In this work we give heed especially to the dominating process which is the solid metal A dissolving in the melt B. During the dissolving, the melt B saturates with the metal A and the process is influenced by convections which are characteristic for the given experimental configuration. A theoretical description of the kinetics of the solid phase dissolving in melt will be presented for the case of planar and cylindrical dissolving. The aim is to derive a relation for the interface boundary (t) movement in dependence on time and a time course of growth of the element A concentration in the melt B. There are problems with an accurate determination of the interface boundary movement after certain heating times of specimens, when it is observed experimentally, since intermetallic phases create in the original A metal at both the diffusion and cooling and some phases segregate at the solidifying melt cooling. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration. We present a theoretical description of dissolving of a long metallic cylinder submerged into a melt column and relations for the rate constant determination from the time of the whole metallic cylinder dissolution are derived. In our experiments were performed in which Cu was dissolving in the Sn melt for a Cu cylinder (wire) diameters 0.8÷2.5 mm and the rate constant K (T = 350°C) was determined. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement (t) in the melt and rates of growth of intermetallic phases in the metal A will be observed. This procedure enables to create surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion.