226 Mr. Chenevix’s Analysis of 
the liquor becomes red, but still gives a blackish green precipi- 
tate ; but, if it is boiled with nitric acid, it then is converted into 
a red liquor, which yields a red precipitate, by all the alkalis and 
earths capable of causing a precipitation. From these observa- 
tions, upon the different combinations of iron with oxygen, 
and of oxide of iron with muriatic acid, some conclusions may 
be drawn, interesting to mineralogy as well as to chymistry. 
The variety of colour in many stones in which iron has 
been found, is a fact which, although we cannot deny our as- 
sent to direct experiments, has never been accounted for in a 
satisfactory manner. In white, green, yellow, black, red, in a 
word, in fossils of every colour, iron, with sometimes the help of 
manganese, and lately of chromium, has been regarded as the 
colouring matter of every shade; but it seems almost para- 
doxical, that the same substance should assume and communi- 
cate so many tints. In mica, kaolin, amianthus, asbestos, rock 
crystal, and all white stones, I believe it to exist as the white 
oxide ; and that state is its first degree of combination with 
oxygen. In them, this metal is not very abundant ; for, if it were, 
I have some reason (as shall be proved immediately) to think, 
that they would obey the loadstone strongly. In lapis ollaris, 
serpentines, and many green stones, we have the green oxide; 
and most of these are magnetic ; nay, as Mr. Humboldt 
has observed, serpentines enjoy the property of polarity. And 
thence I conclude, that the rarity of this metal, in the first class, 
prevents them from participating that quality. This, I believe, 
to be its second stage of combination with oxygen. In the 
state of black oxide, it is frequently found, and is too well 
known to need further comment. I believe this to be its third 
stage of oxidation. But there is a red liquid muriate, which gives 
