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An adsorber consisting of hydrous titanium oxide (HTiO) dispersed in a Dowex-type ion-exchange resin matrix (designated RT resins) has been developed which is capable of removing Al(III)-based colloidal dispersions in the neutral pH condition. The effect of resin crosslinking, particle size, HTiO loading, turbidity level, and flow rate on the turbidity removal efficiency of RT resins has been studied. It is demonstrated that a train of columns comprising RT resin, H+, and OH- form of resins could be used for large-scale purification operations at high flow rates. These columns, apart from removing turbidity and associated radioactivity, can effectively remove dissolved uranium present in ppb levels when used for water purification in nuclear reactors.

Detailed studies were carried out on the electrowinning of antimony from SbCl3-HCl-H2SO4 and SbCl3-HCl baths using a graphite anode and a tantalum cathode, the anode being enclosed in a cylindrical glass compartment provided with a sintered disc. Disintegration of the graphite anode increased with increase in anode current density and duration of electrolysis. Analysis of gas evolved at the anode indicated that the presence of sulphuric acid increased the production of CO2. The anodic disintegration was reduced to a negligibly low value by circulation of 6m HCl through the anode compartment. Optimum conditions were determined for electrowinning of antimony from a SbCl3-HCl bath. The tantalum content in the metal was 0.1–0.2 p.p.m.

This paper describes the method of producing plasma sprayed coatings of hydroxy apatite (HA) on metallic substrates of Ti-6Al-4V. Hydroxy apatite is a material which has similar composition to that of the mineral phase of the human bone. Poor mechanical properties however inhibits its use in the load bearing applications. The powders prepared in our laboratory are sprayed using a plasma spray torch operating in ambient. The deposited coatings are charaterized by X-ray diffraction and found to retain HA in the coatings as per requirements.

An amino acid residue functioning as a general base has been proposed to assist in the hydrolysis of beta-lactam antibiotics by the zinc-containing Bacillus cereus beta-lactamase II [Bicknell & Waley (1985) Biochemistry 24, 6876-6887]. Oligonucleotide-directed mutagenesis of cloned Bacillus cereus 5/B/6 beta-lactamase II was used in an ‘in vivo’ study to investigate the role of carboxy-group-containing amino acids near the active site of the enzyme. Substitution of asparagine for the wild-type aspartic acid residue at position 81 resulted in fully functional enzyme. An aspartic acid residue at position 90 is essential for beta-lactamase II to confer any detectable ampicillin and cephalosporin C resistance to Escherichia coli. Conversion of Asp90 into Asn90 or Glu90 lead to the synthesis of inactive enzyme, suggesting that the spatial position of the beta-carboxy group of Asp90 is critical for enzyme function.

Errors in the determination of low concentrations by spectrophotometry are investigated with the uranium-thiocyanate system as an example. The reagent blank has significant absorption and measurements are made at 375 nm instead of the λmax.

A method is described for the determination of nanogram levels of iodide in saline water samples. The interfering chloride, present in milligram levels, is eluted out of a column of a strong anion exchanger, retaining the iodide quantitatively. The iodide is then recovered from the column with 2 M ammonium nitrate solution. The determination is carried out by the catalytic method based on the reduction of Ce(IV) by As(III) in presence of iodide. The arresting method was found to be more sensitive. The method can be easily adapted in a field laboratory, with accuracy comparable with neutron activation analysis.

Die statistische Beurteilung von Daten der Spurenelementanalyse war lange Zeit durch das Gesetz der Fehler-Normalverteilung geprägt, welches auf der Annahme einer Gaußschen Normalverteilung beruht. Wird der analytische Fehler der Konzentrationsbestimmung von Spurenelementen vernachlässigbar klein gegenüber den tatsächlichen Schwankungen in der Natur, dann werden schiefe Verteilungen häufig wichtiger als Normalverteilungen. Eine gute Näherung ist oft, allerdings nicht immer, die Lognormalverteilung. Der Spurenanalytiker übersieht häufig auch heute noch, vor Beginn der eigentlichen Datenbeurteilung den Typ der vorliegenden Häufigkeitsverteilung seines Datensatzes zu untersuchen.

A research program related to the assessment of toxic heavy metals and essential trace elements in foodstuffs has been carried out in 12 countries under the auspices of the IAEA. The main purpose of this program was to obtain data on the elemental concentrations of potentially toxic elements in foodstuffs in various countries, and to compare them with the maximum permissible levels specified in national legislation and international guidelines. High-priority elements for this study were As, Cd, Cr, Pb, Hg, and Se. Also of interest, but of lower priority, were Sb Cu, and Zn/ Emphasis was placed on the use of nuclear and nuclear-related analytical techniques, complemented by conventional methods, and on quality assurance.