Radioactive silver

After each series of experiments with beams of various intensity the section plate would be removed from the cell and disassembled, with radioactive silver washed out by nitric acid. Radioactivity of the solutions obtained was measured by a multichannel spectrometric scintillation y-counter with sensitivity of up to 10 G, i. e. around 10 of atoms which, according to calculations, is 10 times lower than sensitivity of ZnO sensor 10 G or 10 of Ag atoms respectively [28]. This difference in sensitivity lead to great inconveniences when exposing of targets was used in above methods. Only a few seconds were sufficient to expose the sensor compared to several hours of exposure of the scintillation counter in order to let it accumulate the overall radioactivity. It is quite evident that due to insufficient stability during a long period of exposure time an error piled up. 

Distribution in Rats at Six Days of Intramuscularly Administered Radioactive Silver Tracer Dose when Administered Alone and when Coadministered with Additional Silver as Silver Nitrate... 

The clearance of radioactive silver metal dust in a man who was accidentally exposed illustrated the rapid removal of silver from the lungs primarily by ciliary action, with subsequent ingestion and ultimate elimination in the feces (Newton and Holmes 1966). Lung clearance fit a biexponential profile, with biological half-lives of 1 and 52 days. Radioactive silver was detected in the feces up to 300 days after exposure, but was not detected in urine samples (collected up to 54 days after exposure). 

Gammill JC, Wheeler B, Carothers EL, et al. 1950. Distribution of radioactive silver colloids in tissues of rodents following injection by various routes. Proc Soc Exp Biol Med 74 691-695. 

Matuk Y. 1983. Distribution of radioactive silver in the subcellular fractions of various tissues of the rat and its binding to low molecular weight proteins. Can J Physiol Pharmacol 61 1391-1395. 

PolachekAA, Cope CB, Williard RF, et al. 1960. Metabolism of radioactive silver in a patient with carcinoid. J Lab Clin Med 56 499-505. 

West HD, Goldie H. 1956. Topical localization in mouse of radioactive silver oxide (Ag111)20 introduced by various routes. Proc Soc Exp Biol Med 92 116-120. 

West HD, Elliott RR, Johnson AP, et al. 1950. In vivo localization of radioactive silver at predetermined sites in tissues. American Journal Roentgenology Radium Therapy 64 831-834. 

The exchange of silver ion between a precipitate of silver chloride and a solution of silver nitrate reaches isotopic equilibrium very rapidly (152). Because of the low solubility of silver chloride, a favorable ratio exists at equilibrium between the silver atoms in the precipitate and in the solution. For this reason, If a silver chloride precipitate is added to a solution containing only- trace amounts of radioactive silver, a high percentage of this radioactive silver will have exchanged with the silver in the precipitate by the time equilibrium is attained. 

The use of such techniques for radiochemical work has been discussed In detail (203,250,251). In these studies a platinum electrode of large surface area (52 mesh, 30 mm high, 10 mm i.d.) coated with silver chloride is placed in contact with 10 ml of solution containing a very low concentration of radioactive silver. The solution Is stirred magnetically. The electrode is then removed from the solution, washed with nitric acid, rinsed with acetone, and the radioactivity counted. 

Table I. The Yield of Radioactive Silver from 1 M HNO by the Isotopic Exchange Procedure...

A final example is that of the use of controlled-potential electrolysis for the preparation of carrier-free radioactive silver. Griess and Rogers isolated tracer quantities of radioactive silver, which had been prq>ared by neutron bombardment of palladium, by selectively depositing the silver onto a platinum surface. Although a small amount of palladium was codepo ted, complete separation was achieved by anodic stripping and redeposition. 

Condit and Holt have reviewed the use of radioactive tracers in the study of oxidation. Radioactive platinum has been used to study the oxidation of cobalt and radioactive silver to study the oxidation of molybdenum. If the tracer element remains at the surface it indicates that the oxygen is diffusing into the metal, and if it is located some distance from the surface shows diffusion of the metal through the oxide. The tracer can be detected by autoradiography and its distribution studied by gradual removal of the oxide layer. Its distance from the surface can also be estimated by measurement of the energy of the emitted radiation at some point outside the surface . ... 

Exchange of silver with radioactive silver nitrate solution has been studied by Ting-ley The Ag isotope has a half life of270 days. Various surface treatments... 

Radioactive tracers provide a convenient means of measuring the small concentrations encountered in determining K,p values. Exactly 20.0 mL of 0.0100 M AgN03 solution containing radioactive silver, with an activity of 29 610 counts/min per mL, was mixed with 100 mL of 0.0100 M KIO3, and the mixture diluted to exactly 400 mL. After equilibrium was reached, a portion of solution was filtered to remove any solids and was found to have an activity of 47.4 counts/min per mL. Calculate of AgI03. 

The determination of chloride in water samples by using a radioactive silver chloride (AgCl) precipitate can be taken as an example. A water sample with an unknown concentration of chloride is shaken with an excess of labeled AgCl precipitate and the radioactivity of silver is measured in the equilibrium solution. The higher the chloride concentration the lower is the concentration of silver in solution (owing to the constancy of the AgCl solubility product). The CM ions determined do not react with the AgCl precipitate, they only suppress its dissolution. The amount of chloride in the precipitate has no direct relationship to the concentration of Cl ions in the sample solution. 

The third step, known as bleaching (Fig. 1), converts the deposited silver to AgBr (Glafkides, 1987). Finally, the silver bromide is transformed to silver sulfide by reaction with p S]thiourea (Owunwanne et al., 1982), resulting in a deposit of radioactive silver sulfide at the sites of proteins (Figs. 2 and 3). 

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