j6 Mr, kir wan’s Experiments and Ob/ervatiom on 
I have always found filver to be eafily precipitated from its 
foliation in the nitrous acid by iron. The fum of the quiefcent 
affinities being 625, and that of the divellent 746 ; yet Miv. 
bergman oblcrvedj that a very faturate foliation of filver was 
very difficultly precipitated, and only by fome forts of iron, 
even though the folution was diluted, and an excefs of acid 
added to it * ; the reafon of this curious phenomenon appears to 
me deducible from a circumftance fir ft obferved by Mr. scheele, 
in difl'olving mercury, namely, that the nitrous acid, when 
iaturUted with it, will take up more of it in its metallic 
form f- The fame thing happens in diflolving filver in the 
nitrous acid in a ftrong heat ; for, as I before remarked, the 
laft portions of filver thrown in afford no air, and confequently 
are not dephlogifticated. Now this compound of calx of 
filver, and filver in its metallic form, may well be unprecipitable 
by iron, the filver, in its metallic form, preventing the calx 
from coming in contact with the iron, and extrafling phlo- 
gifton from it : and hence alfo, iron has fometimes been ob- 
ferved not to precipitate a folution of mercury in this acid J. 
It has been long thought, that iron may be precipitated from 
acids by zinc, though newman long ago denied it; but Mr. 
bergman has fatisfaflorily cleared up this point, by fihewing 
that zinc cannot precipitate iron from the vitriolic acid, until 
the folution of iron lofes part of its phiogifton. With regard 
to the nitrous acid, I found, that zinc does not precipitate iron ; 
but, on the contrary, iron precipitates zinc ; but in a fhort 
time the acid re-diflblves the zinc, and lets fall the iron, which 
evidently proceeds from the too great dephlogiftication of the 
calx of iron. But zinc precipitates iron from the marine, 
* Diflert. de Phlog. Quantitate in Metal, p. 6. 
f 39 suensk. Handling, p. 70. 
♦ 2 Crell. Nev. Entdeck. p. 266. 
thnmrh 
