ghter while
cooling, and yellowish when cold. In the presence of a very small
quantity of iron, the bead appears colorless when cold. If the iron is
increased, the bead is opaque while cooling, and of a dirty
dark-yellow color when cold. In the reduction flame, and fused upon
platinum wire, the bead appears dark green (FeO + Fe^{2}O^{3}). By the
addition of some tin, and fused upon charcoal, the bead appears
bluish-green, or not unlike that of sulphate of iron.

Microcosmic salt dissolves the oxides of iron in the oxidation flame
to a clear bead, which, by the addition of a considerable quantity of
iron, becomes of an orange color while hot, but gets lighter while
cooling, presenting finally a greenish hue, and gradually becoming
lighter, till, when cold, it is colorless. If the iron is increased,
the hot bead presents a dark red color, but while cooling a
brownish-red, which changes to a dirty-green, and, when cold, to a
brownish-red color. The decrease of the color during the transition
from the hot to the cold state is still greater in the bead formed by
the microcosmic salt.

In the reduction flame no change is visible if the quantity of iron be
small. By the addition of more iron, the hot bead appears red, and
while cooling, changes to yellow, then green, and, when cold, is of a
dull red. By fusing the bead on charcoal with a small addition of tin,
it exhibits, while cooling, a bluish-green color, but, when cold, is
colorless.

The oxides of iron are not dissolved in the oxidation flame by fusion
with carbonate of soda. By ignition with soda upon charcoal in the
reduction flame, they are absorbed and reduced to the metallic state.
Cut out this portion of the charcoal; grind it with the addition of
some water in an agate mortar, for the purpose of washing off the
carbon particles, when the iron will remain as a grey magnetic powder.

(_b._) _Cobalt_ (Co) occurs in combination with arsenic and sulphur,
and associated with nickel and iron. It is found occasionally in
combination with selenium, and there are a traces of it in meteoric
iron. In the metallic state it is of a light, reddish-grey color,
rather brittle, and only fusible at a strong white heat; at common
temperatures it is unalterable by air or water. At a red heat, it
oxidizes slowly and decomposes water; at a white heat it burns with a
red flame. Cobalt is soluble in dilute sulphuric or hydrochloric acid
by the aid of heat, whereby hydrogen is elimina