Development of an Automatic Analyzer for a Mixed Nitric Acid, Hydrofluoric Acid, and Iron Ion in the Pickling Process.

Abstract

In the preliminary studies, the followings are verified:(1 ) As a method of analyzing hydrofluoric acid, the iron-acetylacetone complexdiscoloration absorbance method is adopted.(2) As a method of ana]yzing nitric acid, the method of subtracting the concentration of hydrofluoric acid from the total acid amounts obtained by neutralization titration is adopted. As a method of analyzing the iron content, the iron-salicylic acid complex absorbance method is adopted, By fu[ly automating the series of analytical processes described above, the following are achieved:(1 ) The work load of line operators can be reduced, making substantial labor saving possible.

Solubility of β-FeF3·3H2O in Mixtures of Nitric and Hydrofluoric Acid

“…It turns out that the present speciation model predicts too high free HF concentrations. However, the difficulties involved in measurement of free HF concentration and the variation of measurement results depending on the analytical method have been treated in a number of papers. , The speciation calculations of Fernando predict approximately the same free HF concentrations as the present speciation model, but the scatter in the predicted concentrations is much stronger. Fernando used two sets of conditional stability constants, all taken from literature data.…”

“…It would be interesting to measure total iron concentration and free fluoride concentration in saturated solutions to check the model. However accurate measurements of free fluoride in pickle bath solutions are not easily obtained, which has been discussed in many papers 31 and been the object of many recent patents. This is why our model could be of great interest for people working with these solutions (e.g., to plan the recycling of the acid solutions or to see when there is a risk for precipitation of iron fluoride hydrate during pickling).…”