344 Transactions.—Chemistry. 
In the second case, that of silver, we have its direct oxidation by the 
free oxygen present, and the reaction of these oxides thus formed upon the 
salt in its vicinity, argentic chloride and caustic potash resulting, to which 
last compound, of course, that alkalinity is induced which we observe. 
In the case of zinc it may be that the reactions which result in this 
alkalinity of the saline liquid surrounding it may not be so simple as I here 
suppose, further investigations seem indeed requisite ere we can fully 
explain them ; but still the results I have described, and several others I 
could cite of an analagous nature to these, certainly tend to show that the 
conception of metallic ‘replacement,’ as given in this paper of Professor 
Gladstone, is as yet scarcely a tenable one, or at least that it requires for 
adequate support considerably more evidence than has yet been tendered in 
its behalf. 
With regard now to the next statement I have to remark upon, viz., that 
‘Mercury and gold in conjunction would decompose mercuric chloride 
with deposition not only of lower chloride, but also of metallic mercury,” I 
think it very possible that floating dust or other impurities, or even light 
had in some way interfered with what should be the legitimate result of the 
experiment described. In support of this view I found that mercury, 
which, for greatest purity, I electro-deposited from its potassic-cyanide 
upon platinum, when not in presence of mercuric-chloride, and kept in the 
dark away from dust, gave a deposit upon gold of mercurous-chloride only. 
I may state that the detection of either mercurous-chloride or mercury here 
appears to me much facilitated if platinum be used in place of gold for the 
receiving plate, as this metal has its lustre greatly dimmed by even traces 
of adherent chloride, and any mercury present is easily rubbed off upon an 
angle of gold, and thus readily identified. Using this modification of 
Professor Gladstone’s apparatus, I was only able to get, even in sixteen 
hours, a deposit of mercurous-chloride of sufficient thickness to perceptibly 
impair the lustre of the platinum upon which it formed; its presence, in 
fact, could not be certainly detected except by the slight ka of this 
platinum in caustic potash. By the addition of pure hydrochloric acid, 
however, to the mercuric-chloride, thicker deposits of this kind were 
obtained, but none of mercury. 
The deposit of this mercurous salt, however, even alone, under the cir- 
cumstances as found and described by these investigators, appears to 
me a very suggestive phenomenon, because, upon first sight, it appears 
inexplicable. I can only attribute the formation of this deposit to the 
action of a free acid or acids upon the mercury ; a minute quantity of nitric 
or nitrous compounds dissolved in the saline solution used (taken from the 
air, etc.) would be competent to thus act upon mercury to the extent 
