『Abstract
　Laboratory experiments were carried out continuously for 30-35 days at 25 and 5℃ in three different buffer solutions of pH 4.0, 2.2 and 8.4 to calculate dissolution rates of two minerals, calcite (CC) and dolomite (DM) and two rocks, leucogranite (LG) and gneiss (GN) from the Himalayan range. Calculated rates in terms of release of targeted elements versus time (Ca for CC; Mg for DM; Si for LG and GN) demonstrate direct correlation with temperature. Dissolution rates are higher at 25℃ compared to 5℃. CC and DM were experimented only at pH 8.4 and results show that both undergo congruent dissolution with CC dissolving 〜5 times faster than DM. Ca and Mg exhibit average apparent activation energies (Ea) of 13.98 and 9.98 kcal mol^-1 respectively at pH 8.4 which reflects greater sensitivity of CC dissolution than DM dissolution towards an increase in temperature. Scanning Electron Microscope attached with Energy Dispersive X-ray Analyser (SEM-EDX) data indicates that dissolution is controlled primarily by surface-reaction processes, with dislocation sites contributing maximum to the dissolution. As compared to CC and DM dissolution, LG and GN undergo relatively slower incongruent dissolution with precipitation of some secondary minerals as revealed from X-ray diffractometer (XRD) results. Rates of dissolution of LG is maximum at pH 2.2, moderate at pH 8.4 and least at pH 4.0, whereas GN shows maximum dissolution at pH 2.2, moderate at pH 4.0 and least at pH 8.4. A comparison in dissolution behavior of LG and GN at experimental conditions reveals that increase in Si-release rate in the temperature range between 5 and 25℃ is maximum at pH 8.4 (〜3.4-4.5 time), moderate at pH 4.0 (〜3-1.8 times) and least at pH 2.2 (〜1.0-1.5 times). Within the experimental temperature range, calculated values of Ea for Si release during LG and GN dissolution advocates positive correlation with pH. A substantial decrease in initial values of Brunauer-Emmett-Teller (BET) surface area of DM, LG, and GN has been encountered at the end of the experiment, except for CC for which an increase is observed. The study clearly demonstrates the dissolution behavior of pure minerals and rocks under controlled conditions. The dissolution rates assume enormous significance for the release of trace elements from rocks/minerals to the reacting water.

Keywords: Calcite; Dolomite; Leucogranite; Gneiss; Dissolution rates; Kinetics』

Introduction
Materials and methods
　Sample characterization, preparation and analytical techniques
　Surface area measurement
　Experimental solutions
　Dissolution experiments
　Activation energy and dissolution rate calculations
Results and discussion
　Mechanism of calcite (CC) and dolomite (DM) dissolution
　Mechanism of leucogranite (LG) and gneiss (GN) dissolution
　Post-experiment decrease in surface area
Conclusion
Acknowledgments
References