51. What determines the drying temperature?

The drying temperature is determined by the solvent type, as different solvents have varying melting points. For instance, zinc chloride has a melting point of 283°C and a boiling point of 732°C, while ammonium chloride begins sublimation at 350°C. This means zinc chloride requires a higher drying temperature than ammonium chloride. Therefore, zinc chloride is typically dried at 200–250°C, whereas ammonium chloride can only be dried at around 120°C. Strictly speaking, the upper limit of the drying temperature is determined by the solvent's melting point, while the lower limit is determined by the temperature at which the solvent's crystallization water can be completely removed.