INACTION OF AMALGAMATED ZINC. 237 



buted this effect to the reduction of a film of oxide of mercury 

 by the nascent hydrogen, but on touching the negative elec- 

 trode thus amalgamated with the positive one, the latter also 

 became frequently amalgamated. After several experiments 

 I found that mercury which had acted in acidulated water as 

 negative electrode of a voltaic battery possessed the property 

 of amalgamating platinum and iron, and that strips of plati- 

 num, iron, and even steel, which had served as negative elec- 

 trodes, were instantly and perfectly amalgamated by immersion 

 in pure mercury. 



Having cleansed from acid particles several portions of 

 mercury which had been used as negative electrodes, I found 

 that they invariably gave an alkaline reaction, and it now 

 became evident that the increased power of amalgamation 

 proceeded from the mercury being alloyed with an alkaline 

 metal. Remembering the highly electro-positive state of 

 mercury which contains the slightest traces of an alkaline 

 metal, a property first noticed by Sir Humphry Davy, it oc- 

 curred to me that the inaction of amalgamated zinc was the 

 effect of polarisation,* but of one which differed from ordinary 

 cases of polarisation, in that the cations of the electrolyte 

 instead of being . precipitated on the surface of the negative 

 metal, combine with it and render it so completely positive 

 that the current is nullified, and not merely reduced in inten- 

 sity as in other cases. To verify this idea I made the following 

 experiments : 



1. I amalgamated half the surface of a strip of copper, and 

 immersed it and a strip of zinc in water, acidulated with 

 sulphuric or phosphoric acid ; on making the plates touch 

 there was a rapid evolution of gas from the unamalgamated 

 part of the copper, while only a few detached bubbles appeared 

 on the amalgamated portion. 



2. I placed a large globule of mercury (about half an 

 ounce) in the bottom of a glass of acidulated water, and by 

 means of a copper wire, the whole surface of which was 

 amalgamated, made it communicate with one extremity of a 



* I know of no other word to express the effect here alluded to ; the word is 

 used in this sense by most French writers, but, from its numerous applications, is 

 sadly inaccurate. 



