ot dissolve much by
fusion with carbonate of soda. If this fusion is effected on charcoal,
the carbonate of soda is absorbed and the lime remains as a
half-globular infusible mass on the charcoal. This is what
distinguishes lime from baryta and strontia, and is a good method of
separating the former from the latter. Lime and its compounds fuse
with borax in the oxidizing and reducing flames to a clear bead, which
remains clear when cold, but when overcharged with an excess or heated
intermittingly, the bead appears, when cold, crystalline and uneven,
and is not so milk-white as the bead of baryta or strontia, produced
under the same circumstances. The carbonate of lime is dissolved with
a peculiar hissing noise. Microcosmic salt dissolves a large quantity
of lime into a clear bead, which is milky when cold. When the bead has
been overcharged with lime, by a less excess, or by an intermittent
flame, we will perceive in the bead, when cold, fine crystals in the
form of needles. Lime and its compounds form by ignition with nitrate
of cobalt, a black or greyish-black infusible mass.

(_d._) _Magnesia_ (MgO).--Magnesia occurs in nature in several
minerals. It exists in considerable quantity combined with carbonic,
sulphuric, phosphoric, and silicic acids, etc. Magnesia and its
hydrate are white and very voluminous, scarcely soluble in hot or cold
water, and restores moistened red litmus paper to its original blue
color. Magnesia and its hydrate are infusible, the latter losing its
water by ignition. The carbonate of magnesia is infusible, loses its
carbonic acid at a red heat, and shrinks a little. It now exerts upon
red litmus paper an alkaline reaction. The sulphate of magnesia, at a
red heat, loses its water and sulphuric acid, is entirely infusible,
and gives now an alkaline reaction. The artificial Astrachanit (NaO,
SO^{3} + MgO, SO^{3} + 4HO) fuses easily. When fused on charcoal, the
greater part of the sulphate of soda is absorbed, and there remains an
infusible mass.

Magnesia and its compounds do not produce any color in the external
flame, when heated in the point of the blue flame. The most of the
magnesia minerals yield some water when heated in a glass tube closed
at one end.

Magnesia, in the pure state, or as the hydrate, does not fuse with
soda. Some of its compounds are infusible likewise with soda, and
swell up slightly, while others of them melt with soda to a slightly
opaque mass. Some few (such as th