Use of organic reagents in inorganic analysis

Summary Thorium and zirconium have been determined gravimetrically with phenylglycine-p-carboxylic acid and zirconium alone with phenylglycine-o-carboxylic acid, almost within the same pH range. Better results are obtained when zirconium is precipitated in acetic acid solution in presence of a little ammonium acetate. A number of foreign ions may be separated from thorium and zirconium with these reagents. Iron and titanium cause heavy interference. The interference caused by iron, may however, be eliminated by adding a little ascorbic acid, before precipitation of the metals. The para acid can also extract thorium from a mixture of cerite earths and from monazite sands.Part V: See Z. anal. Chem. 158, 347 (1957).The author likes to thank Dr. B. N. Bose, Principal of the College and Dr. S. K. Sinha, the Head of the Department of Chemistry for their kind advice and encouragements.     

5:6-Benzoquinaldinic acid as an analytical reagent: Determination of titanium

The reagent 5 :6 -benzoquinaldisic acid precipitates titanium(lV) completely from solution at and above pH 3.0 in the presence of rare earths. Coprecipitation of magnesium and the alkaline earths is easily prevented by the addition of ammonium chloride. Separation from iron(III), thorium or zirconium can be carried out in the presence of complexone III. magnesium sulphate being used as a demasking agent. Separation from aluminium is not possible. The titanium precipitate is not of definite composition and so it is ignited to the oxide before weighing.     

Direct complexometric titration of thorium with versene using SPADNS

Summary The existing volumetric methods for the determination of thorium are indirect and unsatisfactory. A direct titrimetric method for the estimation of thorium has been developed which involves the adjustment ofph, addition of 1 ml. of 0.02% SPADNS indicator, dilution to volume and titration with versene. It is based on the fact that thorium forms a coloured complex with SPADNS and after the bulk of thorium has reacted with versene, the highly coloured thorium- indicator complex is destroyed, marking the end point. Quantity of thorium as small as 5 mg. can be titrated accurately when present in a volume of 50 ml. Determination of thorium can also be made in presence of large amount of iron by adding ascorbic acid prior to the titration. Interferences of various ions have also been studied. The method proposed for thorium is selective and should be of considerable use in many cases.The author's thanks are due to Dr. A. K. Ghosal, Principal Darjeeling Government College, for providing all laboratory facilities and Dr. A. K. Mukherjee, Indian Association for the Cultivation of Science, Calcutta for his kind help in the work.     

Analytical aspects of some organic acids

Summary Back titrimetric procedures for the estimation of aluminium, zirconium, and thorium have been developed, which involved the adjustment of the concentration of the metallic salts, concentration of EDTA,ph, and temperature, addition of indicator solution (namely, 2-hydroxy3-naphthoic acid and back titration with standard 0.1 M ferric chloride solution. This method is based on the fact that the excess EDTA, which is added to the metal solutions may be back titrated with iron(III), which forms a highly coloured complex with the indicator, when present in slight excess. Quantities of aluminium, zirconium and thorium as small as 10.8, 4.6, 11.6 mg respectively, can be back titrated with in experimental error, when present in a volume of 100 ml.Part IV: See Z. analyt. Chem. 172, 356 (1960).     

Gravimetric determination of thorium and zirconium

Summary Thorium and zirconium can be quantitatively precipitated by quinaldinic acid atph 2.7 and 3, respectively. As the precipitates are of nonstoichiometric composition they are to be ignited to oxides. By this reagent thorium can be quantitatively separated from arsenic (As³⁺), mercury (Hg²⁺), rare earths, manganese, magnesium and alkaline earths and zirconium from all the aforesaid ions excepting rare earths which contaminate to a slight extent.     

Liquid-liquid extraction of niobium(V) in the presence of other metals with high molecular mass amines and ascorbic acid

A novel method is proposed for the solvent extraction of niobium(V). A 0.1M solution of Aliquat 336S in xylene quantitatively extracts microgram quantities of niobium(V) from 0.01M ascorbic acid at pH 3.5-6.5. Niobium from the organic phase is stripped with 0.5M nitric acid and determined spectrophotometrically in the aqueous phase as its complex with TAR. The method permits separation of niobium not only from tantalum(V) but also from vanadium(IV), titanium(IV), zirconium(IV), thorium(IV), chromium(III), molybdenum(VI), uranium(VI), iron(III), etc. Niobium from stainless steel was determined with a precision of 0.42%.     

