1902.] Electrical Conduction in Gases, and Luminosity. 101 



[In his complete paper,* Mr. Baker states that he found that 

 hydrogen and oxygen did not interact when subjected to the influence 

 of a coil of thin silver wire heated by an electric current to the melt- 

 ing point of the silver, that is to say, above 1000° ; but that when a 

 similar platinum coil was heated in the dried gaseous mixture an ex- 

 plosion occurred just after the wire became visibly red. Doubtless, in 

 the latter case, the surface over which interaction extended was suffi- 

 ciently large to raise the velocity of change to the explosive rate, 

 owing to the condensing effect exercised by the platinum; and the 

 silver had no effect because it is destitute of the power which platinum 

 possesses in so high a degree of attracting gases and of acting as a 

 catalyst. 



In making this statement, I wish it to be understood that I assume 

 that platinum per se would be without effect. I feel almost confident, 

 in fact, that if they could be dealt with, even free atoms would not 

 associate in the absence of a composite electrolyte, as it appears to me 

 probable that at least one function of the composite electrolyte is to 

 provide the " mechanism " by means of which the energy of chemical 

 change is frittered away. Ostwald, in his lecture on Catalysis (an 

 English translation of this is to be found in ' Nature,' April 3, 1902), 

 defines a catalyst as any substance which alters the velocity of a 

 chemical action without appearing in the final product. I conceive, 

 however, that the catalyst determines the interchange from its begin- 

 ning. I have discussed a number of " catalytic " phenomena — in- 

 cluding these of fermentation and of the dissolution of metals in 

 nitric acid — in the address referred to later on. — Note, added May 2.] 



It appears to me that Brereton Baker's results lead to far-reaching 

 consequences — -that they justify, not only the conclusions I have 

 drawn as to the conditions which determine the occurrence of chemical 

 change, but also the conclusion already stated by me in the note pre- 

 viously referred to, in 1893, that pure gases should be perfect dielec- 

 trics : i.e., that the passage of an electric discharge through a gas, 

 like that of an explosive wave through, say, a mixture of hydrogen 

 and oxygen gases, can only take place if an electrolyte be present, 

 such electrolyte being, it would seem, always a composite system, and 

 one wdiich may be pictured as existing momentarily in a quasi-liquid 

 state/ 



The argument was more fully developed in my Presidential Address 

 to the Chemical Society in 1895, in which I discussed very fully the 

 nature of chemical change, and the conditions which determine it, 

 from various points of view.f 



* ' Chem Soc. Trans.,' 1902, p. 400. 



t No more striking evidence that the occurrence of a discharge in a gas is 

 dependent on the presence of a something besides the gas — on the formation of a 

 complex conducting system — could be given than is afforded by the beautiful 



