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Raman spectroscopic determination of the degree of dissociation of nitric acid in binary and ternary mixtures with HF and H 2 SiF 6
Author(s) -
Langner Thomas,
Rietig Anja,
Acker Jörg
Publication year - 2020
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5769
Subject(s) - nitric acid , raman spectroscopy , chemistry , ternary operation , dissociation (chemistry) , analytical chemistry (journal) , aqueous solution , inorganic chemistry , oxidizing agent , organic chemistry , physics , computer science , optics , programming language
The oxidizing effect of nitric acid in aqueous solutions depends on the concentration of undissociated nitric acid. This makes the concentration of undissociated nitric acid an essential parameter to monitor and control the quality of silicon etching in the industrial manufacturing of solar cells. In the present study, a method known already is extended in such a way that the degree of dissociation of nitric acid can be determined by Raman spectroscopy in HF/HNO 3 /H 2 SiF 6 acid mixtures over a broad concentration range for the first time and without using an internal or external standard to compensate the typical time‐dependent drift of a Raman spectrometer. The method developed requires the calculation of a peak area ratio from the areas of the unimpeded Raman signals assigned to nitrate ( ν N − O ) at 1,048 cm −1 and to undissociated HNO 3 ( ν N − OH ) at 957 cm −1 . The correlation between the peak ratio and the degree of dissociation of nitric acid revealed can be described by a simple empirical equation. Using this equation, the degree of dissociation of nitric acid can be determined over a broad concentration range in binary and ternary mixtures of HNO 3 with HF and H 2 SiF 6 . The impact of the acids HF and H 2 SiF 6 and the total water content in the degree of dissociation of nitric acid is discussed.