Kailash N. Munshi

Metal chelates of rare earths: I. Composition, stability, and analytical applications of Alizarin Red S chelates of scandium and yttrium

Abstract The formation of pink colored chelates between scandium and Alizarin Red S (λ max 500 mμ) and yttrium and Alizarin Red S (λ max 510 mμ) at pH 4.0 have been reported. Absorbance measurements indicate the composition of the chelates to be 1:2 (metal:chelating agent). Adherence to Beers law is observed over a wide range of metal concentration; the color intensities are also stable within a wide range of pH. The values of log K ( K = stability constant) have been calculated by two different methods and are (1) 9.0 and 9.4 for the scandium chelate, and (2) 9.6 and 9.5 for the yttrium chelate (pH = 4.0; temperature = 25 °C). The effect of pH, temperature, time, and diverse ions on the reactions have been studied, and suggestions have been made on the possible use of Alizarin Red S in the determination of scandium and yttrium.

Chelate formation of trivalent gallium with 1,2-dihydroxy-3-anthraquinone sulfonic acid: Spectrophotometric studies on the composition, stability, and analytical applications

Abstract The formation of a red-colored chelate between trivalent gallium and 1,2 dihydroxy-3-anthraquinone sulfonic acid (ARS) with maximum absorption at 490 mμ has been reported. The composition of the chelate has been determined by the methods of continuous variations, mole ratio, and slope ratio with a Unicam SP 500 spectrophotometer for the absorbance measurements. The chelate has the composition corresponding to Ga(ARS)2 and is stable between 3.0–5.0 pH. The stability constant of the chelate has been calculated by four different methods e.g., the (a) method of Dey and coworkers, the (b) method of continuous variations, the (c) method of mole ratio, and the (d) method of calculating the molecular extinction coefficient. The values of log K at 25 °C are (a) 9.8 ± 0.2, (b) 9.3 ± 0.1, (c) 9.3 ± 0.1, (d) 9.5 ± 0.4, respectively. The range of concentration for adherence to Beers law (p.p.m.), the value of molecular extinction and the sensitivity of the color reaction are 0.55–14.0 p.p.m., 0.47 × 104 and 0.07 (γ/cm2), respectively.

Photometric determination of gallium, indium, and thallium employing Solochrome Cyanine R

Abstract The formation of violet color between SCR and Ga(III), In(III), and Tl(III) have been studied. The analytical data for the spectrophotometric determination of these metals with SCR have been calculated. Range for adherence to Beers law, sensitivity, and the values of molecular extinction coefficient, suggest SCR as a sensitive reagent for the spectrophotomctric determination of Ga(III), In(III) and Tl(III).

2-(p-Sulfophenylazo)-1,8-dihydroxy naphthalene-3,6-disulfonic acid as a sensitive reagent for rare earth metals

Abstract A spectrophotometric study of the color reaction of 2-(p-sulfophenylazo)-1,8-dihydroxy naphthalene-3,6-disulfonic acid (SPADNS) with rare earth metals is described for the determination of micro amounts of rare earths. The absorbance curves of the complexes at pH 6.0 show the λmax for La and Ce to be 545 mμ; for Pr, Nd, Tm 550 mμ; for Y 555 mμ; for Eu, Tb, Dy 560 mμ and for Sm, Ho, Er, Er, Yb it is 565 mμ. The λmax of the reagent at this pH is 515 mμ. The study was made at 580 mμ where the reagent absorbs very little. The molar ratio for all the chelates is found to be 1:1 by the method of continuous variations as well as by mole ratio method. The optimum conditions for the microdetermination of rare earth metals using this reagent have been described and include effect of pH on the color intensity of the chelate, effect of excess of reagent on the absorbance of the chelate, range of adherance of Beers law, sensitivity, molar extinction coefficient, rate of color formation, and stability of color at room temperature.

