Parr Instrument Series 3900 - Manual (Page 9)

Hydrogenation Apparatus
w w w . p a r r i n s t . c o m 9
air. If breakage or spills occur, fl ush the contami-
nated area immediately with large volumes of water
and keep the area wet until all traces of catalyst
have been removed.
Vacuum fi ltration through a paper fi lter can be
dangerous if air is drawn through the fi lter in the
presence of a catalyst. To reduce this hazard, keep
the paper covered with solution while it is under
suction, or use a fi lter made of a non-fl ammable
material.
Care must be taken to keep the apparatus free of im-
purities which might poison the catalyst. Although
a small amount of air trapped in the bottle will not
interfere with most hydrogenations, the reaction
rate can sometimes be improved by evacuating the
bottle before adding hydrogen. Or the air can be
removed by fi lling the bottle with hydrogen to 20
or 30 psig and venting it at least three times before
starting the shaker.
If the reaction proceeds too rapidly it can usually
be checked by stopping the shaker. If overheating
becomes a dangerous problem, the bottle can be
cooled by using the A103CA water jacket described
below.
There should be no gas burners or open fl ames near
a hydrogenation apparatus. The room must be well
ventilated and any gas released from the apparatus
should be discharged into an explosion proof hood
or ventilating duct. Care must be taken to prevent
ignition by a static charge from an insulated object.
For this reason, a good ground connection through
the power cord or directly to the base of the appara-
tus must be maintained at all times.
Loss of gas is an annoying factor which can be
avoided by careful maintenance and frequent test-
ing. It should not be necessary to use extreme force
to close any of the valves on this apparatus. If a
tight seal cannot be secured without a hard turn on
the valve handle, dismantle the valve and replace
the 20VB valve seat and any other worn or damaged
parts. If the valve leaks through the packing, back
the needle away from its seat and tighten the 8VB2
packing nut. If this does not stop the leak replace the
4VB3 packing rings.
Catalysts
The most active catalysts for hydrogenation reac-
tions in this apparatus are made of platinum and
palladium. A hydrated platinum oxide, often called
Adams catalyst, is used in many procedures. This
is prepared by drying and heating chloroplatinic
acid in air to form a brown oxide which can then be
reduced to the more active black form by shaking
with hydrogen either before or after mixing with the
sample. Instructions for preparing this and other
catalysts are given in the references on page 15.
Raney nickel is used in certain procedures but other
less active nickel catalysts require pressures outside
the range of this apparatus. Platinum oxide and
other catalytic chemicals can be obtained from most
laboratory supply houses.
Bottle Heater
Bottle temperatures up to 80 ° C can be developed
in the 3911 Hydrogenator by wrapping a glass fabric
heating mantle (A450E) around the 500 mL bottle.
The mantle then takes the place of the perforated
metal guard screen. No special fi ttings are needed
for attaching this heater. Simply wrap the mantle
tightly around the bottle and run the connecting
cord through the slot in the bottle clamp. Use the
plastic cable clip (453E) furnished with the heater
to anchor the heater cord to the top of the bottle
clamp, then run the cord out from the shaker pivot,
arranging it for minimum fl exing when the shaker is
operating.
Water Jacket
The 500 mL reaction bottle can be
cooled while it is clamped in the
shaker mechanism by installing an
A103CA water jacket. This jacket fi ts
into the bottle clamp in place of the
65CA perforated steel guard. A soft
rubber ring seals the neck of the
bottle into the jacket. The only change
required when adding a water jacket
is to use the special cut-down stop-
per which is furnished, or cut 1/4 inch
from the top of the regular 62CA stopper to shorten
the overall height of the combined assembly. Al-
ways install the soft rubber sealing ring with the
large diameter downward and the smaller diameter
at the top: otherwise it will be very diffi cult to re-
move the bottle from the cooling jacket.
A103CA
Water Jacket