Determination of microgram quantities of uranium in thorium

Uranium present in micro amounts in thorium is extracted with 5% tributyl phosphate in presence of EDTA at pH 2.5. Calcium nitrate is used as salting agent. Uranium is back-extracted with ammonium carbonate and determined fluormetrirically. Thoria samples containing as little as 0.4 p.p.m. of uranium have been analysed.     

Spectrophotometric determination of thiourea in microgram quantities

Summary Copper(II) forms a stable colourless complex with thiourea. This property has been utilized to develop a Spectrophotometric method for the determination ofg quantities of thiourea. The complex absorbs in ultraviolet region and the determinations are carried out at 250 nm. The method permits the determination of thiourea from 10–60g with error not exceeding ± 1.0%.

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Zusammenfassung Kupfer(II) bildet mit Thioharnstoff eine farblosa Komplexverbindung, die sich auf Grund ihrer Absorption bei 250 nm zur spektrophotometrischen Bestimmung von Mikrogrammengen Thioharnstoff eignet. 10 bis 60g Thioharnstoff lassen sieh mit einem Fehler von höchstens ± 1,0% bestimmen.

     

Spectrophotometrie determination of microgram quantities of hexavalent uranium

Summary A method is presented for the spectrophotometric determination of microgram amounts of hexavalent uranium by means of the azodyes Monochrome Black Blue G und Diamond Black PBB respectively.These two azodyes react with uranyl ions in an acetate buffered hydrochloric acid-methanolic medium under formation of colored chelates. 10 or 20 g uranium(VI)/10 ml measuring solution can still be determined with relatively high accuracy.

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Zusammenfassung Es wird eine Methode zur spektrophotometrischen Bestimmung von Mikrogrammengen Uran(VI) mittels der Azofarbstoffe Monochromschwarzblau G bzw. Diamantschwarz PBB angegeben. Diese beiden Azofarbstoffe reagieren mit Uranylionen in acetatgepuffertem salzsauermethanolischem Medium unter Bildung gefärbter Chelate. 10 bzw. 20 gUran(VI)/10ml Meßlösungkönnennoch mitrelativ hoher Genauigkeit bestimmt werden.

     

Accurate determination of microgram quantities of uranium by direct and differential polarography

Summary A procedure for the accurate determination of small amounts of pure uranium (5–1,000 g) by direct or comparative polarography is described. The accuracies obtainable for different total quantities are given.

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Zusammenfassung Direkte und differentielle polarographische Verfahren zur Bestimmung von kleinen Mengen Uran (5–1000 g) werden beschrieben und die für verschiedene Gesamtmengen erreichbaren Genauigkeiten angegeben.

     

Direct spectrophotometric determination of microgram quantities of copper in high purity uranium with oxaldihydrazide

Summary The possibility for the direct spectrophotometric determination of microgram quantities of copper in high purity uranium using oxal-dihydrazide-acetaldehyde reagent in ammoniacal medium was investigated. Uranium was complexed with ammonium citrate or ammonium carbonate.It was shown that copper can be determined with fairly good accuracy. At the copper concentration of 0,1 ppm and 1 ppm relative mean deviation in amounts to 7,38 and 0,94 respectively.The selectivity of the reaction is very high, the only interference being cobalt which when present in equal concentrations increases the absobance by about 5%.Thanks are due to Miss Kira Jovanovi for her help in taking the spectrophotometric measurements.     

Spectrochemical determination of rare- earth metals in uranium and its salts

An emission spectrographic procedure is described for the determination of 0.05-4 ppm of rare-earth metals in uranium metal and its salts. Uranium is extracted from the sample with tributyl phosphate, and the impurities are separated by precipitation as hydroxides and oxalates, with yttrium as a carrier. After conversion into the oxides, the rare-earth metals are mixed with graphite and excited in a d.c. arc.     

Spectrophotometric determination of microgram amounts of platinum

2-Ethyl-10-[3-(dimethylamino-2-methyl)propyl]phenothiazine hydrochloride (ethylisobutrazine hydrochloride) forms an orange-red complex with platinum(IV) at room temperature (26 ± 2 °C) in hydrochloric acid-sodium acetate buffer medium containing copper(II) ions. The complexation is complete within 10 min. The complex exhibits an absorption maximum at 529 nm with a molar absorptivity of 1.90 × 10⁴ liters mol^?1 cm^?1. Beer's law is obeyed over the concentration range 0.4–7.8 ppm of platinum. A 50-fold molar excess of the chromogenic reagent is necessary for the development of maximum color intensity. Job's method of continuous variation, the molar-ratio method, and the slope-ratio method indicate a 1:1 composition for the complex. The effects of pH, time, temperature, reagent concentration, order of addition of reagents, and interference of various ions are reported. The reagent has also been used successfully for the determination of platinum in minerals and alloys.     

The determination of microgram quantities of organic nitrogen

A method is descriibed for the determination of microgram quantities of nitrogen in a wide variety of materials. This method involves the Kjeldahl procedure for the conversion of nitrogen to ammonium or amine sulphate. Digestion of the sample with concentrated sulphuric acid and catalyst, and, if necessary, pretreatment with hydriodic acid and red phosphorus, are followed by steam-distillation into a dilute acid solution. The final determination depends on the reaction of ammonia, in a suitably buffered solution, with sodium hypobromite reagent, and measurement of the excess reagent by titration of the iodine liberated by it from acidified potassium iodide, with a standard $\text{N}\text{500}$ sodium thiosulphate solution, using sodium starch glycollate indicator.Since sample size is relatively unrestricted and the final titration can measure 5 micrograms of nitrogen, the sensitivity of the method is very high.Reference is made to existing sub-micro methodes which, although sensitive, are time-consuming and specific in application.     

