Hoefer PR648 - Manual (Page 6)

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p4
5
Carefully set the top block, with letters and numbers
facing up, on top of the membrane support block.
6
Insert the screw into the threaded holes. Tighten
the screws until the knobs just touch the surface of
the block.
7
Hand-tighten each screw only a small amount, following
the sequence shown in Fig 2. Repeat the sequence
one or two times until all screws are snug.
8
Attach the slot blot to a small vacuum pump with
adjustable vacuum and a vacuum gauge. If an adjust-
able vacuum pump is not available, use a water aspi-
rator or a house vacuum and place a bleed valve and
vacuum gauge in the vacuum line.
9
To keep liquids from being sucked into the vacuum
source, set up a liquid trap between the slot blot and
the vacuum source as shown in Fig 3:
a. Use a side arm vacuum flask and a stopper with a
small hole.
b. Insert a glass tube through the stopper hole.
Position the tube so that it extends below the flask
sidearm when the stopper is in place.
c. Stopper the flask. Use a length of rubber tubing
to connect the glass tube in the stopper to the
connector on the Hoefer PR648.
d. Use a second length of tubing to connect the side-
arm of the flask to the intake port of the vacuum
pump or to the vacuum line.
Note: Do not over-tighten.
Over-tightening causes leaks.
Fig 2. Correct order for tightening
the screws.
Fig 3. Correct set-up of the
liquid trap.