82 Mr. Grove on the Inaction of 



circumstance to which I alhide, and which has in all proba- 

 biUty been observed by many others, was this: in decom- 

 posing by a voltaic battery, water acidulated with sulphuric 

 acid, there happened to be a few globules of mercury at the 

 bottom of the operating cell, or glass containing the electrodes 

 of platinum. I remarked that whenever the negative electrode 

 touched the mercury it became amalgamated : at first I attri- 

 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 ne- 

 gative electrode of a voltaic battery, possessed the property of 

 amalgamating platinum and iron, and that strips of platinum, 

 iron, and even steel, which had served as negative electrodes, 

 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 be- 

 came evident that the increased power of amalgamation pro- 

 ceeded 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 polarization*, but of one which differed from ordi- 

 nary cases of polarization, in that the cations of the electrolyte 

 instead of being preci})itated 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 follow- 

 ing experiments. 



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

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

 of 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 ap- 

 peared 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 galvanometer, 



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

 word is used in tills sense l)y most French writers, but, from its numerous 

 npplications, is sadly inaccurate. 



