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  • Author or Editor: M. Sankar Das x
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Abstract  

A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.214Bi,210Bi and212Bi, and applied to the indirect estimation of their corresponding precursors,222Rn,210Pb and212Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed.

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Abstract  

Correlations between the growth of hair and the trace element profile have been investigated by non-destructive neuron activation analysis through gamma-ray speetrometry using NaI(Tl) as well as Ge(Li) detectors. After preliminary investigations to establish the experimental errors, the effect of washing procedures and in-person variations, hair samples belonging to ladies with known case histories, particularly with regard to dietary habits, health and profession, were examined. Scalp-hair samplex 50–100 cm in length, representing an average time span of ∼5–10 years were collected by combing. Samples in their non-anagen phase, differentiated by their roots, were analysed in 10 cm sections. The concentrations of the following elements were determined: Na, Cl, Mn, Co, Cu, Zn, As, Se, Ag, I, Au and Hg. Absolute values for the concentrations are reported for most of the elements, while for the rest relative values for the various sections are given. The values for the different sections vary by large factors for many elements although for some elements, like Cu and Mn, the variations are not appreciable. The unusually large concentrations of elements like Se ang Hg are in broad agreement with the case histories. However, detailed examination of the results with regard to time-dependent variations seem to pose serious problems in the applications to forensic science.

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Abstract  

Various methods of preparing standards for activation analysis have been reported in the literature. This paper describes the feasibility of preparing ion exchange resin based standards containing predetermined levels of ions. Using a solution of known initial concentration of the ion, and given the value of its distribution coefficient, it is possible to predict the resin concentration that will be obtained. Resins containing ppm levels of copper and manganese have been prepared and their stabilities evaluated over a period of time. The feasibility of preparing a multielement standard has been studied with five rare earth elements (La, Ce, Sm, Eu and Dy).

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Abstract  

234U to235U activity ratios were determined in some of the primary and secondary uranium minerals. The conditions for the accurate measurement of this ratio by α-spectrometry were optimized. The activity ratios of234U to238U in U4+ and U6+ fractions were determined. This ratio was found to be more than the equilibrium value in one leaching experiment and is explained as due to the oxidation and selective removal of the234U, relocated by α-recoil. Age values of some of the minerals, which had earlier been dated assuming this ratio to be one, were rectified when necessary.

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Abstract  

The instrumental approach to the determination of elements through annihilation radiation demands a high degree of specificity which has not been fully met by the high resolution Ge(Li) or the two detector (180°) coincidence spectrometry. The triple coincident measurement of the three gamma quanta resulting from the triplet state annihilation of e−e+ system provides enhanced specificity, although at a loss of sensitivity. The development of this approach for the measurement of annihilation radiation is decribed with the determination of copper in orchard leaves as an illustrative example.

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Abstract  

A scheme of analysis for the determination of Na, Mn, U, Th, Hf, Sc, La, Ce, Eu, Tb, Co, Rb and Cs in geological samples using the neutron activation technique has been described. The results obtained in this work on eight geological standard rocks and a trachyte are presented and compared with literature data.

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