AbstractVery high supersaturations, low stability of highly supersaturated solutions, marked secondary changes in the solid phase formed, chemical changes during the ageing of precipitates — this are reasons why our contemporary knowledge on precipitation is far more limited and is also inconsistent compared with mass crystallization of readily soluble substances. In view of this situation, it seems to be highly desirable to show the general fundamentals which could lead us to systematic understanding of the various cases apparently unrelated with each othe