Ammoniacal Medium Research Articles

Separation of metals on ion-exchange resins by means of α-hydroxyisobutyronitrile as complexing agent

α-Hydroxyisobutyronitrile (acetone cyanohydrin, ACH) reacts with metals in ammoniacal medium and yields cyano complexes of negative charge. On this basis, Ni 2+, Cu 2+, Hg 2+, Zn 2+, Cd 2+ and Fe 2+ can be separated on a strongly basic anion exchanger in the chloride form as cyano complexes from Mg 2+, Ba 2+, Ca 2+, Na + and K +. The structure of complexes were examined on a strongly basic anion exchanger in the Cl − form and on a strongly acidic cation exchanger in the H + form. In slightly ammoniacal medium, Cu(CN) 4, Co(CN) 3.6 and Ni(CN) 3.2 were found. The complex adsorbs on the anion exchanger in the Cl − form as a divalent [NH 4Cu(CN) 4] 2− or a monovalent [NH 4Zn(CH) 4] − complex ion.

Study of cadmium ion reduction on the dropping mercury electrode in ammoniacal medium by the potentiostatic triangular pulse method

Study of cadmium ion reduction on the dropping mercury electrode in ammoniacal medium by the potentiostatic triangular pulse method

Study of cadmium ion reduction on the dropping mercury electrode in ammoniacal medium by the potentiostatic triangular pulse method

The composition of the reducible ammonia complex of cadmium and its reduction rate contant were determined. The calculation is based on the assumption that practically only one complex undergoes reduction at the electrode and that the equilibrium between Cd2+ ions, their ammonia complexes and ammonia is perfectly mobile. The form of the current-voltage curves at different rates of potential change confirms the plausibility of these assumptions.

Separation of molybdenum from interfering elements by extraction as phosphomolybdenum blue

A simple method is described for the separation of molybdenum from titanium, zirconium, chromium, manganese, iron, cobalt, nickel, uranium and aluminium in a wide variety of samples in <30 min. Phosphomolybdenum blue is produced by boiling for 2 min a molybdate solution containing phosphate to give Mo/P = 20–37 (w/w) with hydrazine sulphate in 0·1 N sulphuric acid. The volume and acidity are adjusted to give a molybdenum concentration of 0·6-5 my/ml in 0·4–0·5 N sulphuric acid. The phosphomolybdenum blue is 99·5% extracted with methyl isobutyl ketone in a single extraction. The residual molybdenum and hydrazine in the aqueous phase are oxidized with a few drops of liquid bromine and the molybdenum is quantitatively extracted with the same solvent from 1 N sulphuric acid as its reddish brown thiosulphato complex. The molybdenum is stripped by ammonia—hydrogen peroxide solution. The back-extract is heated to boiling and filtered to remove the insoluble hydroxides of traces of accompanying elements. The thiosulphate in the filtrate is destroyed by boiling for 4–5 min with excess of hydrogen peroxide in slightly ammoniacal medium. The molybdenum is determined finally by cerimetry or other standard methods.

Calmagite: The Formation Constants of Zinc(II) Chelates and Its Use as a Metal Indicator

Abstract The acid dissociation constants of Calmagite [1-(2-hydroxy-5-methylphenylazo)-2-naphthol-4-sulfonic acid] and the formation constants of zinc(II) chelates have been determined spectrophotometrically at 25°C and at the ionic strengths of 0.1 and 1.0. In an ammoniacal medium zinc forms mixed-ligand complexes with Calmagite (I3−) and ammonia (X); ZnIXn−. The formation constants of the zinc(II)-Calmagite chelates are logKZnI=11.75, logKZnI2=7.82, logKZnIXx=2.09, and logKZnIX2x=1.70 (μ=1.0). Calmagite is recommended as an indicator for the titration of zinc(II) with EDTA. The color transition of Calmagite is clearer and sharper, and the aqueous solution of the indicator is more stable, than in the case of Eriochrome Black T.

The hydrolysis of ethylene diisothiuronium bromide in the presence of Ni(II), Cu(II) and Zn(II)

The hydrolysis of ethylene diisothiuronium bromide in cold ammoniacal medium in the presence of metal ion [Ni(II), Cu(II) and Zn(II)] gives a mixture of metal ethanedithiolate and metal complex of unhydrolyzed ligand, the relative proportion of which increases in the series Cu < Ni < Zn. This unhydrolyzed ligand has been shown by infrared and mass spectral techniques not to be unhydrolyzed EDIB itself but a mixture of its N-amidino and N-cyano derivatives. The series of Cu < Ni < Zn is explained on the basis of the relative catalytic effects of the metal ions on the hydrolysis of EDIB to ethanedithiol at the expense of the formation reactions of the N-amido and N-cyano derivatives, which are independent of the metal ion. Full hydrolysis of these mixtures to metal ethanedithiolates is promoted by heating in water for nickel and copper or in alkali for zinc.

