The Behavior of Silicon and Aluminum in the Nitrofluor Process

The purpose of this paper is to investigate the mechanism of anomalous behavior of aluminum and silicon in extracting metallic ingredients from ores by the Nitrofluor process. The summary of the results is given below. Reacting with the solvent, aluminum first dissolves in the solution to form the complex aluminum fluoride expressed as AlF_3・3NOF. However, this material loses NOF gradually in the relation between the other attendant ingredients, and changes subsequently into a white precipitate which is equivalent to AlF_3. This information was obtained by measuring the solubility of these complex fluorides and the experimental results of reactions between the complex aluminum fluoride and HF. On the other hand, silicon also dissolves in the solution as the complex silicon fluoride expressed as [NO]_2SiF_6. The concentration of the solution by heating and evaporation produces one or two kinds of azeotrope, and on further evaporation, all of the silicon volatilizes with the solvent