256 M r. Smee's New Definition of the Voltaic Circuit, 



of ammonia on nitrate of barytes, a similar circuit is formed 

 thus:— ^) 



(F) /"Sulphuric acid Ammonia ~\, .* 

 (a) |_Barytes Nitric acidj v' 



In both these cases, however, we have not the means of in- 

 creasing the (r) and (c) to a tangible size (at least I have never 

 been able to do it), and at present these actions have been 

 restricted to the formation of atomic circles. 



There are some cases where we can extend the intermediate 

 parts (c) and (r), and then our definition of the voltaic force 

 with the formula arising from it enables us to form most ex- 

 traordinary voltaic circles, which indeed we never could have 

 formed before, unless we happened to light upon them by 

 chance : thus proto-sulphate of iron, placed on one side of a 

 diaphragm, and nitrate of silver on the other, will give a cur- 

 rent when connected with a platinum wire, and a beautiful 

 deposit of silver will be reduced on the platinum wire, on the 

 nitrate of silver side of the circuit. 



In the same manner circuits may be formed of proto-sul- 

 phate of iron and chloride of gold — of proto-nitrate of mer- 

 cury and chloride of gold — of oxalic acid and chloride of 

 gold, &c. In all of which cases the metal is freely reduced 

 on that part of the platinum wire inserted in the metallic salt. 

 The reason why a galvanic circuit is formed in these cases is 

 sufficiently obvious ; water is the electrolyte or compound 

 decomposed, proto-sulphate of iron is the substance combining 

 with one element, and the metallic salt affords a means for the 

 removal of the second element or hydrogen, and as we have 

 the power of extending the compound (r) and connecting 

 parts (c), not only an atomic circuit, but a working battery 

 may be made. At the diaphragm or the point of juncture of 

 the two liquids, indeed, an atomic or local battery is formed 

 independently of the general or working battery. A second 

 local battery is formed at the point of decomposition of the 

 metallic salt by the hydrogen. The following are the parts 

 of the circuit in the above cases. 



~ _) 



(F)f Proto-sulphate of iron Platinum wire 

 f(a) \_Oxygen Hydrogen {e)f 



* The (e) in this case does not form a secondary voltaic circle, but is 

 the union of two primitive elements. 



f (a) is the removal of the per-sulphate of iron by solution ; (e) is the 

 removal of the hydrogen by the decomposition of the metallic salt. 