Coulometric Titration of Blood Glutathione

Abstract Conditions are described for coulometric titration of reduced glutathione with silver(I), in an ammoniacal medium. pH and buffer capacity of the medium are important variables. Metaphosphoric acid, 50 g/liter, is superior to metaphosphoric acid, 10 g/liter, or sulfosalicylic acid, 25 g/liter, for precipitating blood proteins. Results of the coulometric method are about the same as those obtained with spectrophotometric procedures in which alloxan or 5,5'-dithio-bis-(2-nitrobenzoic acid) is used.

Physiological studies on the genusSclerotium

Respiratory studies onS. rolfsii showed that its endogenous respiration was lower when sodium nitrate was used as the nitrogen source as compared with ammonium sulphate. The endogenous respiration of mycelium grown on either medium was not appreciably altered by the addition of the respective media in which the fungus was grown. On the contrary, the endogenous oxygen uptake and carbon dioxide output ofS. oryzae grown in sodium nitrate was accelerated with addition of the nitrate medium. This effect was not observed in the case of mycelium grown on ammonium sulphate medium. These results, along with changes in the RQ, are discussed in relation to the growth response of the two fungi in the nitrate and ammoniacal media.

Spectrophotometric extracave titrations—VII : Titrations with di-2-naphthylthiocarbazone

An investigation of the possibilities of the use of di-2-naphthylthiocarbazone as titrant in spectrophotometric extractive titrations has been undertaken. A selective procedure for successive titration of silver in an ammoniacal medium has been developed and applied to the analysis of germanium dioxide. It has been established that the consecutive titration of mercury and zinc in the microgram range is possible. Because of low selectivity of this titration, a separation of mercury and zinc from other ions is necessary.

Synthesis of new arylidene derivatives of 3-aminorhodanine

The synthesis of new arylidene derivatives of 3 -aminorhodanine has been effected. It has been established that the condensation of 3-aminorhodanine with aldehydes in an alcoholic medium gives 3′-arylidene derivatives. Similar reactions in an ammoniacal medium lead to 5-derivatives of 3-aminorhodanine. 3′, 5-Diarylidene derivatives can be obtained by condensing 3′-aminorhodanine with an excess of an aldehyde in glacial acetic acid, except for the salicylidene and 9-anthrylidene derivatives, the synthesis of which can be carried out only in two stages.

Molecular structures and catalytic activity: II. Proton reactivity and catalytic polarography of histidine and related imidazole derivatives

The catalytic polarographic activity of histidine, imidazole, imidazole acetic acid, histamine, 3-methyl histidine and 1-methyl histidine was studied in cobaltous ammoniacal medium. The effect of pH, concentration and temperature upon the electrode potential and catalytic current of the polarographic waves of histidine were examined, as well as the effect of pH upon the calalytic polarographic activity of imidazole. The results indicate that the catalytic polarographic waves of histidine and the other imidazole derivatives represent the reduction of protons of protonated amino and imidazole groups. The electron to proton transfer is catalyzed by complex formation of the protonated group with Co 2+. The catalytic electron transfer is limited to a specific electrode potential or energy level and the polarographic waves illustrate the specific energy levels for protons of specific protonated groups in these cobalt complexes, at which the protons can accept electrons.

Isonitrosoacetanilide as an analytical reagent

In a continuation of earlier work on the reactivity of various isonitrosoacetarylides, the simplest of the series, isonitrosoacetanilide was examined. In acidic medium, this reagent gives a specific reaction with palladium (dilution limit 1:400,000), and in ammoniacal medium a very sensitive reaction with cobalt (dilution limit 1:1,000,000). The composition of the complexes involved was established as R 2Pd and R 3Co 2. The effect of substitution on the reactivity is discussed.

Color Reactions of 3-Methyl-2-benzothiazolone Hydrazone with Phenol Derivatives. I. The Spectrophotometric Microdetermination of Catechol, Hydroquinone and Resorcinol

Abstract New spectrophotometric procedures for determining microgram amount of catechol, hydroquinone and resorcinol with MBTH have been described. The sensitivities and selectivites of the reaction are largely dependent on the pH and on the conditions of oxidation: 1) In an ammoniacal medium MBTH gives a stable pink color with catechol and, with hydroquinone, a blue color which is srabilized by acetone. Resorcinol gives only a faint color under these conditions. 2) When ferricyanide is used as a oxidant in a weakly alkaline solution, MBTH gives a sensitive orange color with resorcinol. 3) In an acidic ferric-ferrous redox catechol. At pH 3 the reaction is selective for catechol. 4) Ferric chloride in 1.2n hydrochloric acid is favorable for the determination of hydroquinone and resorcinol in a mixture of the two.

