Spectrophotometric determination of hydroxylamine alone and in the presence of monochloramine

Hydroxylamine (< 3 × 10^?3 mol l^?1) is quantified by ultraviolet spectrophotometry after reaction with an excess of formaldehyde in buffered solution at pH 12.2. The absorbance of the formaldoxime produced is measured at 218 nm (? = 5480 l mol^?1 cm^?1) when hydroxylamine is alone but at 230 nm (? = 3230 l mol^?1 cm^?1) when monochloramine is present.     

Ultraviolet absorption spectra of chloramines and chlorine in carbon tetrachloride

In order to quantify mixtures of chloramines and chlorine in carbon tetrachloride, the ultraviolet spectra of monochloramine, dichloramine, trichloramine and chlorine were measured between 250 and 410 nm. Monochloramine and chlorine absorb at 259 nm (?=484.61 mol^?1 cm^?1 ) and 331 nm (?=95.7 l mol^?1 cm^?1), respectively, while dichloramine and trichloramine exhibit two peaks. For dichloramine, the maximum absorptions are observed at 255 nm (?=126.1 l mol^?1 cm^?1) and 301 nm (?=307.8 l mol^?1 cm^?1) and for trichloramine, at 262 nm (?=635.4 l mol^?1 cm^?1) and 344 nm (?=315.0 l mol^?1 cm^?1).     

Spectrophotometric determination of vanadium in petroleum crudes and derivatives

The spectrophotometric study of the complexation reaction between 5,5′methylenedisalicylhydroxamic acid and V(V) shows that two complexes are formed, the 1:1 (? = 5100 liters mol^?1 cm^?1 at 490 nm, log K_est = 5.8 ± 0.1) and the 1:2 (L:V) (? = 6250 liters mol^?1 cm^?1 at 600 nm, log K_est = 6.1 ± 0.1). A spectrophotometric method is developed for the determination of vanadium (2–9 ppm) at 2 N HCl and 495 nm, which allows its determination in petroleum crude oils with a series of advantages over the ASTM D-1548-63 method.     

Extract-Photometric Determination of Vanadium with Isophthaldihydroxamic Acid

Abstract

The spectrophotometric study of violet complex isophthaldihydroxamic acid-vanadium extracted into solution of trioctylmethylammonium chloride in ethylacetate was made (λ_max = 380 nm, ? = 7500 l.mol^?1.cm^?1; λ_max = 510 nm, ? = 5510 l.mol^?1 .cm^?1; stoichiometries, 1:1 and 1:2, V:reagent). A new method for the extract-spectrophotometric determination of V(V) in the range 14–80 μg of vanadium is proposed.     

Spectrophotometric study of complexes of mercury(II) with mono- and dithiosemicarbazones

The formation of complexes at pH 4.7 of the Hg(II) with five monothiosemicarbazone and two dithiosemicarbazone has been studied. The mercury(II) reacts with monothiosemicarbazones of salicylaldehyde (λ_max = 363 nm, E = 1.69 × 10⁴liters · mol^?1cm^?1), pi-colinadehyde (λ_max = 363 nm, E = 2.38 × 10⁴liters · mol^?1cm^?1), 6-methyl-picolinaldehyde (λ_max = 363 nm, E = 2.28 × 10⁴liters · mol^?1cm^?1), di-2-pyridylketone (λ_max = 380 nm, E = 2.08 × 10⁴liters · mol^?1cm^?1), and o-naphthoquinone (λ_max = 540 nm, E = 1.03 × 10⁴liters · mol^?1cm^?1) and with dithiosemicarbazones of 1,4-dihydroxyphthalimide (λ_max = 430 nm, E = 2.56 × 10⁴liters · mol^?1cm^?1) and dipyridylglyoxal (λ_max = 363 nm, E = 2.37 × 10⁴liters · mol^?1cm^?1). A critical comparison of the stoichiometry and apparent stability constant of complexes with mono- and dithiosemicarbazones is given.     

Spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone)

A simple method is described for the rapid spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone). The yellow color is measured at 460 nm (? = 22,800 liters mol^?1 cm^?1) against a reagent blank at pH 2.5 in a solution containing 60% ($\text{v}\text{v}$) dimethylformamide. Beer's law is obeyed over the range 0.2–2 ppm of nickel.     

Spectrophotometric study of reactions of scandium,ytrium and lanthanum ions with some triphenylmethane dyes in the presence of cationic surfactants

Optimum conditions for the formation of ternary complexes of scandium, ytrium and lanthanum ions with chrome azurol S, eriochrome cyanine R and pyrocatechol violet in the presence of cetyltrimethylammonium, cetypyridinium and tetradecyldimethylbenzyl-ammonium (zephiramine) ions are described. The spectrophotometric determination of scandium with chrome azurol S and zephiramine exhibits the greatest sensitivity (? = 1.50 × 10⁵ l mol^?1 cm^?1 at 610 nm). In the spectrophotometric determination of scandium with eriochrome cyanine R and cetylpyridinium ion (? = 9.2 × 10⁴ at 600 nm), the interference caused by yttrium is the least. In the best method for yttrium (with pyrocatechol violet and zephiramine), the molar absorptivity is 3.3 × 10⁴ at 660 nm. Lanthanum does not form ternary complexes of analytical interest in these systems. Some aspects of the formation of ternary complexes with cationic surfactants are discussed.     

Analytical Properties of 4, 4′-Biazobenzenediazoaminobenzene and its Applications in Spectrophotometry

Abstract

The spectral characteristics and analytical properties of 4, 4′-Biazobenzenediazoaminobenzene as a new chromogenic reagent have been described and the optimum conditions for reaction with eight metal ions are presented. In the presence of Triton X-100 and sodium tetraborate solution, the reagent can be used for the determination of Hg, Ni, Cd. The molar absorptivities are 1.8×10⁵ l.mol^?1. cm^?1 at 515 nm for mercury, 2.0×10⁵ l.mol^?1. cm^?1 at 540 nm for nickel, and 1.8×10⁵ l.mol^?1.cm^?1 at 526 nm for cadmium. The recommended procedure has been used for the spectrophotometric determination of cadmium in waste water.     

A pulse radiolysis study of the reactions of the hydrated electron and hydroxyl radical with the oxalate ion in neutral aqueous solution

The rate constants of the reactions of e _aq ^? and the OH^· radical with the oxalate ion in a neutral aqueous solution were measured by means of the pulse radiolysis technique. They were found to be (3.5 ± 0.5) × 10⁷ and (1.5 ± 0.2) × 10⁷ l mol^?1 s^?1, respectively. The radical anion ^?OOC-C^·OO^2? is characterized by an optical absorption band that has a maximum at 270 nm and a molar absorption coefficient of (2400 ± 200) l mol^?1 cm^?1. The radical anion ^·OOC-COO^?, the product of the reaction with the OH^· radical, exhibits absorption that has no maximum and increases in intensity with a decrease in the wavelength extending to the UV region (?₂₂₀ = 1800 l mol^?1 cm^?1). The mechanism of radiation-chemical transformations in aqueous oxalate solutions is discussed.     

Laser flash photolysis of aqueous acetaminophen solutions

The N-acetyl-4-aminophenoxyl radical, a supposed intermediate of the enzymatic oxidation of acetaminophen in living organisms, was prepared and studied by means of nanosecond laser flash photolysis. A number of important spectral-kinetic parameters of this species were determined, namely, the absorption coefficient at 440 nm ((4.2±0.2)×10³ l mol^?1cm^?1), the quantum yield of acetaminophen photoionization at 266 nm (φ= 0.03), and the rate constants for recombination (2k= (2.4±0.3))×10⁹ l mol^?1s^?1) and the reaction with the superoxide radical (k= (9±2))×10⁹ l mol^?1s^?1).     

