BPFECP OF GALVANISM IN METALLIC ARBORIZATIONS. 2 15 



oFttii&fil^n a «oliiti<Jn»6nce deposited oh thatj which servet 



as its predipitiirif^' it remains there immovable during the 



\thole titne of the experiment; and that the new metallic 



particles proceed to plant themselves on those, that already 



e?{i8ted,'W6' thait'^th^'iirborization increases only (it it^ «]^ 



ttefuiitie^.' ' 



Sect. III. This principle once established, we readily Supposition 



Perceive, how the mutual attraction of the two metals, ?^V^f "^,®^^ 

 . , first revived it- 



added to the predominant affinity of the one for the oxigen tracts more. 



and acid of the other, fnlly explains, in most cases, the re- 

 vival of the first particles, but not of the subsequent ones; 

 and that the employment of all these forces is insufficient 

 to solve the two principal problems. Still they have another 

 defence, who suppose the attraction of one and the same 

 metal sufficiently intense, to act the principal part in the 

 precipitation of metals by one another. They might say, 

 thttt, in proportion as the metal in solution is brought to 

 deposit itself on that already precipitated, the oxigen pf the 

 former remains dissolved in the liquid, and the zinc slowly 

 and gradually lays hold of it. 



Unfortunately the following exj^eriment destroys these Experiment to 

 fine efforts of the imagination. Fill the tube ab, fig. g, confute this, 

 with an aqueous solution of muriate of tin, and immerse in 

 it th«> zim?' eylittdeti^T iw the space of half an hour the 

 cylinder will be covered with a fine tin arborization. Next 

 separate these ramifications from the zinc, withotit destroy- 

 ing them : wliich may easily be done by dexterously ttirtii 

 ing the little cylinder : and let them sink gently as far ag e, 

 keeping them from falling quite to the bottom by giving 

 the tube a proper inclination. It is essential, that the zinc- 

 remain immersed in the liquid, as in fig. 9. In this state 

 the apparatus may continue hours, days, and even weeks, 

 without the arborization c c? receiving the least perceptible 

 addition, though it is suhounded on all sides by oxide of 

 till insolation, ^if you hav^ taken the precaution to pout 

 wat^r gently into the upper part of the tube, so that it 

 does not mix with the muriate of tin occupying the lower 

 part from b io c, the zinc may remain a long while in the 

 Rater, without being covered with fre^h ramifications of tio« : 

 Now if the attraction of <)ne metal were sufficient to as3iau-«. 



12 Ut? 



