Neodymium stability constants

Fig. 7.27. Dependence of the isotopic exchange rate constants (k) and the stability constants (K) of the complexes R(EDTA) on the atomic number of the rare earths. The vertical bars shown in the figure represent the probable error in the k values. The dotted line describing the behavior of the elements lanthanum, neodymium and europium is from the comparison of exchange reactivity attempted by Fomin.

The values of the two stability constants (Ki and K2) for the two neodymium-nitrate complexes existing in the Nd(N03)3-HN03 aqueous phase were determined from the total ionic strengths of the aqueous phase using Equations 20 and 21. The total ionic strength was obtained from the relationship ... 

Chitale V. K. and Pitre K. S., A polarographic study of the composition and stability constants of benzoate, protocatechuate and salicylate complexes of neodymium (III). Natl. Acad. Sci. Lett. 4 (1981) pp. 247-248. 

The lanthanum-nitrate interaction was studied in anhydrous methanol by La NMR (Bunzli et al. 1987), but the absolute stability constants could not be evaluated. The interaction with neodymium, europium and erbium was investigated by UV-VIS spectroscopy in aqueous methanol by Silber et al. (1990) and Silber and Strozier (1987). Stability constants, as well as thermodynamic parameters were calculated. Table 7 lists the stability constants available for solutions with a low water content. 

Dimethylacetamide. The stability constants and enthalpy values for lanthanide-nitrate interactions in anhydrous DMA (R=La, Nd) have been determined by means of calorimetric titration (Airoldi et al. 1982). The experimental results support the existence of the iimer-sphere mono- and dinitrato complexes with the following formation constants A i = 17,. 2= 16 for lanthanum and K =25, K2 = 92 for neodymium (cf. table 7). The enthalpies of formation 1 (La 48.2, Nd l.OkJmol" ) and AH2 (La 23.1, Nd 8.3kJmor ) are all endothermic, although rather small. Finally, mononitrate complexes appear to be less stable for both La(III) and Nd(III) ions compared to the corresponding chloro- and bromo complexes (cf. tables 6, 7). 

The selected stability constants for neodymium at 25 "C and zero ionic strength are... 

There have been very few studies where stability constant data have been given for polymeric species of neodymium(III) (Burkov et al, 1973 Ciavatta, Porto and Vasca, 1989b Luo et al., 1990). All three studies proposed the formation of Nd2(OH)2, but there is very poor agreement between the stabihties proposed for the species. Burkov et al. (1973) and Ciavatta, Porto and Vasca (1989b) both studied the hydrolysis in 3moll perchlorate but at 25 and 60 °C, respectively. However, both studies proposed a stability constant that was almost identical in magnitude. This would not be expected on the basis of the difference in temperature. Table 8.29 contains the data that have appeared in the Uterature. 

Table 8.29 Data for the stability constants of polymeric species of neodymium(lll).

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