The process of dissolution mass transport along a vertical soluble substrate submerged in a large pool of otherwise quiescent molten metal is studied theoretically. Various freestream concentrations varying from zero to a near-saturation value are considered. A mathematical model is developed from the conservation laws and thermodynamic principles, taking full account of the density variation in the dissolution boundary layer due to concentration differences, the influence of the solubility of the substrate on species transfer, and the motion of the solid/liquid interface at the dissolution front. The governing equations are solved by a combined analytical-numerical technique to determine the characteristics of the dissolution boundary layer. Based upon the numerical results, a correlation for the average Sherwood number is obtained. It is found that the Sherwood number depends strongly on the saturated concentration of the substrate at the moving dissolution front and the degree of saturation in the ambient pool.