Methyl Ethyl Ketone (MEK): Properties, Uses, and Safety Information

What is Methyl Ethyl Ketone (MEK)?

Methyl Ethyl Ketone, often called MEK, is a clear, colorless liquid with a sharp, sweet odor. In chemistry labs and on manufacturing floors, many folks call it by its formula, C₄H₈O, or its IUPAC name, Butan-2-one. Its structure includes a four-carbon chain with a ketone functional group, making it a simple yet versatile organic solvent. This compound dissolves many plastics, resins, gums, and oils, giving it a reputation for tough cleaning jobs and as a staple raw material in coatings, adhesives, and chemical synthesis.

Physical and Chemical Properties

MEK’s physical characteristics set it apart in industrial and laboratory settings. The compound boils at 79.6°C, just above water’s boiling point, giving it a relatively low evaporation threshold. Its melting point sits at -86°C, so it stays liquid under most conditions. Its density measures about 0.805 grams per cubic centimeter, making it lighter than water. The molecular weight of MEK clocks in at 72.11 g/mol. Its refractive index stands at about 1.378, which helps chemists identify and separate it during analytical procedures. MEK mixes easily with water, ethanol, ether, and other solvents, but it never forms solid powders, flakes, or pearls at room temperature. You always see it shipped and stored as a liquid because of these traits. Its volatility is both a blessing in terms of drying times and a challenge for safe storage and handling.

Commercial Forms and Packaging

Commercial-grade MEK only appears as a liquid and never as a crystal, flake, powder, or solid pearl—trying to find MEK in those forms leads to a dead end. Drums, tanks, and smaller bottles all carry liquid MEK. Industrial plants use it by the drum or tank, while laboratory technicians rely on smaller containers measured by liter. This is not a chemical handled casually; its strong fumes require tight seals and special precautions for both bulk and smaller-scale storage.

Specifications and Identification

Regulators, customs, and logistics teams identify MEK with its HS Code: 29141200. This code tracks the product through shipping documents and customs checkpoints. For paperwork and safety protocols, workers refer to its molecular formula: C₄H₈O. Specifications dictate purity—often at least 99.5% for solvent-grade materials—plus limits for moisture and impurities that could disrupt product performance or safety.

Applications and Raw Material Role

MEK holds a vital role as a raw material in the manufacture of synthetic rubbers, paraffin wax, plastic cements, lacquers, adhesives, and printing inks. Paint shops count on MEK to thin solutions and clean tools thanks to evaporation properties and solvency strength. Pharmaceutical and cosmetic companies use it during formulation steps, although finished products only rarely hold any trace of MEK. Fabricators of magnetic tapes and lubricating oils depend on it as an extraction and purification solvent. It supports the production of polysulfone resins and tough, chemically resistant plastics, helping to mold products that withstand harsh conditions.

Health, Safe Handling, and Environmental Concerns

MEK brings genuine hazards along with its usefulness. Short-term exposure to vapors or direct contact causes headaches, dizziness, eye and skin irritation, and symptoms of intoxication. Extended breathing of vapors may damage the nervous system. Companies address safety with airtight containers and proper ventilation, keeping atmospheric concentrations below set exposure limits. Flammability ranks high among risks—liquid MEK ignites at just 404°C, and vapors can catch fire from a distant spark or open flame. Industrial sites enforce stringent “no open flame” rules and rely on grounding wires during transfers to avoid static buildup.

Spills of MEK move quickly through concrete, soil, and drains due to the solvent’s low viscosity and high volatility. Cleanup teams deploy absorbent materials and closed recovery systems to keep fumes out of the workplace and environment. Disposal of MEK waste follows hazardous waste regulations, and teams avoid pouring it down the drain or mixing with incompatible chemicals. The Environmental Protection Agency (EPA) and equivalent agencies worldwide classify MEK as a hazardous air pollutant, requiring regular reporting and strict waste management. Personal experience with solvent-laden workplaces showed that air monitors and personal protective equipment like respirators and gloves are essential, not optional.

Molecular Structure and Chemical Reactivity

The MEK molecule, a straightforward carbon chain with a central carbonyl (C=O) group, combines simplicity with high chemical reactivity. Chemists often exploit its ready ability to form addition and condensation products, producing chemicals for further use in tailored material applications. Unlike some ketones and alcohols, MEK does not polymerize or degrade easily, holding its structure under reasonable storage and standard laboratory procedures. This stability, paired with the chemical’s flammability and ability to dissolve heavy residues, has made MEK one of the go-to choices for challenging cleaning and mixing operations in industrial chemistry.

Conclusion: Using MEK Responsibly

MEK gives manufacturers, lab workers, artists, and tinkerers the flexibility to thin paints, clean tools, and develop new polymers. The same properties that make it useful—volatility, solvency, simple structure—demand care and strict procedural oversight. Experience in environments filled with solvent fumes and drum pumps demonstrates that safety data sheets, workplace controls, and personal vigilance matter just as much as technical specifications. MEK sits at the intersection of convenience and potential harm. Respect for its hazardous nature unlocks its value in quality products without putting people or the environment at risk.