2-(8-quinolylazo)-4,5-diphenylimidazole — a sensitive extraction spectrophotometric reagent for mercury

Mercury(II) reacts with 2-(8-quinolylazo)-4,5-diphenylimidazole in aqueous solution; the complex can be extracted with chloroform or 1,2-dichloroethane at pH 4.5–9.5 to give a stable reddish-purple solution. The system conforms to Beer's law; the optimal range in chloroform is 0.05–2 ppm mercury (1-cm cells). Of 25 metal ions investigated, only copper and vanadium interfere seriously. The proposed method is exceptionally sensitive; the molar absorptivity in the chloroform extract is 7.3 × 10⁴ l mol^?1 cm^?1 at 580 nm; the Sandell sensitivity is 0.0027μg Hg cm^?2.     

Spectrophotometric determination of silver with 2-(2-quinolylazo)-5-diethylaminophenol as chromogenic reagent

A new chromogenic reagent, 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP) was synthesized. A highly sensitive, selective and rapid method for the determination of silver based on the rapid reaction of silver(I) with QADEAP has been developed. In the presence of citric acid-sodium hydroxide buffer solution (pH=5.0) and sodium dodecyl sulfonate (SDS) medium, QADEAP reacts with silver to form a violet complex of a molar ratio 1:2 (silver to QADEAP). The molar absorptivity of the complex is 1.33x10(5) L mol(-1) cm(-1)at 590 nm. Beer' s law is obeyed in the range of 0.01-0.6 micro g mL(-1). The relative standard deviations for eleven replicate samples of 0.2 microg mL(-1) is 1.38%. This method was applied to the determination of silver in water with satisfactory results.     

Determination of nickel with 2-(2-quinolylazo)-5-diethylaminoaniline as a chromogenic reagent.

A sensitive, selective and rapid method for the determination of nickel based on a rapid reaction of nickel(II) with 2-(2-quinolylazo)-5-diethylaminoaniline (QADEAA) has been developed. In the presence of pH = 6.0 ammonia-ammonium chloride buffer solution and sodium dodecyl sulfonate (SDS) medium, QADEAA reacts with nickel to form a violet complex having a molar ratio of 1:2 (nickel to QADEAA). The molar absorptivity of the complex is 1.38 x 10(5) l mol(-1) cm(-1) at 595 nm. Beer's law is obeyed in the range of 0.01-0.4 microg/ml. This method had been applied to the determination of nickel with good results.     

4-(8-quinolylazo)resorcinol and 1-(8-quinolylazo)-2-naphthol: Synthesis and sorption properties

A methodology of the synthesis of 4-(8-quinolylazo)resorcinol (QAR) and 1-(8-quinolylazo)-2-naphthol (QAN) was developed. The synthesized compounds were used to modify an oxidized charcoal sorbent. The sorbent efficiently adsorbs copper(II) and zinc(II) cations to form surface electroneutral chelate complexes. The conditions of sorption and desorption of zinc(II) and copper(II) were studied.     

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.     

Salicylhydroxamic acid as an analytical reagent

Summary Salicylhydroxamic acid has been used as a colorimetric reagent for the estimation of uranium, vanadium, molybdenum and iron. It permits the direct estimation of vanadium in presence of molybdenum and uranium, though iron interferes, while the estimation of uranium or molybdenum is not possible in presence of each other or of vanadium. The vanadium complex can be removed from solution by extraction with ethyl acetate and estimated colorimetrically between p_H 0.8 to 3.5. This permits its determination in steels after removal of iron. Sensitivity: U 0.1 g, V 0.017 g, Mo 0.015 g, Fe 0.0125 g.     

