共沉淀过程中微量组分在固相和溶液间的分配(痕量化学之二)

论述痕量化学中共沉淀过程,尤其是在生成混晶的共沉淀过程中,微量组分在固相和溶液间的分配规律以及共沉淀的动力学。依共沉淀的条件不同,微量组分分别按均匀分配律和对数分配律进行分配。同时讨论了一些主要因素,如体系组分数及其物理化学性质、温度、溶液组成和微量组分的浓度等,对共沉淀分配的影响。引进一个描述微量组分进入晶体的动力学的一般方程,并通过将共结晶过程分作三个阶段(诱导期,晶体生长期和陈化期)的方法,用该方程对共沉淀的动力学作了详细分析和阐述。

Distribution of a Microcomponent between the Solid Phase and the Solution in the Course of Coprecipitation (Trace Chemistry,Part Ⅱ)

This paper deals with the laws governing the distribution of a microcomopo- nent between the solid phase and the solution in coprecipitations,especially in the coprecipi- tation by the formation of isomorphous mixed crystals,and with the kinetics of coprecipita- tions.The microcomponent can be distributed between the two phases by either homogeneous distribution law or logarithmic distribution law depending on different conditions of its copre- cipitations.The main factors influencing the distribution of the microcomponent in coprecipi- tation are discussed such as the number of components and the properties of physicochemi- cal,the temperature,the solution composition and the concentration of the microcomponent in solution etc.A general equation is introduced to describe the kinetics of coprecipitation,i.e. the kinetics of incorporation of the microcomponent into the crystals.Furthermore,the kine- tics is analysed in detail by dividing the (co) precipitation process into three stages:the induc- tion period,the period of crystal growth and the period of ageing of the precipitate.