What is mother liquor?

Explanation

**Step-by-Step Solution:**

1. **Understanding Crystallization**:
- Crystallization is a process where a pure soluble substance is separated in crystal form from a hot saturated solution.
- This process involves cooling the solution to allow the solute to form crystals.

2. **Formation of Crystals**:
- When the hot saturated solution is cooled, the solute begins to crystallize out of the solution, forming solid crystals.
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