Due to these we have to modify our understanding of the fundamental reactions involved. While it is simple to indicate that amino groups in tissue attach to carboxyl groups on dyes, the carboxyl groups must first reach the amino groups to be able to attach. Mass action is a way of looking at chemical reactions based on very large numbers of molecules as a whole instead of on the reactions between individual molecules. Instead of viewing a reaction between two entities as a single, unchangeable event, it views chemistry as a dynamic process. It is concerned as much with the process of reaching the desired chemical goal, as the goal itself.
Many chemical reactions are reversible.
As a consequence, the results of these are often a mixture of the original chemicals and their reaction products in equilibrium. If left to go to completion, the products present depend on the amount of each original reactant. This goes on continuously, so that all four compounds are present at all times, once equilibrium is reached. To change the equilibrium point, then, is simply a matter of changing the amount of one of the original reactants. This will alter not only its own presence, but the presence of the products derived from it.