Diphenic acid as an analytical reagent

Summary Diphenic acid can separate thorium completely from moderate amounts of ferrous iron and titanium in almost neutral solutions. As the reagent forms quantitative precipitates with ferric iron and zirconium, workable methods for their separation from thorium and their co-determinations in a mixture with the help of this reagent have also been developed. The reagent can separate thorium from zirconium by precipitating the latter below p_h2, and the same from iron(ic) can be accomplished by the use of ascorbic acid as a masking agent. Ferric iron can be precipitated from solution containing ascorbic acid, by the ammonium salt of the reagent. A convenient process for the estimation and separation of zirconium, thorium, iron(ic) and titanium, when present in a mixture, has also been described, which involves the proper control ofph and the use of ascorbic acid as a complexing agent for ferric iron.My sincere thanks are due to Dr. A.K. Mukherjee of the Indian Association for the Cultivation of Science, Calcutta for his valuable suggestions and to Dr. A. K. Ghosal, Principal, Darjeeling Government College for providing laboratory facilities.     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary 0-carboxyphenyl azo chromotropic acid (sodium salt), named as chromotrope 2 C, is used as a new colorimetric reagent for the determination of micro amounts of thorium and aluminium. The blue-violet and red-violet complexes show maximum absorption at 590 nm and the colour systems obey Beer's law from 0.1 to 8 ppm for thorium and 0.1 to 1ppm for aluminium. However, their optimum concentration ranges are from 1.6 to 8 ppm for thorium and 0.2 to 0.8 ppm for aluminium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.06 and 2.94. The composition of the complexes, as elucidated by the continuous variation method, suggests a metal to reagent ratio of 23 for thorium and a ratio of 11 for aluminium. The instability constants for the complexes are of the order of 4.044×10^–10 and 1.006 × 10^–6 at 30°C.Part I, see Z. analyt. Chem. 174, 197 (1960)     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary O-carboxyphenyl azo chromotropic acid (sodium salt), chromotrope 2C, is introduced as a new metallochromic indicator. Its colour reactions with a few metal ions have been utilised for their quantitative chelatometric determinations with EDTA.     

Diallyldithiocarbamidohydrazine (Dalzin) as an analytical reagent

Summary It has been observed that mercury can be quantitatively precipitated by Diallyldithiocarbamidohydrazine (Dalzin) at a p_H of 3–3.5. It has been separated from nickel, zinc, lead, copper, cadmium and bismuth. The latter three have been kept in solution with the help of EDTA.Part. II: Dutt, N. K., and K. P. Sen Sarma: Anal. chim. Acta (Amsterdam) 15, 102 (1956); cf. Z. analyt. Chem. 155, 353 (1957).     

2-Mercapto-benzimidazole as an analytical reagent

Summary Palladium is quantitatively precipitated at aPH 5.0 to 10.1 by 2-mercapto-benzimidazole and the complex, Pd(C₇H₅N₂S)₂, which is found to be diamagnetic, is stable up to a temperature of 447 C. In presence of EDTA and tartrate or citrate and at aPH between 6 and 8, it is separated from alkalis, alkaline earths, Mg, Fe³⁺, Cr, Th, Zr, Ti, UO₂ ²⁺, Be, Ce³⁺, Ce⁴⁺, rare earths, Zn, Mn, Ni, Co, Pb, Bi, As, Sb³⁺, Sn⁴⁺, Tl⁺, Cu²⁺, Cd, Ir⁴⁺, Rh³⁺, Ru³⁺, Os⁴⁺, CrO₄ ^2–, MoO₄ ^2–, WO₄ ^2–, VO₃ ^–, PO₄ ^3– and AsO₄ ^3–. Pb, Ag and Hg²⁺ are kept in solution by potassium iodide while a small amount of Au³⁺ by thiosulphate. The palladium complex is either weighed after drying at 110 C or dissolved in a cyanide solution and determined volumetrically by back titrating the excess cyanide with a standard silver nitrate solution.     

