(c) Triple point temperature: The 0.01C reference temperature is
established as soon as the inner melt frees the ice mantle from the
thermometer well. The triple point temperature is maintained until the
bottom of the ice mantle melts. This is evidenced by flotation of the
mantle, readily observable with the cover off.
(3) ALTERNATE METHODS OF FREEZING. A number of alternate methods
of freezing the ice mantle can be suggested, using such materials as liquid
nitrogen, a pre-cooled slurry of ice and salt, gases such as ammonia or CO2
discharged from a pressure source through a length of tubing in the thermometer
well, or a flow of alcohol cooled by dry ice.
(4) PRESERVING THE ICE MANTLE. The ice mantle can be kept for several
hours with the glass cell in its normal position in the insulating jacket.
If the ice mantle is to be preserved for a day or longer, the glass cell may be removed
from the jacket and packed in ice inside a wide-mouth Dewar flask. Water forming from
melting ice in the Dewar flask must be removed periodically.
An alternate method (preferred where convenient) is to leave the glass cell, with mantle,
in its insulated jacket and pack the entire Equiphase Cell, including cover, in ice inside a