Q5 GALVANIC PROCESSES. 



Experiment of thin coat of a solution of nitrate of silver be laid upon a picc& 



tSbvTinc' ®f P^3"^ g^^ss, and in the centre of this be laid a bit of zinc 



on the face of a Wire, in a little time a beautiful tree of silver will appear as 



glass plate m j£- o rowino: from the wire. If the process be observed with 

 ranuiications. o o r 



a magnifying glass, the ramifications of silver will be 



seen to increase by the progressive reductions of silver at 

 their farthest extremity from the zinc 5 a clear proof that the 

 oxide of silver does not owe its reduction to the zinc, but to 

 something which exists at the point where the increase Is 

 taking place, and which I shall prove by the following experi- 

 ments to be dependant upon the principles of galvanism. 

 Variation of In the above experiments with the glass plate I made this 



the last experi- ^^^igj-y . j coated one half of the glass with nitrate of silver 



ment. '' ° 



One half of a and the Other with dilute muriatic acid, so as to tov^ch each 



glass plate wa? oj-tigj.. I t^en laid one end of a platina wire upon the nitrate 

 coated With sol. , 1 • r • 



of silver, the of silver, while the other rested on the table, a piece of zmc 

 other half with .^^,j^g ^^^g similarly situated upon that side of the glass covered 

 diluted muna- ■' "^ , . 1 r t • - 



tic acid: zinc wIth the dilute acid : upon uniting those ends ot the wires 



wire touched ^^po^ the table, I soon had the satisfaction to see a beautiful 

 the latter fluid, ,^ ., . , . ,- , 1 • • mL- 



and platina tree of Silver grow from the point of the platina wire. Ihis 



wire the for- effect Ceased as soon as the ends of the wires v/ere separated. 



these wirer'^ ^^ instead of nitrate of silver the whole of the glass had been 



were united at covered with the dilute acid, bubbles of hydrogen would have 



silverlree'n'ew ^"^^^ given out at the platina wire. In this experiment the 



from the plati- water is decomposed, the oxigcn combines with the zinc, 



when"the?'w*tTe ^vhlle the hydrogen enters into some combination by which 



disjoined". it is invisibly carried across the liquid to the jVlailna wire, 



prSi^ Ha°tLn ^"^^^^^^ ^he hydrogen is liberated in its gasseous form. It is 



was galvanic, feasy to observe, tiiat when the platina was in contact with the 



Explanation: j^^t^ate of silver, the hydrogen was employed In reducing the 

 If silver had not ' j o r y o 



been in the so- silver to its metallic form. When a piece of ainc simply Is 

 lution the-pia- j^^^ upon the coating of nitrate of silver, the zinc in the first 



tinawould have ^ .... , . 



developed hy- Instance reduces the oxide or silver immediately m contact 



drogcn. This ^y^^jj jf . ^^g silver and zinc have now become a galvanic 



i? supposed to , . . , , • 1 ♦ r . • • • j ■ 



have been combination, a.nd the remainder 01 the process is earned on 



transmitted ^y means of galvahlsm. The zinc is now oxided by the 

 of oxidatioa oxigen of the water, and the silver is reduced by the hydro-- 

 to the place of gen. In the experiment with zinc and the solution of lead, 

 reduction aiul , 1 . i 1 t t \ t 1 i. 



prc'tipitation ^he same explaiiation holds good. As soon as the least por- 

 tion of .T^et^H'c lead is produced bj the zinc, a dtcomposition'' 



©f 



