ACIDS, BASES, AND SALTS 



13 



TABLE 2 DEGREE OF DISSOCIATION OF NORMAL SOLUTIONS OF SOME 



COMMON ELECTROLYTES 



It is probable that many of the so-called non-electrolytes also dissociate very 

 slightly in solution, but the degree of dissociation of such compounds is so 

 small that it can be detected only by very refined methods, if at all. Even 

 water, as the subsequent discussion will show, dissociates slightly, producing 

 hydrogen and hydroxyl ions." 



Acids, Bases, and Salts. — An acid may be defined as a substance which 

 produces hydrogen ions (H+) when dissolved in water. The characteristic 

 properties of acids are due to the hydrogen ions produced. The most common 

 inorganic acids are hydrochloric (HCl), nitric (HNO3), and sulfuric 

 (H2SO4). In living organisms a large group of more complex, but much 

 weaker acids, known as organic acids, play important roles. The "strength" 

 of an acid depends upon its degree of ionization; the greater the proportion 

 of hydrogen ions an acid produces in solution at a given concentration, the 

 "stronger" it is. 



A base may be defined as a substance which produces hydroxyl ions 

 (OH~) when dissolved in water. The characteristic properties of bases are 

 due to the hydroxyl ions produced. Some of the commonest bases are sodium 

 hydroxide (NaOH), calcium hydroxide (Ca(OH)2), and potassium hydrox- 

 ide (KOH). The "strength" of a base, like that of an acid, depends upon its 

 degree of ionization. The greater the proportion of hydroxyl ions a base 

 produces in solution at a given concentration, the "stronger" it is. 



^ The theory of electrolytic dissociation accounts much more satisfactorily for 

 the behavior of weak electrolytes than of strong electrolytes. For this and other 

 reasons Debye and Hiickel in 1923, and other modern investigators, have postulated 

 that strong electrolytes, at least, are completely dissociated. The fact that they 

 behave as if only partly dissociated is accounted for in terms of interionic attrac- 

 tions. These attractions are supposed to exert what may be roughly described 

 as a "braking effect" upon the movement of the individual ions. This prevents 

 them from operating at their maximum effectiveness in conducting an electric 

 current or in other phenomena depending upon ionic mobilities. The greater the 

 concentration of an electrolyte, the closer together are the ions, and, according to 

 this view, the less their apparent dissociation. 



