SOLUBILITY OF BARIUM(II) TAURODEOXYCHOLATE

The solubility of barium(II) taurodeoxycholate was studied as a functi on of taurodeoxycholate ion concentration at 25-degrees-C and in 0.100 , 0.200, 0.300, 0.400, 0.500, 0.600 and 0.750 mol l-1 N(CH3)4Cl as a c onstant ionic medium. For this purpose the total concentration of bari um(II) was determined by means of atomic absorption spectrometric and polarographic measurements in solutions equilibrated with solid barium (II) taurodeoxycholate and at known hydrogen ion concentration. An att empt was also made to determine the free concentration of barium(II) i ons by measuring the electromotive force (e.m.f.) of galvanic cells in volving a barium(II) membrane electrode. The free concentration of hyd rogen ion was measured by use of a glass electrode. The results of sol ubility and e.m.f. measurements could be explained by assuming the pre sence of associated species between barium(II) and taurodeoxycholate w ith different ratios depending on the concentration of the ionic mediu m. The solubility product and the association constants were determine d for all the ionic medium concentrations. On the basis of the results , a relationship between solubility and free concentration of taurodeo xycholate ions can be deduced.