CAS 142-82-5: Identity and Key Properties
CAS number 142-82-5 identifies n-heptane, a straight-chain saturated hydrocarbon with the molecular formula C7H16 and a molecular weight of 100.21 g/mol. It is a colourless, volatile liquid with a characteristic petrol-like odour, immiscible with water and fully miscible with most organic solvents. The table below lists the properties most commonly quoted on certificates of analysis.
| Property | Value |
|---|---|
| Molecular formula | C7H16 |
| CAS / EINECS | 142-82-5 / 205-563-8 |
| Melting point | ≈−90.5 °C |
| Boiling point | ≈98.4 °C |
| Density | 0.684 g/mL at 20 °C |
| Vapour density | 3.5 (vs air) |
| Vapour pressure | ≈40 mmHg at 20 °C |
| Refractive index | n20/D ≈1.387 |
| Flash point (closed cup) | ≈−4 °C (25 °F) |
| Auto-ignition temperature | ≈204 °C |
What Is N-Heptane Used For?
N-heptane is one of the most important industrial hydrocarbons because its narrow boiling range and clean evaporation profile suit demanding solvent applications.
Octane number standard
N-heptane is the zero point of the research and motor octane scales: pure n-heptane is defined as 0 octane number, while 2,2,4-trimethylpentane (isooctane) is 100. It is therefore an indispensable calibration standard for gasoline knock testing and fuel blending.
Analytical and laboratory use
Its high purity and low UV cut-off make n-heptane a preferred solvent and reference material in gas chromatography, HPLC and spectroscopic analysis, as well as in Karl Fischer and other titration systems.
Industrial solvent applications
N-heptane is used as an extraction solvent for vegetable and animal oils, in quick-drying rubber adhesives, and as a cleaning solvent in coatings, varnishes, quick-drying inks and the printing industry. It also serves as a reaction medium in organic synthesis and in the preparation of experimental reagents.
Safety, Transport and Storage
N-heptane is classified as a highly flammable liquid (GHS H225) and an aspiration hazard (H304: may be fatal if swallowed and enters airways). It is assigned UN number 1206, transport hazard class 3, packing group II. Store it in tightly closed containers in a cool, well-ventilated area away from ignition sources, oxidisers and heat. Use explosion-proof equipment, grounded containers during transfer, and wear protective gloves and goggles. Ensure the SDS and UN-compliant labelling accompany every shipment.
Packaging and Buying
N-heptane is commonly supplied in 160 kg drums, 800 kg IBC totes and ISO tanks. A typical 20-foot container loads 12.8 MT in drums, 16 MT in IBCs or 18.5 MT in ISO tank. When buying, specify the purity grade and test method, request the batch COA and SDS, and confirm UN 1206 transport documentation with your forwarder.
Frequently Asked Questions
What chemical is CAS 142-82-5? CAS 142-82-5 is n-heptane (C7H16), a straight-chain alkane also written as heptane or dipropylmethane.
Is n-heptane the same as heptane? In commercial practice the terms are used interchangeably for the pure normal isomer. The name heptane alone can refer to any isomer of C7H16, but CAS 142-82-5 strictly denotes the straight-chain n-heptane.
Why is n-heptane used in octane testing? By definition, n-heptane has an octane rating of zero and isooctane a rating of 100. Blends of the two calibrate the knock intensity scale used for gasoline.
Is n-heptane miscible with water? No. N-heptane is a non-polar hydrocarbon with negligible water solubility; it forms separate layers with water and is miscible with ethers, ketones, alcohols and other organic solvents.
What is the UN number for n-heptane? N-heptane is transported under UN 1206, class 3 (flammable liquid), packing group II.
How should n-heptane be stored? Store in tightly closed containers in a cool, dry, well-ventilated location, protected from direct sunlight and away from ignition sources and oxidising agents, with bonding and grounding during transfer.