Microcosmic Salt Beads in oxidizing Flame 76

VI. Colors of Microcosmic Salt Beads in reducing Flame 77

[Illustration: THE BLOWPIPE Fig. 1]

[Illustration: BUNSEN BURNER Fig. 2]

[Illustration: CHARCOAL BORERS Fig. 3]

[Illustration: AGATE MORTAR & PESTLE Fig. 4]

[Illustration: FORCEPS Fig. 5]

[Illustration: HAMMER Fig. 6]

[Illustration: 3-CORNERED FILES Fig. 7]

BLOWPIPE ANALYSIS

CHAPTER I

The blowpipe was first applied to mineral analysis in 1733 by Anton
Swab, and its applications have since been improved and extended by
various chemists, among whom may be mentioned Bergmann, Cronstedt, Gahn,
Berzelius, and Plattner.

~Blowpipe.~--The common blowpipe of the jeweller is not particularly well
suited to the operations of blowpipe analysis, since the flame has often
to be kept playing upon the assay for some time, and the condensed
moisture of the breath would seriously interfere with the passage of
the air through the jet. One of the best and least expensive forms of
blowpipe is shown in Fig. 1. This consists, as is seen from the
illustration, of a conical-shaped tube of tin closed at the wide end and
formed into a mouthpiece at the small end; soldered into the tube at the
large end, and at right angles to its axis, is a small brass tube which
terminates in a conical tip pierced with a very fine hole. With this
pipe it is possible to perform all of the operations of mineral
analysis.

Some little practice is necessary to keep the flame steady and to take
the breath at the same time.

No rule can well be given to the beginner, but his experience becomes
his best guide.

~Bunsen Flame.~--Any kind of flame can be used for the blowpipe, provided
it be not too small; but since almost every laboratory to-day is
furnished with gas and the Bunsen burner (Fig. 2), it will only be
necessary to describe the use of the flame from this source. Upon
examining the Bunsen flame with care, it will be seen that the flame
consists of three distinct parts.

A dark inner cone which consists of gas not yet raised to the ignition
point. Beyond this there is a luminous cone, where combustion is
incomplete owing to lack of oxygen, and outside of this we find the
non-luminous cone where the gas is completely burned.

This outer envelope is the hottest portion of the flame, and is known as
the "oxidizing" flame because there is an excess of oxygen which is
imparted to substances pla