Concentrated LiBr Solutions Research Articles

LiBr · 2H2O Crystallization Inhibition in the Presence of Additives

Experiments have been performed to measure the effect of additives on the crystallization temperature of concentrated LiBr solutions cooled at a rate of 20°C/h. The measured crystallization temperatures correspond not to the temperatures of equilibrium solubility but to the critical temperature for heterogeneous nucleation of the hydrated LiBr salt on the glass wall of the test tube containing the sample solution. Various additives at concentrations from 250 to 1500 ppm have been investigated. Some soluble additives further decreased the experimental crystallization temperature by as much as 13°C, corresponding to 22°C below the equilibrium solubility. Large decreases in the crystallization temperature can be correlated with large values of complexation constants of the additive for either the Li+ or the Br− ion in solution. Solution complexation, however, is not sufficient to explain the magnitude of the decrease in the crystallization temperature. The only phenomenon capable of quantitatively explaining the magnitude of the decrease in the crystallization temperature is the change in the crystal/solution interfacial energy due to adsorption of the additive on the surface of the prenucleation embryos. A quantitative model of the crystal/solution interfacial energy due to adsorption has been developed using both the Langmuir and Gibbs adsorption equations, allowing the quantitative prediction of crystallization temperatures with additive concentration.

水酸化物とモリブデン酸イオンを含む高温濃厚LiBr水溶液中における炭素鋼の不動態化

水酸化物とモリブデン酸イオンを含む高温濃厚LiBr水溶液中における炭素鋼の不動態化

473Kまでの濃厚LiBr水溶液中における炭素鋼の腐食挙動

473Kまでの濃厚LiBr水溶液中における炭素鋼の腐食挙動

Effect of surfuctant additive on pool boiling of concentrated lithium bromide solution

The measurements of nucleate pool boiling heat transfer rate and surface tension were made for pure water and 50 wt. % lithium bromide solution with various amounts of n-octanol. Regardless of low concentration, n-octanol additive depresses considerably the surface tension of the liquids. The pool boiling data, however, reveal that the addition of surfactant results in insignificant enhancement of heat transfer for both pure water and the concentrated LiBr solution. With the results of this work, the performance improvement received from using n-octanol additive in working liquid of an absorption heat pump (AHP) is consequently due to the enhancement of heat and mass transfer in the absorber (but not generator) by the induced interfacial turbulence.

高温濃厚ＬｉＢｒ水溶液中における炭素鋼とロウ材との異種金属間腐食

Galvanic corrosion between carbon steel and soldering fluxes was studied in a concentrated LiBr solution at 383 and 433K, using extreme-value statistical analysis of pit depth in soldered parts, measurement of the amount of dissolved Fe2+ and dissolved flux compornents, and corrosion potential and galvanic current measurement. The soldering fluxes used were copper, copper alloys (Cu-Si-Mn, BAg-8, Ag 30-Cu, 70/30 Cupronickle) and nickel.Nickel flux soldered with carbon steel caused considerable galvanic corrosion of carbon steel at 383K, while carbon steel soldered with copper and copper alloy fluxes showed galvanic corrosion of the fluxes at 383 and 433K. The galvanic corrosion rate of fluxes decreased in the order of copper>Cu-Si-Mn>Ag 30-Cu>BAg-8> 70/30 cupronickel at 433K, and Cu-Si-Mn>copper>Ag 30-Cu>BAg-8>70/30 cupronickel at 388K. 70/30 cupronickel flux was considered the most suitable soldering flux in a concentrated LiBr solution at high temperature.

Mutual diffusion in solutions of alkali metal halides Aqueous LiF, NaF and KF at 25[deg

A Taylor dispersion tube has been used to measure mutual diffusion coefficients (interdiffusion coefficients) for binary aqueous solutions of LiF (from 0.002 to 0.050 mol dm−3), NaF (0.002 to 0.900 mol dm−3) and KF (0.002 to 8.00 mol dm−3) at 25 °C. The Taylor results together with previously reported activity and density data are used to evaluate resistance coefficients for the mutual diffusion of aqueous NaF and KF. Diffusion coefficients, resistance coefficients and relative viscosities of the fluoride solutions are compared with the corresponding quantities for aqueous solutions of LiCl, LiBr, NaF, NaCl, NaBr, NaI, KCl, KBr, KI, RbCl and CsCl. In contrast to the resistance coefficients of aqueous KCl, KBr, KI, RbCl and CsCl solutions which are relatively insensitive to changes in composition, the resistance coefficients of concentrated LiCl, LiBr, NaCl, NaBr, NaI and KF solutions increase sharply with increasing salt concentration as a consequence of the higher viscosities of these solutions.

