Indirect ultraviolet determination of cyanide with mercury complexes

Cyanide ion can be determined in the range of 0.50 to 10 parts per million by the decrease in ultraviolet absorption of the mercury complexes HgBr₄^2?, HgCl₄^2?, HgI₄^2?, Hg(SCN)₄^2?, and Hg(SO₃)₂^2?. The decrease in absorbance is linear with cyanide concentration. Reaction of cyanide with the complexes is rapid in pH 6.86 and 9.01 buffers and in water. Solutions of the complexes are reasonably stable.     

Indirect determination of cyanide ion and hydrogen cyanide by adsorptive stripping voltammetry at a mercury electrode

An indirect voltammetric method is described for determination of cyanide ions and hydrogen cyanide, using the effect of cyanide on cathodic adsorptive stripping peak height of Cu-adenine. The method is based on competitive Cu complex formation reaction between adenine at the electrode surface and CN⁻ ions in solution. Under the optimum experimental conditions (pH=6.42 Britton-Robinson buffer, 1×10⁻⁴ M copper and 8×10⁻⁷ M adenine), the linear decrease of the peak current of Cu-adenine was observed, when the cyanide concentration was increased from 5×10⁻⁸ to 8×10⁻⁷ M. The detection limit was obtained as 1×10⁻⁸ M for 60 s accumulation time. The relative standard deviations for six measurements were 4 and 2% for the cyanide concentrations of 5×10⁻⁸ and 2×10⁻⁷ M, respectively. The method was applied to the determination of cyanide in various industrial waste waters such as electroplating waste water and also for determination of hydrogen cyanide in air samples.     

Indirect spectrophotometric determination of cyanide

A spectrophotometric method for cyanide based on its inhibition of the colour formation reaction between nickel(II) and 3-(4,5-dimethyl-2-thiazolylazo)-2,6-dihydroxybenzoic acid has been developed, and allows the determination of down to 0.1 g of cyanide. Most of the interferences can be avoided by displacement of the hydrogen cyanide using an arsine generator.     

Titration of mercury (ii) with sodium tetraphenylboron

A direct visual titration of mercury (II) with sodium tetraphenylboron (“Kalignost”) is described Phenylmercurie salts are formed and the end-point is indicated by a turbidity of insoluble diphenylmercury.     

Potentiometric determination of mercury(ii) with ethylenediaminetetraacetic acid : Analysis of binary mixtures

Potentiometric determination of mercury(II) with EDTA using silver amalgam as indicator electrode, is suitable for 200 μg to 100 mg of mercury. Binary mixtures of mercury (II) with several other metals can be analysed by different methods involving masking agents, selective pH and differential titrations.     

Potentiometric determination of chlorides with an "Air-Gap" cyanide sensor

A new electroanalytical method for determining chloride ions with an Air-Gap cyanide sensor system is described. The method is based on the reaction of chloride with mercury(II) cyanide in dilute sulphuric acid. This reaction leads to hydrogen cyanide which can be determined with an Air-Gap cyanide sensor. Optimum concentrations of mercury(II) cyanide and sulphuric acid were established and an analytical curve was prepared for 1 x 10(-1)-1 x 10(-5)M Cl(-). The slope of the calibration curve was equal to 62.8 mV/log C. The correlation coefficient (R) was equal to 0.9992. The method can determine chloride with good results in high saline solutions and in the presence of surfactants, which is in contrast to direct potentiometry with a chloride electrode. The method was applied for chloride determination in fuses used for initiating explosions. The chlorides were determined both in the raw materials used to prepare the fuse braids and in the other fuse components. Chloride was also determined in drinking water and river water. In dependence of source, chloride amount analyzed in drinking water was in the range 2.18-182.6 mg/l. and 25.8 mg/l. in river water. A comparative analysis was carried out. In the first case, chloride was determined by a turbidimetric method, whereas in the second one by potentiometric titration against a chloride-ISE.     

Indirect spectrophotometric determination of trace cyanide with cationic porphyrins

Three highly sensitive methods for the determination of cyanide have been developed, based on the fact that the complexation of silver ions with three cationic porphyrins, 5,10,15,20-tetrakis-(1-methyl-2-pyridinio)porphine [T(2-MPy)P], 5,10,15,20-tetrakis(1-methyl-3-pyridinio)porphine [T(3-MPy)P] and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphine [T(4-MPy)P], in alkaline media is inhibited by cyanide and the decrease in absorbance of the silver(II) complex is proportional to the cyanide concentration. Sensitivities of the procedures developed are 0.133, 0.126 and 0.234 ng/cm(2), respectively for an absorbance of 0.001. Cadmium(II), copper(II), mercury(II), zinc(II), iodide and sulfide interfere with the cyanide determination. One of the proposed methods was applied to the determination of cyanide in waste-water samples, with satisfactory results.     

Indirect determination of cyanide by molecular emission cavity analysis

Nanogram amounts of cyanide were indirectly determined by molecular emission cavity analysis. The method is based on the reaction of cyanide with sulphite-formaldehyde addition compound and the measurement of the S₂ emission produced either from the sulphite released or from the addition compound. The relative standard deviations are 2.13% and 1.66% and the recoveries are 99% and 100% using the released sulphite peak and the addition compound peak, respectively. Potential interfering anions were investigated.     

Indirect determination of cyanide in water by atomic-absorption spectrophotometry

An indirect method for determination of trace cyanide in water by atomic-absorption spectrophotometry is described. Cyanide forms a stable complex anion with Pd in alkaline solution. This complex anion can form an ion-association complex with tetra-alkylammonium ions which can be extracted into n-butyl alcohol with an efficiency higher than 90%. The extract can be analysed directly for palladium (and hence indirectly for cyanide) by flame atomic-absorption spectrophotometry. The detection limit for cyanide by this method is 0.1 mug ml in the n-butyl alcohol extract. Beer's law is obeyed for 0.13-9 mug of CN(-) per ml of n-butyl alcohol. Several foreign ions do not interfere.     

