The myth of the boiling point.

ABSTRACT

Around 1800, many reputable scientists reported significant variations in the temperature of pure water boiling under normal atmospheric pressure. The reported variations included a difference of over 1[degrees]C between boiling in metallic and glass vessels (Gay-Lussac), and "superheating" up to I12[degrees]C on extracting dissolved air out of water (De Luc). I have confirmed most of these observations in my own experiments, many of which are described in this paper. Water boils at the "boiling point" only under very particular circumstances. Our common-sense intuition about the fixedness of the boiling point is only sustained by our limited experience.

Keywords: boiling point, replications of historical experiments, superheating, water, De Luc, Gay-Lussac

Introduction

We all learn at school that pure water always boils at 100[degrees]C (212[degrees]F), under normal atmospheric pressure. Like surprisingly many things that "everybody knows", this is a myth. We ought to stop perpetuating this myth in schools and universities and in everyday life: not only is it incorrect, but it also conveys misleading ideas about the nature of scientific knowledge. And unlike some other myths, it does not serve sufficiently useful functions.

There are actually all sorts of variations in the boiling temperature of water. For example, there are differences of several degrees depending on the material of the container in which the boiling takes place. Removing dissolved air from water can easily raise its boiling temperature by about 10 degrees centigrade.

The fickleness of the boiling point is something that was once widely known among scientists. It is quite easy to verify, as I have learned in the simple experiments that I discuss below. And it is still known by many of today's experts. So actually the strange thing is: why don't we all hear about it? Not only that, but why do most people believe the opposite of what is the case, and maintain it with such confidence? How has a clear falsehood become scientific common sense?