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THINK I have it straight, now. Ozone in the stratosphere is a Good Thing
because it filters nasty ultraviolet rays out of sunlight before it gets
to us. Ozone in the troposphere, however, is a Bad Thing because it poisons
plants and makes my asthma worse.

But what is ozone? It is, I read in the newspapers, ‘triple oxygen’,
or ‘a substance related to oxygen’, or ‘an oxygen molecule with more oxygen
than it needs’, and much more along the same lines. Now, you and I know
that ozone is O₃, while oxygen is O₂, so all these
definitions project a refracted version of the truth. But the problems journalists
have in writing about science for a non-scientific audience draw attention
to remarkable deficiencies which exist in the vocabulary of science when
it comes to talking about what for simplicity I shall call ‘the elements’.

If you don’t agree with my statement that ‘oxygen is O₂‘,
you are probably a spectro scopist or a coordination chemist and go around
irritating people outside your specialism by calling O₂ ‘d¾±´Ç³æ²â²µ±ð²Ô’.
The rest of us get by on our more limited vocabulary. When communicating
among ourselves we know that when we say ‘oxygen’ we can mean (1) an element;
(2) a molecule consisting of two atoms of that element; (3) a bulk substance
consisting of molecules of that type; (4) the gaseous form of that bulk
substance. By and large the context sorts out which of these meanings is
appropriate in a particular case.

But start trying to communicate with a lay person and there is immediately
an op portunity for serious misunderstanding. Two places where such communication
is attempted are scientific dictionaries and elementary general encyclopedias.
The compilers of such volumes can get themselves and their readers into
real difficulties by not paying enough attention to the imprecision of our
terminology.

Take, for example, the entry ‘Hydrogen’ in Chambers Science and Technology
Dictionary. I choose this book simply because I own a copy. You can read
the same sort of thing in many others.

‘Hydrogen. The least dense element, forming diatomic molecules. Symbol
H, at no 1 . . . It is a colourless, odourless, diatomic gas, water being
formed when it is burnt. It is widely distributed as water . . .’

The entry then continues with lists of manufacturing processes and uses
of the bulk gas and the molecule (nitrogen fixation, balloons, and so on),
followed by:

‘It is of great importance in the moderation (slowing down) of neutrons
as hydrogen atoms are the only ones of similar mass to a neutron . . .’

Chambers starts well by trying to distinguish between the element hydrogen
and the hydrogen molecule but quickly jumps to saying that ‘it’ is a gas
and that ‘it’ is widely distributed as water. When in doubt, ‘it’ it.

The opening phrase of the entry seems to be a case of what linguists
call hypercorrection. We learnt at school not to say ‘Hydrogen is lighter
than air’ but ‘Hydrogen is less dense than air’, in which context it is
evident that we are talking about ‘hydrogen the gas’. Someone seems to have
learnt the lesson but applied it incorrectly to the phrase ‘the lightest
element’ (that is, the element with the lightest atoms) to produce the nonsensical
‘least dense element’. Density is a property of bulk substances, not elements.

The emphasis on the importance of hydrogen in slowing down neutrons
is curious, especially as there is no indication as to where or why one
would wish to perform this trick. Worse, though, is the implication that
it is elementary (that is, uncompounded) hydrogen which is used for this
purpose. The reference is, of course, to thermal nuclear reactors and the
hydrogen used is normally present in the molecules of liquid water.

It would be nice to draw some far-ranging conclusion from all this about
why schoolchildren don’t want to study chemistry or why, if they do, they
then become accountants. Perhaps students who take the latter career path
find a precision in financial figures which chemistry does not provide them
with. If so, the banishing of the balanced chemical equation to the A-level
syllabus must stimulate the flight from chemistry. That aside, there is
a real paradox in the fact that science, in which precision is so important,
uses a tool – language – which is so imprecise. This gives rise to the practical
problem that writers who do not recognise this imprecision can easily mislead
the non-expert reader.

John Feather is a linguist and one-time chemist.