Colorimetric determination of nickel with 2-mercaptobenzothiazole

A colorimetric method has been developed for determining nickel with 2-mercaptobenzothiazole. At pH 7.7–8.1 in an ammoniacal medium nickel forms a yellow-brown complex, insoluble in water but soluble in chloroform. It is suitable for determining nickel in the concentration range 0.4–16 ppm with an average error of 0.5–2%. Cobalt, copper and iron interfere and have to be removed by an anion-exchange method before analysis. Bismuth and lead, if present, are removed with hydrogen sulphide, and complex formation of 2-mercaptobenzothiazole with alkali metals is prevented by fluoridation. No other metals were found to interfere.

Accuracy of the potentiometric titration of cobalt with ferricyanide in ammoniacal medium

With authentically pure metallic cobalt and purified potassium ferricyanide. the accuracy of the titration of +2 colbalt to the +3 state with ferricyanide in strongly ammoniacal medium was examined critically. Quantities of colbalt from about 18 to 200 mg were titrated with a mean error of only +0.02 mg. and an average deviation of ±0.03 mg. The accuracy of this titration is greater than has ever been demonstrated for any other method of determining cobalt. Because of its high accuracy, and since very few other metallic elements interfere, this titration is the best currently available method for the critical assay of cobalt materials.

Complexometric titration of copper (II) using chromotropic acid dioxime as a metal indicator

Chromotropic acid dioxime forms purple coloured complexes with copper in the pH ranges 5.82 to 6.45 and 7.25 to 8.05 respectively which are less stable than the CuII-EDTA complex. On titrating these solutions with EDTA, the purple coloured complexes turn colourless or yellow at the end point. These titrations give satisfactory results in the temperature ranges 20 to 70° C and 20 to 50° C respectively. In acid medium, the titration of copper can be carried out in the presence of magnesium and alkaline earths, but zinc, cadmium, nickel, cobalt, aluminium and iron(III) interfere. The latter two elements can be masked by sodium fluoride. In ammoniacal medium, zinc, cadmium, cobalt, nickel, lead, magnesium and alkaline earths interfere.

A spot test for uranium VI with resacetophenone-oxime

A spot test for the detection of uranium VI using resacetophenone-oxime is developed. It is found that a reddish brown colour develops when solutions of uranium VI and resacetophenoneoxime are mixed in ammoniacal medium. The limit of identification is 0·595 μg.

Amperometric iodimetric determination of nickel(II) at constant voltage with two polarised electrodes

The amperometric iodimetric determination of nickel(II) in presence of excess dimethylglyoxime in ammoniacal medium atph 6.5, has been carried out at 30 millivolts with two polarised electrodes. The redox reaction is quantitative and the results obtained are accurate and satisfactory. The formation of complexes alters the oxidation potential of Ni2+/Ni4+ to a lower value, so as the former is titrable with iodine. The method is simple, sensitive and convenient; and has the advantage that it permits determination of trace amounts of nickel of the order of 10−4 M with fair degree of accuracy. At higher dilutions, error exceeds 5 percent.

Effect of formation of insoluble polysilver salts on argentometric titration of mercaptoacids

High results observed when mercaptoacids are titrated in ammoniacal media with silver nitrate are caused by the formation of insoluble precipitates containing silver in the forms of both the mercaptide and the carboxylate salt. In the presence of a moderate excess of ammoniacal silver, mercaptoacetic acid or β-mercaptopropionic acid can be precipitated quantitatively as a disilver salt. The readiness with which silver combines with the carboxylate ion in compounds of this type is postulated to be favored by the crystal structure of the resulting compound.

The determination of cobalt by oxidation with potassium molybdicyanide

Cobalt has been determined titrimetrieally and coulometrically by oxidation of the bivalent ion with potassium molybdicyanide, K 3Mo(CN) 8, in ammoniacal medium. The break in potential at the equivalence-point is approximately 0.6 volt. Manganese is not oxidized stoichiometrically in citrate media, but the total of cobalt and manganese may be obtained in the presence of fluoride. Iron interferes when fluoride, but not when citrate is used as the complexing agent. The method, therefore, is not directly applicable to steels where both iron and manganese are present.