Na_{2}SO_{4} }
CuCO_{3} = CuO + CO_{2} } (2)
CuO + KCN = Cu + KCNO }

After obtaining beads, it is well to obtain their coatings, for
oftentimes it is only in this way that we can distinguish between the
metals.

~Examination in Tube with Na_{2}CO_{3} and Charcoal.~--If the substance in
a finely pulverized condition be mixed with twelve parts, Na_{2}CO_{3},
and six parts of charcoal powder and the mixture be placed in an
ignition tube and subjected to heat, the acid of the substance combines
with the soda and the metal is set free.

If this metal is volatile, a sublimate is formed in the upper end of the
tube.

Mercury deposits in minute globules, which may be seen with the
magnifying glass. Arsenic forms a ring, which, when examined with the
magnifying glass, is seen to be made up of minute crystals. Ammonia is
recognized by its characteristic odor, and also by its turning a slip
of moistened red litmus (held over the mouth of the tube) blue.

~Examination on Platinum Wire.~--Many substances possess the property of
imparting to the colorless flame of the Bunsen burner characteristic
colors.

The chlorides of these substances exhibit these flame reactions best,
and hence before applying the flame tests we dip the wire which serves
as a support into hydrochloric acid and then into the substance. When
the substance has been taken up on the wire, it is placed in the edge of
the long colorless flame of the Bunsen burner near the apex, when
instantly the flame becomes tinged with the characteristic color of the
substance.

_Illustrations._ Sodium compounds color the flame yellow, and a crystal
of potassium dichromate appears colorless in the sodium light.

This sodium reaction is extremely delicate, it being possible to detect
with ease a quantity of a sodium salt less than 1/3000000 of a milligram
in weight.

Potassium colors the flame purplish-violet.

Barium colors the flame apple-green.

Strontium colors the flame crimson.

Calcium colors the flame orange-red, distinguished from strontium, by
appearing gray when seen through blue glass.

Boracic acid colors the flame green when the substance has been
moistened with glycerine.

~Examination in Borax Bead.~--Borax, Na_{2}B_{4}O_{7}, and microcosmic
salt,

NaNH_{4}H . PO_{4},

possess the property of dissolving many of the metallic oxides at the
temperature of the Bunsen flame.