FTIR: wavenumber runs right to left, by convention020406080100fingerprintC-H / O-H stretchtransmittance (%)Transmittance: what the instrument measures, bands point down100020003000400000.511.52O-H stretchC=O stretchC-O stretchwavenumber (cm^-1)absorbanceAbsorbance: what obeys Beer's law, so what a concentration usesFTIR: wavenumber runs right to left, by convention