Coal Tar
NAME: Coal tar
ALTERATIVE NAME: liquor carbonis detergens,
liquor picis carbonis
LANGUAGE: English and German
TIME: 18th-19th centuries
LOCATION: England and Europe
CATEGORY: Organic by-product of bituminous coal distillation
DISCIPLINE: Industry
SHORT DESCRIPTION: Liquid product resulting from the cooking of coal.
DESCRIPTION: In the early 18th century it had become generally known that the distillation of bituminous coal produced coke (an inflammable gas) and tar, but throughout the 18th century, in the large-scale preparation of coke for the iron industry the by-products were lost as waste.
The first successful attempt to exploit coal gas was made in 1785 <first made by> Archibald Cochrane*, 9th Earl of Dundonald, and within 30 years, through the work of such men as <involved> Murdock* and <involved> Clegg*, a successful system of gas-light* had been established in London and other European centres, producing (as a by-product of the purification of the gas) a large amount of tar. It was Cochrane who first manufactured coal tar at a works on his estate at Culcross, Scotland, and promoted the use of this tar as a substitute for the wood-tar used during the 18th century for water-proofing ships.
The German chemist Friedrich Christian Accum, an employee of The Gas Light and Coke Company, described tar manufacture in two books during the 1810s, and by the 1820s coal tar was being sold as pitch or re-distilled and sold as paint and varnish to preserve wood against wet and dry rot, particularly in ships, and also for water-proofing ropes and making joints gastight. Coal tar was not used on a large scale by developers until the 1830s, when, with the growth of railways and telegraphs, the need for wood preservation became more urgent.
Meanwhile, the Glasgow-based industrialist and chemist <distilled by> Charles Macintosh* (having made a contract with Glasgow Gas Works in 1819 to buy their waste tar) was experimenting with naphtha (coal oil distillate) and thought it might be useful as a solvent for India rubber.
In 1822 he patented a method for cementing two pieces of cloth together using rubber emulsified with coal tar spirits, and this led to the successful marketing of raincoats. Meanwhile, experiments with coal tar were producing improved black varnishes for wood, and its uses were extending to oil-based lighting and paint for ironwork like that on the new Waterloo Bridge. By 1838, another product of coal tar distillation, <distilled for> creosote*, had begun to be used to protect railway crossties, and in the same period pitch was also introduced as a material for surfacing roadways.
In 1834, the German pharmacist <distilled by> Runge* produced aniline blue - the earliest preparation of an artificial organic coloring - from a distillation product of coal tar. This work was continued by, among others, the French chemist Auguste Laurent, who in 1839 was the first to produce purified <distilled for> carbolic acid* (now known as phenol), and by another German chemist, <distilled by> von Hoffmann*, who extended Runge’s work.
In 1865 one of Hofmann's pupils, <distilled by> Perkin*, accidentally discovered mauve as a product of dichromate oxidation of impure aniline, which led to the foundation of the aniline dye industry. The success of mauve led to demands by English textile manufacturers for other new dyes, and by a system of trial and error chemists discovered that reactions of coal tar compounds yield many useful dyes, including aniline red (later named magenta, in 1858, which became the parent of a whole series of violet dyes) and aniline blue and black.
By 1875, many of Hofmann's students had joined German chemical companies, and by 1900 more than 50 compounds had been isolated, many of which were used in the rapidly developing German chemical industry. By 1914, the synthetic dye industry was firmly established in Germany, where 90 percent of the world's dyes were produced.
Coal tar derivatives also found several uses in medicine. From 1867, owing to the efforts of <used by> Lister*, carbolic acid (or phenol) began to be used as the first effective antiseptic in medicine and surgery, while coal tar increasingly came to be used in medical preparations to treat eczema, psoriasis, seborrheic dermatitis, and other skin disorders.
During the early 1880s experiments were also made to test the effects of dyes on living tissue, resulting in the discovery by the German medical scientist <used by> Paul Ehrlich* that methylene blue stained living nerve cells but not adjacent tissue. Ehrlich proposed that compounds might exist that would kill specific disease organisms by bonding to them without damaging the host cells, and suggested the name ‘chemotherapy.’
In 1884, the Danish microbiologist <used by> Gram* discovered that crystal violet irreversibly stains certain bacteria but can be washed from others, a classification that is still used to identify gram-positive and gram-negative bacteria.
Meanwhile, some of these compounds discovered during coal tar research led to the production of the first commercial artificial sweetener, saccharin (discovered by Ira Remsen and Constantin Fahlberg in 1879), and the analgesic <distilled for> aspirin* by the Baeyer Company in 1899.
Extra Connections:
Wright’s Coal Tar Soap is now made in Turkey for the current owners of the brand, with the claim ‘With coal tar fragrance’ appearing on the packaging. Simple Health and Beauty is part of the consumer goods company Unilever UK Ltd. European Union directives on cosmetics have banned the use of coal tar in non-prescription products, resulting in the removal of coal tar derivatives from the formula and replacement with tea tree oil as the main anti-bacterial ingredient.
ONELINER: Coal tar
BIBLIOGRAPHY: EB
Derry, T.K and T.I. Williams, A Short History of Technology, From the Earliest Times to A.D. 1900, New York: Dover Publications, 1958
Singer, Charles etc., A History of Technology, Vol IV: The Industrial Revolution, c. 1750-c.1850, Oxford: Clarendon Press, 1950.
Coal Tar: How Corrupt Politics and Corporate Greed Are Killing America's Children is a 2018 book by private investigator and wrongful conviction advocate Bill Clutter. In 1990, Clutter began investigating an epidemic of a rare childhood cancer called neuroblastoma in Taylorville, Illinois.