Plat/n inn and Palladium Wires at Hujli Temperatures. 483 



from atmospheric air by phosphorus, and the remaining gas 

 passed through a solution of potassium permanganate, and 

 over caustic potash and phosphoric pentoxide. As an example 

 I may state that a platinum wire at a clear red heat lost 0"84 

 per cent, of its weight in two hours ; at a white heat 3*89 per 

 cent.; the initial weight in both cases being 170 milligrammes, 

 and the surrounding atmosphere air. 



The following results were obtained from experiments 

 with atmospheric air at ordinary pressure : — 



(a) For both platinum and palladium wires the loss by 

 disintegration decreases as the glowing is continued. Thus 

 in one set of experiments the same platinum wire was used 

 six times consecutively, each experiment lasting two hours, 

 and the temperature of the wire being the same in each. The 

 loss of weight gradually decreased from OG8 per cent, of the 

 original weight in the first experiment to Oil per cent, in 

 the sixth. This phenomenon was observed without exception 

 for both platinum and palladium wires. 



(b) The amount of disintegration is the same whether the 

 air be dry or moist. 



(c) The amount of disintegration was not altered by sur- 

 rounding the glowing wire with a brass tube kept at zero 

 potential by metallic connexion with the water-pipes of the 

 laboratory. 



As the pressure of the air decreased the disintegration 

 decreased in the case of platinum, but increased for palladium. 

 Thus in an experiment with air at atmospheric pressure the 

 loss of weight of a platinum wire after two hours was 1'65 

 per cent, of its original weight, while at the same temperature 

 with air whose pressure was 1*25 millim. the loss after two 

 hours was 0*64 per cent. For a palladium wire the loss was 

 066 per cent, at atmospheric pressure and 11'84 per cent, at 

 pressure 1'25 millim. This result was confirmed by three 

 experiments with platinum and four with palladium. 



In hydrogen platinum does not disintegrate even at a clear 

 white heat, while palladium undergoes a very much smaller 

 loss of weight than in air. Thus for a palladium wire the 

 loss of weight after two hours was 0*66 per cent, in air at 

 atmospheric pressure, 0"096 in hydrogen at atmospheric 

 pressure, and 0'02 per cent, in hydrogen whose pressure was 

 3 millim., the temperature being the same in each case. 



In nitrogen the disintegration is exceedingly small, for 

 both platinum and palladium wires. After two hours the loss 

 of weight of a platinum wire was - 002 per cent, in nitrogen 

 at atmospheric pressure, while in nitrogen at pressure 3 millim. 

 it was zero. For a palladium wire the losses were 0'04 per 

 cent, at atmospheric pressure, and zero at 3 millim. pressure; 



