What is the Optimal Derivative Order

This fundamental question can only be answered generally the best order is apparent when all shoulders and inflection points are resolved in extrema, oscillating more or less around the baseline. As a rule, this point is reached using the fourth to sixth-order derivative. 

In Fig. 4-41, the first to ninth derivative was generated from the flat fundamental spectrum of potassium nitrate. We see in this case that d does not resolve the curve. Even d has a shoulder which is only resolved in the sixth to eight order. 

Spectra catalogs are mainly limited to IR spectra, because the spectra of liquid or solid substances taken in the visible or UV region are mostly flat and only marginally characteristic. Higher-order derivatives are destinated to become the tool for making the fine structure of these signals more visible. 

Above all, three points make the basis of organizing a data base of derivative spectra the standardization of spectroscope technique, the normalizing of the deriv- 

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