GENERAL REMARKS REGARDING ELEMENTS. 67 



In many cases the syllables ous and io are used to distinguish the 

 proportions in which two elements combine ; the syllable ous being 

 used for the simpler or lower, the syllable ie for the more complex or 

 higher form of combination. For instance : Phosphorous chloride, 

 PC1 3 , and phosphoric chloride, PC1 5 ; ferrous oxide, FeO, feme 

 oxide, Fe 2 O 3 . 



The syllables mono and sesqui also are used occasionally to mark 

 this difference, as, for instance, monoxide of iron, FeO, sesquioxide of 

 iron, Fe 2 O 3 . 



When two oxides of the same element ending in ous and ic form 

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

 used to distinguish these acids. Phosphoroits oxide, P 2 O 3 , forms 

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



The salts formed by these acids are distinguished by using the 

 syllables ite and ate. Phosphite of sodium is derived from phospho- 

 rous acid, phosphate of sodium from phosphoric acid. Sulphites 

 and sulphates are derived from sulphurous and sulphuric acid, 

 respectively. 



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. 



Writing 1 chemical equations. It has been shown that chemical 

 changes are expressed in chemical equations by means of symbols. 

 These equations are formed by placing the molecules which are to act 

 upon one another, and which are called factors and are connected by 

 the sign -f, to the left of the sign of equality, and by placing the 

 molecule or molecules which result from the decomposition, and are 

 called product or products, to the right of the sign of equality, con- 

 necting them also by the + sign if more than one product be formed. 



Every correct chemical equation is correct mathematically also 

 i. e. y the sum of the atoms as well as that of the molecular weights of 

 the factors equals the sum of the atoms and that of the molecular 

 weights of the products respectively. For instance : Sodium car- 