Extractive separation of Th(IV), U(VI), Ti(IV), La(III) and Fe(III) from Zarigan ore

In this study, the effects of various extraction parameters such as extractant types (Cyanex302, Cyanex272, TBP), acid type (nitric, sulfuric, hydrochloric) and their concentrations were studied on the thorium separation efficiency from uranium(VI), titanium(IV), lanthanum(III), iron(III) using Taguchi^??s method. Results showed that, all these variables had significant effects on the selective thorium separation. The optimum separations of thorium from uranium, titanium and iron were achieved by Cyanex302. The aqueous solutions of 0.01 and 1 M nitric acid were found as the best aqueous conditions for separating of thorium from titanium (or iron) and uranium, respectively. The combination of 0.01 M nitric acid and Cyanex272 were found that to be the optimum conditions for the selective separation of thorium from lanthanum. The results also showed that TBP could selectively extract all studied elements into organic phase leaving thorium behind in the aqueous phase. Detailed experiments showed that 0.5 M HNO₃ is the optimum acid concentration for separating of thorium from other elements with acidic extractants such as Cyanex272 and Cyanex302. The two-stage process containing TBP-Cyanex302 was proposed for separation thorium and uranium from Zarigan ore leachate.     

Recovery of uranium and thorium from zirconium oxychloride by solvent extraction

A solvent extraction process is proposed to recover uranium and thorium from the crystal waste solutions of zirconium oxychloride. The extraction of iron from hydrochloride medium with P350, the extraction of uranium from hydrochloride with N235, and the extraction of thorium from the mixture solutions of nitric acid and the hydrochloric acid with P350 was investigated. The optimum extraction conditions were evaluated with synthetic solutions by studying the parameters of extractant concentration and acidity. The optimum separation conditions for Fe (III) are recognized as 30% P350 and 4.5 to 6.0 M HCl. The optimum extraction conditions for U (VI) are recognized as 25% N235 and 4.5 to 6.0 M HCl. And the optimum extraction conditions for Th (VI) are recognized as 30% P350 and 2.5 to 3.5 M HNO₃ in the mixture solutions. The recovery of uranium and thorium from the crystal waste solutions of zirconium oxychloride was investigated also. The results indicate that the recoveries of uranium and thorium are 92 and 86%, respectively.     

Rapid determination of thorium in ores : Estimation of trace amounts of thorium in complex minerals and ores

A very rapid method for the estimation, of trace amounts of thorium up to 0.01 per cent. or thereabouts even in complex minerals like ilmenite and columbitetantalite has been described. Thorium is collected in an acid solution with phosphates of zirconium and titanium without prior separation of silica, after decomposition of the mineral with sodium peroxide. Thorium is next collected as fluoride with lanthanum as a carrier, precipitated as thorium iodate in potassium iodate-oxalic acid mixture and finally titrated against 0.01N sodium thiosulphate. Accurate results are obtained within a short time of two working days.     

Organic azo-dyes in quantitative analysis

Summary Chrom Red Brown 5 RD has been found as a sensitive reagent for the spectrophotometric determination of thorium. Concentrations as low as 1 g thorium/1 ml can be easily determined at wave length 485 nm. Sulphate, chloride, ferric and zirconium ions badly interfere, while Li, Na, K, Ni, Co, Cu²+, Cd, Ca, Mg and Cr³⁺ do not. U⁶⁺ and Ce⁴⁺ are permissible as traces.Part II: Zaki, M. R., and K. Shakir: Z. analyt. Chem. 177, 196 (1960).     

Diphenic acid as an analytical reagent

Summary Diphenic acid behaves as a selective reagent for the estimation of thorium in presence of phosphate, arsenate, molybdate, alkaline, earths, copper, cadmium, lead, bismuth, tin, aluminium, chromium, nickel, cobalt, zinc, manganese, magnesium and palladium. Thorium can be successfully separated from the cerite earths by the reagent from solutions having thoria: earth oxide ratio 126 by single precipitation and by double precipitation when the above ratio is 144. The reagent can separate thorium from solutions having ThO₂U₃O₈ ratio upto 180 by double precipitation. The metal can also be recovered from monazite sands.Thanks are expressed hereby to Dr. A. K. Ghosal, Principal, Darjeeling Government College and Dr. A. K. Mukherjee of Indian Association for the Cultivation of Science, Calcutta, for their kind encouragement and to the Government of India, Ministry of Natural Resources and Scientific Research for a gift of Indian Monazite for analysis.     

Omega chrome green BLL: A new analytical reagent

Summary Omega Chrome Green BLL was used as a metal indicator for the direct complexometric titration of copper, lead, thorium and for the back titration of aluminium using thorium as a back titrant. It was also used as a colorimetric reagent for the microdetermination of copper and vanadium. A large number of anions and cations do not interfere in such a determination even if they are present in 10 folds the amount of copper or vanadium. Interference due to ferric iron is simply eliminated by the addition of few crystals of ascorbic acid to reduce it to the ferrous state.     

