PART II. 



CHAPTER I. 



NON-METALLIC ELEMENTS. 



SECTION I. 

 OXYGEN. 



Equivalent 100, or 8 on hydrogen scale ; symbol O ; density 

 1102.6 (air = 1000) ; combining measure Q (one volume.) 



THE following thirteen of the fifty-five elementary bodies 

 known are included in the class of non-metallic elements : 

 oxygen, hydrogen, nitrogen, carbon, boron, silicon, sulphur, 

 selenium, phosphorus, chlorine, bromine, iodine, and fluorine. 

 Of these, oxygen, from certain relations which it bears to all 

 the others, and from its general importance, demands our first 

 attention.* 



The name oxygen is compounded of o&g acid, and JEWCLM I 

 generate, and was given to the element of which I am about 

 to treat by Lavoisier, with reference to its property of forming 

 acids in uniting with other elementary bodies. Oxygen is a 

 permanent gas, when uncombined, and forms one fifth part of 

 the air of the atmosphere. In a state of combination, this 

 element is the most extensively diffused body in nature, enter- 

 ing as a constituent into water, into nearly all the earths and 

 rocks of which the crust of the globe is composed, and into 

 all organic products with a very few exceptions. It was first 

 recognised as a, distinct substance by Dr. Priestley in this 

 country, in 1 774, and about a year afterwards by Scheele in 

 Sweden, without any knowledge of Priestley's experiments. 

 From this discovery may be dated the origin of true chemical 

 theory. 



* To the class of metals an addition has recently been made by the discovery of 

 Lantane, which makes the 55th elementary body. (An. de Ch. et de Ph. t. 70, p. 222.) 



