A.K. Majumdar

SEPARATION OF NIOBIUM AND TANTALUM WITH N-BENZOYL-N-PHENYLHYDROXYLAMINE

Abstract The use of N-benzoyl-N-phenylhydroxylamine for the separation of niobium and tantalum, allows a satisfactory estimation of niobium from a tartrate solution at an acidity of 2.0 N . The pH range for complete precipitation can be extended to 6.5. For tantalum precipitation, the pH of the solution should be below 1.5 and the acidity may even be above 2.0 N . At pH 3.5–6.5, niobium is completely precipitated and tantalum remains in solution; the latter is precipitated by lowering the pH. Niobium and tantalum in ratios of 1:16 to 100:1 can be separated by a single precipitation, in the case of a ratio of 1:100 precipitation must be carried out twice. Titanium, zirconium, vanadate and molybdate interfere with the determination of niobium though other ions have no effect in the presence of complexone III and tartaric acid. The precipitates are granular and easy to filter and wash. The time taken for a complete analysis is much less than that of other methods

Spectrophotometr1c determination of palladium : Bismuthiol i as an analytical reagent

Abstract The reagent, bismuthiol l, has been successfully utilized for the spectrophotometric determination of palladium. The colour reaction is instantaneous and the system is stable for at least 24 hours in the pH range 6 to 10 but shows no sharp peak of maximum absorption. The system obeys Beers law at a palladium concentration of 0.8 μg to 8.0 μg per ml at any wavelength between 400 mμ and and 410 mμ giving a sensitivity of 0.08 μg of palladium per cm2 (practical); 0.01 μg of palladium per cm2 (sandell). Ethyl alcohol stabilizes the system against any deviation due to appearance of turbidity. A large excess of the reagent and almost all thc cations and anions, except platinum, gold, copper, chromium, iron, mercury, silver, thallium, uranium, vanadate and cyanide, do not interfere. By applying jobs method of continuous variation it was found that the complex contains thc reactants in 1 : 1 ratio and that the average value of the dissociation constant of the complex is 3.2 . 10-5 at 25°.

Spectrophotometric determination of vanadium with n-benzoyl-o-tolylhydroxylamine

N-Benzoyl-o-tolylhydroxylamine is shown to provide a virtually specific reagent for the spectrophotometric determination of vanadium. The reddish-violet complex formed with the reagent in 4–8 N hydrochloric acid after extraction with chloroform shows absorption maxima at 510 mm, and obeyes Beers law from 0.5 to 10 μg with an optimum range of 2–10 μg; the percent relative error is 2.7. The sensitivity is 0.0108 μg V/cm2. The complex contains the metal and the reagent in a ratio of 1:2 and the dissociation constant is of the order of 10-9.

Direct estimation of niobium by n-benzoyl-n-phenylhydroxilamine

Abstract N-benzoyl-N-phenyl hydroxylamine, with niobium, forms a complex of composition NbO(C13H10NO2)3 which is stable up to a temperature of 229°. Niobium, thus, can be separated from tantalum and other elements as this complex and weighed, directly after being dried at 110°.

α-Picolinic acid as a colorimetric reagent: Determination of ferrous ion

α-Picolinic acid has been used as a reagent for the colorimetric estimation of ferrous ion. The transmittancy measurements show that iron from 0.08 p.p.m. to 12 p.p.m. may be easily determined with a cell of capacity 16 ml and thickness 20 mm. The effect of time, temperature and of diverse ions on the coloured system with an absorption maximum at 440 mμ have been critically examined. The optimum range with minimum relative error is found to be in the region of 1.6 to 8 p.p.m. By jobs method the composition of the ferrous complex, which is highly soluble and stable in water, is Fe(C6H4O2N)2 with a dissociation constant in the order of 10-5. α-Picolinsaure wurde als Reagens zur kolorimetrischen Bestimmung von Ferroionen benutzt. Mit dieser Methode kann man leicht Eisen in einer Konzentration von 0.08-12‰ in einer Zelle mit einem Fassungsvermogen von 16 ml und einer Dicke von 20 mm bestimmen. Der Einfluss der Zeit, der Temperatur und verschiedener anderer Ionen auf das gefarbte System mit einem Absorptionsmaximum bei 440 mμ wurde kritisch uberpruft. Der optimale Bereich mit dem geringsten relativen Fehler wurde in dem Gebiet von 1.6-8‰ gefunden. Die Zusammensetzung des Ferrokomplcxes, der ausserordentlich gut loslich und stabil in Wasser ist, ist nach der Jobschen Methode Fe(C6H402N)2 und besitzt eine Dissoziationskonstante in der Grossenordnung von 10-5.

