I J IP 



Dr. Andrews on the Properties of Voltaic Circles. 155 



Two similar iron wires, I and I', were placed in a glass tube 

 containing concentrated sulphuric acid, I being alone, and I' con- 

 nected with a platina wire finer than itself. When first immersed 

 in the acid the fine bubbles before described appeared at P and I, 

 none at I'. On heating the liquid vast volumes of gas were extri- 

 cated from I, but there was no gas visible at P or I' till the liquid- 

 was raised nearly to the point of ebullition, when there was some 

 effervescence at P, and slight local disengagement of gas at I'. 



When pencils of tin, T and T', (T being unconnected, and T' connected 

 with the platina P, and similar designations are used for the following metals, ) 

 were substituted for the iron wire ; the same phenomena occurred in the cold 

 acid as with zinc and Iron. Heat being applied to the acid, gas appeared at the 

 same time at T and P ; but on raising the temperature a little higher, the action 

 suddenly became so violent on T that it was impossible to observe the surfaces 

 of T' and P. By heating T' and P in a separate tube, the quantity of gas at P 

 became very considerable, but far less than that before given off from T. There 

 was also an obvious extrication of gas from T'. 



With bismuth no gas appeared in the cold. On applying heat the surface of 

 B became covered with a dark fill.., -<fcd soon afterwards that of B'. Continuing 

 to apply the heat, gas was disengaged from P and B, but in much greater quan- 

 tity from the latter. There was very little gas from B'. 



Antimony gave precisely similar results to bismuth, except that there was 

 rather more gas extricated from the metal connected with the platina when the 

 temperature was high. 



With silver no gas appeared in the cold. On applying heat S and S' became 

 dark nearly at the same moment ; as the heat was raised, gas was abundantly 

 disengaged from S, and in smaller quantities from S' and P, but in the case 

 of this metal the quantities of gas extricated from S' and P appeared to be 

 equal. 



With arsenic and mercury there was no action in the cold. When the acid 

 was heated the disengagement of sulphurous acid appeared to be scarcely, if at 

 all, diminished, by connecting these metals with platina. The quantity of gas 

 also extricated at the surface of the platina was very trifling. 



Taking a general view of these results, it will be observed, that the evolution 



