Disintegration of Metals at High Temperatures. 21 1 



catalytic. There are in addition, moreover, certain experi- 

 mental facts which at first sight appear to militate against 

 a theory that the disintegration is due to direct oxidation : — 



1. No matter how much a platinum wire is heated it 



remains clean and bright. 



2. Under certain conditions (along the edge of the 



platinum strip in a resistance furnace) platinum 

 crystals may be formed ; this would seem to point to 

 volatilization of the metal. 



3. Under some circumstances the rate of disintegration is 



more rapid in the early heatings than in the later 

 ones. Since the platinum metals absorb hydrogen 

 readily, this might seem to be due entirely to the 

 loss of weight of hydrogen ; or again, since platinum 

 in a finely divided state is black, the black deposits 

 on the walls of a (comparatively cool) vessel con- 

 taining a glowing platinum wire might be thought to 

 be due to the spontaneous emission of minute metallic 

 particles from the wire, or to such particles being 

 detached by the escaping gas. 



4. Since the platinum metals absorb other gases, such as 



oxygen, to a certain extent, hydrogen and oxygen 

 might form explosive mixtures in minute cells near 

 the surface of the metal, and on heating the metal 

 the explosions might cause particles of metal to be 

 ejected. This is the view of two French scientists *. 

 I do not think, however, that this is likely to be the 

 true explanation of the phenomenon. 



The disintegration of the platinum metals has been 

 investigated gravimetrically by Berliner f, Elster and 

 Geitel J, Nahrwold §, Stewart ||, Holborn and Austin If, 

 and Sir W. Crookes**, who have shown that : — 



1. The amount of disintegration in a given time at a 



given temperature diminishes after prolonged heating. 



2. If, however, wires of pure metals are used, there is no 



diminution in the rate of disintegration (Holborn 

 and Austin, and Crookes). 



3. The disintegration is practically zero in the absence of 



oxygen. In the case of palladium, however, the 

 disintegration increases with diminution of pressure 

 of surrounding gas. 



•* Reboul and Bollemont, Journal de Physique, July 1912. 

 t Berliner, J Elster and Geitel, § Nahrwold, Wied. Ann. 1887, 1888. 

 || Stewart, Phil. Mag. 1889. 

 If Holborn and Austin, Phil. Mag. 1904. 

 ** Crookes, Proc. Boy. Soc, May 1912. 



