104 LIFE: ITS NATURE AND ORIGIN 



Similarly, a tiny quantity of a catalyst may determine the building 

 up or the breaking down of an enormous number of molecules; but 

 catalysts may be "poisoned" and rendered inoperative for certain 

 reactions by physical or chemical change, or by adsorbed impurities. 



In developing what is known as the theory of active centers on 

 catalytic surfaces, Professor Hugh S. Taylor of Princeton, in a paper 

 sent to the Royal Society of London in 1925, discussed the phenomenon 

 of progressive poisoning. Thus the surface of a nickel catalyst can 

 be "progressively and successively poisoned for the hydrogenation of 

 benzene with thiophene as a poison, then for the hydrogenation of 

 ethylene which occurs on a surface whose activity for benzene hydro- 

 genation has been destroyed by the poison used. A surface poisoned 

 for both reactions could still serve for the reduction of nitrobenzene." 11 



It must be remembered that though the active catalyst areas 

 may be but a small fraction of the total area of any particle or 

 surface, what happens at this active area may have great and far- 

 reaching consequences, e.g., the production of a hormone, a vita- 

 min, or the carrier or the prosthetic group of other catalysts. A 

 tiny zipper key can open a very large bag. The importance of 

 local happenings is also illustrated when a grindstone is used to 

 sharpen steel tools. Without the use of water, oil or some similar 

 lubricant, the local temperature at the metallic edge being ground 

 may rise high enough to draw the temper of the steel. A dry 

 grindstone immediately throws off a shower of sparks from steel. 

 The frictional heat developed by a shoe brush melts the wax in 

 the shoe polish, locally and momentarily. Sir George Beilby 12 

 showed that when metals are burnished or polished, molecular or 

 atomic flow occurs; crystalline surface structure is practically 

 fluidified and converted into an "amorphous" layer resembling a 

 highly viscous liquid. Conduction dissipates the local heat 

 developed. 



It is common industrial practice to provide means for absorbing 

 and removing the large amounts of heat locally developed by catalysts. 

 For example, the vanadium pentoxide catalyst used to oxidize naphtha- 

 lene vapor to phthalic anhydride in the presence of a limited supply 

 of air, is kept at a safe operating temperature by insertion of iron 

 tubes containing mercury, which boils at 357° C and thus prevents 

 fusion of the catalyst or charring of the organic substances in process. 13 

 The various impurities in the naphthalene also suffer chemical or 

 physical changes, but no investigation has been made to see if these 

 are due to local heat, to specific action of the catalyst, or to both. In 

 industry, the "waste heat" from the main reactor (where the main 



