NUCLEATION OF KCL, NH4CL AND BACL2 - THE INFLUENCE OF ADDITIVES ON SUPERCOOLINGS

The nucleation phenomena in inorganic salt solutions were studied by measuring distributions of supercoolings with an automated apparatus. Secondary and primary (heterogeneous) nucleation could be observed. The linearity of the experimental data (nucleation rate) in a Pound plot (ln(JVDELTAt) versus 1/(DELTAT)2) was examined. The influence of additives (1000 ppm related to the weight of water-free salt) was also studied. Some systems (KCl/PbCl2, KCl/K4[Fe(CN)6] and KCl/K3[Fe(CN)6]) showed a shift of the supercoolings to higher values (retarding effect), while in the system NH4Cl/PbCl2 an accelerating effect was observed. Most of the used additives did not influence the nucleation supercoolings significantly. The method is a short screening test to examine the influence of additives (impurities) in a crystallization process.