Letting off steam (Collage: K. Brazier)
We all know that water boils at 100 掳C. So was the 18th-century scientist who pushed the boiling point to 112 掳C wrong? There was only one way to find out
While researching a book on the history of the thermometer, Hasok Chang found himself reading accounts of old experiments on boiling water. Soon he had steam coming out of his ears. 鈥淚鈥檓 going, these guys must be crazy or badly mistaken or taking the mickey,鈥� says the historian of science at the University of Cambridge.
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What raised his hackles was the repeated assertion that water could boil at temperatures other than 100 掳C. There was 101 掳C, 103 掳C 鈥� even, in one account of work by the 18th-century Swiss scientist Jean-Andr茅 de Luc, 112 掳C. The researchers involved were reputable, and the procedures they followed seemed legitimate. So what was going on?
There was only one way to find out. 鈥淲ithin minutes of stepping into the lab I found out they were right,鈥� says Chang. Historians of science often speak of the concept of 鈥渢acit鈥� knowledge 鈥� knowledge considered so common that it wasn鈥檛 worth writing it down. What Chang seemed to have rediscovered, on the other hand, was knowledge that was once known, but has since been forgotten.
Shake it
We鈥檙e familiar with the idea that water boils at lower temperatures when air pressure is reduced, for example on mountaintops. But other factors are also relevant: the speed of heating, the shape and material of the container and the amount of air and other substances dissolved in the water. De Luc achieved his 112 掳C by the admittedly extreme measure of carrying a container of water around for four weeks, .
Such complexities are apt to be ignored. 鈥淵ou don鈥檛 want to spend time confusing your students on where water boils when you want to move them on to quantum mechanics,鈥� says Chang. 鈥淪o you get a Mickey Mouse version of the story when you鈥檙e 10 and then it disappears.鈥� He thinks that is dangerous. 鈥淚t provides a false sense of security about scientific knowledge.鈥�
Reviving such ideas is certainly timely. With the increasing emphasis on energy efficiency, engineers are beginning to look again at basic, overlooked thermodynamic effects: how the presence of nanoparticles can increase the flow of heat into water, for example, providing a route to more efficient refrigerators and steam turbines.
Chang has since moved on to recreating some of the first experiments on electrochemical batteries from the early 19th century. He thinks many other neglected effects could be lurking in historical experiments that were never repeated. 鈥淭hese experiments are not only recovery, but an extension of the past,鈥� he says. 鈥淲e are discovering phenomena they didn鈥檛 write about.鈥�
Read more: 鈥�Reliving five eureka moments lost in history鈥�
This article appeared in print under the headline 鈥淟etting off steam鈥�
