Why are there no crystals of potassium nitrate or ammonium chloride in the weather bottle, only camphor crystals?

Generally speaking, the analysis of crystal growth mainly needs to consider the characteristics of solute, solution system, solute concentration, temperature and temperature change rate. In the laboratory, long crystals usually start from these parameters, and adding bad solvent, volatilization, cooling and controlling crystal nucleus are common methods. Sometimes, electric fields, magnetic fields and pressurization can also be used to regulate crystal growth.

The change of crystallization in the bottle is mainly due to the change of solubility of camphor in ethanol solution with temperature. Potassium nitrate, ammonium chloride and water are used to control the continuous nucleation during the high-speed growth of crystals. When the temperature changes, camphor crystals will precipitate, and the speed of temperature change will affect the growth size and structure of crystals.