BUCHI Melting Point M-560 - Manual (Page 14)

4 Description of function
14 Melting Point M-560 Operation Manual, Version D
4 Description of function
This section explains the basic principle of the Melting Point M-560 and provides a functional descrip-
tion of the assemblies.
4.1 Melting Point
The Melting Point M-560 is an instrument for manual (visual) determination of melting point, melting
range, and boiling point at ambient temperatures +10 °C up to 400 °C. The melting point of three
samples can be determined at the same time. The boiling point can be determined for one sample.
Samples have to be observed through the lens.
The melting point capillary sits in a hollow of the metal block, which is heated electrically and
controlled by a temperature sensor. The heating block is capable of being maintained accurately at a
pre-defined temperature by the heating element, and of being heated at a defined rate.
4.2 Boiling Point
The boiling point is determined by the “Siwoloboff” method.
The Melting Point M-560 can be used to determine the boiling point of a small amount of liquid. The
heating block has one insert available for boiling point tubes (outside left). The moment of boiling is
determined visually.
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 oven temperature and sample temperature. During
this delay time some air bubbles escape from 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].