224 



Dr. J. Monckman. Occluded Gases and [May 31, 



the resistance of the wire containing the hydrogen was found to have 

 increased about one-thousandth part. It is not necessary to try the 

 effect of hydrogen on palladium, as the resistance is known to be 

 increased considerably by the absorbed gas. 



Carbon. — Two thin rods about 2 mm. diameter were electroplated 

 at the ends and soldered to insulated copper wires. After protecting 

 the plated portion with marine glue, the whole was fixed to a 

 convenient frame, and placed in dilute sulphuric acid. As was done 

 in the case of the platinum wires, the rods were balanced against each 

 other in order to eliminate changes of temperature, &c. 



"When used as the poles of a battery the change of resistance was 

 considerable, but greater on the rod that had been the positive pole. 

 By using a platinum electrode, hydrogen or oxygen was produced 

 at will upon the same rod, the other rod remaining unchanged. It 

 then appeared that oxygen increased the resistance much more than 

 hydrogen, rising in some cases as high as nine times ; that when 

 oxygen was liberated twice or thrice in succession, the resistance 

 increased each time. This continued increase was probably due to 

 chemical changes produced by the active oxygen. Hydrogen gave an 

 increase of resistance, not continuing beyond a certain point, and not 

 becoming greater on repeated charging with the gas. 



Generally also the effect of the hydrogen was temporary, disappear- 

 ing, wholly in some cases, partially in others, when short circuited. 



The following series of observations afford an example of this : — 



1. When rod A was charged with oxygen its 



resistance was 4*15 ohms. 



2. When rod A was charged with hydrogen its 



resistance was 4*1633 „ 



3. When rod A was charged with hydrogen its 



resistance was 4*1633 



4. When rod A was charged with oxygen its 



resistance was 4*2833 „ 



5. When rod A was charged with oxygen its 



resistance was , 4*2966 ,, 



6. When rod A was charged with hydrogen its 



resistance was 4*3099 „ 



7. Allowed to rest short circuited 4*2966 ,, 



8. Again charged with hydrogen 4*3066 „ 



9. Allowed to rest 4*303 „ 



In the case of hydrogen, the increase was 0*0133 ohm in two 

 experiments, and 0*01 in the other, while it recovered completely after 

 observation "No. 6 and partially after No. 8. 



Superposition of Polarisations. — Part of the change in the carbon is 

 evidently produced by the mechanical action of the gases evolved, 



