[en] Short communication

[en] The electrical conductivity, σ, and thermopower, S, of molten (AgX)_1-c(Ag₂Se)_c mixtures (X = Br, I) have been measured as a function of temperature. The conductivity of the mixture is observed to decrease rapidly on the addition of AgX to Ag₂Se and reaches a minimum on the AgX side. The thermopower on the Ag₂Se side decreases gradually as the concentration of AgX increases until c = ∼0.4 at which point there is rapid change to large positive thermopowers. The value of S (+325 μV K^-1 (AgBr), +420 μV K^-1 (AgI)) on the AgX rich side decreases rapidly on addition of Ag₂Se with the result that a minimum value of S (∼-125 μV K^-1) is observed at the composition c = ∼0.4 in both mixtures. A discussion of these results is presented in terms of the change from predominantly electronic transport in liquid Ag₂Se to the predominantly ionic transport in AgX. The increasing importance of the contribution of the inhomogeneous thermopower to the total thermopower of the salt rich compositions is also discussed. The decrease in the electronic conductivity with composition for c≥0.6 is analysed in terms of the Kubo-Greenwood equations. (author)

[en] The 24 s and 2.4 mn short halft-life Ag₁₁₀ and Ag₁₀₈ isotopes were used to determine the quantity of silver remaining in developed nuclear emulsions after exposure to various neutron and gamma radiations. The test carried out should lead to the development and construction of automatic measurement equipment

[en] AgPO₃-AgX glasses present a prepeak in the 0.5-0.9 A^-1 Q-range. Using isotopic substitution in 0.75 AgPO₃-0.25 AgCl(³⁵Cl, ³⁷Cl, natural Cl and ³⁵Cl-³⁷Cl) provokes a dramatic variation in the prepeak intensity, which is strong with ³⁷Cl and disappears for ³⁵Cl. The intensity of the prepeak is well correlated to the contrast term (ρ_AgPO3-ρ_Agx)² corresponding to the square of the relative neutron scattering length densities. As in colloidal systems, this peak can be associated with an intermediate structure of particles lying inside a continuous host. The interparticle distance (comprised between 8 and 10 A) may be analysed in two models; (i) 'AgX' microdomains repeated in the AgPO₃ matrix, or (ii) '(PO₃)∞' chain microdomains repeating inside a connective tissue made essentially of disordered AgI. The latter model could be more appropriate to describe other physical properties such as ionic conductivity. (author). 18 refs.; 5 figs.; 3 tabs

[en] Tracer ^110mAg was used to investigate the speciation of silver in natural waters, which may contain chloride, sulfide or humate ions. Silver chloride or oxide is readily absorbed from waters by many materials, and some may be photochemically reduced to metallic silver. Absorbed silver, silver chloride and silver sulfide may be distinguished by their desorption behaviour. Humates form complexes with silver chloride, silver sulfide and with the silver cation, which can be separated from smaller species by gel permeation chromatography. (author)

[en] The lower range in Q (from 0.2 to 2 A^-1) of interference functions S(Q) is very sensitive to the nature of the X nucleus and to the concentration of AgX doping salt. In particular, the progressive enrichment in ³⁷Cl isotope in ³⁵Cl-³⁷Cl mixtures gives rise to an increase of a prepeak located at Q ∝ 0.88 A^-1 for the content 0.75 AgPO₃-0.25 AgCl. A very detailed experiment (at the LLB) has been done with five AgI concentrations. This prepeak has been assigned to (111) reflexion in a cfc network in which the diffusing objects are small aggregates of AgI defined by a radius R. The linear variation of the interplanar d distance (2π/Q) versus the volumic fraction in AgI implies necessarily that the diffracting objects are bigger and bigger when AgI content increases. Therefore, one may consider a medium ordering structure of nanoaggregates of AgI embedded inside the phosphate matrix. (orig.)

[en] A radiochemical displacement method for the determination of small amounts of mercury has been developed. The method involves the displacement of spiked (^110mAg) silver from its dithizonate complex in chloroform. The effects of various ions on the extent of displacement are reported. By this process, ∼80 μg of Hg(II) can be determined. The results of this method are highly reproducible

[en] The collargol was synthesized. The technology of collargol obtaining was elaborated. As initial material were used casein and silver nitrate. For each operation of collargol obtaining the optimal conditions were determined.

[en] The detection of stable Ag isotopes in meteorites at the ppB level was attempted in an AMS experiment using the Munich MP tandem accelerator in conjunction with a time-of-flight detection system. The sensitivity of detecting Ag at this level was established by observing a counting rate of 17 ions of ¹⁰⁷Ag per sec from a Au sample, which had been spiked with the radioisotope ¹⁰⁵Ag (T/sub 1/2/ = 41 d) at a concentration of 1.0 ppB. A blank Ta sample gave no ¹⁰⁵Ag counts in 13 min, which corresponds to a detection limit of 7.5 x 10^-5 ppB. Although this sensitivity was clearly sufficient to perform ¹⁰⁷Ag and ¹⁰⁹Ag measurements in the desired concentration range, experiments with these isotopes were hampered by a currently irreducable background of stable Ag in the ppM range, possibly originating from the ion source itself. Indications of extraordinarily high Ag concentrations, far above this background, were observed in some of the investigated meteorites, but conclusions on their actual existence must await a better understanding of the origin of the general Ag background. 10 refs., 4 figs., 3 tabs

[en] The diffusion coefficient of silver in RbAg₄I₅ was measured in both superionic phases using radiotracer Ag-110m and serial sectioning with a low temperature sectioning apparatus. The activation energies for diffusion in alpha-RbAg₄I₅ and beta-RbAg₄I₅, respectively, are 0.11 +- 0.01 eV and 0.20 +- 0.04 eV. An isotope effect for diffusion was also measured in both superionic phases. Ag-105 and Ag-110m radioisotopes were used with gamma spectroscopy and energy discrimination. The effect is small, with no significant temperature variation, with the value at 333⁰K being 0.12 +- 0.01. The second-order phase transition at 208⁰K has a small effect, if any, on the magnitude of the effect. The data suggest that a highly cooperative transport mechanism is responsible for the unusually high values of both the conductivity and diffusion coefficient. Although it is not possible to deduce the particular mechanism involved, theories inolving ionic polarons, or cooperative motion, such as crowdions or solitons, seem consistent with the observed results