combine with a portion of the base equally with the phosphoric acid,
or else do not combine at all, but float about in the bead, as is the
case particularly with silicic acid. Many of the silicates give with
borax a clear bead, while they form with microcosmic salt an
opalescent one.

It frequently happens, that if a metallic oxide will not give its
peculiar color in one of the flames, that it will in the other, as the
difference in degree with which the metal is oxidized often determines
the color. If the bead is heated in the reducing flame, it is well
that it should be cooled rapidly to prevent a reoxidation. Reduction
is much facilitated by the employment of metallic tin, whereby the
protoxide or the reduced metal may be obtained in a comparatively
brief time.

The following tables, taken from Plattner and Sherer, will present the
reactions of the metallic oxides, and some of the metallic acids, in
such a clear light, that the student cannot very easily be led astray,
if he gives the least attention to them. It frequently happens that a
tabular statement of reactions will impress facts upon the memory when
long detailed descriptions will fail to do so. It is for this purpose
that we subjoin the following excellent tables.

* * * * *


TABLE I.


A. BORAX.