Williams, Charles Greville

Synthetic rubbers include a variety of compounds that mimic the properties of natural rubber. In 1860, Charles Greville Williams (1829-1910) isolated the monomer isoprene from rubber, showing that rubber was a polymer of isoprene ... 

The compositional details of caoutchouc, gutta-percha (an isomer of caoutchouc) and caoutchoucine were finally settled by Charles Greville Williams (1829-1910) [10]. In 1860 he carried out a substantially more careful dry distillation of caoutchouc in an iron alembic and isolated two volatile fractions. The lower boiling one (37-38 °C) had a (modem) molecular formula of CsHg, not just an empirical formula. He called it isoprene, to distinguish it from the cmde fractions obtained by previous workers. A dimer was also isolated and characterized. All these materials had the same pure hydrocarbon empirical formula. 

It was well known at the turn of the century that rubber has the empirical composition, C5H9. Michael Faraday elucidated its composition in 1826 by careful elementary analysis. His work, an effort of extreme complexity, has been diminished by the years, but it regains its stature when you recall that over thirty years passed before the next major step was performed. In those thirty years rubber was blended, dissolved, and even vulcanized (by Charles Goodyear in 1839), but it was in 1860 that its major chemical component was discovered. This important finding was made by Greville Williams. He named the product of the destructive distillation of rubber, isoprene. 

After Bunsen had detected and isolated caesium, spectroscopy was taken up with great enthusiasm by William Crookes, and this led to his detection and isolation of thallium in 1861.191 Crookes letters to Charles Hanson Greville Williams, who was also working with the spectroscope, and who felt he deserved some of the credit for the discovery of thallium, have been published.192 The use of spectrochemistry in the search for hitherto unknown chemical elements in Britain over the period 1860-1869 has been described. It was perceived that, like Crookes, a scientist could make his reputation by discovering a new element. This resulted in several claims for the existence of new elements that later proved to be unfounded.193 Once Kirchhoff had established beyond doubt that the dark Fraunhofer lines were caused by the same element that caused emission lines of identical wavelengths, the way was open for the chemical analysis of the atmosphere of the sun and stars. This was a process which had been declared to be an impossibility by Auguste Comte less than 30 years previously.194... 

Crude rubber is primarily hydrocarbon in nature. In 1826 English chemist Michael Earaday (1791-1867) analyzed natural rubber and found it to have the empirical (simplest) formula C5H8, along with 2 to 4 percent protein and 1 to 4 percent acetone-soluble materials (resins, fatty acids, and sterols). In 1860 English chemist Charles Hanson Greville Williams (1829-1910) confirmed Earaday s analysis and in 1862 distilled natural rubber to obtain the pure monomer, which he named isoprene. He determined isoprene s vapor density and molecular formula, and he showed that it polymerizes to a rubbery product—an observation that led to the notion that rubber is a linear polymer of isoprene, proposed in 1910 by English chemist Samuel Shrowder Pickles (1878-1962). 

The history of the use and study (it occurred, as in so many other cases, in that order) of rubber goes way back. Pietro Martyre d Anghiera described it in 1511. In 1839, Charles Goodyear found that sulfur could vulcanize rubber, thus its usefulness was greatly expanded. Still rubber, except for Faraday s report on its empirical composition, was an unknown, until Greville Williams destructively distilled the material in 1860 and identified the distillate as isoprene. 

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