CAUTION:  The glass cell is extremely fragile and cannot be replaced.  Place powdered dry ice into the re-entrant tube.  This will freeze the water in the tube that is next to the dry ice.  Next insert the aluminum rod and gently warm the inner sides of the tubes until the ice jacket is able to turn.  Insert the thermometer and start recording temperatures.  NOTE:  The insertion of the aluminum rod and the melting away of the ice at the inner point of the tube is a delicate operation, so make sure you take your time during this process so as not to break the glass.