Meaning and mechanism
Recrystallization is the process of obtaining a solute as a solid crystal again by utilizing differences in solubility depending on temperature, etc. In cooling recrystallization, a hot, saturated solution is cooled.
If the temperature decreases and the amount of material that could melt is reduced, then excess solute precipitates out. Actual crystal formation requires both nucleation and growth time, so the equilibrium amount may not appear immediately.
Relationships and conditions
The equilibrium crystal yield is the initially dissolved mass minus the maximum mass that can remain dissolved at the final temperature. If the difference is negative, set the yield to 0; use a consistent water-mass basis.
The calculation assumes no solvent loss and no chemical reactions, and assumes that the system has reached a sufficient equilibrium. In actual purification, the solubility of impurities and losses during filtration are also important.
What to observe in the simulation
Total solute = dissolved solute + crystal is preserved. If you added less than the dissolution limit at the end temperature, the amount of precipitation is 0 g.
This is an educational table of virtual substances A and B. This is not actual reagent data. Assuming 0~100 °C, 1 atm, the unit is g/100 g of water, and linear interpolation is performed between sections. Only run solutions that are fully dissolved at the start. It is a constant water mass/equilibrium cooling model and omits evaporation, nucleation, supersaturation, growth rate, and filtration loss. The cooling time on the screen is a representation and is not a prediction of actual cooling speed or recovery rate.
Key relationships and symbols
Precipitation amount = max(0, m₀ − S(T end) × water mass/100)
| Symbol | Meaning | Unit |
|---|---|---|
| m₀ | Initial mass of dissolved solute | g |
| S(T_final) | Solubility at the final temperature | g/100 g of water |
Worked example
What is the formula for calculating the amount of precipitation when cooling without evaporation or loss?
Only the amount that can be dissolved at the final temperature remains in the solution. More solutes than that come out as crystals.
Common misconceptions
- If it is cooled, the solute that was initially dissolved does not entirely revert to a crystalline form.