SODIUM AND SODIUM HYDROXIDE 169 



solution added to an alkali in water solution produces an in- 

 tense red (when dilute, pink) coloration. Addition of excess acid 

 renders the solution colorless again. 



The alkalies, however, are simply the more active members 

 of a much larger class of substances called bases. Solutions of the 

 less soluble bases, of which cupric hydroxide is an extreme ex- 

 ample, do not show, distinctly, all the properties exhibited by 

 alkalies. Thus, those which are least soluble have, naturally, 

 no taste, do not visibly affect litmus, do not conduct the electric 

 current very well in solution, and are not soapy to the touch or 

 corrosive towards glass. But they all show the tendency to 

 double decomposition, in which the group (OH) is transferred, as it 

 was from NaOH to Cu(OH)2 in the foregoing example. 



Uses. Sodium hydroxide is used in immense quantities along 

 with fats, in the manufacture of soap. Some bleaching liquids 

 are made by saturating it with chlorine. It is employed also in 

 making many other sodium compounds which are used in the arts. 



Exercises. 1. In the electrolysis of sodium hydroxide, why 

 is the metal not liberated as a solid or as a vapor, but as a liquid? 



2. Make molecular equations for the burning of sodium in 

 chlorine and in oxygen. 



