J. G. Sen Gupta

Spectrophotometric determination of osmium : O-Aminophenol-p-sulphonic acid as a reagent

Abstract o -Aminophenol- p -sulphonic acid is suggested as a very sensitive reagent for spectrophotometric determination of osmium (VI) and (VIII) at pH 2 5–4. The absorption maximum is at 440 mμ and the optimum concentration range is from 2 to 8 p p m of osmium Moderate amounts of Pd +2 , lr +4 , WO 4 -2 , Cr +3 , Zn +2 , Zr +4 , Mg +2 , Ba +2 and Sr +2 do not interfereSummarym-Amino benzoic acid in large excess reacts with tetra-, hexa- and octavalent osmium at theph range 4.5–6 to give a purple complex having absorption maximum at 500 nm. Beers law is obeyed for 0.5 to 8 ppm of osmium(VI) and osmium(VIII) with optimum concentration range of 2 to 8 ppm of osmium(VI) and 3 to 8 ppm for osmium(VIII). The per cent relative error per 1% absolute photometric error is 2.8 for both osmium(VI) and osmium(VIII). Ions such as Pd2+, Rh3+, Ir4+, W6+, U6+, Co2+, Hg2+, Mg2+, Ca2+, Ba2+, Sr2+, Th4+ and Zr4+ do not interfere in the determination.Molar ratio method indicates that the reagent first reduces osmium (VIII) and osmium(VI) to osmium(IV), which then probably forms a 1∶1 complex with the excess unoxidised reagent.

Spectrophotometric determination of osmium: Anthranilic acid as a reagent

Abstract Anthranilic acid has been found to be a highly sensitive reagent for the spectrophotometric determination of osmium(IV), osmium(VI) and osmium(VIII) at pH 6.0. In all three valence states the metal reacts with the reagent to form a dark-violet coloured compound, which shows maximum absorbance at 460 mμ. Osmium(IV) can be determined in the presence of diverse ions, if EDTA (disodium salt) is used as a masking agent. The optimun concentration range for the method is 2 to 6 p.p.m. of osmium(IV), where the % relative error per 1% absolute photometric error is only 2.8. By applying J ob s method of continuous variation, the molar ratio method and the slope ratio method, it was established that a 1 : 1 complex is formed between osmium(IV) and the reagent. The reaction of the reagent with osmium tetroxide or osmate indicates that the reagent is first oxidised and that then the reduced osmium(lV) forms a 1 : 1 complex with unoxidised excess reagent. The complex is stable in water and alcohol and has an average dissociation constant of 4.6 · 10-5.

Spectrophotometric determination of platinum

SummaryAnthranilic acid when heated on the steam bath with chloroplatinic acid at pH 5.0 gives a reddish violet complex having absorption maximum at 500 nm. The violet coloured system obeys Beers law from 4 to 64 ppm of platinum (IV) with an optimum concentration range of 16 to 48 ppm where the per cent relative error per 1% absolute photometric error is 2.87.Composition studies by three techniques suggest the formation by platinum(IV) of a 1∶1 complex with the reagent, and the dissociation constant of the complex is 2.6 · 10−4 only when measured at 28° C.

Spectrophotometric determination of ruthenium

SummaryA new method for the spectrophotometric determination of ruthenium with anthranilic acid has been described. The reagent, at PH range 5.2–6, forms with ruthenium(III) a green complex having absorption maximum at 620 nm. The colour system obeys Beers law for 1 to 20 ppm with an optimum concentration range of 4 to 16 ppm where the per cent relative error per 1% absolute photometric error is 3.2. Job and molar ratio methods indicate the formation of a 1∶2 complex between ruthenium(III) and the reagent and the average dissociation constant of the complex is 1.74 · 10−8 at 24° C.

Spectrophotometric determination of osmium

m-Amino benzoic acid in large excess reacts with tetra-, hexa- and octavalent osmium at theph range 4.5–6 to give a purple complex having absorption maximum at 500 nm. Beers law is obeyed for 0.5 to 8 ppm of osmium(VI) and osmium(VIII) with optimum concentration range of 2 to 8 ppm of osmium(VI) and 3 to 8 ppm for osmium(VIII). The per cent relative error per 1% absolute photometric error is 2.8 for both osmium(VI) and osmium(VIII). Ions such as Pd2+, Rh3+, Ir4+, W6+, U6+, Co2+, Hg2+, Mg2+, Ca2+, Ba2+, Sr2+, Th4+ and Zr4+ do not interfere in the determination.

Estimation of palladium

In presence of tartaric acid and ammonium chloride, quinaldinic acid quantitively precipitates palladium from a hot solution at a pH range 3 to 7 whereas other ions such as arsenic (As3+ and As5+), mercury (Hg2+), cadmium, bismuth, antimony, iron, chromium, aluminium, beryllium, thorium, cerium (Ce3+), titanium, zirconium, uranium (UO22+), vanadate, molybdate, tungstate, cobalt, nickel, manganese, magnesium, calcium, barium and strontium remain in solution. The palladium complex is quite insoluble in hot water and can be dried at any temperature up to a maximum of 353° C when it decomposes.

Gravimetric determination of thorium and zirconium

SummaryThorium 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.