Calorimetric Study Of The Interaction Of Tri- And Tetrametaphosphate With Some Trivalent Cations

Tri- and tetrametaphosphate were used in calorimetric titrations of Al3+, Y3+, La3+ and [Co(NH3)6]3+ in aqueous solutions. The enthalpies of reaction and equilibrium constants were determined for the complexation reactions. In every case, the ion pair of metal to cyclic phosphate in a 1 : 1 proportion is the complex species. The thermodynamic data as calculated by the least-squares method range between 2.28 and 37.8 kJ mole-1 for the enthalpies, and 56 and 190 J K-1 mole-1 for the entropies. These thermodynamic data indicate that the stability of these complexes is mainly due to the gain in entropy. © 1983.6818389Monk, Davies, (1949) J. Chem. Soc., p. 413Monk, 239. The condensed phosphoric acids and their salts. Part VII. Ion association between some tervalent cations and the tri- and tetra-metaphosphates (1952) Journal of the Chemical Society (Resumed), p. 1317Gross, Gryder, (1955) J. Am. Chem. Soc., 77, p. 3695Serra, Giesbrecht, (1968) J. Inorg. Nucl. Chem., 30, p. 793Gushikem, Giesbrecht, Serra, (1972) J. Inorg. Nucl. Chem., 34, p. 2179Nazarenko, Nevskaya, (1969) Russ. J. Inorg. Chem., 14, p. 1696Frink, Peech, (1963) Inorg. Chem., 2, p. 473Usherenko, Skorik, (1972) Russ. J. Inorg. Chem., 17, p. 1533Amaya, Kakihana, Maeda, The Hydrolysis of Y3+, La3+, Gd3+, and Er3+ Ions in an Aqueous Solution Containing 3 M (Li)ClO4 as an Ionic Medium (1973) Bulletin of the Chemical Society of Japan, 46, p. 1720Giesse, Gushikem, Volpe, (1982) Thermochim. Acta, 54, p. 257Eatough, Christensen, Izatt, Determination of equilibrium constants by titration calorimetry (1972) Thermochimica Acta, 3, p. 203Rigano, Rizzarelli, Sammartano, (1979) Thermochim. Acta, 33, p. 211Ahrland, Enthalpy and Entropy Changes by Formation of Different Types of Complexes (1967) Helvetica Chimica Acta, 50, p. 306Hinton, Amis, (1971) Chem. Rev., 71, p. 627Lincoln, (1971) Coord. Chem. Rev., 6, p. 309Kawaizumi, Miyahara, Hydration of the Cobalt(III) Complexes. II (1971) Bulletin of the Chemical Society of Japan, 44, p. 1979Nancollas, (1960) Q. Rev. Chem. Soc., 14, p. 402Irish, Chang, Nelson, (1970) Inorg. Chem., 9, p. 42