Salt Lattice Research Articles

New types of cation‐order in the rocksalt lattice: The structure of Li3SbO4 and Li3NbO4

AbstractLi3SbO4 and Li3NbO4 have structures based on a 3 : 1 order of univalent and pentavalent cations in the rock salt lattice, the order being different for the two compounds.

Isotope effects in solid Li2SO4 at 600-790 °C

Three different isotope fractionation processes have been studied in the same experiment, when solid Li 2 SO 4 was electrolysed in a Vycor cell using a liquid zinc cathode and a gold anode. The main object was to study the enrichment of 7 Li at the anode due to the difference in ion mobility. For this electromigration process the mass effect (i. e. relative difference in ion mobility/relative difference in mass) was µ = - 0,14, independent of temperature. The mass effect is thus about the same as in molten lithium halides. The principal difference between electromigration experiments in solid and molten salts is that in the former the salt lattice forms the « separation column », which is gradually consumed during the run, while for a melt the hydrostatic forces produce a counterflow which keeps the separation column filled with salt.The two other isotope effects were found for the competing cathode reactions. Thus a lithium-zinc alloy was formed due to a deposition reaction while, simultaneously, reduction reactions gave a mixture of lithium oxide, sulfide, and also some sulfite. As to the deposition reactions, 6 Li was enriched in the alloy with a separation factor of 1,01. The detection of an isotope effect for the reduction reactions was complicated by the fact that the reaction products were thoroughly mixed with remaining sulfate. However, a fraction of the products was insoluble in water, and a significant difference in isotope abundance was established between the soluble and the insoluble material.

Radiation Damage and the Ferroelectric Effect in Rochelle Salt

Rochelle salt 45° X-cut square plates were exposed to Co60 radiation of 8.6×103 to 2.6×107 R and reactor radiation up to 2.4×106 R gamma plus 3.5×1015 neutrons/cm2. Measurements were made over a temperature range including both Curie points (−30° to +30°C) of dielectric constant and loss, elastic stiffness coefficients c44D, and mechanical Q. In addition, double-crystal x-ray rocking curves were made above the upper Curie point to check line broadening. All the data indicate an initial improvement in crystal perfection (Curie points are sharper, linewidths narrower) up to 8.6×104 R, with subsequent degradation (Curie point and linewidth broadening: finally coalescence of Curie points) including elimination of the ferroelectric phase after 2.6×106 R Co60 radiation or 2.4×106 R gamma plus 3.5×1015 neutrons/cm2 reactor radiation. The Q rose with radiation dosage as the ferroelectric phase disappeared, dropping only at the highest dosage. Destruction of the ferroelectric phase by radiation is compared to similar effects due to substitution of NH4 for K in the Rochelle salt lattice.

Die Acidität der Sulfane und die Zusammensetzung wässeriger Polysulfidlösungen

AbstractThe pure salts Na2S2, K2S2, K2S3, Na2S4, K2S4 and K2S5 have been prepared. Titration curves of these polysulfides in aqueous solution have been obtained with a special streaming apparatus, with which the mixing of the polysulfide solution with HCl and the pH determination of the fresh mixture is accomplished within 10−2 seconds. This time is too short for decomposition of the protonated polysulfide anions into sulfur and monosulfide or H2S respectively to occur. With K2S5 the buffer regions S52− ⇄ HS5− ⇄ H2S5 were obtained readily, furnishing the pK's of H2S5. The solutions of the lower polysulfides, however, do not contain simply the anions present in the lattice of the solid salt. As soon as the solid salts are dissolved disproportionation reactions take place giving rise to mixtures. From the protonation curves of these mixtures—taken with the streaming device mentioned—their composition can be deduced, and it was found that all solutions contain the ions OH−, SH−, S42− and S52−. The ions S22− and S32− were never detected. The equilibrium between mono‐, tetra‐ and pentasulfide has been elucidated and the pK's of H2S4 have been obtained. The results have been checked with photometric measurements on the polysulfide solutions.