the Attradlwe Powers of Mineral Acids. 75 
and alfo from the neceflity of adding more acid to a turbid 
folution of iron, in order to re-effablifh its tranfparency. The 
calces of copper alfo precipitate a dephlogifficated folution of 
iron, as they fhould, the affinity of the acid to fuch calx of 
iron being 240, and that to copper being 260. With regard to 
the folution of iron in nitrous acid, the fame thing happens ; 
but as this folution contains a large excefs of acid, a portion of 
copper is diffolved even before any of the iron is precipitated. 
With regard to a folution of iron in the marine acid, though 
expofed to the open air, copper precipitates nothing from it in 
24 hours. 
But if a clean piece of iron be put into a folution of copper 
in the vitriolic acid, the copper is immediately precipitated ; for 
here the quiefcent and divellent affinities exhibited in the firfl 
fcheme arc reverfed, the quiefcent becoming the divellent, and 
vice verfd . It is needlefs to add, that copper is in the fame 
manner precipitated by iron from the nitrous and marine acids. 
Hence the praCfice of extracting copper from fome mineral 
waters by means of iron. Thefe waters, therefore, furnifh 
afterwards, by evaporation, vitriol of iron ; but it is remarka- 
ble, that this vitriol is much paler than the common, and lefs 
fit for dying, 2 schlutter 507. The reafon of which is, 
that it is more dephlogifficated, not only becaufe old iron is 
chiefly ufed, but becaufe copper, containing more phlogiffon 
than an equal weight of iron, deprives it of more of its phlo- 
giffon than it would lofe if barely diffolved in the vitriolic 
acid. 
Caff iron, according to schlutter, will fcarcely precipi- 
tate a folution of copper; and in effeCt Mr. bergman has 
found that it contains lefs phlogiffon than bar iron. 
L 2 
I have 
