the Attractive Pouters of Mineral Acids. ^9 
precipitate appears ; for this precipitate (till retains the marine 
acid : on the contrary, lead precipitates iron from this acid, 
though very (lowly. 
Of precipitations of and by mercury . 
Though the difference betwixt the quiefcent and divellent 
powers be very fmall, yet mercury is quickly precipitated from 
the vitriolic acid by copper ; becaufe the attraction of the calx 
of mercury to phlogifton is very ftrong, and a very fmall pro- 
portion of that contained in copper is fufficient to revive it. 
Silver does not precipitate mercury from the vitriolic acid, 
unlefs it contains copper, and then it does precipitate it; yet if 
(liver and turpeth mineral be diddled, the mercury will pafs in 
its metallic form, wenzel 42. ; which ("hews that the affinity of 
calx of mercury to phlogifton is increafed by heat. The difference 
betwixt the quiefcent and divellent powers is indeed very (mail. 
Silver appeared to me to precipitate mercury from the nitrous 
acid, though very (lowly, when the folution of mercury was 
made wfth heat, and not over faturated ; but when the folu- 
tion of mercury was made without heat, it was not at all pre- 
cipitated. O11 the other hand, mercury precipitates filver from 
this acid, not by virtue of the fuperioritv of the ufual divellent 
powers, but by reafon of the attraction of mercury and (liver 
to each other, for they form partly an amalgama and partly 
vegetate, and fcarce any of either remains in the folution. 
The fame thing happens, that is, they vegetate, if folutions of 
both metals in the fame acid be mixed together. 
Silver does not precipitate mercury from the folution of 
fuhlimate corrof ve ; but, on the contrary, mercury precipi- 
tates fiver from the marine acid : and if a folution of horn 
fiver in volatile alkali be triturated with mercury, the fiver 
will 
