Mixed acid, which consist of HF and HNO₃, is used as a good etchant for silicon dioxide in the wet etching and pickling process of stainless steel. The optical detection of concentration for such mixed acids is crucial to optimize and cut costs in the manufacturing process. Optical detection in the IR regime has been utilized to measure the concentration of the mixed acid for HF and HNO₃, because that has several strong absorption peaks, which is contributed by vibrational mode of each acid molecular in this spectrum. In this research, we observed the concentrations of mixed acid to consist of HF and HNO₃, as we measured the absorption intensity of OH- stretch and NO₃ - stretch band by optical spectroscopy. The concentration range of HF over 1.5-3 wt% and that of HNO3 over 2-10 wt% were studied in room temperature.

Date Published: 13 February 2009
PDF: 7 pages
Proc. SPIE 7183, Multiphoton Microscopy in the Biomedical Sciences IX, 71832A (13 February 2009); doi: 10.1117/12.809955

Published in SPIE Proceedings Vol. 7183:
Multiphoton Microscopy in the Biomedical Sciences IX
Ammasi Periasamy; Peter T. C. So, Editor(s)