Hexane is a colorless, fast-evaporating liquid solvent derived from petroleum. It is best known as the solvent used to extract vegetable oils from seeds like soybeans, canola, and sunflowers, but it also shows up in adhesives, cleaning agents, and gasoline. Its chemical formula is C₆H₁₄, meaning each molecule contains six carbon atoms and fourteen hydrogen atoms, making it one of the simplest hydrocarbons used in industry.
Basic Properties of Hexane
Hexane boils at about 69 °C (156 °F), which is relatively low. That low boiling point is one reason it’s so useful: after hexane does its job dissolving fats or oils, it can be easily boiled off and recovered, leaving the extracted product behind. It has a faint petroleum-like odor and is practically insoluble in water, mixing at only about 0.001% concentration. It does, however, dissolve readily in alcohol, chloroform, and ether.
Because hexane is less dense than water and evaporates quickly at room temperature, it exists almost entirely as a vapor once released into the air. In the atmosphere, it breaks down through reactions with naturally occurring hydroxyl radicals, with a half-life of roughly 1.8 days. That means it doesn’t persist in the environment for long, but it is classified as a volatile organic compound (VOC) and a hazardous air pollutant.
Where Hexane Comes From
Hexane is produced from naphtha, one of the lightest fractions collected during petroleum refining. Naphtha makes up about 20% of crude oil by weight and contains a mixture of hydrocarbons with five to ten carbon atoms. To isolate hexane, refiners first remove sulfur and other impurities, then distill the naphtha into heavy and light fractions. Light naphtha, which contains hydrocarbons with six or fewer carbons, is split further into a six-carbon-rich fraction. That fraction may undergo an additional step to remove aromatic impurities like benzene, depending on the purity needed for the end use.
Why the Food Industry Relies on Hexane
Hexane is the solvent of choice for extracting oils from seeds and crops worldwide. Two properties make it especially suited for this: it has a strong selectivity toward fats and lipids (meaning it pulls out the oil while leaving most other plant components behind), and its low boiling point makes it easy to separate from the finished oil through simple distillation. After extraction, the hexane is evaporated, recovered, and reused, while the oil moves on to further refining.
This process is standard for soybean oil, canola oil, corn oil, and many other cooking oils you’ll find on store shelves. Oils labeled “expeller-pressed” or “cold-pressed” skip the hexane step entirely, relying on mechanical pressure instead. These methods extract less oil from the same amount of seed, which is why hexane extraction remains dominant at industrial scale.
Other Common Uses
Beyond food processing, hexane appears in a range of everyday products and industrial settings:
- Adhesives and glues: Quick-drying hobby glues and rubber cement often contain hexane because it evaporates fast, helping bonds set quickly.
- Gasoline: Hexane is a natural component of gasoline blends.
- Industrial cleaning: Its ability to dissolve grease and oils makes it useful as a degreasing solvent in manufacturing.
- Laboratories: Hexane is a common solvent in chemical analysis and chromatography.
Health Risks and Nerve Damage
The primary health concern with hexane is its ability to damage peripheral nerves, the nerves that run from your spinal cord out to your hands and feet. Hexane itself isn’t the direct culprit. When you inhale hexane vapor, your liver breaks it down through a series of steps. One of those steps produces a metabolite called 2,5-hexanedione, which is the actual neurotoxic substance. This metabolite reacts with proteins inside nerve cells, causing them to cross-link and clump together, which gradually disrupts the nerve’s ability to transmit signals.
The result, after prolonged or heavy exposure, is a condition called peripheral neuropathy: numbness, tingling, and weakness that typically starts in the fingers and toes and can progress inward. This kind of nerve damage has been documented in workers at factories with poor ventilation, and in people who habitually inhale glue fumes. Short, incidental exposure (like briefly smelling glue while doing a craft project) is not the same as the sustained, high-concentration exposure that causes these problems.
Workplace Exposure Limits
There is a significant gap between what regulators consider safe in the workplace. The Occupational Safety and Health Administration (OSHA) sets a permissible exposure limit of 500 parts per million (ppm) averaged over an eight-hour workday. However, the National Institute for Occupational Safety and Health (NIOSH) recommends a much lower limit of 50 ppm, reflecting more recent understanding of hexane’s neurotoxicity. The NIOSH number is the one most occupational health professionals treat as the meaningful benchmark, since the OSHA limit dates back decades and has not been updated to reflect current science.
Hexane in Your Cooking Oil
If you use conventional vegetable oil, hexane was almost certainly part of its production. The practical question is whether any remains in the finished product. After extraction, refiners heat the oil to evaporate residual hexane, and further refining steps (bleaching, deodorizing) reduce traces even more. Because hexane evaporates so readily, the amounts left in refined oil are extremely small. The FDA classifies hexane as “generally recognized as safe” for use in food processing, though it does not set a specific limit on residual levels in finished oils. For context, the European Union caps residual hexane in food-grade oils at 1 mg/kg.
If avoiding hexane entirely matters to you, look for oils labeled “expeller-pressed,” “cold-pressed,” or “organic” (USDA organic standards prohibit hexane extraction). These are widely available for olive, coconut, avocado, and even soybean and canola oils.
The Push for Alternatives
Despite its effectiveness, hexane raises two concerns that are driving industry to look for replacements: its toxicity to workers and the fact that it comes from petroleum, a nonrenewable resource. Researchers are actively testing bio-based solvents, supercritical carbon dioxide, and other approaches that could match hexane’s selectivity for fats without the health and environmental downsides. None has yet achieved the same combination of low cost, high efficiency, and easy recovery that keeps hexane in place, but the field is moving steadily in that direction.