Supplementary
documents
Acknowledgements

The superheating race

In the course of the 19th century, further study revealed boiling to be an even more complex and unruly phenomenon than De Luc and Gay-Lussac had glimpsed. The next significant step was only taken 30 years after Gay-Lussac’s work, by the Genevan professor of physics François Marcet (1803-1883)--son of Alexandre, émigré physician in London , and Jane, well-known author of popular science. Marcet (1842) produced superheating beyond 105°C in ordinary water, by using glass vessels in which strong sulphuric acid had been boiled; clearly, somehow, the acid had modified the surface in such a way as to make boiling more difficult. Superheating became a clearly recognized object of study after Marcet's work, stimulating a string of virtuoso experimental performances vying for record temperatures. François Marie Louis Donny (1822-?), chemist at the University of Ghent, combined surface effects with a revival of De Luc's ideas about the role of air, and produced a stunning 137°C using airless water in his own special instrument. Donny declared:

"The faculty to produce ordinary ebullition cannot in reality be considered as an inherent property of liquids, because they show it only when they contain a gaseous substance in solution, which is to say only when they are not in a state of purity." (Donny 1846, 187-188)

In 1861 the work of Louis Dufour (1832-1892), professor of physics at the Academy of Lausanne, added yet another major factor for consideration. Dufour (1861, esp. 255) argued that contact with a solid surface was the crucial factor in the production of ebullition, and demonstrated the soundness of his idea by bringing drops of water floating in other liquids up to 178°C, without even purging the air out of the water. Even Dufour was outdone, when Georg Krebs (1833-1907) in 1869 achieved an estimated 200°C with an improvement of Donny's technique (Krebs's work is reported in Gernez 1875, 354).

The superheating race must have been good fun to watch, but it also presented a great theoretical challenge (an intriguing parallel might be drawn between this superheating race and the modern-day race to reach higher and higher temperatures in superconductivity). All investigators now agreed that the raising of temperature to the "normal" boiling point was not a sufficient condition to produce boiling (read more about the theoretical debates in the 19th century). What they could not agree on was the list of additional conditions needed for the production of boiling. And if these additional conditions were not met, it was not clear how far superheating could go. Donny in 1846 had already expressed bemused uncertainty on this point: "one cannot predict what would happen if one could bring the liquid to a state of perfect purity." Krebs, in the work mentioned above, opined that water completely purged of air could not boil at all. In the more careful view of Marcel Émile Verdet (1824-1866), renowned professor of physics in Paris credited with introducing thermodynamics to France, there was probably a limit to the degree of superheating, namely that point at which there is enough heat to vaporize the whole mass of water instantly. Verdet, however, admitted that there was only one experiment in support of that view, namely the now-classic work of Charles Cagniard de la Tour (1777?-1859) on the critical point, a temperature above which a gas cannot be liquefied regardless of pressure. (See the review of the works on superheating given in Gernez 1875. Donny's statement is quoted on p. 347, and the report of Verdet's view can be found on p. 353.) There was sufficient uncertainty on this question even towards the end of the 19th century. In 1878 the 9th edition of the Encyclopaedia Britannica reported: "It has been stated that the boiling of pure water has not yet been observed." (William Garnet, "Evaporation," vol. 8 (1878), 727-733, on p. 728.)

Read about the modern theoretical view on superheating

Return to the History section of the main page

Return to the start of the main page