4 HYDROGEN ION CONCENTRATION 



condition in which chemical changes actually occur, but in such 

 manner that at any given instant as much of any given kind of 

 molecule is being produced as is being destroyed. For the mainte- 

 nance of this stationary condition no external work is required, and 

 conversely no work can be gained from these constantly occurring 

 processes within this stationary state. Furthermore, the algebraic 

 sum of all the work which may be derived from the various com- 

 ponent processes of this state, as well as tlie smn of work expended 

 for these processes, is equal to zero. This differentiates the sta- 

 tionary state of chemical equiUbrium from the so called dynamic 

 equilibrium as represented in a living organism. The latter is also 

 a chemical system which may frequently keep its chemical com- 

 position unaltered for a long period of time, but for the maintenance 

 of this condition it requires a constant supply of energy. 



The apparently resting condition of a living organism does not 

 come within the scope of the above definition of the law of mass 

 action for a closed system. Nevertheless this does not preclude 

 the validity of the application of the mass law to many particular 

 processes occurring in the living organism. Thus processes which 

 progress with a great velocity, such as ionic interreactions, take place 

 also in the living cell in such a manner that a true chemical equi- 

 librium is established. Thus, when free carbonic acid reaches the 

 alkaline blood, a part of it is at once bound, i.e., it produces ions and 

 salts, and exactly the same condition of equihbrium is established, 

 as if the blood were not a component of a living organism. On the 

 other hand the slowly progressing reactions in an organism do not 

 result in the true chemical equihbrium, but at best reach a dynamic 

 equihbrium. For example, the true condition of equilibrium for 

 the combustion of sugar in the blood with the aid of the oxidizing 

 ferments and oxygen is the practically complete destruction of the 

 sugar. Tlds state of true equilibrium is, however, never reached 

 during life, for before it is reached new sugar is brought in from the 

 food or from the glycogen depots, so that the concentration of sugar 

 in the blood is constantly maintained at a fairly fixed level. 



In this book we shall deal with ionic reactions only. These occur 

 so rapidly that they always reach true equihbrium. Given two 

 different blood samples containing different concentrations of 

 hydrogen ions, the difference in these two concentrations never 

 signifies that the reaction between the hydrogen ions and the other 



