Ammonia IR Absorbance Measurements with an Equilibrium Vapor Cell

摘要

Infrared (IR) absorbance spectra were acquired for 18 ammonia vapor pressures. The vapor pressures were generated with 15 gravimetrically prepared aqueous solutions and three commercial aqueous solutions using a dynamic method I.E., EQUILIBRIUM VAPOR CELL (EVC). Background IR spectra were obtained using the vapor pressure of distilled water. The IR absorbance (A) measurements were analyzed by computing ammonia vapor mole fractions (Y) or partial pressures (P) as a function of solution mole fractions (X). The Y versus A furnished a superior data fit over P versus A for the prepared and two commercial solutions. The linear regions of these data fits allowed prediction of Y and P for the third commercial 5% VN ammonia solution. Eight times zero filling of IR interferogram data allowed a more accurate determination of the ammonia spectral band peak positions. The zero filled results were compared to the results with no zero filling. Program listings, analysis results, and IR absorbance spectra were tabulated in an extensive set of appendixes. Titration of two prepared aqueous ammonia solutions demonstrated the reliability of gravimetric solution preparation, as well as showing that storage of an aqueous ammonia solution for a period exceeding 2 years had no significant effect on ammonia concentration.