BUCHI Melting Point M-565 - Manual (Page 18)

4 Description of function
18 Melting Point M-565 Operation Manual, Version D
4 .1 .2 Boiling points
The boiling point is determined by the “Siwoloboff” method.
The Melting Point M-565 can be used to determine the boiling point
of a small amount of liquid. The heating block has one insert avail-
able for boiling point tubes (outside left). The moment of boiling is
determined automatically or visually.
Detection is done as follows:
The beam of light illuminates the boiling point tube from the front,
and the camera records the image.
Fig. 4.3: Boiling point
The process for boiling point determination is analogous to that for determining a melting point:
• The start temperature is set 5 to 10 °C lower than the expected boiling point.
• The sample is put into the heating block as soon as the start temperature is reached.
• A delay time allows the equilibrium between sample oven temperature and sample temperature.
During this delay time some air bubbles turns out of the boiling point capillary.
• Starting from the start temperature, the sample is heated at a temperature gradient of 1 °C/min.
• As the temperature rises, bubbles of gas rise slowly and regularly from the immersed end of the
boiling point capillary.
• The boiling point of the liquid has been reached when the flow of steam bubbles reaches a
frequency of 0.6 Hz [Hertz].
The instrument records the curve and displays the result. At the beginning of the measurement, the
current pressure has to be entered to obtain correct results. The system detects the boiling tempera-
ture. The boiling point is calculated and corrected for current pressure.