2-Mercapto-benzothiazole as an analytical reagent

Summary The reagent 2-mercapto-benzothiazole quantitatively precipitates palladium at a PH 5.6 to 10.2. The red coloured compound, Pd(C₇H₄NS₂)₂, is diamagnetic and is stable up to a temperature of 388 C. Palladium is separated from alkalis, alkaline earths, Mg, Fe³⁺, Cr, Th, Zr, Ti, UO₂ ²⁺, Be, rare earths, Ce³⁺, Ce⁴⁺, Zn, Mn, Co, Ni, Pb, Bi, Sb³⁺, As³⁺, Sn⁴⁺, Tl+, Cu²⁺, Cd, Ir⁴⁺, Rh³⁺, Ru³⁺, Os⁴⁺, CrO₄ ^2–, MoO₄ ^2–, WO₄ ^2–, VO₃ ^–, PO₄ ^3– and AsO₄ ^3– at apH 6–8 in presence of EDTA and tartaric or citric acid. Besides Pb, Ag and Hg²⁺ are kept in solution with potassium iodide and Au in a limited quantity forms a soluble complex with thiosulphate. The palladium complex is either weighed after drying and determined gravimetrically or dissolved in an excess of cyanide and determined volumetrically by back titrating the latter with silver nitrate.     

5-(4-Carboxylphenylazo)-8-aminoquinoline as an analytical reagent for the spectrophotometric determination of gold

The synthesis and analytical application of 5-(4-carboxylphenylazo)-8-aminoquinoline (CPAQ) are described. A simple, rapid, selective, and sensitive spectrophotometric method for the determination of microgram amounts of gold is developed, based on the colour reaction between the metal ion and CPAQ in the presence of cetyltrimethyl ammonium bromide. Gold (III) reacts with the reagent in the ratio 1 3 (metal to ligand) in alkaline solution to form a blue-green complex with an absorption maximum at 608 nm. Beer's law is obeyed over the concentration range 0–1.8 g · ml^–1 (ppm) of gold. The molar absorptivity and Sandell's sensitivity of the method are 9.11 × 10⁴ l · mole^–1 · cm^–1 and 0.00216 g · cm^–2, respectively. The interference of various ions has been studied and conditions were developed for the determination of gold in an ore and anode slimes.     

Solid phase extraction and spectrophotometric determination of silver with 2-(2-quinolylazo)-5-diethylaminophenol as chromogenic reagent.

A new chromogenic reagent, 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP), was synthesized. A sensitive, selective and rapid method has been developed for the determination of microg/L level silver ion based on the rapid reaction of silver(l) with QADEAP and the solid phase extraction of the colored chelate with C18 cartridge. The QADEAP reacts with Ag(l) to form a violet chelate of a molar ratio 1:2 (silver to QADEAP) in pH 3.5-8.0. This chelate was prconcentrated by solid phase extraction with C18 cartridge. An enrichment factor of 100 was achieved. The molar absorptivity of the chelate is 1.30 x 10(5) L mol(-1) cm(-1) at 590 nm in measured solution. Beer's law is obeyed in the range of 0.01-0.6 microg/ml. The relative standard deviation for eleven replicate samples of 0.01 microg/ml is 1.15%. The detection limit is 0.02 microg/L in the original samples. This method was applied to the determination of microg/L level silver ion in water with good results.     

2-Hydroxy-1-naphthaldoxime as an analytical reagent for titanium(IV)

2-Hydroxy-1-naphthaldoxime is proposed as a new selective and sensitive reagent for titanium. The oxime complex can be dried to constant weight at 105-110 degrees and the conversion factor is 0.1793. The method is sensitive and gives reproducible results. Quantitative separation of titanium(IV) from iron(III) and other metals by this method gives good results. The method has been applied to the gravimetric determination of titanium(IV) in ilmenite and the results are in good agreement with those obtained by the cupferron method. The dried complex has definite composition [TiO(OH)(C(11)H(8)O(2)N)](2) and is a non-electrolyte. The dimeric structure proposed for the complex is based on evidence from elemental analysis, molecular weight determination, magnetic susceptibility and infrared spectral data.     

