Abstract: The solubility of lanthanum chloride heptahydrate in water was determined by static equilibrium method.The solu?鄄bility data were fitted and evaluated by Apelblat empirical equation and λh equation，respectively.The width of the metastable zone in cooling crystallization process of the lanthanum chloride aqueous solution was determined by the laser scattering method.Based on the initial nucleation rate，the effects of the operating parameters such as the temperature，the stirring rate and the cooling rate on the metastable zone width and the nucleation series of the lanthanum chloride were analyzed.The experimental results indicated that both solubility models could well fit the solubility of lanthanum chloride heptahydrate in water，and the metastable zone width of lanthanum chloride was much larger than that of general inorganic salts，which became wider with the increase of cooling rate and the decrease of stirring rate，and the size of the nucleation series was affected by the temperature and became larger with the temperature increased.

Key words: lanthanum chloride heptahydrate；solubility；metastable zone；nucleation series