4. Empirical or semi-empirical approach

As in classical organic chemistry, all the physical properties (melting and boiling temperatures, density, refractive index), all the information contained in a spectrum or chromatogram can be considered as a fingerprint of the sample studied.

The fingerprint is not perfect, and it may be necessary to cross-check the information obtained by several different methods to gain certainty; however, it can be used in the vast majority of cases for an empirical or semi-empirical approach to the analysis of a material. Let's take the example of a practitioner who needs to identify a sample and has spectrometric or chromatographic data at his disposal, but is unable to interpret the details:

• he knows that his sample is available in a limited range of materials, so he can carry out a direct comparative study;

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