Spectrophotometric determination of lanthanides using 4-(2-Pyridylazo) resorcinol

SummaryThe formation of red colour produced by the interaction of 4-(2-pyridylazo) resorcinol (PAR) and rare earths has been studied to determine the composition, stability and other characteristics of the chelates formed. Theλmax of all the chelates was found to be 515 nm atph 6.2 whereas theλmax of the PAR reagent at this pH is 410 nm. The composition of the chelates was found to be 1∶2 (metal∶PAR) and has been established by two different methods. The stability constant values have been calculated by three different methods. The values of logK, lies in the range of 9.2–10.4 for different rare earth chelates. The chelates are stable over a wide range of pH. A tentative suggestion has also been made for the position of the chelate ring.ZusammenfassungDie rote Farbreaktion von 4-(2-Pyridylazo)-resorcin (PAR) mit Seltenen Erden wurde untersucht, um die Zusammensetzung, die Stabilität und andere Merkmale der dabei entstehenden Chelate zu bestimmen. Beiph 6,2 wurde das Absorptionsmaximum aller Chelate bei 515 nm, das Absorptionsmaximum von PAR bei 410 nm gefunden. Die Zusammensetzung entspricht dem Verhältnis Metall: PAR=1∶2; sie wurde nach zwei verschiedenen Methoden ermittelt. Die Komplexkonstante wurde auf drei verschiedenen Wegen bestimmt. logK liegt bei den verschiedenen Seltenen Erdmetall-Chelaten zwischen 9,2 und 10,4. Die Chelate sind in einem weitenph-Bereich beständig. Die Lage des Chelatrings wurde erörtert.

ABSORPTIOMETRIC STUDY OF THE CHELATES FORMED BETWEEN THE LANTHANOIDS AND XYLENOL ORANGE.

SummaryThe formation of violet coloured chelates (λmax=570 nm) between the lanthanoids and Xylenol Orange at pH 5.5 is reported. Absorbance measurements indicate the composition of all the chelates to be 1∶1 and the chelates are stable over pH 4.0 to 7.0. The values of logK for various lanthanoid chelates of DCAC lie in the range of 4.5 to 5.4. The dissociation constants of Xylenol Orange have been evaluated and the position of the chelation has been suggested.ZusammenfassungÜber die Bildung violett gefärbter Chelate (λmax=570 nm) aus Lanthanoiden und Xylenolorange bei pH 5,5 wurde berichtet. Absorptionsmessungen weisen in jedem Fall auf die Zusammensetzung 1∶1 hin. Die Stabilität der Chelate ist zwischen pH 4,0 und 7,0 gegeben. Der Logarithmus der Komplexkonstanten der verschiedenen Lanthanoidchelate mit Xylenolorange beträgt 4,5 bis 5,4. Die Dissoziationskonstanten von Xylenolorange wurden ermittelt und die Stellung des Chelatrings angegeben.

Absorptiometric study of ammonium aurintricarboxylate as a reagent for palladiumII

Abstract A new colorimetric method for the determination of bivalent palladium with ammonium aurintricarboxylate (Aluminon) is described. The method involves the formation of a violet chelate of palladium-Alummon at pH 4.0. The colour reaction has a sensitivity of 0.026 μg. cm−2 for log I0/I = 0.001, and obeys Beers law over the range 0.14–7.7ppm of palladium. The effects of pH, time, order of addition of the reagents, temperature, and diverse ions have been investigated, and a procedure for the microdetermination of palladium is described. The composition of the complex has been confirmed by three different methods as 1:2 (metal :reagent), and an equilibrium constant of 109.8 was found by the method of Dey et al. at pH 4.0, temperature 25° and ionic strength 0.1 M.

Spectrophotometric determination of indium using gallion

SummaryThe formation of violet coloured chelate of indium with Gallion has been studied. Indium forms only one chelate with Gallion at pH 4.5 havingλmax 610 nm. The composition of the complex formed has been determined by various methods and is found to be 1∶1 (M∶R). 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.ZusammenfassungDie Bildung eines violetten Chelates von Indium mit dem Reagens „Gallion“ wurde studiert. In bildet damit ein einziges Chelat bei pH=4,5 undλmax=610 nm. Die Zusammensetzung des entstandenen Komplexes wurde nach verschiedenen Methoden ermittelt und gleich 1∶1 (Metall∶Reagens) 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.

SPECTROPHOTOMETRIC DETERMINATION OF TRIVALENT RUTHENIUM AND RHODIUM WITH THORON.

Abstract Thoron was proposed as a sensitive and selective chelating reagent for the spectrophotometric determination of ruthenium (III) and rhodium(III). The mixture, metals and the reagent have to be maintained at boiling water temperature for 70 and 80 minutes, respectively, to give characteristic coloration. The molar ratio is 1:2 (metal:reagent) in both the chelates. The stability of the chelates, its composition, and analytical applications also were investigated and suggestions were made for the structure of the chelates.