Some new aromatic hydroxylamines as spectrophotometric reagents for vanadium

Abstract A comparative study is described of the use of N-benzoyi- o -tolyl-, N-benzoyl- m -tolyl, N-benzoyl- p -tolyl-, N-benzoyl- p -chlorophenyl- and N-phenylacetylphenyl-hydroxylamines, as spectrophotometric reagents for the determination of vanadium, after extraction with chloroform. All the reagents form 1:2 (metal:reagent) complexes in hydrochloric acid media or at pH 4.8–6.0; the dissociation constants of the complexes are of the order of 10 -9 and 10 -8 , respectively, except those of N-benzoyl- p -chloro-phenylhydroxylamine which are of the order of 10 -8 in both media. The reactions in hydrochloric acid media are more selective and sensitive than those at pH 4.8–6.0. In presence of alcohol, the wavelengths of maximum absorption decrease. The p K a values of the hydroxylamines were determined in water and in alcohol-water (1:1) solutions.

Separation of niobium and tantalum from zirconium with salicylhydroxamic acid

Abstract Salicylhydroxamic acid can be used for the separation of zirconium from niobium above pH 2 5 in presence of hydrogen peroxide. Niobium can be precipitated from the filtrate with N-benzoyl-N-phenylhydroxylamine.

Spectrophotometric determination of palladium: A comparative study of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole as analytical reagents

As spectrophotometric reagents for palladium 2-mereaptobenzothiazole and 2-mereaptobenzothiazole behave more or less in the same way. Colour system formed by them at a pH region of 3.0 to 6.5 obey Beers law at 380 mμ palladium concentration of 0.4 to 6.0 mμ per ml and the optimum range with the minium is from 1.6 to 4.0 μg of palladium per ml at 30.1% and 35.8% treansmission with 2-mereaptobenzothiazole and 2-mereaptobenzothiazole respectively. By applying jobs method it was found that in solution the ratio of metal to reagent in the complexes is 1:2 and that the dissociation constants of the order of 10-12.

Spectrophotometric determinations of iron(III), titanium(IV) and vanadium(V) and their separation from each other and from other ions with 1-(o-carboxyphenyl)-3-hydroxy-3-phenyltriazene

Abstract 1-( o -Carboxyphenyl)-3-hydroxy-3-phenyltriazene is shown to be an excellent spectrophotometric reagent for the determination of iron (III), titanium(IV)and vanadium(V). Iron(III) forms an intense violet complex in presence of tartaric acid at pH 9.5 and titanium (IV) and vanadium(V) form yellow and green comlexes, respectively, at pH 1.0. The wavelengths of maximum absorption of the complexes of iron(III), titanium(IV) and vanadium(V) in chloroform are 500, 430 and 410nm, respectively. Beers law is valid with optimum ranges 1.0–11.0 p.p.m. for iron(III), 0.5–4.0 p.p.m. for titanium(IV) and 1.0–6.0 p.p.m. for vanaduim(V), where the relative errors are 2.78, 2.76 and 2.83%. The reagent forms 1:2 complexes with iron(III) and titanium(IV) and a 1:1 complexe with vanadium(V), with instability constants of the order of 10 -10 , 10 -9 and 10 -8 , respectively. Interfering effects of other anions and cations on the color systems were studied; common complexing agents, such as fluoride, phosphate, citrate and tartrate when present even to the extent of 400 p.p.m. have no effect. A procedure for the separation and determination of iron, titanium and vanadium in presence of each other is described.

Electro-chromatography in the separation of ions : Part II. Separation of precious metals

Abstract An electrochromatographic study of the migration rates and sequences of the precious metals, as Pt +4 , Os +4 , Ir +4 , Ru +3 , Rh +3 , Au +3 and Pd +2 , on paper strips, reveals that quite a large number of electrolytes effectively separate in distinct zones at least four ions present in microgram amounts in a mixture, when the voltage is maintained at 150 V for 5 hours.