Spectrophotometric determination of iron (II) with quinisatin oxime

A sensitive spectrophotometric determination of iron is based on the blue color (absorption maximum at 660 mμ) formed by reaction of iron (II) with quinisatin oxime in buffered solution containing ethyl alcohol and a small amount of dimethylformamide. The color develops rapidly and is stable for a few h. The absorbance is well reproducible, and conforms to Beer's law. The optimum concentration range at 1 cm optical path is about 0.5 to 2.5 p.p.m. of iron. Small amounts of iron(III) are reduced by the reagent and cause no difficulty. Cobalt and nickel interfere. Iron(II) and quinisatin oxime react in a 1:3 mole ratio; some possible modes of complex formation are suggested.     

Spectrophotometric determination of osmium with p-(morpholino)-n-(4'-hydroxy-3'-methoxy)benzylidineaniline

A sensitive spectrophotometric determination of osmium is based on the blue color (absorption maximum at 615 mμ formed by reaction of osmium with p-(morpholino)-N-(4'-hydroxy-3'-methoxy)benzylidineaniline (“anil”) in acetate-buffered solution containing ethanol to prevent formation of a precipitate, Full color development is attained in I h at room temperature, and the color is stable for several hours. The absorbance is reproducible. The optimum concentration range for I-cm optical path is about I to 4 p.p.m. of osmium. Several transition elements interfere ; osmium can be separated as its tetroxide by the usual distillation method. The blue product is a cationic complex formed by reaction of anil with osmium in a 2 : I mole ratio. When osmium is in excess a red cationic complex (absorption maximum at 466 mμ) is formed by a I : I reaction between osmium and the reagent. The I : I complex is slowly converted to the 2 : I complex by excess reagent.     

Colorimetric determination of osmium (VI) with 1-naphthylamine-3,5,7-trisulfonic acid

An investigation has been made of the organic compound, 1-naphthylamine-3,5,7-trisulfonic acid, for use as a colorimetric reagent for the determination of trace quantities of osniiun(Vl). When this compound is added to an osmium (OsO₄^-2) solution, a violet colored organo-osmium complex is formed which has highest sensitivity at wavelength 560 mμ. The complex reaches maximum color intensity after four hours. The solution should be brought to pH 1.5 and maintained at tins pH with a buffer, after maximum color development. The colored complex conforms to Beer's law over an osmium concentration range of 0 to 6 p.p.m. Its absorbance is not affected by either excess reagent (up to a 7 : 1 ratio) or by temperature variation over the range 15° to 35° C. Many metallic ions interfere with the color reaction and hence require a separation, of osmium from these ions.The nature of the complex in solution was studied by the following three methods: (1) mole ratio, (2) continuous variations and (3) slope ratio. All three methods indicate a ratio of reagent to osmium of 2 to 1.A procedure for the colorimetric determination of osmium(VI) has been developed; it has a sensitivity of 1 part osmium in 15,000,000 parts of solution, with good precision.     

Tiron as a spectrophotometric reagent for the estimation of osmium

A method for the spectrophotometric determination of osmium with tiron as a reagent has been described. The reagent forms a soluble and stable coloured complex on heating with osmium in the presence of sodium acetate. The regions of maximum and minimum absorptions are at 470 mμ and 410 mμ, respectively, and the system obeys Beer's law from 2 to 32 p.p.m. of osmium. But the optimum range, with the relative analysis error of 2.878% per 1% absolute photometric error, is from 8 to 24 p.p.m. of osmium. The sensitivity of the reaction is 0.033 μg/cm² (SANDELL) and the molar extinction coefficient is 5706. In solution, the complex is formed when the osmium and the reagent are in a ratio of l : 1 ; it has an instability constant equal to approximately 5.57? 10^-5.     

Spectrophotometric determination of osmium: Sulphanilic acid as a reagent

Sulphanilic acid has been found to be a very effective reagent for the spectrophotometric determination (if hexavalent and octavalent osmium in the pH range between 1.8 – 3.5. In these two valence states, the element forms a dark-violet complex with the reagent, the absorption maximum of the complex being at 490 mμ. As most of the other ions interfere in the determination, the element must be separated as osmic acid by nitric acid distillation. Beer's law is obeyed in the case of 0.5 to 9 p.p.m. of osmium (VIII) and l to 18 p.p.m. of osmium (VI); tin-optimum concentration ranges are from 2 to 8 p.p.m. for osmium(VIII) and from 4 to 16 p.p.m. for osmium(Vl). In these ranges, the % relative errors per 1% absolute photometric error are 3.02 for osmium (VIII) and 3.1 for osmium(VI). Application of the method of continuous variations and the molar ratio method indicates that in solution hexavalent osmium and the reagent form a 1:2. complex, with an average dissociation constant of 1.2 ? 10^-7.     

