The heat capacity and density of solutions of barium and tetrabutylammonium iodides in N-methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of barium and tetrabutylammonium iodides in N-methylpyrrolidone (MP) were studied at 298.15 K by calorimetry and densimetry. The standard partial molar heat capacities and volumes (\(\overline {C_{p^2 }^ \circ } \) and \(\overline {V_2^ \circ } \)) of the electrolytes in MP were calculated. The standard heat capacities \(\overline {C_{pi}^ \circ } \) and volumes \(\overline {V_i^ \circ } \) of the Ba²⁺ and (C₄H₉)₄N⁺ ions in solution in MP at 298.15 K were determined. With the tetrabutylammonium ion, these values were in agreement with those calculated on the basis of the tetraphenylarsonium-tetraphenyl borate and tetraphenylphosphonium-tetraphenyl borate assumptions. The results are discussed in relation to the special features of solvation in solutions of the salts studied.