DEFINITE CHEMICAL ACTION OF ELECTRICITY. 109 



electrode, in sulphate of soda or solution of common salt, gave the same constancy of 

 operation. 



813. Experiments of a similar kind were then made with bodies altogether in a dif- 

 ferent state, i. e. with fused chlorides, iodides, &c. I have already described an ex- 

 periment with fused chloride of silver, in which the electrodes were of metallic silver, 

 the one rendered negative becoming increased and lengthened by the addition of 

 metal, whilst the other was dissolved and eaten away by its abstraction. This expe- 

 riment was repeated, two weighed pieces of silver wire being used as the electrodes, 

 and a volta-electrometer included in the circuit. Great care was taken to withdraw 

 the negative electrode so regularly and steadily that the crystals of reduced silver 

 should not form a metallic communication beneath the surface of the fused chloride. 

 On concluding the experiment the positive electrode was re-weighed, and its loss ascer- 

 tained. The mixture of chloride of silver, and metal, withdrawn in successive portions 

 at the negative electrode, was digested in solution of ammonia, to remove the chlo- 

 ride, and the metallic silver remaining also weighed : it was the reduction at the cat- 

 hode, and exactly equalled the solution at the anode ; and each portion was as nearly 

 as possible the equivalent to the water decomposed in the volta-electrometer. 



814. The infusible condition of the silver at the temperature used, and the length 

 and ramifying character of its crystals, render the above experiment difficult to per- 

 form, and uncertain in its results. I therefore wrought with a chloride of lead, using 

 a green glass tube, formed as in fig. 17- A weighed platina wire was fused into the 

 bottom of a small tube, as before described (789.). The tube was then bent to an 

 angle, at about half an inch distance from the closed end ; and the part between the 

 angle and the extremity being softened, was forced upward, as in the figure, so as to 

 form a bridge, or rather separation, producing two little depressions or basins a, b, 

 within the tube. This arrangement was suspended by a platina wire, as before, so 

 that the heat of a spirit-lamp could be applied to it, such inclination being given to 

 it as would allow all air to escape during the fusion of the chloride of lead. A posi- 

 tive electrode was then provided, by binding up the end of a platina wire into a knob, 

 and fusing about twenty grains of metallic lead on to it, in a small closed tube of 

 glass, which was afterwards broken away. Being so furnished, the wire with its 

 knob was weighed, and the weight recorded. 



815. Chloride of lead was now introduced into the tube, and carefully fused. The 

 leaded electrode was also introduced ; after which the metal, at its extremity, soon 

 melted. In this state of things the tube was filled up to c with melted chloride of 

 lead ; the end of the electrode to be rendered negative was in the basin h, and the 

 electrode of melted lead was retained in the basin a, and, by connexion with the 

 proper conducting wire of a voltaic battery, was rendered positive. A volta-elec- 

 trometer was included in the circuit. 



816. Immediately upon the completion of the communication with the voltaic bat- 

 tery, the current passed, and decomposition proceeded. No chlorine was evolved at 



