Through the center of the lid passes
the tube, g h, by which the water enters. In the interior of the vessel
upon iron hooks stands a wooden vessel saturated with paraffine, open at
the ends, and over one end of which the finest hair cloth is stretched
at o p. The water which enters the vessel runs off through the siphon.
The proceedings are as follows: Turn the granulated gelatine and the
water in which it is contained into the horsehair sieve, m n o p. Place
the lid upon the apparatus and turn on the water. The whole apparatus
fills with water until the siphon begins to act. If the diameter of
the siphon be properly measured--one inch should be sufficient for the
largest apparatus--and the cock by which the water is turned on properly
adjusted, more water will run out by the siphon than runs in through the
supply pipe, and the apparatus becomes completely empty.
The siphon has then performed its function, the apparatus fills again,
and the play begins anew. The tube, g h, which reaches right down nearly
to the bottom of the sieve, takes the water so deep into the vessel
that, as long as the water in the apparatus stands high enough above o
p, the gelatine nodules are in continuous motion. In order to prevent
the finest particles of the emulsion from stopping up the pores of the
sieve too much, and thereby incurring the danger of the water in the
sieve overflowing its upper edge, thus occasioning loss of emulsion,
the tube, g h, is now sometimes omitted and replaced by a supply pipe,
represented in the diagram by the dotted lines, x y.
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