Publication costs assisted by Israel Chemicals, Limited Potassium and sodium halides can be extracted from their aqueous solutions by dibenzo-18-crown-6 and dicyclohexo-18-crown-6 dissolved in protic solvents, which solvate the anions effectively. Both separate ions and ion pairs are extracted, the order of extractability among the halides being fluoride > iodide > bromide > chloride, apparently reflecting the solvation of the anions. The solubility of the crown ethers in a series of solvents are correlated with the solvent properties. The results are summarized in a prescription for selecting the best crown ether/solvent combination for effective extraction of the alkali halides.

No abstract

No abstract

The effects of pyrophosphate (PP), pH, ionic strength, EDTA, and DTPA on zinc (Zn) sorption by montmorillonite were studied in order to evaluate the role of pyrophosphate in Zn solubilization. In such a system PP dissolution of organic matter and its subsequent complexation of Zn was limited and would not affect the interpretation of the results. The effectiveness of PP in complexing Zn was dependent on the levels of Ca, initial PP concentration, and pH of the montmorillonite suspension. Decreased sorption of PP with increasing pH, as well as markedly greater sorption of PP by Ca‐montmorillonite than by K‐montmorillonite, suggests the existence of a sorption process which could include surface adsorption and precipitation.At initial PP concentrations of 1.92 mM, Zn solubilization decreases monotonically with increasing pH, while at 9.6 mM initial PP, a minimum in Zn solubilization is observed at about pH 6.0. This trend of solubilization could be attributed to decreased Zn sorption and increased Zn complexing with PP. At pH greater than about 7.5, PP is comparable to EDTA and DTPA in Zn solubilization, but only at PP molar concentrations some 40 times greater than the organic ligands. Equilibration time (2 to 192 hours) had little effect on PP concentration or on Zn concentration. Regardless of which of the ligands was used, the sorption of Zn reached completion in most cases within 2 hours. For EDTA and DTPA, provided that their concentration was greater than Zn concentration, sorption of Zn was found to be a relatively slow process. Approximately 40% (EDTA) and 20% (DTPA) of the initial Zn was sorbed after 192 hours.

The [(H20)5CrSCH2CH2NH3]3+ ion has been prepared via chromium(II) reduction of the (V,S-(2-mercaptoethylamine)bis-(ethylenediamine)cobalt(III) ion in aqueous perchloric acid and subsequent ion exchange separation of the product mixture. In aqueous perchloric acid (0.01-1.99 F), this complex aquates according to the rate law -d(ln [CrSR]3+)/df = k0 + ic1(H+). At µ = 2.00 F (LiC10"), 25°, the specific rate constants are k0 = (4.5 ± 0.2) X 10~® sec"1 and k, = (1.31 + 0.02) X 10"4 F"1 sec"1. The corresponding activation parameters are AH0* = 27.6 ± 0.4 and AH,* = 20.6 ± 0.3 kcal/mol, and AS0* = 14.0 ± 1.2 and AS, * = -7.1 ± 0.9 eu. Data are correlated to show that for pentaaquochromium(III) complexes of ligands derived from weak acids, the k0 and k, terms in the title rate law are similarly dependent upon the ability of the coordinated ligand to be protonated. This provides the first positive evidence that the k0 term of these complexes describes separation of HX from [(H20)4(0H)Cr]2+ and not X from [(H20)sCr]3+. It is also shown that the former k0 mechanism operates when the pKa of HX is >2, while the latter k0 mechanism operates when the of HX is <0.

No abstract

No abstract

No abstract