Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions
on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:122Sn(n,γ)123mSn:σth=0.145 barn, I=0.79 barn;122Sn(n,γ)113Sn:σth=0.52, I=25.4 barn;112Sn(n, 2n)111Sn:
A method was developed for the determination of 15 trace elements in tin. High-purity tin samples (99.9999% and 99.999%) as
well as tin of technical quality were analysed. Reactor neutron activation of the tin samples was followed by distillation
of the matrix activities from a HBr−H2SO4 medium and Ge(Li) gamma-ray spectrometry of the distillation residue. The sensitivity of the method is generally high. For
the high-purity samples the detection limits vary from 0.02 ppb (scandium) to 200 ppb (iron) for irradiation of 1 g of tin
for 1 week at a thermal flux of 5·1012n·cm−2. ·sec−1. To decontaminate the surface of the tin samples, pre- and post-irradiation etching procedures were applied. The efficiency
of these etching techniques was studied.
For the determination of very low concentrations of copper in tin, an analytical method involving reactor neutron activation
was developed whereby the copper activity was separated from the tin matrix by extraction of the Cu(I) cuproin complex in
n-amyl alcohol. A new decontamination technique was sought in order to remove the copper contamination present on the tin
surface. Pre-irradiation removal of the tin surface combined with post-irradiation etching appeared to be the most efficient.
Neutron activation analysis for bismuth in lead was performed through the separation and measurement of210Po, using two different extraction procedures. The reproducibility of the results was good for lead containing bismuth in
higher concentrations. For high purity lead, variations in the bismuth content have been found by different analyses of the
same sample, owing to inhomogeneity in the distribution of the Bi metal traces. An independent analysis of the same lead samples
gave comparable Bi concentrations.
A quantitative separation procedure for210Po in lead has been developed by cupferron and dithizone extraction. The210Po activity is plated on a silver foil for counting with a ZnS(Ag) scintillator, or by α-spectrometry with a surface barrier
semiconductor. Different lead samples were analyzed ranging from very old lead with a negligible210Po content to recently manufactured lead samples showing up to 9100 disintegrations per hour and per gram of lead. The reproducibility
and the accuracy of the analyses are satisfactory.
Two methods are described to determine indium and managenese in high-purity tin. In the first method indium and manganese
are separated from the tin and antimony matrix activities on Dowex 1X8 anion exchanger. Tin and antimony are adsorbed in 10M HF while indium and manganese are eluted. In the second method the incident γ-ray intensity due to the tin matrix is reduced
by placing a lead absorber between the sample and the detector. The reproducibility and the sensitivity of both methods are
of the order of 10 ppb for manganese and of 1 ppb for indium for 1 g samples and a neutron flux of 1011 n·cm−2·sec−1.
The use of thermal analysis in studying ancient mortars in English cathedrals is explained. Thermal analysis can be used to
investigate both mortar and stone in dated structures. Analysis of ancient mortars show that though recarbonated, they remain
soft, yielding to structural deformations. The use of hard (cement mortar) in modern renovation can result in micro-cracking
in the stone and subsequent chemical attack from the atmosphere. Contrary to the literature, data developed in the present
study suggests that most medieval mortars have reached a near total state of recarbonation.
Arsenic, selenium and antimony were determined in four different tin samples. After distillation from HBr−H2SO4 medium arsenic and selenium were precipitated with thioacetamide, and antimony was subsequently separated by deposition on
iron powder. The separated samples were counted on a high-resolution Ge(Li) γ-spectrometer. The sensitivity of the method
is highly satisfactory.
Authors:F. Adams, J. Hoste, J. Bartosek, and J. Mašek
New circuits are presented to determine precisely the counting losses suffered in the entire gamma-ray spectrometer and to
allow automatic correction for them even in the case of time-dependent counting rates as encountered in the measurement of
short-lived radioisotopes. Experimental proof is given that the proposed circuitry allows accurate quantitative measurements
in gamma-ray spectrometry. With counting rates up to 20,000 cps losses amount to less than 1.5%.