132 PRINCIPLES OF CHEMISTRY, 



acids (by entering in combination with water), the same syllables are 

 used to distinguish these acids. Phosphor<n*s oxide, P 2 O 3 , forms 

 phosphoroits acid ; phosphoric oxide, P 2 O 5 , forms phosphoric acid. 



The salts formed by these acids are distinguished by using the syl- 

 lables lie and ate. Phosphite of sodium is derived from phosphorous 

 acid, phosphate of sodium from phosphoric acid. Sulphites and sul- 

 phates are derived from sulphurous and sulphuric acid, respectively. 



When an element forms more than two acids the syllables hypo and 

 per are often used to designate the nature of these acids, as also that 

 of their respective salts. Hypo is prefixed to the compound contain- 

 ing less oxygen than the ous acid ; and per is prefixed to the com- 

 pound containing more oxygen than the ic acid. For instance, hypo- 

 chlorous acid, HC1O ; chlorous acid, HC1O 2 ; chloric acid, HC1O< ; 

 perchloric acid, HC1O 4 . The salts formed from these acids are called 

 hypochlorites, chlorites, chlorates, and perchlorates. 



According to the new nomenclature, the name of the metal precedes 

 that of the acid or acid radical in an acid. For instance, sodium 

 phosphite, instead of phosphite of sodium ; potassium sulphate, instead 

 of sulphate of potassium. The acids themselves are looked upon as 

 hydrogen salts, and are sometimes named accordingly : hydrogen 

 nitrate for nitric acid, hydrogen chloride for hydrochloric acid, etc. 



When the number of elements and the number of atoms increase in 

 the molecule, the names become in most cases more complicated. The 

 rules applied to the formation of such complicated names will be 

 spoken of later. 



How to study chemistry. In studying chemistry, the student 

 is advised to impress upon his memory five points regarding every 

 important element or compound. These points are : 



1. Occurrence in nature. Whether in free or combined state; 

 whether in the air, water, or solid part of the earth. 



2. Mode of preparation by artificial means. 



3. Physical properties. State of aggregation and influence of heat 

 upon it ; color, odor, taste, solubility, etc. 



4. Chemical properties. Atomic and molecular weight ; valence ; 

 amount of attraction toward other elements or compounds ; acid, 

 alkaline, or neutral reaction ; reactions by which it may be recog- 

 nized and distinguished from other substances. 



5. Application and use made of it in e very-day life, in the arts, 

 manufactures, or medicine. 



Of the most important elements and compounds, the history 



