The question of whether coal oil and kerosene are the same is rooted in a historical shift in fuel production, which created enduring confusion in terminology. While they are often used interchangeably, especially by consumers, they are technically distinct products based on their origin and refinement process. Coal oil was the predecessor, derived from solid materials, while modern kerosene is a product standardized through petroleum distillation. Both are liquid hydrocarbon fuels primarily used for illumination and heating, but their chemical purity and production methods separate their identities.
The Historical Origin of Coal Oil
The original “coal oil” was a mid-19th-century invention born from the need for affordable lamp fuel to replace expensive whale oil. This fuel was manufactured through destructive distillation, which involves heating bituminous coal or oil shale to high temperatures in the absence of air. This pyrolysis process “cracked” the large organic molecules, yielding various products, including a collectible liquid fraction.
The resulting liquid was chemically similar to kerosene, consisting of alkane hydrocarbons with 10 to 16 carbon atoms per molecule. However, the destructive distillation method was difficult to control, leading to a product of variable quality that often burned with a smoky, strong-smelling flame. Early coal oil was primarily used for outdoor lamps, as its impurities made it less desirable for indoor lighting compared to cleaner alternatives. Scottish chemist James Young pioneered the industrial production of this coal-derived oil in the 1850s, patenting the process for extracting it from coal and shale.
The Standardization of Kerosene Refining
The process and name associated with modern lamp fuel were standardized by Canadian geologist and physician Abraham Gesner in the late 1840s. Gesner developed a method to distill a clean, stable illuminating oil from various bituminous sources, which he trademarked as “kerosene.” The name is derived from the Greek words for wax and oil. Gesner’s initial process also used coal and shale oil, but his purification techniques yielded a superior product to the earlier, smokier coal oil.
The true shift occurred after the discovery of abundant crude petroleum in Pennsylvania in 1859. Refiners quickly realized that processing liquid crude oil was much cheaper and yielded a higher volume of product than distilling solid coal or shale. They adapted Gesner’s fractional distillation techniques to separate the desired illuminating oil fraction from the crude petroleum. This shift lowered the fuel cost significantly, making petroleum-derived kerosene the dominant lamp fuel. Kerosene became the standardized trade name for the cleaner product, effectively replacing the older, less refined “coal oil.”
Modern Identity and Functional Equivalence
Today, the substance sold globally as kerosene is a refined petroleum distillate, chemically distinct from the original, historical coal oil. Modern kerosene is classified as a middle distillate, meaning its boiling range of approximately 175 to 325 degrees Celsius places it between lighter fuels like gasoline and heavier ones like diesel. It is a mixture of hydrocarbons, largely saturated straight-chain and ring-shaped paraffins.
A defining safety characteristic of modern kerosene is its flash point, the minimum temperature at which its vapors will ignite, which is regulated to be 38 degrees Celsius or higher. This high flash point makes it a relatively safe fuel to store and handle compared to more volatile fuels like gasoline. Kerosene is used for lamps and heaters, and is also the base for commercial jet fuel, such as Jet A, demonstrating its standardized quality and clean-burning properties. When modern consumers use the term “coal oil,” they are referring to this contemporary, petroleum-derived kerosene, showing that the historical name has persisted as a colloquial synonym.