Spectrophotometric determination of osmium with 1-naphthylamine-4,6,8-trisulfonic acid

This investigation was undertaken to determine if the naphthylamine sulfonic acid-osmate (OsVI) reaction is suitable for a spectrophotometric determination of osmium. The 1-naphthylamine- 4, 6,8-trisulfonic acid osmate complex is water-soluble and forms a stable violet-colored system at PH 1 to 1.5 that is independent of reagent concentration. At 555 mμ the colored complex obeys Beer's law over a concentration range of 0.1 to 6.5 p.p.m. osmium and remains stable with respect to time and temperature. The effects of pH, temperature, reagent concentration, and diverse ions were studied. The nature of the organo-osmate complex in solution was studied by three techniques and the effect of temperature and pH on the rate of complex formation was determined. A procedure for the removal of osmium from all interfering ions was developed based on well known distillation techniques.A convenient, sensitive, reproducible and accurate method for the spectrophotometric determination of osmium has been developed.     

The simultaneous determination of ruthenium and iridium in osmium sponge by neutron activation analysis

A radiochemica1 separation procedure for Os-Ru-Ir is decribed based upon selective distillation. In sulfuric acid-hydrogen peroxide 99.999–99.9999% of the osmium can be distilled if reoxidation of the osmium with permanganate is applied. From sulfuric acid-sodium bromate solution more than 99% of the ruthenium activity can be recovered. More than 99.995% of the iridium remains in the residue.The method was applied to neutron activation analysis of Io-mg samples of osmium sponge and allows the determination of traces of ruthenium down to approximately ro p.p.m. and of iridium down to 0.5 p,p.m. For lower iridium contents, second-order interference of the osmium must be taken into account, the error being approximately 0.05 p.p.m. after an irradiation period of 5 days at a flux of 4–10¹¹ n/sec/cm².     

Colorimetric determination of molybdenum with disodium-1,2-dihydroxybenzene-3,5-disulfonate

A procedure for the colorimetric determination of molybdenum with disodium-1, 2-dihydroxybenzene-3,5-disulfonate (Tiron) has been presented. The maximum absorbancy of the yellow colored complex is at 390 mμ the optimum pH range is 6.6-7.5; and the Tiron concentration is 1.5-2%.The color reaction conforms to Beer's law and has a practical sensitivity of 0.1 p.p.m. molybdenum. The color formation is instantaneous and stable for at least three weeks. There is no temperature effect over the range of 15° — 40° C.The tolerances of the colored complex to many diverse ions have been established. The separation of molybdenum from interfering ions is accomplished by precipitation of the former with α-benzoinoxime. Molybdenum and tungsten are separated photometrically.The colorimetric determination of molybdenum with Tiron was successfully applied to a variety of steels and other materials.     

The spectrophotometric determination and solvent extrāction of osmium with o-(β-benzoylthiourido)benzoic acid as reagent

o-(β-Benzoylthiourido)benzoic acid is proposed as a spectrophotometric reagent for the determination of osmium. The brownish yellow complex formed is soluble in alcohol and in other organic solvents. The colour system obeys Beer's law from 3 to 18 p.p.m. of osmium at 410 mμ with an optimum range of 3–15 p.p.m., where the percent relative error per 1% absolute photometric error is 2.75%. A 1:1 complex is formed and the dissociation constant is of the order of 10^-5. With prior extraction of palladium as the axide complex with n-butanol, osmium can be separated from almost all ions, including those of platinum metals, by extraction witli ethyl acetate.     

Spectrophotometric methods for the determination of osmium-II Extraction and determination of osmium in situ with 1.5-diphenylcarbohydrazide

A method has been developed for the spectrophotometric determination of microgram quantities of osmium in uranyl sulphate solutions. The osmium is oxidised to osmium tetroxide, then extracted with chloroform. The extracts are added to an ethanolic solution of 1:5-diphenylcarbohydrazide. A blue-violet coloured reaction product is formed which exhibits maximum absorbancy at 560 mμ. After a period of 2 hr for colour development the molar absorbancy index is about 31,000. Beer's law is adhered to over a range of 30 to 100 μg of osmium with a coefficient of variation of about 4%. A study was made of the effects of foreign substances and only chloride and octovalent ruthenium were found to interfere. Both of these interfering ions can be eliminated.     

