Lives and Times of Great Pioneers in Chemistry by Rao C. N. R. Rao Indumati

Author:Rao, C. N. R.,Rao, Indumati.
Language: eng
Format: epub
ISBN: 9789814689076
Publisher: World Scientific Publishing Company
Published: 2016-04-30T04:00:00+00:00

Catalysis

Catalysis had been observed in many chemical reactions long before Ostwald. As the concept of the rate of reaction was unknown at that time, Berzelius could not explain the phenomenon and had ascribed it to catalytic force. Ostwald did not agree that the phenomenon of catalysis was the result of catalytic force.

“The development of a rational view of the nature of catalysis was thus absolutely dependent on the creation of the concept of the rate of chemical reaction” (From Ostwald 4).

Ostwald’s work on catalysis had its origin in his attempt to link rates of reactions to the chemical affinity of the substances taking part in the reaction. During the same period, Ostwald and his students conducted many experiments to measure the rates at which esters hydrolysed when they reacted with mineral acids. Ostwald discovered that the concentration of the acid affected the rate at which the reaction proceeded towards the equilibrium state. As Ostwald had studied acid-base chemistry, he found that acids with high chemical affinity increased the rate of the chemical reaction. He soon realised that a catalytic reaction was caused by the addition of a foreign compound to the substances taking part in the reaction and this substance or the catalyst (from the Greek word katalusis, meaning dissolution – dissolving all obstacles to the chemical reaction taking place) was responsible for the change in the velocity of the reaction. Using the principles of thermodynamics, he showed that catalysts did not have any effect on the equilibrium constant as the rate constants of both the forward and backward reactions were altered to the same extent. He defined a catalyst as “a substance which alters the velocity of a chemical reaction without appearing in the final products” (From Partington 5 & Moore 6) After his studies of the homogeneous catalysis, Ostwald started his investigations on heterogeneous catalysis.

Ostwald’s greatest contribution to the area of catalysis was the invention of the process for the preparation of nitric acid from oxidation of ammonia in bulk. This process came to be known as Ostwald process. This discovery had far reaching implications both for chemical theory and fertilizer industry (where it is used even today).

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