Stabilité des carboxylates de terres rares, II. Bis‐hydroxyméthyl‐2,2‐propionates

Abstract

1873thermostatted chromium trioxide solution was added and the mixture stirred with a glass rod. Liquid samples were added directly by means of a syringe to the chromium trioxide solution in the cell. The concentration of chromium (VI) at the beginning of all kinetic runs was ca. 5 x 1 0 -4~. A t least a ten-fold excess of organic substrate was used for the determination of first-order rate constants.Under the conditions employed solvent oxidation was found to be negligible. The disappearance of chromium (VI) was followed by continuously measuring the absorbance at 350 nm. Good straight lines were obtained, plotting log ( A -A m ) against time. The second-order rate constants were calculated by division of the pseudo-first-order rate constants with the initial concentration of organic substrate. The values given are averages from 3 to 6 runs and were reproducible to 5%.Summary. The stability constants of 2,2-bis-hydroxymethyl-propionates of rare earths have been determined a t ionic strength 0,100 (NaC10,) at 25.0" C by a potentiometric method. The ligand forms 1 : 1 and 1 : 2 complexes with all the rare earths and weak 1 : 3 complexes with light rare earths only. In these last complexes, it binds in a unidentate way. The dissociation constant of the acid has also been measured.