While the use of CO2 as a refrigerant is specified on the nameplate, alternate methods
may be used. The actual method or refrigerant used makes no difference whatsoever as
far as the actual triple point temperature is concerned so long as the criteria given below
are carefully observed.
(1) FREEZING THE ICE MANTLE.
(a) Drain the thermometer well. (See figure 5) To do this, first remove the
insulating cover from the Equiphase Cell. Grasp the cover with both hands
and lift straight up to clear the inner glass cell. Then grasp the jacket with
both hands and slowly invert, leaving the glass cell in its normal position
in the jacket. Be certain that no water remains in the well. If there is any
doubt, pour 2 to 3 cc of alcohol into the well, then invert and pour out the
alcohol. The precaution against water is necessary because water in the
well freezes and slows the freezing of the mantle. The result is an uneven
mantle which will not last as long as a uniform mantle.