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

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, WO₄^-2, Cr⁺³, Zn⁺², Zr⁺⁴, Mg⁺², Ba⁺² and Sr⁺² do not interfere     

The determination of traces of osmium in ruthenium sponge by neutron activation analysis

Tracer techniques confirmed that a quantitative separation of osmium and ruthenium is possible by distillation from a hydrogen peroxide-sulphuric acid solution. Osmium distils quantitatively as OsO₄ at a temperature of 105 ± 5° in about 30 min. The ruthenium contamination is approximately 0.01 %.In the present work a neutron activation analysis is described for the determination of traces of osmium in ruthenium sponge. When quantities of osmium below 30 p.p.m. are determined, the ruthenium contamination of the distillate must be taken into account, when the measurement is made with a 3” x 3” NaI(Tl) crystal. This can easily be achieved by measurement in two energy regions with a γ-spectrometer or with a multichannel pulse-height analyzer. With a NaI(T1) wafer as detector, the correction for ruthenium can be omitted for osmium concentrations above 10 p.p.m.With the addition method of analysis, 10–2000 p.p.m. in 10-mg samples of ruthenium sponge can be determined by neutron activation analysis. Chemical separation is necessary but no carriers are required. The lowest limit of determination is about 3 p.p.m. for a 3” x 3” crystal; for the wafer, about 1 p.p.m. can be determined.     

Spectrophotometric determination of palladium(II) with 5 (p-dimethylaminobenzylidene)rhodanine

A sensitive spectrophotometric method has been developed for tlie deternination (of pallaudium, busing 5(p-dimethylaminobenxylidene)rhodanine reagent in formic, hydrochloric, or propionic acid solution. The systems conform to Beer's law. The specific absorptivity is in the range 0.38 to 0.40 per p.p.m.-cm in the different solvents. The optimum range for 1.00-cm optical path is about 0.4 to 2.5 p.p.m. of palladium. At higher concentrations of palladium a violet-red precipitate forms within a few minutes. In propionic acid solution maximum color is attained at room temperature in 10 to 15 min, and is stable for more than two hours. The system is somewhat sensitive to hydrogen ion concentration; maximum absorbance and stability are attained at 0.01 N hydrochloric acid in tlie final .solution, Platinum (IV), ruthenium (III), iron(lll), iron (III), chromium (VI), and copper(ll) interfere if present in amounts several times greater than the amount of palladium ; gold(ll1) interferes very exensively. Tlie mole ratio method, the continuous variations method, and the slope ratio method all show the mple ratio of DMABR to palladium to be 2 : 1 in the color-forming reaction.     

Nature of the cherry-red transient formed during the interaction of osmium tetroxide with hydrogen peroxide

Summary A cherry-red transitory coloration is formed when OsO₄ or osmium(VI) is added to alkaline hydrogen peroxide solution in the pH range 9–13. The transient has an absorption maximum at 530 nm and its concentration depends on the pH of reaction mixture reaching a maximum at pH 10.5–11. The transient is designated as a peroxo-derivative of osmium(VIII) [or an osmium(VII) — Superoxide radical pair if the peroxoderivative undergoes a fast intramolecular one-electron transfer].Many decades ago it was observed¹ that a cherry-red coloration appears transiently when osmium tetroxide solution is added to alkaline hydrogen peroxide solution. However, to our knowledge, there are no literature data about the nature of this transient. Further, we observed recently that there is a close connection between the rate of decomposition of hydrogen peroxide catalysed by osmium tetroxide and the intensity of the coloration, and therefore an attempt was made to investigate the transient by using a fast spectrophotometer technique.     

Spectrophotometric study of the ruthenium(III,II)–2,2′,2″- terpyridine system

Ruthenium(III) reacts with 2,2′,2″-terpyridine in aqueous solution at pH 3.0–4.5, when heated at 85 °C for 2 min, giving a green cationic complex with an absorbance maximum at 690 nm. The color is stable for at least 25 h. The system conforms to Beer's law. The optimal range for measurement (1.00-cm optical path) is 2–10 p.p.m. Ru; the molar absorptivity is 8.3 ·10³. Ruthenium(II) reacts with terpyridine at pH 5.5 to develop an amber cationic complex (absorption maximum at 475 nm) on heating at 95° C for 45 min. The color is apparently stable indefinitely. The system conforms to Beer's law; the optimal range is 1–5 p.p.m. Ru; the molar absorptivity is 1.45·10⁴ l mol^?1 cm^?1. Common anions do not interfere; separation as RuO₄ is necessary when iron and a few other transition cations are present. The green complex, a strong oxidant, is converted to the ruthenium(II) complex by oxidation of water, slowly at room temperature, or more quickly by longer heating and/or higher temperature, and by increase of pH. The Ru(II) complex can be converted to the Ru(III) complex by strong oxidants such as Ce(IV). In the amber complex, the reaction ratio is 1 Ru: 2 terpyridine, in which the ligand is tridentate, whereas in the green complex the reaction ratio is 1 Ru : 3 terpyridine, the latter acting only as a bidentate ligand. Short gentle warming of a mixture of ruthenium(III) and terpyridine first produces a transient unidentified blue-colored species (absorbance at 790 nm).     

