ELECTROCHEMICAL AND SPECTROSCOPIC CHARACTERIZATION OF BARIUM ACID SALTS OF 3,5-DISULFOPHENYLPHOSPHONIC ACID

Barium salts of 3,5-disulfophenylphosphonic acid (H4Y) having formulae Ba2Y, Ba1.8H0.4Y, BaKHY and BaH2Y have been prepared and characterise d by X-ray powder diffraction, thermogravimetry, -IR spectroscopy, ac conductivity and e.m.f. measurements. Ba2Y is orthorhombic, with a = 8 .126, b = 4.691, c = 8.649 Angstrom, Ba1.8H0.4Y and BaKHY have similar cell parameters to these. BaH2Y is also orthorhombic, but with all ce ll parameters close to double those of the former salts. The anhydrous salts are stable in air up to at least 300 degrees C. The ac conducti vity (sigma) has been measured at 100 degrees C and controlled relativ e humidity (RH) in the range 50-80%; at 70% RH, sigma increases from c a. 10(-8) up to ca. 10(-2) S cm(-1) according to the sequence: Ba2Y < Ba1.8H0.4Y < BaKHY < BaH2Y. Electromotive force measurements have show n K+ and H+ to be the main charge carriers in BaKHY and BaH2Y. respect ively. In both salts protons are localized on the phosphonate group at 53% RH, but IR spectroscopy provides evidence for a degree of proton transfer to water molecules in BaH2Y at 75% RH.