2-Mercaptoquinoline (thiocarbostyril) as an analytical reagent for copper and palladium

Summary 2-Mercaptoquinoline is introduced as a sensitive and selective reagent for copper and palladium. Spot test detections and spectrophotometric determinations of these metals have been carried out. 0.03 g Cu at a limiting concentration of 1 430,000 can be detected by the spot technique on a filter paper, and 0.025 g Cu at a limiting concentration of 1 10⁶ by means of the spot plate method. Palladium was determined by measuring the optical density of the orange-yellow colour at 450 m developed in alcoholic medium at p_H 1.4–2.8. The sensitivity is 0.009 g Pd per cm² (Sandell).The author feels deeply indebted to Professor P. Rây, Director and Professor (Hony) of Inorganic Chemistry, for his helpful suggestions, and to Dr. P. C. Banerjee for his kind interest in the work.     

2'-hydroxychalcone as an analytical reagent for beryllium

Several o-hydroxychalcones were examined to develop specific reagents for the precipitation of beryllium in the presence of elements such as aluminium and iron, which occur in its ores. All these reagents showed specificity only in the presence of EDTA. Among them, the readily obtainable 2'-hydroxychalcone is proposed as a new specific reagent for beryllium. The chalcone complex can be dried to constant weight at 105-110 degrees and the conversion factor is 0.01978. A probable structure for the complex has been suggested. Quantitative separation of beryllium from aluminium and iron carried out by this method gave good results. This method was applied for the gravimetric determination of beryllium in beryl and the results were in good agreement with those obtained by the oxide and pyrophosphate methods.     

Nicotinamidoxime as an analytical reagent

Summary Alkaline solutions of nicotinamidoxime containing traces of nickel(II) give a deep blue color on treatment with iodine. At a p_H of 10.5–11.5 in presence of an excess of the amidoxime the color develops almost instantaneously and is stable for at least 24 hrs. The system adheres to Beer's law in the range of 0.3–10 ppm of nickel, and the optimum range for measurement (1 cm cell) is 3–10 ppm of the metal. The color reaction is highly sensitive (spectrophotometric: 0.014 g Ni cm^–2 at 575 nm identification limit: 0.5 g Ni ml^–1; 12 · 10⁶).All the common anions are without any effect excepting CN^– and EDTA which interfere seriously. Interference of Pb²⁺, Bi³⁺, Al³⁺, Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ can be masked by excess tartrate; while in the presence of Cu²⁺, Co²⁺, Zn²⁺, Mn²⁺ and Fe³⁺, the Ni²⁺ is first separated by the anion exchange method of Kraus and Moore ³ and then determined as usual.From the results of polarographic investigations it has been concluded that in alkaline medium nicotinamidoxime is first oxidized possibly to an azo type of compound which interacts with nickel(II) forming the deep blue color.Part II: K. K. Tripathi and D. Banarjea: Z. analyt. Chem. 168, 407 (1959).     

Preliminary evaluation of biacetyl bis(2-pyridyl)hydrazone as an analytical reagent

With the purpose of introducing biacetyl bis(2-pyridyl)hydrazone as an analytical reagent, the pyridylhydrazone literature has been reviewed. BBPH acts as a general chromogenic reagent. The fundamental solution chemistry of the complexes formed by BBPH with the metal ions has been studied. BBPH appears to be a promising reagent for the colorimetric estimation of cobalt and palladium. It may be advantageously compared with benzil bis(2-pyridyl) hydrazone which has the same basic chelate structure.     

Bismuthiol as an analytical reagent

Summary Lead can be determined from its Bismuthiol II complex volumetrically by dissolving it in an excess of EDTA at a p_H of about 10 and titrating the excess of the EDTA against a magnesium or lead solution. In the same way silver can be determined by dissolving the complex in an excess of cyanide and back titrating the excess against a standard silver nitrate with iodide as the indicator. The results of the former are fairly accurate while those due to latter are highly satisfactory with silver less than 20 mg. With higher amounts of silver, however, the results are within +2%.Part VIII see Z. analyt. Chem. 156, 103 (1957).