Celebrating 24 Years on the Web
Find science on or your birthday


Stories About Chemistry


17. How Many Waters
Are There on Earth!

Three isotopes of hydrogen have been found by scientists in nature, and each of them can combine with oxygen. Hence, one may speak of three kinds of water: protium, deuterium, and tritium waters: H2O, D2O and T2O, respectively.

There may also be �mixed� waters containing, say, an atom of protium and an atom of deuterium, or an atom of deuterium and one of tritium in their molecules. This increases the list of waters: HDO, HTO, and DTO.

But the oxygen contained in the water is also a mixture of three isotopes: oxygen-16, oxygen-17 and oxygen-18, the first being by far the most common. Taking into account these varieties of oxygen, another 12 possible waters can be added to the list.

When you draw a cup of water from a lake or river, you probably never suspect that you have in your cup eighteen different kinds of water. And so water, no matter where it comes from, is a mixture of different molecules, the lightest being H2O16 and heaviest, T2O18. Chemists can now prepare each of these eighteen kinds of water in the pure form.

Hydrogen isotopes differ perceptibly in their properties. And what about the different kinds of water? They differ in some ways, too. For example, they have different densities, and different freezing and boiling points.

And still the relative content of the different kinds of water in nature is always and everywhere different. For example, tap water contains 150 grams of heavy deuterium water, D2O, per ton. But its content in the water of the Pacific Ocean is noticeably higher: about 165 grams.

A ton of ice from the Caucasian glaciers contains 7 grams of heavy water more than a cubic metre of river water. In a word, the isotopic composition of water is different everywhere. The reason for this is that there is a mighty process of isotope exchange occurring continuously in nature.

The different hydrogen and oxygen isotopes keep replacing one another under various conditions. Is there any other natural compound with as large a number of varieties? There is not.

Of course, we have to do mainly with protium water. But the other kinds of water cannot be disregarded. Some of them are widely used in practice, especially heavy water D2O. It is used in nuclear reactors for moderating neutrons which cause uranium fission. Besides, scientists use various kinds of water for investigations in the field of isotope chemistry.

Eighteen kinds, and no more?

Actually, the varieties of water may be much more numerous. Besides the natural isotopes, there are also man-made radioactive isotopes of oxygen: oxygen-14, oxygen-15, oxygen-19, and oxygen-20. And just recently the number of hydrogen isotopes has also increased: we can now speak of H4 and H5.

Now if we take into account the man-made isotopes of hydrogen and oxygen, the list of possible waters increases to over 100. You can easily count up the exact number yourself�

< back     next >

Thank you for sharing.
- 100 -
Sophie Germain
Gertrude Elion
Ernest Rutherford
James Chadwick
Marcel Proust
William Harvey
Johann Goethe
John Keynes
Carl Gauss
Paul Feyerabend
- 90 -
Antoine Lavoisier
Lise Meitner
Charles Babbage
Ibn Khaldun
Ralph Emerson
Robert Bunsen
Frederick Banting
Andre Ampere
Winston Churchill
- 80 -
John Locke
Bronislaw Malinowski
Thomas Huxley
Alessandro Volta
Erwin Schrodinger
Wilhelm Roentgen
Louis Pasteur
Bertrand Russell
Jean Lamarck
- 70 -
Samuel Morse
John Wheeler
Nicolaus Copernicus
Robert Fulton
Pierre Laplace
Humphry Davy
Thomas Edison
Lord Kelvin
Theodore Roosevelt
Carolus Linnaeus
- 60 -
Francis Galton
Linus Pauling
Immanuel Kant
Martin Fischer
Robert Boyle
Karl Popper
Paul Dirac
James Watson
William Shakespeare
- 50 -
Stephen Hawking
Niels Bohr
Nikola Tesla
Rachel Carson
Max Planck
Henry Adams
Richard Dawkins
Werner Heisenberg
Alfred Wegener
John Dalton
- 40 -
Pierre Fermat
Edward Wilson
Johannes Kepler
Gustave Eiffel
Giordano Bruno
JJ Thomson
Thomas Kuhn
Leonardo DaVinci
David Hume
- 30 -
Andreas Vesalius
Rudolf Virchow
Richard Feynman
James Hutton
Alexander Fleming
Emile Durkheim
Benjamin Franklin
Robert Oppenheimer
Robert Hooke
Charles Kettering
- 20 -
Carl Sagan
James Maxwell
Marie Curie
Rene Descartes
Francis Crick
Michael Faraday
Srinivasa Ramanujan
Francis Bacon
Galileo Galilei
- 10 -
John Watson
Rosalind Franklin
Michio Kaku
Isaac Asimov
Charles Darwin
Sigmund Freud
Albert Einstein
Florence Nightingale
Isaac Newton

by Ian Ellis
who invites your feedback
Thank you for sharing.
Today in Science History
Sign up for Newsletter
with quiz, quotes and more.