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- Beckmann's
Freezing Point apparatus-The fact that the
temperature of an over-cooled liquid rises to the freezing point
when solidification occurs, has been made the basis of a method
of determining freezing points. Beckmann's apparatus is shown
in Fig. 77. It consists of a test tube A, provided with a side
inlet tube D, and a cork through which a thermometer T and a
platinum wire stirrer S2 pass. This test tube is surrounded
by a larger tube B, the space between the two forming an air
jacket. Both are surrounded by a larger vessel C, which call
be filled with a suitable freezing mixture. The latter is kept
in circulation by means of the wire stirrer S1.
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- The method of using the above apparatus is as follows:--
Some of the liquid of which the freezing point is required, is
introduced '
 into A, by way of the inlet
tube D, which is afterwards closed by a cork. A suitable freezing
mixture is introduced into C, and the whole apparatus is allowed
to stand till the thermometer T indicates a temperature one or
two degrees below the probable freezing point of the liquid.
The platinum wire stirrer S2 is then moved briskly
up and down, when solidification will generally occur. The temperature
indicated by T rises and shortly attains a value which remains
constant some time. This temperature is the freezing point of
the liquid.
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