Prochlorperazine bismethanesulfonate: Sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium

Prochlorperazine bismethanesulfonate (PCPMS) is proposed as a new sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium. PCPMS forms a red-colored species with osmium(VIII) or osmium(VI) instantaneously at room temperature in 5 M phosphoric acid medium. The red species exhibits maximum absorbance at 529 nm. Beer's law is valid over the concentration range 0.05–3.6 ppm for osmium(VIII) and 0.15–6.4 ppm for osmium(VI). Sandell's sensitivity of the reaction is 2.89 nm cm^?2 for osmium(VIII) and 4.24 ng cm^?2 for osmium(VI). The effects of time, temperature, acidity, order of addition of reagents, reagent concentration, and diverse ions are investigated. The application of the proposed method in the determination of osmium content in synthetic ores has been explored.     

Spectrophotometric determination of osmium

Summary 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. Beer's 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 11 complex with the excess unoxidised reagent.Part III.: Anal. chim. Acta 22, 306 (1960); cf. Z. analyt. Chem. 177, 291 (1960).     

Rapid and selective determination of osmium(IV) by UV-visible spectrophotometry using o-methylphenyl thiourea as a chromogenic chelating ligand: sequential separation of osmium(IV), rhodium(III) and platinum(IV)

The objective of this research work was to develop a simple, highly sensitive and precise method for spectrophotometric determination of osmium(IV). O-Methylphenyl thiourea (OMPT) coordinates with osmium(IV) as a 1:1 (osmium(IV)–OMPT) complex in hydrochloric acid media (0.8 mol l^?1). The novelty of the investigated method is instant complex formation at room temperature with no need of heating or standing. The complex is stable for more than 8 days. The method is applicable over a wide linearity range (up to 110 µg ml^?1). A low reagent concentration is required (2 ml, 0.009 mol l^?1 in ethanol). The complex exhibits maximum absorption in the range of wavelength 510–522 nm and 514 nm was selected for further study. The molar absorptivity was 1.864 × 10³ l mol^?1 cm^?1, Sandell’s sensitivity was 0.102 µg of osmium(IV) cm^?2. Proposed method was successfully applied for separation and determination of osmium(IV) from binary and ternary synthetic mixtures containing associated metal ions. A scheme for mutual separation of osmium(IV), rhodium(III) and platinum(IV) is developed.     

Rapid Spectrophotometric Determination Of Osmium With Cyclohezane 1,3-Dione Bisthiosemicarbazone Monohydrochloride: Simultaneous Determination of Osmium and Platinum

Abstract

A simple, sensitive and rapid spectrophotometric method has been developed for the determination of osmium using cyclohexane 1,3-dione bisthiosemicarbazone mono-hydrochloride (1,3-CHDT.HCl). The method is based on the instantaneous colour reaction between 1,3-CHDT. HCl and osmium(VIII) in sodium acetate—acetic acid buffer medium (pH range 3–6). The osmium complex shows maximum absorbance at 375 nm and considerable absorbance at 510 nm. Although the complex formed between platinum(IV) and reagent (1,3-CHDT.HCl) shows maximum absorbance at 375 nm, it does not show any absorbance at 510 nm. Simultaneous determination of osmium and platinum is carried out when present alone and in presence of other foreign (associated) ions. Some physico-chemical and analytical characteristics of osmium and platinum complex are described. Interference of various foreign ions have studied and osmium is estimated selectively in the presence of constituents of platinum ores.     

Spectrophotometric determination of gallium with 1-(2,4-dihydroxyphenylazo)-2-naphthol-4-sulfonic acid

A new spectrophotometric method for the determination of gallium is described using 1-(2,4-dihydroxyphenylazo) -2-naphthol-4-sulfonic acid (DHPAN) as a reagent. The color reaction has a sensitivity of 0.013 μg Ga per cm² for log 1₀/1=0.005 at 500 mμ and obeys Beer's law up to 2.8 p.p.m. The effects of pH, time, order of addition of the reagents, temperature and diverse ions were investigated. Gallium is separated from interfering ions by solvent extraction.