ced therein.

The luminous cone is known as the "reducing" flame, for in it metallic
oxides are reduced, the oxygen being taken up by the small incandescent
particles of carbon.

If the air-holes at the base of the Bunsen burner be opened, the two
inner cones become elongated, and the flame appears almost colorless.

The blowpipe enables us to get an oxidizing and a reducing flame of
better form and greater power. To do this we cut off the air supply at
the base of the burner and turn off the gas until the flame is about 1
cm. high; then upon introducing the blowpipe, and blowing a strong
continuous jet of air across the Bunsen flame, we produce an oxidizing
flame about 4-5 cm. in length. If the tip of the blowpipe be held
outside of the Bunsen flame, and the pressure of the stream of air be
diminished, we obtain a reducing flame.

~Supports.~--For supports, charcoal, platinum, and glass are chiefly used.
The charcoal should be made from some light wood, such as alder. It
should be well burnt, and should not scintillate or smoke.

The platinum supports are generally in the form of wire and foil.
Platinum-tipped forceps are frequently employed in blowpipe analysis.

Glass is used in the form of tubing.

Hard glass tubing, 3 mm. bore, is drawn off into ignition tubes 7-8 cm.
in length. Several dozen of these tubes should be made before commencing
the tests of the next chapter.

~Apparatus.~--A small agate mortar, 4-5 cm. in diameter, should be
provided in which to grind the samples to be examined.

The pestle, which should also be of agate, must be adapted to the
mortar in shape and size.

Two pairs of forceps will also be needed.

One pair should be of steel, and the other pair of brass, with fine
points.

Of other apparatus, the most necessary is:--

A small hammer and anvil.

Two three-cornered files.

Small piece of cobalt glass, about 5 x 10 cm.

Pocket magnifying lens.

Several small watch glasses--for metallic beads, etc.

~Chemicals.~--A list of the principal chemicals is here given:--

Sodium carbonate, Na_{2}CO_{3}.

Borax, Na_{2}B_{4}O_{7} + 10 H_{2}O.

Microcosmic salt, (HNaNH_{4}), PO_{4} + 8 H_{2}O.

Cobalt nitrate, Co(NO_{3})_{2} + 5 H_{2}O.

Potassium cyanide, KCN.

Hydrochloric acid, (dilute), HCl + nH_{2}O.

Litmus paper, red and blue.

Brazil-wood paper.

Any other special reagents which may be needed will be me