ed by
solutions containing both silver and ammonia may have explosive
properties, especially when dry.

CHAPTER V

Extemporised Glass-Blowing Apparatus--The Use of Oil or
other Fuels--Making Small Rods and Tubes from Glass
Scrap--The Examination of Manufactured Apparatus with the
View to Discovering the Methods Used in Manufacture--Summary
of Conditions Necessary for Successful Glass-Blowing.

If, in the early stages of his study of glass-blowing, the student
should attempt to work with the very simplest appliances, it is probable
that his progress will be hindered; the use of the apparatus will
require an undue amount of care and his attention will be distracted
from the actual manipulation of the glass. The case is widely different
after he has acquired a certain facility in glass-blowing.

_A Simple Form of Blowpipe._--Although there are even more simple forms
than that described here, we are not concerned with them. The form
described is the simplest with which any considerable amount of
glass-blowing can be carried out with certainty.

This form consists of a tube through which air may be blown with the
mouth, a condensation chamber in which any moisture from the breath can
condense, a blowpipe jet, a supporting piece and a source of flame.

The tube, condensation chamber, and jet are combined in the ordinary
Black's blowpipe, such as is used for blowpipe tests in qualitative
analysis; it consists of a conical tin tube having a mouthpiece at the
small end and a side tube which carries a brass jet. A support for such
a blowpipe may be cut out of a piece of brass or tin-plate, and should
be fastened to a small, flat, wooden board. A source of flame may
consist of an ordinary brass elbow, such as is used on gas fittings, and
into which a piece of thin brass tube (the body of a fish-tail burner
from which the perforated non-metallic plug has been removed will serve
quite well) has been fitted. It is an advantage to flatten the brass
tube somewhat and to file the flattened end to a slope which corresponds
with the angle at which the blowpipe jet enters the burner. The whole
source of the flame should be mounted on a separate base, in order that
it may be moved while adjusting the apparatus to the best relative
positions of flame and blowpipe jet. The complete apparatus is shown by
_a_, Fig. 16.

[Illustration: Fig. 16]

In order to take full advantage of this blowpipe, it is de