(1) 



de 



^ = 1853 



dt 



(2) 



*= 785 



dt 



(3) 



de = 



dt 



ELECTRICAL PROPERTIES OF HYDROGENISED PALLADIUM. 179 



From these numbers the following facts were deduced : — 

 If e is the electromotive force expressed in volts, and t the temperature in 

 degrees centigrade, it is found that — 

 Up to 200° C, temperature rising, 



e= T67xl0- 5 x l"ll(*-8). 



From 200° to 300° C, e is practically steady. 

 From 300° to 200°, temperature falling, 



e = 1-67 xl0" 5 (- 105-5 + '945*+ -000313* 2 ). 

 From 200° to temperature of air, 



e = 1-67 xlO" 5 x -47(*-6). 

 Hence we find, in C.G.S. units, 



from 0° to 200° C. beating, 

 from 200° to 0° C. cooling, 

 from 200° to 300° C. heating. 



(4) $ = 1578 + 1-044* from 300° to 200° C. cooling. 

 dt 



Finally, assuming the palladium to be the same as that investigated by 

 Tait, we find for the thermoelectric powers of hydrogenium, in conditions (1) 

 and (2), referred to lead (as in Evekett's Units and Physical Constants*) the 



expressions — 



(1) # = 1128 -3*59*. 



(2) p= 160-3-59*. 



Hence, on the thermoelectric diagram the hydrogenium line is something 

 like this. It begins near the iron line, runs parallel to the palladium line till 

 200° C. is reached, when it falls somewhat quickly to the palladium line, which 

 it hugs up to 300° C. During cooling, it seems to start from the point it 

 would have occupied had its course remained unchanged during the whole 

 heating. From thence it runs at a less inclination than the palladium line 

 until the temperature of 200° C. is reached, after which it remains parallel to 

 the palladium line down to ordinary temperatures, and comes out a little 

 below copper at 0° C. 



Adopting Tait's values as given by Everett for iron, copper, and 



* The signs are here changed so as to agree with Tait's theory, which connects the inclinations of 

 the thermoelectric lines with the Thomson effects in the corresponding metals. I shall always speak of 

 iron as lying above lead, and palladium as below lead, on the thermoelectric diagram. 



VOL. XXXIII. PART I. 2 B 



