Coal tar

Coal tar is what remains when coal is heated in the absence of air—a thick, black, foul-smelling liquid that coke producers initially considered waste. By the 19th century, this industrial byproduct had become the feedstock for synthetic dyes, medicines, and plastics, demonstrating how unwanted residues can birth new industries.

The first systematic coal tar production began around 1665 when Johann Joachim Becher heated coal in sealed retorts. The process liberated volatile gases (later used for lighting) and left behind coke (used for iron smelting), with tar accumulating as a troublesome remainder. Disposing of tar was an early industrial pollution problem.

The transformation began when chemists investigated tar's composition. In 1825, Michael Faraday isolated benzene from coal tar. By the 1840s, August Wilhelm von Hofmann and his students at London's Royal College of Chemistry were systematically extracting and characterizing tar components. This was tedious work—tar contains hundreds of compounds—but it revealed a chemical treasure.

William Henry Perkin, Hofmann's 18-year-old student, accidentally synthesized mauveine in 1856 while attempting to make quinine from coal tar derivatives. The purple dye launched the synthetic dye industry. Within decades, German chemical firms had industrialized coal tar chemistry, producing dyes, pharmaceuticals, and eventually explosives that would shape World War I.

The cascade continued: aspirin came from coal tar derivatives; plastics like Bakelite emerged from tar-based phenols; the entire organic chemistry industry traced its feedstock to this black residue. Coal tar was the crude oil of the 19th century chemical industry.

Path dependence locked in coal tar's centrality. German chemical education, German industrial organization, and German patent strategies all optimized around coal tar derivatives. When petroleum chemistry emerged in the 20th century, it inherited techniques and corporate structures that coal tar chemistry had established.

What coke producers had considered waste became the foundation of industrial chemistry.