For example, with oxide of cobalt, the following reactions take place
with the two fluxes:--

CoO + Na_{2}B_{4}O_{7} = Co(BO_{2})_{2} + 2 NaBO_{2}.

On heating, NaNH_{4}H. PO_{4}, it is decomposed into the metaphosphate
of sodium, NaPO_{3},

CoO + NaPO_{3} = CoNaPO_{4}.

Now in such cases of solution the metallic oxides impart a
characteristic color to the flux.

The platinum wire is the best support,--it is heated to incandescence in
the Bunsen flame, and then is quickly dipped into the borax, when a
small globule will adhere,--this is removed to the flame again when the
borax melts to a clear glassy bead. While the bead is still melted,
touch it to the finely pulverized substance and replace in the flame.
In a few seconds the small particles of the substance will have
dissolved, and the bead will be seen to have assumed the color
characteristic of the substance. Note the color when hot and then when
cold; often there is a wide difference. Then, too, the test should be
made in both O. F. and R. F.

Some analysts prefer to make a small loop in the end of the wire before
taking up the borax to make the bead. Care should be taken to see that
the bead is colorless before bringing it in contact with the substance.

As the depth of color produced is largely dependent upon the amount of
substance taken, some little caution should be exercised to insure
taking up about the same quantity each time.

_Illustrations._ Make several beads, and note the colors characteristic
of the following oxides: cobalt, nickel, iron, manganese, chromium, and
copper.

The microcosmic salt bead dissolves almost every oxide except silica,
SiO_{2}, and this is seen to float about in the melted mass. This is
used as a test for silica.

~Examination with Co(NO_{3})_{2}.~--If after examination on the Ch. _per
se_, a white infusible residue remains, it is moistened with a drop of
cobalt nitrate Co(NO_{3})_{2} and re-ignited before the Bp., when a
change of color will be observed. This change in color is owing to the
fact that the heat of the Bp. flame decomposes the cobalt nitrate,
nitric acid being driven off, and the remaining CoO forming with the
oxide of the residue a colored mass.

_Illustrations._ Ignite before the Bp. on Ch. the following
oxides,--allow to cool, add a drop of Co(NO_{3})_{2}, re-ignite, and
note color,--aluminum, magnesium, zinc, and calcium.

Care should be taken to thoroughly ignite before adding the c