210 An Analysis of two Mineral. 
here, again, there is a difference between this and 
the former water; for though copper is dissolv- 
ed in it, none can be precipitated on iron in its 
metallic form, as we have seen (1v. 1.). The iron 
in this water does not seem to be in that high degree 
of oxygenation that it is in the other. This I 
infer because, 3. the precipitate formed by tincture 
_of galls is of a much darker colour, even when the 
water has been much evaporated; sometimes, when 
the water has been reduced to half its original bulk, 
‘I have remarked even a very slight green tinge com- 
municated by prussiat of potash, but not till it has 
been added to it many hours. 
- As the oxygenated salts are formed by the action 
of hepatic gas on the metals, it cannot be doubted 
that they are very common. Bergman observes, 
« that cold martial waters, when fresh, almost always 
have an hepatic smell:’* it seems very probable then 
that this salt of iron may be found in almost all such 
waters. .I doubt not that it has been frequently 
mistaken for muriat of lime, to which in its proper- 
ties it approaches very nearly. 
Though I have purposely avoided all medical 
discussions in this essay, I cannot abstain from be- 
stowing a moment’s consideration on one very ob- 
vious question. _What, it will be asked, are the 
medical properties of manganese? Is it useful? 
.* Bergman, Dissertation v11, 6, 
