The present work was developed in the Copahue-Caviahue volcanic Complex in the Neuquén province, Argentina. The main goal is to analyze the dilution process of the hydric volcanic system acidic waters due to the income of melted waters and the posterior precipitation of iron and aluminum hydroxisulfates, schwertmannite and basaluminite, respectively, when certain pH values are reached. These minerals are typically found in highly acidic environments, either related to active volcanoes or to acid mine or rocks drainage systems. For both minerals, solubility constants have been previously defined, but specifically in mine drainage environments. Never-theless, because of the characteristics that these naturals systems have, the solubility constants can vary significantly according to pH, redox conditions and ionic concentrations of the analyzed system. In this work, solubility constants for an active volcanic environment (Copahue volcano) are defined for the first time. For that, we have obtained a log(Kps) for the schwertmannite of 17.7 ± 1.29 and 21.40 ± 2.04 for the basaluminite, using iron (III) and aluminum activity variation, respectively, according to pH. Meanwhile, from the ionic activity product average depending on pH, the log(Kps) obtained for the schwertmannite was 17.64 ± 3.42 and the basaluminite was 23.95 ± 1.26.