McELFRESH. — OCCLUDED HYDROGEN IN PALLADIUM. 



329 



stirrer, operated continuously by an electric motor, insures a uniform 

 temperature throughout the apparatus and so eliminates disturbing 

 thermo-electric currents. 



The method of measuring the resistance of the palladium wire is shown 

 in Fig. 6. 



M 

 m 



Figure 6. 



In this diagram, x is the palladium wire, and MN is the wire of a cylin- 

 drical rheostat (a Wheatstone-Kirchhoff bridge), while m and n are points 

 on this wire whose potentials are equal respectively to those of the points 

 p and q. If Fis the total resistance of the wire MN, and if v is the 

 resistance of the portion included between m and n, then 



v (R 1 + i? a ) 

 X ~ fi 3 + ]? i + v-v' 



i? 3 and R i were each equal to about 300 ohms, while R r and 7? 2 were 

 5-ohm coils. The various resistances were kept at constant temperature 

 (within one degree), and reversals of direction of current flow should have 

 eliminated any errors due to thermo-electric effects. The resistance of 

 the palladium wire was in the neighborhood of 0.1 of an ohm, and the 

 method of measuring gave results which agreed amongst themselves to 

 within one-tenth of one per cent. 



The charging current was between 0.02 and 0.03 of an ampere, and 

 was measured by a shunted ammeter which gave readings to within a 

 hundred-thousandth of an ampere. The value of the current strength 

 was needed solely for the purpose of calculating the volume of hydrogen 

 liberated in a given length of time, and therefore it seemed best to cali- 

 brate the ammeter by actually measuring the volume of hydrogen liberated 

 per minute under the conditions of the experiment. Accordingly, at the 



