Abstract Cyclodextrins (CyD’s) were precipitated in aqueous medium at 25 °C as inclusion complexes with twenty-two volatile nonelectrolytes (guests). The guest/CyD molar ratios of precipitates were measured immediately after preparation and after drying. Drying the precipitates for five hours at 50 °C under reduced pressure using a water-suction pump gave the same guest/CyD molar ratios as those obtained by drying in a desiccator over diphosphorus pentaoxide and stored there for two weeks. An iodine–α-CyD complex is quite stable on drying and, next to it are 1,2,3-trimethylbenzene–α-CyD and 1,2,4-trimethylbenzene–β-CyD complexes; other guest–CyD complexes are more or less unstable. The stability was found to be roughly correlated to the van der Waals volume of guest molecule(s) resident maximally in the CyD cavity.
A simple method is presented that allows estimation of 1:1 association constants between volatile and nonvolatile solutes in aqueous medium. On introducing an inert gas at a constant flow rate into the aqueous phase, the volatile solute is expelled from the solution, and the amount of the released solute is measured as a function of aeration time. Measurements are made in two separate runs at the same inert gas flow rate, one in the absence and the other in the presence of nonvolatile solutes. The releasing rate of the volatile solute is reduced with increasing association between both the solutes in the aqueous medium. The method was used to estimate formation constants of 1:1 acetylacetone complexes with metal ions, Cu(II), Ni(II), Co(II), Mg(II), Fe(II), Fe(III), and Al(III), at 25.0°C and I=0.1 (NaClO4), results being compared with literature values.
Abstract Dithizonates of some metals, Zn(II), Cd(II), Pb(II), Hg(II), Bi(III), Co(II) and Cu(II) were chromatographed on Sephadex LH-2O gel column using carbon tetrachloride as an eluent. Among them, the metal ions of Zn, Cd, Pb, Hg and Bi were adsorbed at the top of the column, and the liberated dithizone was easily eluted out of the column, while dithizonates of Co and Cu were eluted out unchanged. These phenomena are very curious but somewhat analogous to the stripping procedure in the solvent extraction process. The mechanism of this “stripping-like phenomenon” seems to be difficult to elucidate but it can be conveniently applied to the purification ,of dithizone reagent as well as to separate some metal dithizonates.
Abstract Aus den Au?ösungsuntersuchungen von Olivin in wäßrigen H 2 SO 4 ‐, HCl‐ und HClO 4 ‐Lösungen bei 35, 50 oder 65°C sollen Informationen über Veränderungen und Auslaugvorgänge in sauren heißen Quellen erhalten werden.
Abstract Formation constants of the following aromatic hydrocarbons with α-,β-, and γ-cyclodextrin(CyD) were determined in aqueous medium at 25°C in the presence of excess CyD : benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, (o-, m-, and p-)xylene, and (1,2,3-, 1,2,4-, and 1,3,5-)trimethylbenzene. The technique used to study association between host(CyD) and guest (hydrocarbon) is based on the facts that the guest molecules can be driven out to gaseous phase by introducing an inert gas at a constant flow rate into the aqueous solution and that the volatilization rate of guest decreases with increasing association with the host in the aqueous solution. The 1 : 1 and 2 : 1 (host : guest) formation constants were evaluated. As a measure of hydrophobicity of guest molecules, the free energy change of dehydration derived from Henry’s law constant was used. Based on hydrophobicity and a host-guest spatial-fitting model, the formation constants have been discussed.
Abstract By making use of the volatilization rate of iodine from aqueous into gaseous phase, association constants of α-cyclodextrin with electrolytes (chlorides, nitrates, and perchlorates) have been determined at 25 °C; the counter cations are found to be largely responsible for the association.
Abstract By making use of the solute vapor, the equilibrium solubilities of benzene and three alkylbenzenes in AgNO3 solutions have been measured. The complex formation constants of silver ions are estimated for each solute, and the results are compared with literature values.
