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Dual Furnace Models M17705, N17706 & 17707 Iss.09 – 12/14
GENERAL NOTE ON ISOTECH METAL FREEZE POINT CELLS
Isotech freeze point cells contain metal that is 99.9999+% pure, except that aluminium cells may be filled with metal
not less than 99.999% pure, depending upon the availability of aluminium in suitable physical form.
The metal is contained in crucibles of high-purity graphite. After machining the graphite, any residual metal oxides
are removed by exposure to fluorine at a very high temperature. Graphite, even of high density, cannot be
guaranteed to be non-microsporous. Some cells, in preparation or after use, will be seen to exude droplets or
spicules of the contained metal on to the outer surface of the graphite crucible; some may show a film of metal. This
is considered not to be a defect of the cell; it does not reduce its useful life nor change its equilibrium plateau
temperature.
The cell is a fragile device. Although it is as rugged as is consistent with its materials and purpose, it must still be
regarded as a kilogram, or more, of mass, loosely contained in a frangible shell. Cells should never be inverted,
although they may be slowly turned to the horizontal and laid on their sides. Transporting cells by common carrier is
not recommended and, as furnished, they must be hand-carried. A broken cell cannot, in general, be repaired,
although a cell which is broken but sufficiently intact to contain its metal can be used for some time if contamination is
avoided.
Each cell can be supplied with an Inconel container or basket 400mm (16") in length, in which the cell should be
placed to facilitate removal from the furnace. The basket has two diametrically-opposite holes near its upper end in
which a wire handle of suitable material (for example, 14 SWG Nichrome) may be temporarily attached. It is urged
that the basket always be used with tin cells, because the recommended practice includes removal of the cell from
the furnace as part of the freeze cycle.