mixed xylenes remain liquid at far lower temperatures because the other isomers depress the freezing point; m-xylene freezes at -54°F and o-xylene at -13°F.