In this work, elastic wave propagation through a composite medium, consists of solid and colloidal liquid in a one-dimensional phononic crystal has been studied. The behavioural change in mechanical properties for sol to gel phase transformation is obtained in this experiment. When, a wave of certain range of frequency passes through such a medium, propagation is blocked for some frequency range due to the presence of specific periodic structural arrangement. This range of frequency is termed as forbidden band gap. Calculations for the structure of one dimensional N mass system are performed and are generalized for a bi-mass system (assuming N = 2). Considering different structural and mechanical parameter of the medium, the range of the forbidden gap is calculated and is verified with the experimental analysis. Along with this, the transition time for sol to gel phase transformation is obtained.