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ON THE PLACE OF FISH IN 



Names used 

 by chemists 

 have more 

 exact mean- 

 ings than 

 familiar 

 names. 



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 



