Method for analyzing free fluoride in solutions containing hydrofluoric acid solution, and apparatus for practising the method

摘要

Free fluoride is measured in a hydrofluoric acid-containing solution with a coexistent metallic ion based on a total fluoride concentration, a total acid concentration, a metallic ion concentration, the equilibrium constant of hydrofluoric acid, and equilibrium constants of metal fluoride complexes. It is possible to accurately analyze free fluoride in a hydrofluoric acid-containing solution without being affected by a coexistent metal and by the passage of time. This technique may be used to accurately control the concentration of free fluoride in a hydrofluoric acid-containing mixed acid pickling solution at the production site of a stainless steel so that improvement in descaling capability as well as reduction in the amount of chemical materials can be achieved.