Cyclic growth and dissolution of camphor crystals in quinary, ternary, and binary solutions: A study on crystal behavior in storm glass

• Appearance of camphor crystals under cyclic temperature change was observed in three types of solutions.
• Equilibrium temperatures of camphor crystals as a function of camphor concentration were obtained to estimate the weights of crystals precipitated.
• Difference in the crystal patterns formed resulted in the differences in the precipitated crystal height and the amplitude of height variation.

“Storm glass” is a hermetically sealed glass tube containing a solution of camphor. In 19th-century England, the pattern and quantity of the crystals were observed and interpreted as a weather forecasting tool. In the present study, the appearance of camphor crystals under cyclic temperature change was studied in three sample solutions, the storm glass solution (quinary system), camphor–ethanol–water (ternary system), and camphor–ethanol (binary system), to elucidate the effect of components in the storm glass on the appearance of camphor crystals. Equilibrium temperatures of camphor crystals as a function of the camphor concentration were also obtained to estimate the quantity of camphor crystals precipitated in the solutions. During the temperature cycles, the crystal height increased and decreased. The ranges (local maxima and minima) of crystal heights gradually decreased to approximately a constant range. Not only the crystal height but also the amplitude of the height variation in the quinary and ternary systems were much larger than those in the binary system, although the estimated weights of crystals precipitated in the quinary and ternary systems were smaller than that in the binary system. This fact resulted from the formation of dendrites in the quinary and ternary systems, which caused high porosity of sedimented crystals.