Diffusion of alkali and alkaline earth chlorides through a parchment-supported silver iodide membrane

1972 ◽  
Vol 25 (9) ◽  
pp. 1837 ◽  
Author(s):  
Beg M Aijaz ◽  
S Pratap
Keyword(s):  
Silver Iodide ◽  
Alkaline Earth ◽  
Diffusion Rate ◽  
Activation Parameters ◽  
Weak Field ◽  
Thermodynamic Quantities ◽  
Constant Flow ◽  
Ion Hydration ◽  
Diffusion Rates ◽  
Alkaline Earth Chlorides

Diffusion rates of KCl, NaCl, LiCl, BaCl2, CaCl2, and MgCl2 through a parchment-supported silver iodide membrane have been measured at various temperatures using a constant flow method. Activation energies and various Eyring activation parameters for the diffusion of these electrolytes have also been evaluated. The diffusion rate sequences obtained are KCl > NaCl > LiCl and BaCl2 > CaCl2 > MgCl2 and they point towards the weak field strength of the membrane fixed charged groups. Diffusion coefficients and the various Eyring activation parameters have been related to the ionic hydrated sizes and the various thermodynamic quantities of ionic hydration thus emphasizing the importance of ion hydration in diffusion across the membrane.

scholarly journals Mechanistic aspects of oxidation on L-tyrosine by diperiodatocuprate(III) complex in alkali media: a kinetic model

2009 ◽  
Vol 7 (4) ◽  
pp. 929-937 ◽  
Author(s):  
Nagaraj Shetti ◽  
Rajesh Hegde ◽  
Sharanappa. Nandibewoor
Keyword(s):  
Alkaline Medium ◽  
Activation Parameters ◽  
Spectral Studies ◽  
Slow Step ◽  
Isokinetic Temperature ◽  
Thermodynamic Quantities ◽  
Radical Intermediate ◽  
Different Temperatures ◽  
Reactive Oxidant ◽  
Reaction Constants

AbstractOxidation of an amino acid, L-tyrosine (L-Tyr) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.1 mol dm−3 was studied spectrophotometrically at different temperatures (288.1–313.1 K). The reaction between DPC and L-Tyr in alkaline medium exhibits 1:4 stoichiometry (L-Tyr:DPC). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidence, a mechanism involving monoperiodatocuprate(III) (MPC) as the reactive oxidant species has been proposed. A suitable mechanism is proposed through the formation of a complex and free radical intermediate. The products were identified by spot test and characterized by spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and are discussed. The thermodynamic quantities were determined for different equilibrium steps. Isokinetic temperature was also calculated and found to be 252.3 K.

Novel methods of processing cement gel to examine and control microstructure and properties

1983 ◽  
Vol 310 (1511) ◽  
pp. 155-166 ◽  
Keyword(s):  
Surface Tension ◽  
Compressive Strength ◽  
Pore Water ◽  
Diffusion Rate ◽  
Exchange Process ◽  
Hydrated Cement ◽  
Diffusion Rates ◽  
And Control ◽  
Kinetics Of ◽  
Counter Diffusion

The microstructure of the gel produced by hydrating cement is sensitive to the manner in which the original pore water is removed. Exchange of the pore water with a miscible, low surface-tension fluid by a process of counter-diffusion is examined. Diffusion rates in the hydrated cement can be assessed from the kinetics of the exchange process. Evaporation of the low surface-tension fluid from the pores caused less alteration to the microstructure than direct removal of the original pore water. The sensitivity of the microstructure of hydrated cement to normal environmental drying is industrially significant because it is associated with increases in diffusion rates that could affect the durability of concrete. Drying lowered the correlation between diffusion rate and compressive strength. Possible methods of processing the cement gel to make it more resistant to the disruptive effects of drying are discussed.

A spatial SIS model with Holling II incidence rate

2019 ◽  
Vol 12 (08) ◽  
pp. 1950092 ◽  
Author(s):  
Wenhao Xie ◽  
Gongqian Liang ◽  
Wei Wang ◽  
Yanhong She
Keyword(s):  
Incidence Rate ◽  
Total Population ◽  
Diffusion Rate ◽  
Reproduction Number ◽  
Sis Model ◽  
Sis Epidemic Model ◽  
Asymptotic Profile ◽  
Number Formula ◽  
Diffusion Rates ◽  
Two Populations

A diffusive SIS epidemic model with Holling II incidence rate is studied in this paper. We introduce the basic reproduction number [Formula: see text] first. Then the existence of endemic equilibrium (EE) can be determined by the sizes of [Formula: see text] as well as the diffusion rates of susceptible and infected individuals. We also investigate the effect of diffusion rates on asymptotic profile of EE. Our results conclude that the infected population will die out if the diffusion rate of susceptible individuals is small and the total population [Formula: see text] is below a certain level; while the two populations persist eventually if at least one of the diffusion rates of the susceptible and infected individuals is large.

Ionization of alkaline earth additives in hydrogen flames - I. Hydrogen atom concentrations and ion stabilities

1974 ◽  
Vol 338 (1613) ◽  
pp. 155-173 ◽  
Keyword(s):  
Alkaline Earth ◽  
Molecular Ions ◽  
The Other ◽  
Hydrogen Atoms ◽  
Ion Hydration ◽  
Atomic Ions ◽  
Charged Species ◽  
Hydration Energies ◽  
Three Body ◽  
Species Being

The ions present in flames of H 2 +O 2 + N 2 with trace quantities of an alkaline earth M ( = Ca or Sr) added to them have been studied mass spectrometrieally. Those detected were principally MOH + and M + , the only negatively charged species being the free electron. It was established that the reaction M + +H 2 O = MOH + +H was rapid enough to be balanced everywhere in a flame. Detailed studies of (I) provided a means for measuring the concentration of hydrogen atoms at the point of sampling in the flame from observations of [M + ]/[MOH + ]. It proved possible to make absolute determinations of [H]. In addition, the ionization potentials of CaOH and SrOH were measured as 5.7 ± 0.3 and 5.4 ± 0.3 eV, which values are slightly less than those for the corresponding alkaline earth atoms. Hydrates of MOH + and M + were observed, but it was concluded that ion-hydration is not an important flame process in this case, but rather one associated with cooling of gases as they are sampled into the mass spectrometer. It appears that molecular ions hydrate in a two-body process, e. g. MOH + + H 2 O → MOH + . H 2 O with a velocity constant, which is independent of temperature and approximately 1 x 10 –10 ml molecule –1 s –1 . Atomic ions on the other hand initially undergo hydration by a slower three-body step requiring a chaperon molecule. The first hydration energies at absolute zero for CaOH + and SrOH + were measured to be 120±20 and 109±15 kJ mol –1 respectively. These exceed the corresponding quantities for Ca + and Sr + , which were found to be 75±16 and 60±16 kJ mol –1 .

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