CHAPTER XXIV. 



CHEMISTRY. 

 INTRODUCTION. 



WHAT CHEMISTRY IS THE ELEMENTS METALLIC AND NON-METALLIC 



ATOMIC WEIGHT ACIDS ALKALIS BASES SALTS CHEMICAL 



COMBINATION AND STUDY. 



CHEMISTRY is the science of phenomena which are attended by a change 

 of the objects which produce them. We know that when a candle burns, or 

 when wood is burned, or even a piece of metal becomes what we term 

 '" rusty," that certain chemical changes take place. There is a change by 

 what is termed chemical action. Rust on iron is not iron ; it is oxide of 



Fig. 301. The Laboratory. 



iron. The oxygen of the air causes it. So we endeavour, by Chemistry, to 

 find out the nature of various bodies, their changes, and the results. 



In nature we have simple and compound bodies. The former are 

 called ELEMENTS. We must not confuse these elements with the so-called 

 elements earth, air, fire, and water. These are really compound bodies. 

 An element is a substance or a gas which is not composed of more than one 

 constituent ; it is itself a compound of perfectly identical particles. Every 

 " compound " body, therefore, must be made up of some of the elements, of 

 which there are sixty-five. These bodies are divided into non-metallic and 

 metallic elements, and all bodies are composed of them, or are these bodies 



