Sonic velocity measurement is used to determine crystallization parameters and to control crystallization processes. This measuring method enables the detection of the nucleation and saturation point and thus the metastable range.
During the crystallization, it is possible to measure the difference to the saturation (degree of saturation), the degree of supersaturation or the crystal content, using as a control variable for influencing the crystallization. When a solid substance is dissolved in a liquid, the liquid is absorptive up to a certain concentration. If further substance is added to the liquid, it will no
longer be dissolved, the solution is saturated and the substance remains in its solid form. This “maximum“ concentration of a solution is called solubility or saturation concentration. The saturation concentration depends on the temperature. The temperature, at which the solution becomes saturated, is called saturation temperature. If the temperature is increased, more substance can be dissolved (except for negative solubility), and the saturation concentration becomes larger.
If the concentration is lower than the saturation concentration, the solution concerned is called unsaturated solution.