breakthroughs soon led to more economical and larger-scale production of fertilizers and explosives, of which Germany was in short supply during World War I. The process is often referred to as the Ostwald Process. The process remains in widespread use in contemporary times for manufacture of nitric acid. Ostwald's dilution law Ostwald also conducted significant research on dilution theory leading to his conceptualization of the law of dilution which at times is referred to as "Ostwald's Dilution Law". This theory holds that the behavior of a weak electrolyte follows the principles of mass action, being extensively dissociated at infinite dilution. This characteristic of weak electrolytes can be observed experimentally, such as by electrochemical determinations. Catalysis Through his research on chemical reaction rates and velocities and his studies of acids and bases, Ostwald found that the concentration of acid or the concentration of base in a solution of certain chemical reactants can have a strong influence of the rate of chemical processes. He realized that this is manifestation of the concept of chemical catalysis first articulated by Berzelius. Ostwald articulated the idea that a catalyst is a substance that accelerates the rate of a chemical reaction without being a part of either the reactants or the products. Ostwald's advances in the understanding of chemical catalysis were widely applicable in biological processes such as enzymatic catalysis and also in many industrial processes. A catalyst is used in the nitric acid process that Ostwald invented. Crystallization Ostwald studied the crystallization behavior of solids, especially those solids that are capable of crystallizing in different forms, in the phenomenon known as polymorphism. He discovered that solids do not necessarily crystallize in their most thermodynamically stable form but instead sometimes crystallize preferentially in other forms dependent on the relative rates of crystallization of each polymorphic form. Ostwald found that the relative rates were dependent on the surface tension between the solid polymorph and the liquid form. Many common materials exhibit this type of behavior, including minerals and various organic compounds. This finding came to be known as Ostwald's rule. Ostwald realized that solid or liquid solutions can continue to evolve over time. While the a non-thermodynamically preferred polymorph may crystallize first, more thermodynamically stable forms can continue to develop as the solution ages. Often this results in large crystals forming, since they are more thermodynamically stable than are large numbers of small crystals. This phenomenon came