Classics of Biology

By August Pi Suñer; Charles M. Stern | Go to book overview

CHAPTER IV
BIOCATALYSTS

CATALYSIS

IN 1812 Kirchhof discovered that if starch were heated with sulphuric or other strong acid solution it was converted into sugar without any change or loss in the acid itself. Thénard noticed that hydrogen peroxide solution decomposed, giving off oxygen in the presence of undissolved bodies, such as finely divided platinum, silver, manganese dioxide or blood fibrin, not entering into the reaction, whose mere presence was sufficient to produce this effect. Sir Humphry Davy showed that platinum in the powdered or spongy state, and therefore of greatly increased surface area, can oxidize alcohol vapour exposed to the air without the application of heat.

Berzelius in 1837 called general attention to the meaning of these facts: "In reactions of this nature there is present a chemical force quite distinct from any hitherto known," and he proposed to call such operations catalytic in view of their being absolutely different from analytic actions resulting from the use of those reagents normally used in chemical research. In ordinary analytical processes the reagents come in according to the laws of affinity of normal chemical relationships, whereby they are transformed whenever they are present. On the other hand, in catalysis, the factors giving rise to the action have their effect merely by being present and in themselves suffer no intrinsic change whatever.

Prior to this basic statement by Berzelius, which is one of the cornerstones in the history of chemical science, Dubrunfaut in 1830 had already made one important discovery, namely that fermented barley extract or malt converts starch into glucose even in the cold state, similarly to the way an acid acts in the presence of heat as above mentioned. Shortly thereafter, Payen and Persoz in 1832 succeeded in separating the amylolytic principle from malt by extraction in water and precipitation with alcohol, giving it the name diastase. They considered this agent identical with the natural ferments, which cause souring in wine or milk. Robiquet consequently showed that bitter almonds contain a protein substance which breaks amygdalin

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