J 081 AH WILLABD GIBBS 41 



JOSIAH WILLAED GIBBS AND HIS EELATION TO 

 MODEEN" SCIENCE. Ill 



By FIELDING H. GARRISON, M.D. 



ASSISTANT LIBRARIAN, ARMY MEDICAL LIBRARY, WASHINGTON, D. C. 



Catalysis, Colloids and Chemical Burity. — When chemical change 

 can be produced in a system by the mere presence of small quantities 

 of another substance which itself usually remains unchanged at the 

 end of the process, such an effect is called catalysis and the agent em- 

 ployed a catalytic agent. Of the varied aspects of catalytic processes 

 we have different examples in the decomposition of substances by the 

 presence of finely divided metals like platinum or colloidal nickel, in 

 the rapid evolution of oxygen from potassium chlorate when a small 

 quantity of manganese dioxide is present, in the solution of insoluble 

 chromic chloride through the mere presence of chromous chloride, in 

 the inversion of cane sugar by acids, in the saponification of fats and 

 esters, in the synthesis of indigo by oxidation of naphthalin, in the 

 standard manufacture of sulphuric acid in the leaden chambers and 

 the later improvements of the method through the presence of platinum 

 or ferrous oxide, in catatyptic photography without light, in the re- 

 versible physiologic and therapeutic action of the animal and vegetable 

 ferments and enzymes, in the synthesis of nuclein during the develop- 

 ment of the embryo, and in the pathologic effects of poisons, venoms 

 and the toxins of disease. Many theories of catalytic action have been 

 advanced, of which the earliest and most original is that of Leibig. 

 Liebig supposes catalysis to be due to the fact that the catalytic agent 

 has power, like that of a tuning fork, to set up sympathetic molecular 

 vibrations in the substance acted upon, producing chemical change. 

 This theory has been proscribed by Ostwald because, being a figment 

 of the mind, it is neither capable of proof nor susceptible of refutation, 

 leading the subject into a blind alley, from which further scientific 

 advance is impossible. 101 It has therefore remained, like Hamlet's 

 father, " quietly inurned," as a beautiful, imaginative hypothesis which 

 we can neither prove nor disprove. Of other theories of catalysis 

 the most important is that of Ostwald himself, summed up in his 

 famous definition : A catalytic agent is one which modifies the velocity 

 of a chemical reaction without appearing in its final process. This 

 statement introduces two new ideas, the notion of infinite swiftness 

 and infinite slowness in chemical change and the fact that catalytic 

 change may be brought about by a series of intermediate reactions. It 

 will be seen that Ostwald's definition is elastic enough to include as 



101 Ostwald, " Ueber Katalyse," Leipzig, 1902. 



