482 



Dr. W. Stewart on the Disintegration of 



was at least materially favoured by the presence of atmo- 

 spheric air ; he considered that the oxygen of the air was 

 the potent agent. 



The following is a description of some experiments on the 

 disintegration of platinum and palladium wires brought by 

 an electric current to a " glowing " temperature in air, 

 hydrogen, nitrogen, and oxygen at various temperatures. 

 The temperature of the glowing wire ought to be independent 

 of the nature of the surrounding gas ; to effect this object 

 the specific resistance of the wire was kept constant by a 

 proper regulation of the current strength. 



The wire to be experimented upon was suspended (fig. 1) 

 by short thick platinum hooks soldered to the thick copper 



Fie. 1. 



wires CD, EF. A current from a battery B passed through 

 an adjustable resistance R, a manganin resistance M of 0232 

 ohm, and the experimental wire. The difference of potentials 

 between the ends of the experimental wire, and between the 

 ends of the manganin resistance, was measured by the volt- 

 meter V, the resistance of the experimental wire calculated, 

 and the variable resistance R adjusted so as to keep the 

 specific resistance of the experimental wire constant. The 

 thickness of the wires was 025 millim., their length about 

 170 millim., and the loss of weight was determined which 

 they underwent after two hours'' glowing. The hydrogen 

 used was prepared from chemically pure zinc and dilute sul- 

 phuric acid. To prepare nitrogen the oxygen was removed 



