of manganese with borax, upon a platinum wire, in the oxidation flame,
when a violet-red glass will be obtained; or if too much of the oxide
be used, a glass of a dark color and opaque will be obtained. By
submitting this glass to the reduction flame, it will become colorless
in correspondence to the perfection with which the flame is produced.
Or a piece of tin may be fused upon charcoal, and kept in that state
for a considerable time, while it presents the appearance of a bright
metal on the surface. This will require dexterity in the operator;
for, if the oxidation flame should chance to touch the bright metal
only for a moment, it is coated with an infusible oxide.


COMBUSTION.--Any flame of sufficient size can be used for blowpipe
operations. It may be either the flame of a candle of tallow or wax,
or the flame of a lamp. The flame of a wax candle, or of an oil lamp
is most generally used. Sometimes a lamp is used filled with a
solution of spirits of turpentine in strong alcohol. If a candle is
used, it is well to cut the wick off short, and to bend the wick a
little toward the substance experimented upon. But candles are not the
best for blowpipe operations, as the radiant heat, reflecting from the
substance upon the wax or tallow, will cause it to melt and run down
the side of the candle; while again, candles do not give heat enough.
The lamp is much the most desirable. The subjoined figure, from
Berzelius, is perhaps the best form of lamp. It is made of japanned
tin-plate, about four inches in length, and has the form and
arrangement represented in Fig. 5. K is the lamp, fastened on the
stand, S, by a screw, C, and is movable upwards or downwards, as
represented in the figure. The posterior end of the lamp may be about
one inch square, and at its anterior end, E, about three-quarters of
an inch square. The under side of this box may be round, as seen in