Chloroform is a colorless, sweet-smelling liquid used primarily as a solvent in laboratories, a raw material in chemical manufacturing, and a key tool in molecular biology for extracting DNA and RNA. While most people associate it with its old reputation as an anesthetic or its portrayal in crime fiction, its real-world applications today are far more technical. It also shows up in places you might not expect, including your tap water.
Laboratory Solvent and DNA Extraction
The most widespread modern use of chloroform is in research laboratories. It dissolves fats, oils, resins, and many organic compounds easily, making it valuable as a general-purpose solvent for chemical reactions and sample preparation. Its density (about 1.48 g/cm³, notably heavier than water) and low boiling point (61°C) make it practical for techniques that require separating substances into layers, then evaporating the solvent off quickly.
One of chloroform’s most important scientific roles is in extracting genetic material from biological samples. In a widely used technique called phenol-chloroform extraction, researchers mix a sample with a phenol-chloroform solution, then spin it in a centrifuge. The mixture separates into two layers: the upper water-based layer holds the DNA, while the lower chloroform-rich layer traps the unwanted proteins. Scientists can then pull off the DNA layer and purify it further with alcohol. The same basic approach works for RNA extraction. Though the method is effective and relatively simple, phenol is toxic and flammable, which has pushed some labs toward newer extraction kits that avoid it.
Chloroform also serves as a standard solvent in nuclear magnetic resonance (NMR) spectroscopy, one of the primary tools chemists use to identify the structure of molecules. A specially prepared form, called deuterated chloroform, dissolves most organic compounds without interfering with the readings.
Chemical Manufacturing
By volume, the largest industrial use of chloroform is as a feedstock for producing other chemicals. Most commercially manufactured chloroform goes toward making refrigerants and fluoropolymers (the family of materials that includes nonstick coatings). Chloroform also appears in the production of dyes, pesticides, and various pharmaceutical intermediates. In drug research and natural product chemistry, it’s routinely used to extract biologically active compounds from plant material for further study.
Its Famous Past as an Anesthetic
Chloroform’s most well-known historical use was in surgery. Scottish obstetrician James Young Simpson performed the first chloroform anesthesia on November 4, 1847, initially testing it on himself before using it during childbirth. It quickly became popular because it worked faster and smelled less unpleasant than ether, the other anesthetic available at the time. Queen Victoria famously received chloroform during labor in 1853, which helped legitimize its use.
Doctors eventually abandoned chloroform as an anesthetic because the margin between an effective dose and a dangerous one was too narrow. It caused fatal heart rhythm disturbances and severe liver damage in some patients. Modern anesthetics are far safer and more controllable. No legitimate medical procedure uses chloroform for sedation today.
An Unintended Presence in Tap Water
Chloroform forms as an accidental byproduct when water treatment plants use chlorine to disinfect drinking water. The chlorine reacts with naturally occurring organic material in the source water, things like decomposing plant matter, producing a group of compounds called trihalomethanes. Chloroform is the most common of these. Haloacetic acids, another group of byproducts, form through the same process.
The concentrations in treated drinking water are very small, and the EPA sets legal limits on the total amount of trihalomethanes allowed. Your local water utility is required to test for these compounds and report the results in an annual water quality report. If you’re curious about the levels in your area, that report is typically available on your utility’s website.
How Chloroform Affects the Body
Chloroform is toxic to several organ systems, with the liver and kidneys taking the biggest hit. When you inhale or ingest chloroform, your liver processes it using a specific enzyme system (CYP2E1). That breakdown produces phosgene, a highly reactive compound that damages liver cells by binding to their proteins and depleting the liver’s natural antioxidant defenses. When those defenses are overwhelmed, liver tissue dies. The same enzyme system operates in the kidneys, making them vulnerable to the same kind of damage.
At lower exposures, chloroform acts as a central nervous system depressant, which is exactly why it once worked as an anesthetic. Breathing moderate concentrations causes dizziness, nausea, and headaches. Higher exposures lead to loss of consciousness, and prolonged or heavy exposure can be fatal through respiratory failure or cardiac arrest. The respiratory system itself can also be damaged by inhaling chloroform vapor, particularly the lining of the nose and airways.
Workplace exposure is regulated by OSHA, which sets the permissible exposure limit at 2 parts per million averaged over an eight-hour workday. That limit reflects how readily chloroform vapor can accumulate in poorly ventilated spaces, since the liquid evaporates at relatively low temperatures.
Why It Persists Despite the Risks
Chloroform remains in use because it has a combination of chemical properties that are hard to replace. It dissolves a wide range of organic compounds, separates cleanly from water-based solutions, evaporates at a low temperature without leaving residue, and doesn’t catch fire under normal conditions. For DNA extraction, pharmaceutical chemistry, and industrial synthesis, these properties make it uniquely practical. The key difference between its historical use and its modern role is containment: today it’s handled in fume hoods, enclosed industrial systems, and controlled laboratory settings rather than dripped onto a cloth held over someone’s face.