Chemical Science^ 46S 



when very feeble electricities are g^enerated in any point of a metallic 

 circuit, interrupted by a saline solution, a current of electricity is 

 formed or noty according as the two similar metallic terminations, 

 which dip into the solution^ belong to an oxidahle or non-oxidable 

 metal. If the saline solution be replaced by an acid, then a current 

 will be obtained, though platina wires be used; because that kind of 

 fluid does not interrupt the current. 



With respect to the production of new compounds by electro- 

 chemical powers, very much depends upon the strength of the 

 power employed, and M. Becquerel only pretends, as yet, to indicate 

 a new field of research, and not to point out the precise paths to be 

 pursued. Two methods may be adopted. As an illustration, let a 

 tube, from 4 to 8 hundredths of an inch in diameter, be bent into the 

 form of the letter U, and place a plug of amianthus at the bend, to 

 prevent the mixture of the fluids in the limbs: into one leg put a 

 mixture of deutoxide of copper and solution of the sulphate of 

 copper, the former will fall to the bottom ; into the other put a satu- 

 rated solution of common salt, and also an excess of the dry sub- 

 stance, then communicate the two fluids by a plate of copper. Very 

 shortly the end plunged in the sulphate will be covered with me- 

 tallic copper, and the acid set free will act upon the oxid6 of copper 

 below and form more sulphate, so that a set of decompositions and 

 recompositions will occur, and ultimately comparatively large crys- 

 tals of copper will be obtained. 



In the other branch of the tube, a portion of the salt will be de- 

 composed, the muriatic acid will act upon the copper, which is 

 oxidised in consequence of its positive state, and will probably 

 produce an oxychloride, which will combine with the chloride 

 of sodium, and then octoedral crystals will be formed on the plate 

 of copper. The effects are produced either with or without access 



iair. 



When the crystal? are well dried and inclosed in a tube herme- 

 tically sealed, they suffer no change ; but they are decomposed by 

 water into chloride of sodium and submuriate of copper. 



If the voltaic experiment be continued for one or two months, the 

 crystals, from being colourless and Hmpid, become violet, and ulti- 

 mately acquire an emerald green hue, still remaining transparent. If 

 the 6hloride of sodium side be tested, it will be found that soda is 

 evolved during the experiment. A piece of copper simply immersed 

 in a solution of common salt, produces nothing more than a sub- 

 muriate of copper, which precipitates. 



fFith silver. — If a similar tube to that described have both 

 limbs filled with a solution of salt, a platina wire introduced into 

 one limb, a silver wire into the other, the extremities of the wire 

 connected so as to form a voltaic circuit, and the whole left for 

 some months, in about fifleen days crystals will be observed on 

 the silver wire ; these will gradually increase and assume a rhom- 

 boidal form. They have not yet been particularly examined, but 



2HS 