Synergistic Spectrophotometric and Atomic Absorption Spectrometric Analysis of Zinc in Alloys and Environmental Samples with N-p-MEthoxyphenyl-2-Furylacrylohydroxamic Acid and Pyridylazo Reagents

Abstract

Zinc (II) was selectively extracted from aqueous solutions of pH 7.8–8.5 into chloroform with N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA). 1-(2-pyridylazo)-2-naphthol (PAN) or 2-[(5-nitro-2-pyridyl)azo]-1-naphthol (NPAN) were added to the extract to form intensely coloured ternary complexes measurable spectrophotometrically at 550 nm (? = 6.03 × 10⁴ 1 mol^?1 cm^?1) and 625 nm (? = 8.15 × 10⁴ mol^?1 cm^?1) respectively. For atomic absorption spectrometric analysis, methyl isobutyl ketone (MIBK) was used as extracting solvent instead of chloroform and the zinc-MFHA-MIBK extract was aspirated directly into an air-acetylene flame. The absorbance was measured at the 213.9 nm resonance line with a detection limit of 0.05 ppb, which was significantly better than the limit of 1.0 ppb achieved for zinc previously with flame AAS. The method tolerated a large number of anions and cations normally occurring with zinc in environmental samples, and was applied to the trace analysis of zinc in alloys, coal, plant tissues, animal tissues and natural waters. The combinations of MFHA and PAN/NPAN were chosen from eleven hydroxamic acids and nine pyridylazo reagents as detailed in the paper.     

Analytical applications of picolinealdehyde salicyloylhydrazone: II. Extraction and spectrophotometric determination of vanadium(V)

Picolinealdehyde salicyloylhydrazone reacts with vanadium(V) to produce a yellow 1:1 complex (λ_max = 400 nm, ? = 2.17 × 10⁴ liters · mol^?1 cm^?1) in aqueous ethanolic solution. The yellow complex can be extracted into chlorobenzene (λ_max = 425 nm, ? = 2.16 × 10⁴ liters · mol^?1 cm^?1) and used for the spectrophotometric determination of trace amounts of vanadium. Interferences have been investigated. The method has been applied to the determination of vanadium in steel and in lead concentrates.     

Isophthaldihydroxamic acid as analytical reagent: Spectrophotometric determination of manganese

The reactivity of isophthaldihydroxamic acid against inorganic ions is established. The spectrophotometric study of its reaction with Mn(II) shows that a complex of stoichiometry 1:2 (Mn:L) is formed (? = 3760 liters · mol^?1 · cm^?1 at 490 nm). A spectrophotometric method is developed for the determination of manganese in the range 3–9 ppm.     

2,2′-Dihydroxybenzophenone thiosemicarbazone as a spectrophotometric reagent for the determination of copper,cobalt, nickel,and iron trace amounts in mixtures without previous separations

2,2′-Dihydroxybenzophenone thiosemicarbazone forms complexes with Cu(II) (λ_max = 385 nm, ? = 8.60 × 10³ liter · mol^?1 · cm^?1); Ni(II) (λ_max = 380 nm, ? = 15.4 × 10³ liter · mol^?1 · cm^?1); Co(II) (λ_max = 380 nm, ? = 12.3 × 10³ liter · mol^? · cm^?1); and Fe(III) (λ_max = 365 nm, ? = 7.9 × 10³ liter · mol^?1 · cm^?1) and have been applied to the analysis of these metal ions in binary, ternary, and quaternary mixtures. The determination procedures are based exclusively on the different pH values of the formation complexes, hence the extraction step is not necessary.     

Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system

The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q⁺Cl^?) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)₂,nQ⁺Cl^?₍₀₎(?⁵⁰⁰ = 3.73·10⁴l mol^?1cm^?1) at about pH 5 and 2Q⁺ NiR^2-_2(o)(?⁵⁰⁰ = 8.08·10⁴ l mol^?1 cm^?1) at above pH 8.5. The extraction constant for 2Q⁺ NiR^2-_2(o) was evaluated as [2Q⁺ NiR^2-₂]₀/[NiR^2-₂] [Q⁺]² = 10^11.16 at μ = 0.1 (Na₂SO₄. Synergic extraction studies of the Ni(HR)₂ species under slightly acidic conditions show that the species is Ni(HR)₂(H₂O)₂in auqeous solution and is extracted into chloroform as the adduct Ni(HR)₂(TBP)₂ (?⁵³⁵ = 3.57·10⁴ l mol^?1 cm^?1. Based on the extraction behavior of these complexes, the structures of the Ni²⁺—PAR complexes are discussed.     

