ll tubing through this cork, and attach the flanged
piece of small tube to this by means of a short piece of rubber tubing,
so that when the whole is inserted in the large tube it is arranged as
in _a_, Fig. 11. The piece of glass tubing projecting out through the
cork is now cut off so as to leave an end about 1/2 inch long when the
cork is firmly seated and the inner tube pushed into contact with the
center of the end of the large tube, as shown in the drawing. Care
should be taken that the little rubber tube which joins the two pieces
is arranged as in the figure; _i.e._, most of it on the piece of tubing
which passes through the cork, and very little on the other piece, so
that when the cork is removed after the small tube has been sealed
through the large one, the rubber tube may easily come with it. Select a
short piece of the small tubing of suitable length for the piece which
is to be on the outside of the large tube as a continuation of the
piece inside, and another piece for the delivery tube. A small bulb may
be blown in the latter at a point about 2-1/2 inches from the closed
end, and the open end cut off about 1-1/2 inches from the bulb. A cork
or cork-boring of suitable size to stopper the small tube is prepared,
and laid ready with the other (unbored) cork for the large tube.

[Illustration: FIG. 11.--Gas-washing tube.]

When everything is in readiness, the rounded end of the large tube is
slowly heated until it softens and joins firmly to the small tube
inside. After it has shrunk down well, it is blown out to its original
size, placing the whole end of the large tube, cork and all, in the
mouth. Now with a fine-pointed flame the glass covering the end of the
small tube is heated to the softening temperature, and then is blown out
to an excrescence by blowing on the end of the small tube which passes
through the cork. The end of this excrescence is heated and blown off in
the usual way, so as to leave the small tube sealed on the inside of the
large one and opening through it into this short tube which has been
blown out. The end of the small tube which passes through the cork is
now closed with the cork prepared for it, and the short outer tube is
joined to the tube that has just been blown out, so that the joint
appears like _b_, Fig. 11. Use the first method (Exercise No. 1) for
this joint. Reheat the whole of the end of the tube nearly to the
softening temperature, anneal it a little, and allow to co