Names used 
by chemists 
have more 
exact mean- 
ings than 
familiar 
names. 
4 ON THE PLACE. OF FISH IN 
copper and zinc, and table-salt into chlorine and 
sodium. An “element” cannot be split up into any- 
thing different from itself. When an element is not 
combined with another element to form a compound 
it is called “free.” That is how the words are used. 
As to knowing what are elements and what are com- 
pounds that is a matter of examination and trying. 
Oxygen was found to be an element in 1774, Hydro- 
gen in 1781, and other bodies have been at different 
dates discovered to be elements, to which names have 
been given to distinguish them. Most of the names 
have Latin or Greek terminations, and the significance 
of the distinction between these and the familiar 
English names, where there are any, is this: the 
chemical name is definite and exact, the familiar 
name is loose and inexact. As an example, Aurum 
is used only for gold absolutely pure, but we speak 
loosely of “gold” coinage or “gold” rings which are 
not pure. 
One reason, then, why the words Carbon, Hydrogen, 
Oxygen and Nitrogen are not more often met with, 
is that, unlike many words in common use, they 
have very definite and exact meanings and can only 
properly be used when referring to the elements to 
which these names are given, though the words 
“oxygenated” and “carbonised” are often loosely 
and inaccurately used. As these elements can be 
obtained separate and pure only by special precau- 
tions the names are seldom used except in relation 
to laboratory work. . 
The most satisfactory way of conveying correct 
ideas about them is of course to show by a few simple 
experiments some of their characteristic ways of 
