392 Disintegration of the Platinum Metals. 
The loss of weight which is given in the last column of the 
table is in most cases the mean of several observations. The 
values are calculated for 30 minutes heating, the actual time 
being given in the last column but one. 
As the table shows, the behaviour of platinum and rhedium 
is very similar. The disintegration at atmospheric pressure 
in oxygen is about five times as great as in air, in air at 
25 mm. about half as much as at 760 mm., and in nitrogen 
it becomes very small. That it does not disappear entir ely, 
is probably due to the 1:7 per cent. of oxygen that was 
mixed with the nitrogen. In the work with the broad strips 
it was found that the loss of weight of platinum and rhodium 
under the same circumstances was the same. ‘The differences 
here shown in the two metals are due to the fact that on 
account of its irregular width the rhodium strip reached the 
disintegration temperature in only | a comparatively narrow 
zone. “Iridium, which disintegrates about ten times as rapidly 
in the air as platinum, behaves in a similar way except that 
the differences are much greater. At 25 mm. pressure its 
loss in weight is only } that at 760 mm. , while in oxygen the 
loss is eleven times as great. 
In palladium the phenomena were entirely different. The 
disintegration in air increased with decreasing pressure, 
while the nature of the surrounding gas seemed to be without 
influence, the results being the same in air, oxygen, and 
nitrogen. According to Stewart, palladium, like platinum, 
should show little disintegration in nitrogen. 
For the experiments in hydrogen the gas was prepared 
electrolytically, and freed from oxygen by passing through 
several wash-bottles containing alkaline pyrogallol solution, 
and dried by passing through tubes of calcium chloride and 
phosphorus pentoxide. The whole apparatus was several 
times pumped out and filled with hydrogen before the final 
filling. 
The experiments with palladium in hydrogen were difficult 
on account of the absorption of the gas by the metal. It 
was not found possible at atmospheric pressure to keep the 
metal for any length of time above the temperature where 
the disintegration begins. In most cases it melted before 
reaching this temperature, and also showed an increase in 
weight due to the absorbed gas, which made any attempt at 
measuring the disintegration impossible. At lower pressures 
the experiments were more successful. During the _pre- 
liminary fillings and pumpings, the palladium was kept at a 
dull red heat. Finally, when hydrogen was admitted until 
the pressure reached 30 mm. Hg, and the temperature was 