1-Hydroxy-ethylidene-1,1-diphosphonic acid as a titrimetric agent

1-Hydroxy-ethylidene-1,1-diphosphonic acid (HEDPHA) has been proposed as a highly selective titrimetric reagent for thorium. In the presence of 1,2-diaminocyelohexanetetra-acetic acid (DCTA) a soluble binuclear ternary complex, Th(2)(DCTA)(2)(HEDPHA), is formed. The determination of thorium is carried out in a slightly acidic medium, buffered with urotropine, with 0.025M HEDPHA, and Xylenol Orange as indicator. DCTA masks all bivalent metals, rare earths, scandium, yttrium, bismuth, iron, gallium and indium. Only zirconium, titanium, aluminium and large amounts of thallium(III) interfere.     

Rapid titrimetric determination of thorium with fluoride using SPADNS

Summary A rapid titrimetric method for the estimation of thorium in the range from 5 to 88 mg. in a 50 ml. of final volume has been developed which involves the adjustment of P_h at 3.0, addition of 2 ml. of 0.02% SPADNS indicator, dilution to volume and titration with standard NaF until the colour obtained matches a blank containing the buffered solution of the indicator alone. The method has been standardised against known amounts of thorium and a calibration curve relating the titre of the fluoride solution to thorium content has been prepared. Interferences of various cations and anions have also been studied. From the results, the quantitative nature of zirconium interference has been confirmed. The method for the determination of thorium is very rapid and the colour change being sharp from blue-violet to scarlet-red, the detection of endpoint is not at all difficult.The author wishes to thank Dr. A. K. Ghosal, Principal, Darjeeling Government College, for providing Laboratory facilities and Prof. P. Ray and Dr. A. K. Mukherjee of the Indian Association for the Cultivation of Science, Calcutta for their encouragement in the research work.     

Determination of titanium in high-purity molybdenum and tungsten metals with diantipyrylmethane after separation by extraction of its cupferron complex

A method for determining 0.0005–0.10% of titanium in high-purity molybdenum and tungsten metals is described. After sample dissolution, titanium is separated from the matrix materials by chloroform extraction of its cupferronate from an alkaline (pH 8) tartrate-EDTA medium, then determined spectrophotometrically with diantipyrylmethane at 390 nm. Interference from manganese during extraction is eliminated with sodium sulphite. Iron, zirconium, thorium, tin, aluminium and antimony are partially extracted under the proposed conditions, but moderate amounts of these elements may be present in the sample solution without causing error in the results. Interference from iron(III) during colour development is eliminated with ascorbic acid. Other impurities in the two high-purity metals described do not interfere in the proposed method.     

Use of organic reagents in inorganic analysis

Summary Seven anilic acids obtained from phthalic anhydride and aromatic amines were studied for their quantitative precipitating action on zirconium. The anilic acids from p-toluidine, m- and p-nitranilines and -naphthylamine were only found effective for the quantitative determination of zirconium. Zirconium is completely precipitated at a little lowerph value with these reagents, than thorium. Compositions of the zirconium salts of these acids are not definite, so ignition of the precipitates to zirconia is necessary. Separation of zirconium from common elements like Cu, Al, Cr, Mg, Zn, Ti etc. may be done with ease. But for iron, uranium, cobalt and nickel double precipitation is essential. A considerable amount of thorium has been separated from zirconium, by extraction with amylacetate.     

Column chromatographic separation of thorium(IV) from ascorbic acid medium using poly-(dibenzo-18-crown-6)

A simple separation method has been developed for thorium(IV) using poly-(dibenzo-18-crown-6) and column chromatography. The separation was carried out from ascorbic acid medium. The adsorption of thorium(IV) was quantitative from 0.001-0.01M ascorbic acid. The elution of thorium(IV) was quantitative with 4.0-8.0M HCl, 3.0-6.0M HClO₄, 4.0-8.0M H₂SO₄ and 1.0-8.0M HBr. The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.379±0.01 m^.mol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary as well as in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).     

The determination of zirconium in fluoride-containing solutions

In the recommended procedure the zirconium is first precipitated from solution as the insoluble barium fluozirconate. After separation, the precipitate is dissolved in a mixture of nitric and boric acids and the zirconium is then precipitated as its hydroxide. This precipitate is separated, dissolved in hydrochloric acid and this solution is evaporated to fumes of perchloric acid to remove completely fluoride ions. The zirconium content is then determined volumetrically by adding a slight excess of a standard solution of ethylenediaminetetra-acetic acid and back titrating with a standard iron solution at pH 2.3 using potassium benzohydroxamate as indicator and the photometric technique for end-point detection. This method is applicable to the determination of milligram amounts of zirconium in fluoride-containing nitric or hydrochloric acid solutions provided that the concentration of these acids is below 3N. It is also suitable for the determination of zirconium in the presence of any of the following elements - uranium, titanium, niobium, tantalum, molybdenum, tungsten, lead, iron, copper and tin.