But
the fine thread of glass so made is really a tube, and not a rod,
as might be supposed. This can be demonstrated by blowing through
it at a gas flame, or by immersing it in colored liquid. The
solution will be seen to rise some distance within the tube, the
amount depending on the diameter of the tube.
The file is for cutting the glass tubing into lengths convenient
to handle. It should be a three-cornered file, of medium fineness,
and is used simply to nick the glass at the place it is desired to
cut it. The two thumbs are then placed beneath the tube, one on
each side of the nick, and the tube bent, as if it were plastic,
at the same time pulling the hands apart. The tube will break off
squarely at the nick, without difficulty.
The entire outfit may be purchased from any dealer in chemical or
physical apparatus, or any druggist will order it. Enough tubing
to last many days, the Bunsen burner, blowpipe, file and charcoal
should not exceed $2 in cost.
** Cadmium and Solder [421]
The addition of cadmium to soft solder composed of tin and lead,
lowers its melting point and increases its strength.
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