Spectrophotometric determination of nickel(ii) with molybdophosphoric acid

A sensitive spectrophotometric method for the determination of nickel, based on the reduction of a complex formed between molybdophosphoric acid and Ni(II) at pH 4.3 has been developed. Excess of molybdophosphoric acid is eliminated by complexation with sodium citrate. The method is rapid and the system obeys Beer's law up to 5 ppm of Ni(II). The molar absorptivity is 1.30 x 10(3) 1.mole(-1).mm(-1). The technique compares favourably with existing photometric methods for nickel in sensitivity and is reasonably selective.     

Flow-through sensor for the fluorimetric determination of cyanide

A fluorimetric method for the determination of cyanide, based on its reaction with pyridoxal-5-phosphate and the use of an anion-exchange resin (QAE Sephadex) located in the detector flow-cell, is proposed. The merging-zone flow-injection manifold used allows simultaneous injection of the sample and reagent, development of the reaction along the transport system, and retention of the reaction product in the flow-cell. The calibration graph for cyanide is linear over the range from 50 ng/ml to 3.0 mug/ml and the relative standard deviation and sampling frequency are 1.4% (for 2 mug/ml cyanide) and 10 per hr, respectively. The selectivity of the method is much better than that of the conventional fluorimetric and photometric flow-injection methods for cyanide.     

Formation of mercury(ii) ethylenediaminediacetate and its mixed-ligand complexes with anions

The complexes of mercury(II) with EDDA and the formation of mixedligand complexes with some anions have been investigated spectrophotometrically. Mercury(II) reacts with EDDA to give 1:1 and 1:2 complexes, which have stability constants of 15.4±0.1 and 24.2±0.2 respectively, at ionic strength 0.1. These complexes react with anions (X), such as cyanide, thiocyanate, iodide, bromide and chloride, to form the mixed-ligand 1:1:1 complexes. Hg(EDDA)X. The apparent stability constants (log K_x) of the chloro, bromo, and thiocyanato mixed-ligand complexes are 9.9, 12.0, and 10.8, respectively.     

Analytical applications of ternary complexes-V Indirect spectrophotometric determination of cyanide

An indirect spectrophotometric method is proposed for the determination of cyanide down to 0.2 ppm. It is based on the fact that cyanide prevents the formation of the strongly absorbing ternary complex between silver(I), 1,10-phenanthroline and Bromopyrogallol Red in nearly neutral aqueous solution. Among 17 cations examined, only mercury(II) could not be tolerated. Zinc, cadmium and cobalt interfered only when present in large amounts. A 1000-fold molar excess (over cyanide) of 14 anions can also be tolerated. Bromide, iodide and thiocyanate interference is overcome by addition of lead nitrate, ammonium sulphate and barium nitrate, followed by centrifugation.     

Determination of chloride by displacement of hydrogen cyanide from mercury(II) cyanide

A method, based on the passivity of mercury(II) cyanide in dilute sulphuric acid and its reaction with hydrochloric acid to produce hydrogen cyanide, has been developed for the determination of small amounts of chloride. Hydrogen cyanide, distilled from a mercury(II) cyanide-halide-dilute sulphuric acid system is found by iodometric measurement to be directly proportional to the amount of chloride or bromide and of hydrogen ion in acids such as sulphuric acid. A linear correlation also holds for iodide but the stoichiometry is different, the titration values being about three times larger than expected. By conversion of the cyanide into a dye by means of the pyridine-pyrazolone reagent, 0.014-0.43 mug ml chloride concentrations have been determined. The method is also applicable to bromide and sulphuric acid in small amounts but not to fluoride and iodide. Results are reproducible to within +/-2%.     

Volumetric determination of mercury(I) with permanganate

Summary A new permanganametric procedure has now been developed for the direct volumetric titration of mercury(I) to an iodine monochloride end point.One of the authors, K.Bhaskara Rao, wishes to express his grateful thanks to the Ministry of Education, Government of India, for the award of a Research Scholarship and the authorities of Andhra University for kind permission to work in the Chemical Laboratories.     

High frequency titrations: The mercury(ii)-thiocyanate reaction

Soluble complex-formation of mercury(II) thiocyanate has been studied oscillometrically. The titration of mercury(II) nitrate with thiocyanate gives one inflection corresponding to the formation of Hg(SCN)₂, while in the reverse titration the formation of Hg(SCN)⁺ is also indecated. The method is useful for a rapid determination of very small quantities of mercury or thiocyanate in highly dilute solutions. The titrations can be effected in presence of nitric acid provided its total acidity in the system does not exceed about $\text{1}\text{300}$N. Further Work on the mercury(II) -halide and mercury(II)-cyanide reactions is in progress.     

Extraction and spectrophotometric determination of cobalt(ii) with 2-thenoyltrifluoroacetone

The rapid extraction and simultaneous spectrophotometric determination of mg amounts of cobalt(II) by means of 2-thenoyltrifluoroacetone is described. The yellow cobalt(II)-TTA chelate solution in acetone-benzene obeys Beer's law at 430 mμ over the range 12 to 51 μg of cobalt(II) per ml. At pH 5.1–6.8 a single extraction with 0.15 M TTA in acetone is satisfactory. The system is stable for 96 h. Silver, zirconium, strontium, thorium, zinc, lead(II) and mercury(II) do not interfere.     

Copper(ii), cobalt(ii), manganese(ii) and nickel(ii) bis(hexafluoroacetylacetonate) complexes with N-vinylimidazole

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