Chapter 22. Perkin (Aniline Dyes)

 

The real inventor of practical gas-lighting is William Murdoch, who in 1792 lit his workshops at Redruth, Cornwall, with a gas obtained from coals. His operations remained unknown abroad for some ten years, and hence the French consider Lebon as the inventor of gas-lighting, since he lit (1801) his house and garden with gas obtained from wood. The first more extensive gas-work was established in 1802 by Murdoch, at the Soho Foundry, near Birmingham, the property of the celebrated Boulton and Watt; and in 1804 a spinning-mill at Manchester was lighted with gas. From that period gas-lighting became more and more generally adopted in factories and workshops, but not before the year 1812 did this mode of lighting become introduced into dwelling-houses and streets, a few of which in London were lit with gas in this year; while in Paris gas was first introduced in 1820. From that year gas-lighting may be said to have become of general importance in Europe, and now there is hardly any important place on the Continent where it is not in use, while as regards the United Kingdom in no portion is gas-making and lighting so general over town and country as in Scotland.

 Wagner's Chemical Technology, 1872 AD [1]

22.1.

Gas! Now that's a business to be in.

I don't believe it! Here I am, supposedly the representative of the alchemical element air, waiting patiently for a chapter that might possibly have some remote connection to the element for which I am supposed to speak, and when one finally comes around the Author assigns it to a confabulating bug with about as much air-worthiness as a lead Zeppelin. And it makes me wonder.

If there's a bustle in your hedgerow, don't be alarmed now. This chapter isn't about gas; it's really more about tar. See, folks had been making charcoal from wood since God was a child. Now, to make charcoal, you put wood in a sealed container, and heat the bejeezus out of it in the absence of air. Bejeezical water goes up the smoke stack, like it shows in Equation 1-1, and the stuff that's left behind is charcoal, which is mostly carbon. That charcoal burns hotter and cleaner than wood and so it's great for smelting metals and all.

Now all this wood burning caused a scarcity of wood in Europe, a kind of energy crisis. Coal was an obvious alternative since it, like charcoal, consists primarily of carbon. But coal wasn't any good for smelting metals because it contains impurities like sulfur which weaken metals. It wasn't until 1603 that a fellow named Hugh Platt tried heating coal anaerobically, driving off bejeezical gases and producing purified carbon in the form of coke. Coke was a big hit with steel-makers, but it would be another two hundred years before anyone got the bright idea to do something with the gas from the coke ovens.

That's where Phillipe Lebon comes in. See, he grew up in a charcoal-producing region of France and was inspired to use the gas from the charcoal ovens for illumination. He got a patent in 1799 for his "Thermolamp" and even thought up an engine to run off of gas; he was way ahead of his time. Who knows what he would have come up with if he hadn't been stabbed to death in 1804?

Something quite remarkable, no doubt, but returning to events that actually materialized, William Murdock began experimenting with gas from the coke ovens, lighting his workshops in 1792. When news of Lebon's work reached Murdock's employer, Matthew Boulton, they pushed forward with commercial development of gas lighting. Murdock described the basic principles of gas lighting to the Royal Society in 1808.

The recovery of gas from a coke oven may be viewed as a kind of distillation. In the distillation of Chapter 16 a mixture is simply separated into its components, for example, a solution of alcohol and water is separated into alcohol and water. Turn up the temperature, however, and the material you are distilling may start to decompose. Wood, for example, may decompose into charcoal and water. In such a destructive distillation the materials recovered were not present at the beginning, but were produced during the distillation. The destructive distillation of coal produces four products which are easily separated from one another; coke remains in the pot; gas driven from the pot is passed through a condenser where some of it condenses into an aqueous solution of ammonium carbonate; separating from this solution is a tar which is insoluble in water; the remaining gas is ready for distribution as illuminating gas.

But like I said at the beginning, this chapter is not so much about the gas; it's about the tar. That tar is a complicated mixture of compounds and folks started to wonder what they were and what could be done with them. In 1825 Michael Faraday isolated benzene from the destructive distillation of whale oil. Pretty soon everybody and her dog were destructively distilling things to see what would come of it. In 1826 Otto Unverdorben isolated aniline from indigo and in 1834 Friedlieb Runge isolated aniline and phenol from coal tar. So with a second, non-destructive distillation folks started producing chemicals from coal tar, chemicals like benzene, toluene, aniline, phenol, and naphthalene. Folks figured that since these compounds came from the destruction of organic compounds, maybe it would be possible to make good and useful things by putting them back together again.

Gas had become a major industry—

—but this chapter is more about tar. See, at that time malaria was a problem for the British Empire, on account of its rampant colonialism, and the best treatment for malaria was quinine, extracted from the bark of a South American tree. To promote chemical innovation the British started up the Royal College of Chemistry in 1845, with the great German chemist, Wilhelm Hofmann, as director. In 1856 Hofmann's assistant, William Perkin, set out to synthesize quinine from coal tar. Perkin reacted aniline with potassium dichromate, a really strong oxidizing agent; the resulting black goo was definitely not quinine, but it made a beautiful purple solution in alcohol. Perkin called it "mauveine" and dropped out of college at the age of 18 to develop his new synthetic dye. British dyers didn't think that mauve would catch on, but the Paris fashion houses liked it so much that Perkin was able to retire at the age of 36. I told you it was a great business.[2]

And—

—once folks knew that it was possible to make artificial dyes from coal tar, new dyes started coming out of the gasworks, so to speak. Variations on the original synthesis produced dozens of dyes from aniline: aniline reds, aniline violets, aniline greens, yellows, browns, and blues. Substituting phenol or naphthalene for aniline produced two more distinct families of artificial colors. There seemed to be few colors which could not be fashioned by art and ingenuity from coal tar.

Hofmann's leadership at the Royal College had given the British a head start in synthetic dyes, but when Hofmann returned to Germany in 1865 British dyestuffs dropped the ball. In France, synthetic dye manufacturers charged so much for their products that demand there shifted to natural and imported dyes. But in Germany, the situation was ideal for the development of these new wonder dyes. State-subsidized technical schools fed talented students to the universities; the universities promoted collaborative work, sending students to study in Britain and France; and universities cooperated with industry on joint research projects. Furthermore, with thirty-nine states in the German Confederation, patent enforcement was a problem and the resulting competition produced lean, mean, dye-making machines. German unification in 1871 made patent enforcement easier, but by that time the big players in German dyestuffs were off and running; Badische Anilin und Soda Fabrik (BASF) was out of the gate in 1861, followed by Farbwerke Hoechst in 1862; Freidrich Bayer rounded the bend 1863, followed by Kalle & Co in 1864; and a late starter from 1867 was reorganized in 1873 as Aktien Gesselschaft für Anilin Fabrikation (AGFA). Throughout a century of wars, depressions, revolutions, and mergers Bayer, Hoechst, and BASF were the top dogs of the chemical industry.

I guess you could say, "They were buy-y-ing a ta-ar-way to heaven."

Notes

[1]

Reference [29], pp. 645-646.

[2]

For a popular account of Perkin's career, see Reference [59]. For the early history of the synthetic dye industry, see Reference [74].