! 

 128 EFFECT or GALVANISM IN METALLIC ARBORIZATIONS. 



sits it on the silver. It follows from these facts, .that tlae 

 galvanic electricity excited by the contact of two metals is 

 sufficient, to effect the precipitation of a metal held in so- 

 lution, which would not have been precipitated by iither 

 of the uietals taken separately. - • . .; 



Theory, of the Sect*\m It novr remains to solve the two- problems' in 

 composition Sect. I. Perhaps the reader will have already remarked, 

 ot water. that they are nearly the same as present themselves in the 



galvanic decomposition of water, and that they may be 

 all solved on the same principles. On this account I think 

 it necessary to recapitulate in a few words the theory I 

 gave of the latter phenomenon in a short paper in the Ann, 

 de Chim. for April, I8O6. I first proved, that water, tra- 

 versed by a current of galvanism, becomes oxigenized at 

 the positive pole, and hidroguretted at the negative pole. 

 Though the contrary has been presumed ; and though it 

 has been said, that it becomes neither oxigenized nor hidio- 

 garetted; my recent experiments appear to me evidently 

 to confirm the piinciple I have announced. 1 will relate 

 only two. ^'fiiuoij^i.i 



Proofs that the a. Hidroguretted sulphuret of barytes, exposed to the 



water isoxi- action of the pile, affords gradually round the positive pole 

 jenizedat the , , ^ . ° , . - •. . 1 • i i_ 



positive,and an abundant quantity of a white precipitate, which has 



hidroguretted jj|| |.jje characters of sulphate of barvtes; while the liquid 

 at the nega- . , • , , • 1 * , » i 1 , • 



tWepole. round the negative pole becomes evidently clearer, and ulti- 



mately colourless. 



b^ If the galvanic current traverse, an alkaline solution 

 of indigo, niade by means of some disoxigenizing sub- 

 stance, immediately there is formed at the zinc pole a 

 precipitate of a hne blue colour, which is capable of being 

 completely redissolved, if ths respective places of the two 

 jpoles be changed*. 

 Water, when Sect. W. Water becomes a real secondary pile while it 



galvam2ed,be- experiences the galvaiiic action. On this occasion we may 



comes a se- 1 1 r« .» 



condary pile, recollect the remark of Volta, that a piece of wet paper, 



each extremity of which touches one of the poles of the 



pile, retains for some minutes the chauge Teqeived, even 



* In these trials I have never immersefl the poles, by which term I 

 meari the conducting -jvires, more than four or five lines below the surface 



