In this work the use of a nephelometric probe for the investigation on crystallization kinetics is reported. The nephelometric signal was proven to be directly proportional to the overall surface of the suspended solid. An experimental investigation on the nucleation of potassium sulphate crystals from aqueous solution was carried out by applying both polythermal and isothermal methods. The nephelometer allowed to properly detect the nucleation point both in polythermal and isothermal runs. The recorded signal during the first period of time after nucleation was related to the growth of the crystal mass by means of a simplified model. The nephelometric signal was proven to well represent the overall crystal surface evolution at the starting of the crystallization operation.
