Binary mixts. of inorg. salts in aq. solns. can be analyzed quant. by near-IR spectrometry (NIRS). Each component influences the structure of H2O by misc. cation/anion-OH interactions causing specific effects in the NIR spectra which can be evaluated in a quant. way. The calibrations described were performed using principal component regression (PCR) and optimized with respect to the std. error of anal.