Determination of sulfuric acid, nitric acid, and hydrofluoric acid in etch solutions


Two separate titration sequences are required to analyze the mixture:

- titration of the HF content with Al(NO3)3 (the «elpasolite» reaction)
- titration of the H2SO4 with BaCl2 followed by titration with NaOH to determine the «total acids» content

The HF, H2SO4, and «total acids» contents are converted to a HNO3 equivalent, with the HNO3 content found by subtracting the HF and H2SO4 from the «total acids» content.