A study of the molar absorptivity of ascorbic acid at different wavelengths and pH values.

A spectral study of ascorbic acid was made in buffer solutions of different pH. The molar absorptivities of the unionized (?_HA) and ionized (?_A-) forms of ascorbic acid were determined at six wavelengths. An isosbestic point occurs at 250.7 nm; the molar absorptivity at this wavelength is 8250 ± 150 l mol^-1 cm^-1. The spectral information presented is of importance for the spectrophotometric assay of samples containing vitamin C.     

Spectrophotometric determination of chromium(VI) through ion-pair formation with phenylfluorone

Two successive outer sphere complexes with mole ratios of 1:1 and 1:2 are formed between chromium(VI) and phenylfluorone at pH 1.5 in 40% ethanol. These have absorption maxima at 490 and 470 nm, respectively. The 1:1 complex obeys Beer's law at 500 nm (? = 2.1 × 10⁴ 1 mol^-1 cm^-1) in the range 13–1700 ng l^-1 chromium(VI).     

Spectrophotometric determination of osmium with phthalimide dithiosemicarbazone by means of complex formation and catalytic reactions

Phthalimide dithiosemicarbazone forms a 1:1 complex with osmium at pH 3.3–4.5 (?₄₅₀ = 1.3 · 10⁴ l mol^?1 cm^?1 ) which is applied to the photometric determination of osmium; Beer's law is obeyed for the range 1–12 μg Os ml^?1. The oxidation of the reagent with cerium(IV) is catalyzed by osmium(VIII), and this reaction allows a more sensitive procedure for the determination of osmium; the calibration curve is linear over the range 0.05–0.4 μg Os ml^?1. The interferences in both procedures are described.     

Spectrophotometric determination of titanium(IV) as a mixed thiocyanate—monooctyl-α-anilinobenzylphosphonate complex

Extraction of titanium(IV) thiocyanate complexes by monooctyl-α-anilinobenzylphosphonate (MOABP) dissolved in chloroform has been investigated as a function of hydrochloric and sulfuric acid concentration. Chloroform solutions follow Beer's law and are stable for at least 24 h. A sensitive and reproducible spectrophotometric determination of titanium is possible. Two complexes were identified; the first formed at acid concentrations less than 1 M, has the ratio Ti:SCN:MOABP 1:1:2 and the second, formed at higher acidity, has the ratio Ti:SCN:MOABP 1:2:2. The method is based on the extraction of titanium thiocyanate with MOABP from either 0.5 M H2SO4, and measurement of the absorbance at 336 nm (? = 11 000 l mol^-1 cm^-1 ), or from 6.5 M HCl, and measurement of the absorbance at 420 nm (? = 22 000 l mol^-1 cm^-1). The polymerization of thiocyanate has been studied; isoperthiocyanic acid has been identified as the polymerization product. Although both procedures give reproducible results, extraction from 6.5 M HCl is more sensitive, fewer elements interfere, and the precipitation of isoperthiocyanic acid is avoided.     

Ene reaction between 4-phenyl-1,2,4-triazoline-3,5-dione and hex-1-ene. The enthalpies,entropies, and volumes of activation and reaction in solution

The rates of an ene reaction between 4-phenyl-1,2,4-triazoline-3,5-dione and hex-1-ene were studied in a temperature range of 15–40 °C and in a pressure range of 1–2013 bar. The enthalpy of reaction in 1,2-dichloroethane (?158.2±1.0 kJ mol^?1), the enthalpy (51.3±0.5 kJ mol^?1), entropy (122±2 J mol^?1 K^?1), and volume of activation (?31.0±1.0 cm3 mol^?1), and the volume of this reaction (?26.6±0.3 cm³ mol^?1) were determined. The high exothermic effect of the reaction suggests its irreversibility.