Hydroxide complexes of lanthanides-IV ytterbium(III) in perchlorate medium

From the precipitation borderline in the pM'-pC(H) diagram, determined experimentally under CO(2)-free conditions, the stability constants of the mononuclear species of ytterbium hydroxide have been established. The values found are log *beta(1) = -7.7, log *beta(2) = -15.5, log *beta(3) = -23.2, log *beta(4) = -37.5, log *beta(5) = -51.9, log *beta(6) = -66.2 and log *K(S0) = 18.0. The data refer to fresh precipitates, prepared at room temperature (21.5 +/- 0.2 degrees ) in sodium perchlorate medium with an ionic strength of 1. The formation of polynuclear hydroxide complexes has been considered and rejected as unlikely to occur.     

Solubility and protonation of EDTA, DCTA and DPTA in acidic perchlorate medium

From measurements of solubility as a function of pC(H), the protonation constants of EDTA, DCTA and DTPA for the first dissociation and addition steps have been determined. The following values were found: EDTA: log k(6) = -0.10 +/- 0.05, log k(5) = 1.45 +/- 0.02, log k(4) = 1.95 +/- 0.02 and log k(3) = 2.50 +/- 0.03; DCTA: log k(5) = 1.78 +/- 0.02, log k(4) = 2.30 +/- 0.02 and log k(3) = 3.50 +/- 0.03; DTPA: log k(7) = 0.75 +/- 0.03, log k(6)= 1.22 +/- 0.02 and log k(5) = 2.08 +/- 0.02. The experiments were done in acidic perchlorate medium (I = 1.0) at room temperature (21 degrees ).     

Semi-xylenol orange and its purification by high-pressure liquid chromatography

By Mannich condensation of o-Cresol Red, iminodiacetic acid and formaldehyde, Semi-Xylenol Orange (SXO) has been prepared in a 10-hr batch-procedure with a yield of about 30%. From the crude product SXO has been isolated by reversed-phase HPLC with perchloric acid-acetone mixtures as the mobile phase and C(18)-bonded silica as the stationary phase. The SXO fraction was freed from accompanying perchloric acid by a second separation on the same column, with water as eluent. After elution with acetone, the SXO was crystallized by evaporation.     

The stability constants of PdeDTA and its chloride complexes

From the position of the equilibrium Th + PdEDTA <--> Pd + ThEDTA, the stability constant of PdEDTA can be related to that for ThEDTA. If log k(ThEDTA) = 25.3 is taken as the most reliable value currently available, log k(pdEDTA) = 25.6 +/- 0.2 is found (NaClO(4) medium, 21 +/- 1 degrees ). Repetition of the experiments at different chloride concentrations gives an estimated log K = 5.3 +/- 0.1 for the equilibrium PdEDTA+Cl(-) <--> PdEDTACl(-). The stability constants of ThEDTA and PdEDTA are not very dependent on ionic strength in the range 0.1-1.0.     

Hydroxide complexes of cerium(III)

From the experimentally determined borderline of precipitation in the pM'-pH diagram the stability constants of the mononuclear and polynuclear species of cerium hydroxide have been determined graphically. The stability constants found are log*beta(1) = -8.1, log*beta(2) = -16.3, log*beta(3) = -26.0, log*beta(5,3) = -32.8 and log*K(s0) = 20.1. These values refer to freshly prepared precipitates, at room temperature and an ionic strength of 1, and are precise to about 0.2 log units.     

Hydroxide complexes of lanthanides-VI

Experiments performed previously with cerium(III), samarium and gadolinium have been extended to conditions of high pC(H) in order to discover any amphoteric character. Up to pC(H) 14.6, the solubility of gadolinium hydroxide and of cerium(III) hydroxide does not increase, so the previously reported constants hold up to this pC(H). The solubility of samarium hydroxide increases at high pC(H), and the value log ( *)beta(4) = -36.7 can be deduced. This should be added to the previously reported set, now applicable up to pC(H) 14.5.     

Photometric determination of the stability constant of the palladium(II)-pyridine-2,6-dicarboxylate complex

From the absorption spectra it has been concluded that Pd(II) forms a 1:1 complex with pyridine-2,6-dicarboxylic acid in aqueous solution at pH 2. The influence of various concentrations of chloride on the spectr has been examined. Ternary complex formation with chloride does not occur to a measurable extent. The conditional stability constant has been determined from data collected near the equivalence point of the titration curve. With allowance for the different side-reactions in this medium at an ionic strength of 0.2, a value of log K = 16.0 +/- 0.2 has been found for the stability constant.     

Mixed hydroxide complex formation and solubility of bismuth in nitrate and perchlorate medium

From the precipitation borderlines in the pBi'-pH diagram, determined experimentally under CO(2)-free conditions, the stability constants of bismuth hydroxide, bismuthoxynitrate and bismuthoxyperchlorate have been established. The following values have been found Nitrate-medium: Perchlorate-medium: log *K(SO)(OH) = 5.2, log *K(SO)(OH) = 5.2; log *K(SO)(NO(3)) = -1.2, log*K(SO)(ClO(4)) = -0.9; log *beta(2) = -4.0, log *beta(2) = -4.1; log *beta(3) = -10.0, log *beta(3)= -9.9; log *beta(4) = -21.5, log *beta(4) = -21.5; log *beta(1,0,1) = 1.2, log *beta(1,0,1) = 3.5. The constants refer to precipitates equilibrated for 30 min, prepared at room temperature (23 +/- 0.5 degrees) in sodium perchlorate or sodium nitrate medium with an ionic strength of 1.00 +/- 0.01. Concerning error propagation it is stated that pBi' values calculated with these constants will have a standard deviation of about 0.1 log unit.     

Hydroxide complexes of lanthanides-III Gadolinium(III) in perchlorate medium

From the precipitation borderline in the pM′—pH diagram, determined experimentally under CO₂-free conditions, the stability constants of the mononuclear and polynuclear species of gadolinium hydroxide have been established. The values found are log*β₁ = −7.3, log*β₂ = −14.6, log*β₃ = −21.9, log*β_4,3 = −19.0 and log *K_s0 = 17.0. They refer to fresh precipitates, prepared at room temperature in sodium perchlorate medium with an ionic strength of 1.     

Hydroxide complexes of lanthanides-V Erbium(III) in perchlorate medium

From the precipitation borderline in the pM'-pC(H) diagram, determined experimentally under CO(2)-free conditions, stability constants for the mononuclear species of erbium hydroxide have been established. The values found were log ( *)beta(1) = -6.3, log ( *)beta(2) = -14.5, log ( *)beta(3) = -23.1, log ( *)beta(4) = -36.8 and log ( *)K(0) = 18.0. The data refer to precipitates prepared at room temperature (21.5 +/- 0.5 degrees ) in sodium perchlorate medium with an ionic strength of 1. The formation of polynuclear hydroxide complexes has been considered and rejected as unlikely to occur.