Simultaneous determination of uranium and thorium in high grade thorium ores

A routine procedure has been developed for the simultaneous determination of uranium and thorium in high concentration thorium ores. INAA is used to determine the uranium and thorium concentration. However, for very low concentrations of uranium a radiochemical procedure based on the use of NPy/benzene as an extractant has to be employed. The precision and accuracy of the method has been determined by analyzing IAEA and NBL standard thorium/uranium ores.     

Spectrophotometric determination of silicon in thorium oxide

A method is described for the spcctrophotometric determination of microgram quantities of silicon in the presence of thorium. Thorium oxide is dissolved by heating it at 70 to 8o°C in 4M HNO₃ that contains 2 drops of HF. Under these conditions, no silicon is lost through volatilization. The silicon is estimated as the blue ailicomolybdate complex. Under the conditions selected for development of color, a precipitate of thorium molybdate is obtained ; the thorium molybdate is, however, dissolved without affecting the color of the complex by the addition of tartrate and adjusting the pH of the solution to 3.0. The lower limit of detection is about 5 p.p.m. of silicon.     

The determination of microgram quantities of sulphide in biological materials

Several methods for the estimation of microgram quantities of sulphide in biological material and enzymatic reaction mixtures were investigated- The optimum conditions for separation of sulphide by isothermal distillation are given. The formation of méthylène blue is recommended for the spectrophotometric determination of sulphide; modifications are described to improve the reliability and sensitivity of the method.     

The polarographic determination of microgram quantities of oxalic acid

A brief critical summary of possible methods for the determination of micro quantities of oxalic acid in solution is presented, and details are given of a satisfactory polarographic procedure for the determination of this material down to a level of 10 microg per ml in the final solution. This method involves the adjustment of the pH of the sample solution, followed by precipitation of the oxalic acid as europium oxalate. The excess europium is then determined polarographically. The method is applicable in the presence of 1M ammonium nitrate and in the presence of ammonium salts of other common acids. Iron and chromium interfere and must be absent.     

Spectrophotometric determination of indium using gallion

Summary The formation of violet coloured chelate of indium with Gallion has been studied. Indium forms only one chelate with Gallion at p_H 4.5 having _max 610 nm. The composition of the complex formed has been determined by various methods and is found to be 11 (MR). The values of stability constant have been calculated by three methods and the average value of logK obtained is 5.6 ± 0.1. A procedure for the spectrophotometric determination of indium has been suggested.

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Zusammenfassung Die Bildung eines violetten Chelates von Indium mit dem Reagens Gallion wurde studiert. In bildet damit ein einziges Chelat bei p_H=4,5 und _max=610 nm. Die Zusammensetzung des entstandenen Komplexes wurde nach verschiedenen Methoden ermittelt und gleich 11 (MetallReagens) gefunden. Die Stabilitätskonstante wurde nach drei Verfahren berechnet, wobei sich als Mittelwert logK=5,6±0,1 ergab. Eine Arbeitsvorschrift für die spektrophotometrische Bestimmung des In wird vorgeschlagen.

     

Polarographic determination of microgram amounts of thorium(IV)

Summary Among various salt solutions tested 0.01 N LiNO₃ proved to be most suitable as supporting electrolyte for the polarographic determination of microgram amounts of thorium. Well-developed, maxima-free and reproducible waves were obtained for a Th(IV) concentration range of 1.4–23 g/ml. The minimum detectable limit of the element was 0.8 g/ml. No relationship has been found between Th(IV) and H⁺-ion concentration.

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Polarographische Bestimmung von Mikrogramm-Mengen Thorium(IV)

Zusammenfassung Von verschiedenen untersuchten Salzlösungen hat sich als Grundelektrolyt 0,01 N LiNO₃-Lösung als am günstigsten erwiesen. Es wurden damit gut ausgebildete, maxima-freie und reproduzierbare Stufen für einen Konzentrationsbereich von 1,4–23 g Th(IV)/ml erhalten. Die Nachweisgrenze betrug 0,8 g Th(IV) in 1 ml Lösung. Es wurde kein Zusammenhang zwischen Thoriumkonzentration und H⁺-Ionenkonzentration nachgewiesen.

     

Spectrophotometric determination of microgram amounts of chlorpromazine with chloranil

A simple spectrophotometric method for the determination of small amount of chlorpromazine has been developed. The reaction of chloranil as π-acceptor reagent with chlorpromazine was studied. The method is rapid, simple, and relatively sensitive and precise (RSD 1.8%). Beer's law was followed within the approximate concentration range of 50–900 μg in a final volume of 25 ml. Negative deviation was abserved beyond these limits. The general analytical and physical parameters were also established.     

Quantitative inorganic paper chromatography direct determination of nickel in microgram quantities

A method has been developed for the direct determination on filter paper of nickel, after Chromatographic separation of interfering elements. The sample is dissolved in ₃N hydrochloric acid and the solution is spotted on filter paper, together with standard solutions of nickel. After chromatographic development with a mixture of acetone, hydrochloric acid and acetylacetone, the nickel spot, which has scarcely moved, is made visible by spraying with a solution of rubeanic acid, and its reflectance is measured with a Beckman DU Spectrophotometer at 625 mμ. Most interfering elements have moved away because of their high R_F values. In the presence of large amounts of aluminiun, chromium, titanium or vanadium, a preliminary extraction of the nickel is necessary. Several technical alloys have been analyzed successfully by this method, for which only 0.045 ml of solution, containing 0.45–9 μg of nickel, are needed, although its precision is equal to that of the best colorimetric methods.