大気酸化処理による炭素鋼の高温濃厚LiBr水溶液中での腐食抑制作用

大気酸化処理による炭素鋼の高温濃厚LiBr水溶液中での腐食抑制作用

高温濃厚LiBr水溶液中におけるLiNO<sub>3</sub>, Li<sub>2</sub>MoO<sub>4</sub>およびLiNO<sub>3</sub>/Li<sub>2</sub>MoO<sub>4</sub>混合インヒビターによる炭素鋼の腐食抑制機構

高温濃厚LiBr水溶液中におけるLiNO<sub>3</sub>, Li<sub>2</sub>MoO<sub>4</sub>およびLiNO<sub>3</sub>/Li<sub>2</sub>MoO<sub>4</sub>混合インヒビターによる炭素鋼の腐食抑制機構

モリブデン酸リチウムによる高温濃厚LiBr水溶液中の炭素鋼の腐食抑制

モリブデン酸リチウムによる高温濃厚LiBr水溶液中の炭素鋼の腐食抑制

The nature of pb(II)-bromide complexes in propylene carbonate

The greatly increased solubility of PbBr 2 in propylene carbonate (PC) caused by addition of LiBr indicates that PB(II) interacts strongly with bromide ion in propylene carbonate to form stable Pb(II)-bromide complexes. Solubility and spectrophotometric data for LiBr solutions saturated with PbBr 2 indicate the presence of two Pb(II)-bromide complexes whose bromide:lead ratios are respectively 3.00 and 2.75. The former, which predominates in dilute (<0.03 m) solutions of LiBr saturated with PbBr 2 , was shown by potentiometry and solubility data to be PbBr 3 − , a species also formed when PbBr 2 dissolves in PC in the absence of LiBr. The latter, which is predominant in more concentrated LiBr solutions saturated wih PbBr 2 , was shown by spectrophotometry and solubility data to be the polynuclear complex Pb 4 Br 11 −3 . Both complexes are sufficiently stable that the free bromide ion concentration in these solutions corresponds to only a small fraction of the total bromide concentration. In LiBr solutions unsaturated with respect to PbBr 2 , the major Pb(II) species are PbBr 3 − and PbBr 4 −2 .

Kinetics of thermal unfolding of lysozyme.

AbstractA reversible unfolding of lysozyme has been studied by means of the temperature‐jump method by measuring the absorbance change of pH indicator p‐nitrophenol (p‐NP). In the presence of 4.5M lithium bromide three relaxation processes were found. The fastest process with a relaxation time τ of about 30 μsec is found to come from the proton‐transfer reaction between p‐NP and His 15 in lysozyme. Only the slowest process (τ ≃ 15 sec) is a first‐order reaction and attributable to the unfolding of lysozyme. These results suggest that the all‐or‐none model can be applied to the unfolding of lysozyme as a fairly good approximation. This shows good agreement with the result of Tanford et al. (J. Mol. Biol., 15, 489 (1966); J. Mol. Biol., 73, 185 (1973)). The enthalpy, entropy, and specific heat change between a native and a denatured form are found to be close to 53 kcal/mol, 168 cal/mole/°K, and 2.1 kcal/mol/°K, respectively. The enthalpy and entropy of activation and the specific heat change for the unfolding and the folding are also obtained from kinetic experiments. In the folding reaction, the enthalpy of activation is negative. In the unfolding reaction, the specific heat change is nearly equal to zero. These results suggest that a number of intramolecular hydrogen bonds are broken, but most residues remain tightly folded in the activated state. Our results in concentrated LiBr solutions are compared with those of Tanford in concentrated GuHCl solutions.

Der aktivitatskoeffizient des aktivierten komplexes der elektrodenreaktion

A relation between the activity coefficient of the activated complex γ* and the activity coefficients of reagents γ i and reaction products γ k has been obtained for reactions obeying the Bronsted rule: γ* = Πγ i ßΠγ k α The barrierless hydrogen evolution in concentrated LiBr solutions has been investigated, and on this basis the influence of the activity coefficient of water on hydrogen overvoltage has been studied. The obtained results together with the data of earlier investigations by Frumkin and Jofa on the influence of the activity coefficient of hydrogen ions confirm the equation given above.

Interaction of poly- L-proline with lithium bromide

The role of solvation in stabilizing the poly proline II helix as well as the related question of the mechanism of action of the neutral salts (specifically LiBr) in destabilizing the poly proline II conformation have been investigated. Results indicate that water does not have a unique structural role in the stabilization mechanism. Direct evidence is presented demonstrating that the conformational pattern of poly- L -proline in aqueous and anhydrous LiBr solutions is due to a specific type of binding of the salt to the peptide linkages. A LiBr-poly proline complex has been isolated from both aqueous and anhydrous LiBr solvents, and dilute solutions of the complex in solvents of low water content are found to give optical rotatory and viscosity properties qualitatively similar to those observed in the concentrated salt systems. Results are consistent with a binding of LiBr at the peptide linkages, leading to a lowered barrier to rotation of the rings about the peptide bonds. LiBr-polymer complexes of poly- L -hydroxy proline, poly sarcosine, poly- DL -alanine, poly glycine and gelatin have also been isolated and the weight fractions of bound LiBr determined. The physico-chemical properties of polypeptide chains in concentrated LiBr solutions are discussed.