LAWS OF ELECTROLYTIC DISSOCIATION 39 



Of the organic bases only the quartenary ones are comparable to 

 those above. The other organic bases, especially the important 

 ones, such as the amino- and oxonium-bases, as well as some others, 

 are to be regarded as pseudo-bases. It was shown earlier in this 

 chapter how the basic character of NH3 may be explained either by 

 the hypothesis of the formation of an extremely small amount of 

 NH4OH and its subsequent dissociation, or, in a simpler way, by 

 means of the addition reaction NH3 + H+ — > NH4+. The same 

 holds true for all other weak bases. In table 9 the (apparent) 

 dissociation constants of some weak bases are given. 



As it was stated before, the dissociation constants of all organic 

 bases are ''apparent." Nothing is experimentally known of the 

 true dissociation constant of NH4OH. But it will not be far amiss to 

 include it among the quite strong bases in analogy with the alkali 

 metal hydroxides. Ammonia, NH3, possesses as a base an appar- 

 ently very small constant only because it forms in solution im- 

 measurably small amounts of NH4OH. But the NH4OH is best 

 considered as being almost completely dissociated. 



12. The hydrogen ion concentration in pure acid solutions 



Thus far it has been established in a purely qualitative sense 

 that acids increase the hydrion concentration of water and that 

 bases decrease it. We shall now pass to the quantitative relations 

 existing between the [H+] and the kind of acid, its dissociation 

 constant and its concentration. Given a solution of an acid in 

 water, then the concentration of its acid ions must be equal to that 

 of the H+ ions. Therefore, we can substitute in equation (1) on 

 page 29 [H+] = [S~] and obtain the expression 



[HS] 



or, 



[H+1 = Vk [HS] 



Let us assume that A moles of an acid are dissolved in one liter of 

 solution. Part of the acid is dissociated into H-ions and acid 

 ions, the rest of it remaining undissociated. The concentration of 



