PRECIPITATION OF OXIDES BY THEIR OWN METALS, ^C) 



evolution of gas. The iron in contact with the solution was 

 covered with a coat, that had sometimes the colour of indigo 

 or of copper, and acquired the brightness of iron by rub- 

 binti-; which appeared to indicate a separation of iron in the 

 metallic state, and in a pulverulent form, though I am not 

 inclined to adopt this o[)inion. The too speedy mixture 

 of the two liquors having destroyed the chain, I could not 

 procure myself enough of this black powder to make an ac- 

 curate examination of it, and to determine what it was with 

 more certainty. 



Conclusion. 



From all the experiments I have described it appears to General de- 

 me we may infer, that almost all metals are capable of^"'^^'^"^* 

 forming a chain with their own solutions and water, the elec- 

 tric action of which precipitates the metal in the metallic 

 state ; and that an evident anomaly appears to take place, 

 as if the metal dissolved were precipitated by the pure me- 

 tal, which would seem contradictory to the received laws of 

 aflTmity between a metal and oxigen. It has always appear- 

 ed to me, that the following conditions are necessary to our 

 complete success. 



1. The metal must form a solution with some acid, which The acid miHt 

 is altered very slowlv or not at all by the pure metal ; and l>f'<^f'e' hat acts 



,-, i.i"'i.- r-j c ■ I '^"^ little on 



which consequently contains no excess ot acid or or oxide ; ii,o same mc- 

 \n order that the electric current formed by the chain may tai: 

 act without being checked on the metallic oxide in the so- 

 lution. 



2. The solution must be sufficiently concentrated, 'not to the solution 

 mix easily and readily with the supe.-natunt liquor, and an- "^"^^"^ 



J J I 1 ' strong: 



nihilate the ciiairi. 



3. The mehi}, that is to form the chain, should be oxida- and the n>etal 



ble by water, uiid thus determine the electric cunent so as ""-'st b^ ox;d- 



abie oy waiur. 

 not to oceabion a mixture of the two liquors, and thus destroy 



the chain too quickly. 



It is to be presumed, that gold, platina, bismuth, man- Other metals. 

 ganese, tuiig^ten, and other metals, would likewise form 

 electro-galvanic chains, and exhibit the apparent auomnly 

 of a piece of m;"i:il precipitating the oxide o!" the same me- 



\oj,. XXV. Jan. 1810. E tut 



