In this third part of our research on the 5,5'-azobis[1H-tetrazol-1-ides] (ZT) of the lanthanoids, we present two compounds with La 2 (ZT) 3 moieties with very different coordination modes between the cations and the anions. One La 2 (ZT) 3 -containing compound is interesting, because it contains trimeric La 3 (ZT) 3 III cations, which are arranged in a windmill-like structure. Moreover, the first double salt of a ZT compound, namely the carbonate compound La 2 (ZT) 2 (CO 3 ) · 12 H 2 O, is presented and discussed. Another highlight of nitrogen chemistry is the first molecular structure of a 5-azido-2H-tetrazole (CHN 7 ) molecule, in the form of the spectacular compound Dy 2 (ZT) 3 · 4 CHN 7 · 24 H 2 O. This is the first known complete molecular structure of an azidotetrazole molecule (the organic molecule with the highest nitrogen-content: 88.3% N). All compounds have been characterized completely including elemental analyses, vibrational (IR and Raman) spectroscopy, and X-ray crystal-structure determination. We summarize our nitrogen-rich compounds of the lanthanoids project and extensively discuss selected literature on this topic and compare previously published results with ours.

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Many pyrotechnic devices contain barium nitrate which is used as an oxidizer and colouring agent primarily for green-coloured fireworks. Similarly, strontium nitrate is used for red-coloured pyrotechnic effects. Due to their chemical similarities to radium, barium and strontium ores can accumulate radium, causing a remarkable activity in these minerals. Radium in such contaminated raw materials can be processed together with the barium or strontium, unless extensive purification of the ores was undertaken. For example, the utilization of 'radiobarite' for the production of pyrotechnic ingredients can therefore cause atmospheric pollution with radium aerosols when the firework is displayed, resulting in negative health effects upon inhalation of these aerosols. In this study, we investigated the occurrence of gamma-photon-emitting radionuclides in several pyrotechnic devices. The highest specific activities were due to K-40 (up to 20 Bq g −1 , average value 14 Bq g −1 ). Radium-226 activities were in the range of 16-260 mBq g −1 (average value 81 mBq g −1 ). Since no uranium was found in any of the samples, indeed, a slight enrichment of Ra-226 in coloured pyrotechnics can be observed. Radioactive impurities stemming from the Th-232 decay chain were found in many samples as well. In the course of novel developments aiming at the 'greening' of pyrotechnics, the potential radioactive hazard should be considered as well.

We investigated the interference of radiolead in the isolation of radiostrontium using a strontium-specific resin by means of 85Sr and 212Pb radiotracers. The resin was found to be almost equally specific for lead ions as well. Elution of Pb2+, however, was found to occur at very low acid concentrations (£0.02 M HNO3) of the elutant. Even with pure distilled water as the elutant, elution of lead cannot compete with strontium, due to the delayed elution dynamics caused by residual acid in the column. In contrast to strontium, which is eluted quickly from the column and almost quantitatively after 4 mL elutant (practically independently of the acid concentration of the elutant), lead is eluted with much delay and not completely after the 10 mL elution. The Eichrom method for the determination of radiostrontium in water proposes elution with 0.05 M HNO3, which was found extremely useful, because at such an acid concentration, no radiolead is eluted from the column and allows the production of a pure radiostrontium fraction which can be measured by liquid scintillation counting