No abstract

Crystal size distribution of potassium aluminium sulphate dodekahydrate prepared under various conditions has been used for characterization of the degree of agglomeration of crystals. Six series of batch precipitation experiments with batch times from 2 to 80 minutes have been represented by a) dried crystals, b) the same crystals partially de-agglomerated before the measurement, c) wet crystals taken directly from the batch, d) the same crystals partially de-agglomerated before the measurement, e) wet crystals taken directly from the batch occurring under ultrasonic action, and f ) these crystals partially de-agglomerated just before the measurement. Degree of agglomeration decreases in this sequence. Der Aggiomerationsgrad von Kalium Aluminium Sulfat

A simple model is proposed to express the dependence of the mean crystal size on the rate of stirring in precipitating or salting-out systems. The nucleation rate is taken to be proportional to the interfacial area of segregated regions. This area is a function of the dissipated energy. The derived relations are applied to results of a series of experiments in which aluminium-potassium sulphate was salted out by the addition of aqueous solutions of methyl alcohol.

The dependence of the mean crystal size of the products from batch crystallizers on the batch time occasionally exhibits a maximum, which can be explained by secondary nucleation due to the attrition of crystals. A kinetic equatation of nucleation, comprising a term for crystal attrition, can be used for the theoretical description of such behaviour. A mathematical model of a batch crystallizer with crystal attrition has been verified on the calcium sulfate precipitation.

The influence of periodical temperature (or supersaturation) changes on the behaviour of individual crystal particles immersed in their solution is studied.In dieser Arbeit sind Bedingungen dargelegt, unter denen der Umlosungsvergang durch periodische Temperaturschwankungen erheblich beschleunigt werden kann.