• Sigma Aldrich FT-IR library : The Sigma-Aldrich Library of FT-IR Spectra is a comprehensive collection of FT-IR spectra sourced from the laboratories of Sigma-Aldrich by Merck KGaA Darmstadt, Germany. Featuring over 11,000 pure compounds and over 11,250 spectroscopic records. The Sigma-Aldrich Library of FT-IR Spectra includes compound properties (molecular formula, mass, compound class) and FT-IR spectroscopic data, which has been evaluated by Wiley and third-party experts. Featured spectra were measured in the spectral range of 4000 to 400 cm -1 and compound classes. Sigma Aldrich's commercial IR library is available with a yearly subscription.