Mixed melting point
The mixed melting point , also known as the mixed melting point , is a simple method of analytical chemistry for checking the identity of a sample with a solid physical state .
The determination of the melting point of a substance is of great importance in qualitative analysis , including identity testing, since many organic chemical substances can be identified by their melting point. To check the identity via the mixed melting point, a "spatula tip" of the sample to be examined with the melting point S is carefully rubbed (mixed) in a mortar with approximately the same amount of a substance with a known structural formula , which also has the melting point S (or a very close one ). If the melting point of the mixture is again S, one can usually conclude that the substances are identical.
In the specialist literature, it is recommended to first check the identity of two substances using the simple and quick method of measuring the mixed melting point, before resorting to more complex methods such as infrared spectroscopy (IR), mass spectrometry (MS) or nuclear magnetic resonance spectroscopy (NMR). However, this advice is not often followed these days.
Individual evidence
- ^ Walter Wittenberger: Chemische Laboratoriumstechnik , Springer-Verlag, Vienna, New York, 7th edition, 1973, pp. 218-219, ISBN 3-211-81116-8 .
- ^ Organikum , Wiley-VCH Verlag GmbH, 23rd edition, 2009, pp. 77 and 80, ISBN 978-3-527-32292-3 .