ELECTRICAL PROPERTIES OF HYDROGENISED PALLADIUM. 173 



It is striking that the rates of change of the palladium in its two states are 

 such that their total changes through a large range of temperature are the 

 same. 



Experiment of February 4, 1886. 



Resistance of hydrogenium at 7° C. = 119*3 (10~ 2 ohm). 



Heating Curve — 



From 0° to 140° dR/dt = -194 , 

 and 



R = 118 +194*, 

 or 



r = 1 +-00165*. 



From 140° to 260°, the resistance grows to a maximum, such that dRjdt 

 changes continuously, increasing to a maximum (*385) at temperature 

 225° ±5°, and then diminishing to zero. 



At 260° dR/dt changes sign and continues to increase numerically very 

 rapidly, so that at 300° the resistance has fallen from 282*5 to 136. This 

 means a very rapid rate of change at about 295°, approximately equal 

 to 5. 



The cooling curve gives, as average value, 



dR/dt = -219 

 and 



R = 66-5 + -219 t , 

 or 



r = 1 + '0033 t. 



These descriptions, with the accompanying curves (A) on Plate XL, are 

 sufficient to bring out the peculiarities of the case. The various experiments, 

 made with wires of different charge, gave very similar results. From these it 

 appears that, up to a temperature of 150° C, hydrogenium of all degrees of 

 charge behaves like palladium, except that the temperature-coefficient is 

 generally, and always for the higher charges, smaller than for pure palladium. 

 At higher temperatures the resistance seems to grow at a more rapid rate, and 

 this peculiarity is more marked for the more highly charged metal. This is shown 

 also in the fact that the difference between the lowest and highest resistances is 

 greater for the more strongly hydrogenised wire. A little above 200°C, the 

 hydrogen begins to escape, the first effect being that the resistance increases 

 more and more slowly till it reaches a maximum. Diminution of resistance 

 then sets in, sometimes with great rapidity, so that before 300° is reached the 

 resistance has fallen nearly, if not quite, to what its value would be at that 

 temperature for the original palladium. The rate at which this diminution 



