Solubility determination and thermodynamic modelling of 3-amino-1,2,4-triazole in ten organic solvents from T=283.15 K to T=318.15 K and mixing properties of solutions

The solubility of 3-amino-1,2,4-triazole in ten organic solvents including ethanol, isopropanol, n-propanol, methanol, ethyl acetate, acetone, acetonitrile, 1,4-dioxane, N-methyl-2-pyrrolidone and 2-butanone was determined experimentally by the isothermal saturation method over a temperature range from T = 283.15 K to T = 318.15 K under 101.1 kPa. For the studied temperature range, the solubility of 3-amino-1,2,4-triazole in mole fraction in the solvents increased with a rise of temperature. On the whole, they obeyed the following order from high to low in different solvents: N-methyl-2-pyrrolidone > methanol > ethanol > n-propanol > (isopropanol, acetone) > 1,4-dioxane > 2-butanone > (ethyl acetate, acetonitrile). The determined solubility results of 3-amino-1,2,4-triazole in the solvents studied were correlated using the modified Apelblat equation, Buchowski-Ksiazaczak lambda h equation, Wilson model and NRTL model. The maximum values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 9.45 x 10 (4) and 2.16%, respectively. In general, the four thermodynamic models were all acceptable for describing the solubility behaviour of 3-amino-1,2,4-triazole in these solvents. Furthermore, the mixing properties including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (gamma(infinity)(1)) and reduced excess enthalpy (H-1(E,infinity)) were acquired. The solution process of 3-amino-1,2,4-triazole was spontaneous and favourable in the selected solvents. The solubility values obtained and the thermodynamic studies would be very useful for optimizing the purification process of 3-amino-1,2,4-triazole. (C) 2016 Elsevier Ltd.