IONIZATION 189 



FRACTION IONIZED IN 0.1 AT SOLUTIONS AT 18 



D ,, ACIDS 



Nitric acid (H+,NO 3 -) 0.92 



Sulphuric acid (2H+,SO 4 =). .0.61 

 Oxalic acid (H+,HC 2 O 4 -). . .0.50 

 Phosphoric acid (H+,HaPO 4 -) . 27 



Hydrofluoric acid (H+,F~) 0.085 



Carbonic acid (H+,HCO 3 -) 0.0017 



Hydrosulphuric acid (H+,HS-) .0.0007 

 Boric acid (H+,H 2 BO 3 -) 0.0001 



BASES 



Sodium hydroxide 



(Na+,OH-) 0.91 



Potassium hydroxide 



(K+,OH~) 0.91 



Barium hydroxide (Ba++,2OH~) . 77 

 Ammonium hydroxide 



(NH 4 +,OH-) 0.013 



SALTS 



Potassium chloride (K+,C1~) 0.86 

 Sodium chloride (Na+,Cl~) 0.85 

 Potassium fluoride (K+,F~) 0.85 

 Sodium nitrate (Na+,NO 3 ~) 0.83 

 Silver nitrate (Ag+,NO 3 -) . .0.81 



Barium chloride (Ba++,2Cl-^ . . .0.76 

 Sodium sulphate (2Na+,SO 4 =) .0.70 



Zinc sulphate (Zn++,SO 4 =) 0.40 



Copper sulphate (Cu++, S0 4 - ) . . . . 40 

 Mercuric chloride (Hg++,2Cl-)<0.01 



lonisation and Chemical Activity. From a consideration 

 of the above figures and the results given by other acids, bases 

 and salts, the following important conclusions may be drawn: 



1. Salts, with the exception of a few mercuric salts, are all 

 extensively ionized in 0.1 N aqueous solution. The salts which 

 ionize most simply show the greatest degree of ionization. Com- 

 pare, for example, the series sodium chloride, sodium sulphate, 

 copper sulphate. 



2. Acids show the most extreme differences in their degrees 

 of ionization. That is to say, equivalent solutions contain very 

 different concentrations of hydrogen ion. Since their activity 

 as acids depends upon this substance (p. 191), it follows that 

 acids will exhibit very marked differences in chemical activity 

 (for example, in their action on metals). In fact, they may be 

 divided roughly into three classes : 



(a) Strong acids, such as hydrochloric acid, nitric acid, sul- 

 phuric acid. These substances are highly ionized in 0.1 TV solu- 

 tion. Their solutions conduct the electric current excellently, 

 and are chemically most active. 



