380 Dr. G. Bird oji certain Properties acquired by the 



mercury ; these cups, and the platina plates connected with 

 them, may be called respectively A and B. 'The basin was 

 filled with dilute sulphuric acid, and a tube full of the same 

 fluid inverted over each plate of platina ; a rod of amalgamated 

 zinc, lo one end of which was soldered two thin copper wires, 

 was immersed in the contents of the basin, and the ends of 

 the wires dipped into the cups of mercury A and B, by which 

 the rod became metallically connected with the platina plates. 

 Rapid decomposition of water instantly commenced, bubbles 

 of hydrogen being evolved from the platina surfaces: in five 

 minutes the tubes were examined, and instead of the gas col- 

 lected being in equal volume in either tube, as would a priori 

 be expected, I found, as stated by the original observer, that 

 one contained nearly twice as much as the other. 



Upon reflecting on this experiment, I suspected that as the 

 apparatus had been employed as a volta-electrometer a short 

 time previoush^, the platina plates might have assumed and 

 retained some peculiar state from their connexion with the 

 battery. 



Exp. 2. The basin filled with the dilute acid was connected 

 with a battery of six alternations of zinc and copper, separated 

 by jars of porous earthenware and excited by sulphate of 

 copper and sulphate of soda; the cup A was connected with 

 the negative, and B with the positive wire : decomposition of 

 water was allowed to proceed for a few minutes, contact was 

 then broken with the battery : the tubes filled with diluted 

 acid were inverted over the respective plates and the amal- 

 gamated zinc immersed in the acid, its wires dipping into A 

 and B. Hydrogen was copiously evolved at the surfaces of 

 the platina, and in 10 minutes the zinc was removed. 



In the tube over the plate A was collected 1 • inch hydrogen. 



B 2-15 ^— 



During the evolution of gas, the difference in the appear- 

 ance of the bubbles from the two plates was remarkable : those 

 from the plate B were large, rose rapidly to the top of the 

 tube, and were given off" from isolated points of the electrode ; 

 whilst those from A were small, rose much slower in the 

 tube, and were given off" from every part of the plate, re- 

 sembling the bubbles of oxygen evolved in the voltaic decom- 

 position of water. It is remarkable that the platina plate (A), 

 which when in connexion with the battery gave off" the great- 

 est volume of gas, (hydrogen) now evolved the smallest, and 

 that (B), which had evolved the smallest (oxygen), now gave 

 off" twice the volume of the other. It is needless to state that 

 the gas in both tubes was hydrogen. 



Exp. S. The apparatus was refilled, again connected with 



