ACIDS BASES SALTS ANHYDRIDES, ETC. 29 



In the case of bases the metallic portion is electro- 

 positive and the hydroxyl is electro-negative. This is 

 indicated in the following formulas of bases: 



+ - + + - 



Na(OH), Ca(OH) 2 , Fe(OH) 3 . 



There are reasons for believing that when acids or bases 

 or salts are dissolved in water, even when no electric cur- 

 rent is passing through the solution, the compounds to 

 some extent break up, or, as it is termed, dissociate into 

 ions highly charged either positively or negatively. The 

 ions with electro-negative charges are acid-forming. They 

 are either the non-metallic elements or are radicals con- 

 taining non-metals. According to the dissociation theory, 

 acids are electro-negative elements or radicals united to 

 hydrogen, and bases are electro-positive elements united 

 to hydroxyl (OH), and salts are electro-positive elements 

 united to electro-negative elements or radicals, 



28. Nomenclature of Compounds. Names are given 

 to most chemical compounds according to a few simple 

 rules. 



(1) Nomenclature of Binary Compounds, (a) Compounds 

 composed of two elements have names ending in ide. This 

 affix is attached to the abbreviated name of the non- 

 metallic part of the compound. Thus oxygen forms oxides, 

 as calcium oxide, CaO; sulphur forms sulphides, as lead 

 sulphide, PbS; chlorine forms chlorides, as sodium chloride, 

 NaCl. To indicate the number of atoms of the non- 

 metallic element in the compounds, the prefixes mono for 

 one, di, for two, tri for three, and tetra for four, are used; 

 thus CO is carbon monoxide; SO2 is sulphur dioxide; AsCls 

 is arsenious trichloride; CCU is carbon tetrachloride. 



(6) In case two compounds are made by the same two 

 elements entering into combination in varying propor- 

 tion, the name of the metallic element is modified by the 

 terminations ous or ic. Thus HgCl is called mercurows 



