228 INDUCTIVE AFFINITY. 



2. The exciting compound or zincolyte must have a polar 

 molecule, which requires it to consist of single zincous and 

 chlorous atoms. 



3. The molecules of the zincolyte must also have mobility 

 and be able to assume a polar arrangement, or place themselves 

 with their unlike and attractive poles together, so as to form 

 a polar chain. This necessitates fluidity of the zincolyte 

 (Faraday). 



4. Of the metallic portions of the circle, the molecule is 

 indifferently polarizable, that is, either side of it indifferently 

 may become chloro-polar or zinco-polar, according to the direc- 

 tion of the induction affecting it. Hence these portions of the 

 circle need not be fluid like the zincolytes. 



5. In a closed voltaic circle, a certain number of lines or 

 chains of polarized molecules is established, each chain being 

 continuous round the circle. Hence the polar condition of the 

 circle must be every where the same. The same number of 

 particles of exciting fluid are simultaneously polar upon the 

 surface of every zinc plate in the active cells, and also upon the 

 surface of the zincoid in the cell of decomposition, and the 

 consequent chemical change, or decomposition occurring, is of 

 the same amount in the same time in all the cells. Such 

 equality in condition and results is essential to a rotal induction, 

 such as exists in the voltaic circle. 



The number of polar chains that can be established at the 

 same time in a particular voltaic arrangement, is obviously af- 

 fected by several circumstances : 



(1) By the size of the zinc plate ; the number of particles of 

 zinc that may be simultaneously acted upon by the exciting 

 fluid, being directly proportional to the extent of metallic sur- 

 face exposed. 



(2) By the nature and accidental state of the exciting liquid, 

 some zincolytes being more easily acted on by the positive me- 

 tal than others ; while the state of dilution, temperature, and 

 other circumstances may affect the facility of decomposition of 

 any particular zincolyte. 



(3) The adhesion of the gas bubbles of hydrogen to the 

 copper plate, at which they are evolved, interferes much with 

 the action of a battery. By taking up the hydrogen, by means 

 of a solution of sulphate of copper in contact with the copper 

 plate, Mr. Daniell increased the amount of circulating force six 

 times. 



