SIMPLE VOLTAIC CIRCLE. 211 



acid liquid, is sufficient to develope, and which accounts for 

 the discharge of the hydrogen upon the surface of the copper 

 in such an arrangement, the remarkable phenomenon by a de- 

 scription of which this subject was introduced. 



It remains for us to apply the same principles to explain 

 the additional phenomena of the second case described, in 

 which the connecting wire, supposed to be of platinum, between 

 the zinc and copper plates, is divided, and the broken ex- 

 tremities introduced into hydriodic acid (Fig. 3. page 1U9.) 



Broken at any point, as at K, (Fig. 12.), it is evident that 

 if the polarized condition be still sustained, the portion of the 

 metallic segment connected with the copper plate will termi- 

 nate with a zincous pole at K, and that connected with the 

 zinc, with a chlorous pole ; which may be indicated respectively 



FIG. 13. 



A B CDF 



by K and L in Fig. 13. When hydriodic acid is interposed 

 between K and L, the breach is repaired by the polarization of 

 a chain of particles of that acid. The extremity K, being zincous 

 induces chlorous polarity in the side of the hydriodic acid par- 

 ticle which it touches, in consequence of which the iodine atom 

 (the analogue of chlorine) of the hydriodic acid molecule is 

 presented to that pole, and liberated there when decomposition 

 occurs. The extremity L of the zinc or positive metal element 

 is chlorous, and therefore induces zincous polarity in the 

 particle of hydriodic acid which it touches, and hydrogen (the 

 analogue of zinc) is liberated there. The polarity in an induced 

 circle must necessarily be of equal intensity at every point in 

 it, and being sufficient at A to cause the decomposition of the 

 hydrochloric acid, must also decompose the hydriodic acid 

 between K and L, otherwise it is never established at A, nor 

 any where else. 



In the present arrangement, the voltaic circle is broken into 



p 2 



