Abstract
Kinetic dissolution experiments show that the rate of Al3+ dissolution from microcline is greater in sulfuric acid than in hydrochloric acid of the same pH value and temperature. Approximately linear relations were obtained by plotting the concentration of Al3+ against those of H+, Cl- and HSO4- in 27 water samples collected in the Kusatsu hot-spring area; the highest value of the correlation coefficients was found for Al3+ - HSO4-, which suggests that Al3+ and HSO4- might have been derived from the same source. Since sulfuric acid is considered to be formed at or near the earth's surface, it is reasonable to suppose that Al3+ in the thermal solution was extracted from wall rocks of relatively shallow depths under the influence of sulfuric acid.
