o-Xylene, also written ortho-xylene or 1,2-dimethylbenzene, is an aromatic hydrocarbon with the formula C8H10 and CAS number 95-47-6. It is a clear, flammable liquid, and industrial demand comes from two directions: solvent duty in paints, coatings and printing inks, and chemical duty as a feedstock for downstream synthesis. Buyers normally qualify o-Xylene on purity, isomer composition and batch-to-batch consistency.
What Is o-Xylene?
o-Xylene is one of the four C8 aromatic isomers, together with p-xylene, m-xylene and ethylbenzene. Its two methyl groups sit on adjacent carbon atoms of the benzene ring at positions 1 and 2, which separates it from the para and meta isomers. That structural difference affects melting behaviour, separation economics and downstream reactivity, so o-Xylene is normally specified as its own product stream rather than as mixed xylenes.
| CAS number | 95-47-6 |
| Molecular formula | C8H10 |
| Molecular weight | 106.16 g/mol |
| Boiling point | About 144 degC at 101.3 kPa |
| Density | About 0.880 g/cm3 at 20 degC |
| Flash point | About 32 degC, closed cup |
| Appearance | Clear, colourless liquid |
o-Xylene is a liquid of moderate volatility that mixes readily with most organic solvents and is practically insoluble in water, so it is handled as a non-aqueous solvent in coating, ink and rubber systems.
o-Xylene as a Solvent in Paints and Coatings
Coating producers use o-Xylene where an aromatic solvent with strong solvency for alkyd, acrylic, epoxy and related resin systems is required. Aromatics dissolve a wider range of resins than aliphatic hydrocarbons alone, so o-Xylene is usually blended into a solvent package rather than used on its own.
Solvency for alkyd resins, epoxy esters and selected acrylic systems
Control of viscosity and flow in solvent-borne industrial coatings
Adjustment of the evaporation profile when blended with other solvents
Use in wood coatings, general industrial coatings and maintenance paints
Final performance depends on the resin, the other solvents in the blend and the ratio used, so formulators evaluate the complete solvent system rather than one component in isolation.
o-Xylene in Printing Inks and Rubber Processing
In printing inks, o-Xylene acts as an aromatic component of the solvent system that dissolves or disperses resin and binder components. The solvent package influences ink viscosity, drying speed and transfer behaviour on press, so ink makers compare solvency and evaporation characteristics against other aromatic and oxygenated solvents before locking a formulation.
In rubber processing, o-Xylene is used as an organic solvent in selected compounding steps, for example where rubber or rubber-related materials must be dissolved, diluted or carried through a process stream. Because rubber compounds vary widely in composition, the solvent is normally chosen as part of a wider solvent system.
o-Xylene as a Chemical Intermediate
Beyond solvent duty, o-Xylene is an important chemical feedstock. The largest established outlet is the vapour-phase oxidation of o-Xylene to phthalic anhydride, a key intermediate for plasticisers, unsaturated polyester resins, alkyd resins and a range of fine chemicals. Feed purity directly affects catalyst life and product quality, so intermediate producers set tight limits on isomer content and trace impurities. o-Xylene is also used in the synthesis of dyes, pigments and selected organic intermediates.
Specification, Packaging and Handling
Assay or purity, typically 99 percent and above for solvent and feedstock grades
Isomer distribution, including limits on p-xylene, m-xylene and ethylbenzene
Moisture content, colour on the Pt-Co scale and appearance
Sulphur and other trace impurities where catalyst performance is critical
Supporting documents such as a certificate of analysis, safety data sheet and technical data sheet
Packaging and logistics are part of the specification as well. Typical options include steel drums, intermediate bulk containers, ISO tank containers and bulk delivery by tanker, and the packaging must suit the receiving site.
o-Xylene is a flammable liquid classified for transport under UN 1307, Class 3, packing group III. Storage areas should be cool, dry and well ventilated, away from ignition sources, oxidising agents and strong acids. Earthing and bonding during transfer and closed handling systems are standard practice.
Frequently Asked Questions
Q: What is the CAS number of o-Xylene?
A: The CAS number of o-Xylene is 95-47-6, and its systematic name is 1,2-dimethylbenzene.
Q: What is o-Xylene mainly used for?
A: It is used as an aromatic solvent in paints, coatings and printing inks, in rubber processing, and as a feedstock for phthalic anhydride.
Q: How does o-Xylene differ from p-xylene and m-xylene?
A: All three share the formula C8H10, but the methyl groups sit in different positions on the ring: adjacent in o-Xylene, opposite in p-xylene and separated in m-xylene.
Q: What purity is normally available?
A: Industrial grades are commonly offered at 99 percent and above, with limits on isomer content, moisture and colour set by the application.
Q: Is o-Xylene soluble in water?
A: It is practically insoluble in water and mixes readily with most organic solvents, so it is used in non-aqueous systems.
Q: Which documents should a buyer request?
A: A certificate of analysis, safety data sheet and technical data sheet are usual, and each batch should be checked against the agreed specification.