Solid–liquid equilibrium of dicyandiamide in different solvents

• Solubility of dicyandiamide in five different solvents was first measured systematically.
• Validity of the assumptions in predicting the ideal solubility was evaluated.
• Activity coefficient in different solvents was calculated.

Solubilities of dicyandiamide in five different solvents including water, methanol, ethanol, glycol and acetone were determined at temperature ranging from 273.15 to 338.95 K at atmospheric pressure using a gravimetric method. Fusion enthalpy, ΔHf, melting temperature, Tm, and the difference in molar heat capacity of the liquid and solid form of dicyandiamide, ΔCp, were determined by differential scanning calorimetry. On this basis, the ideal solubility of dicyandiamide was calculated, and validity of heat capacity assumptions (specifically, ΔCp = 0) in predicting the ideal solubility has been evaluated. Further, the measured solubility data was used with the calculated ideal solubility to obtain activity coefficients, which were then fitted to a van’t Hoff like regular solution equation.