Coagulation of silver halide sols by thorium nitrate in the presence of potassium nitrate and potassium sulfate

Summary When silver iodide, silver bromide and silver chloride solsin statu nascendi are coagulated by thorium nitrate in the presence of potassium nitrate, three coagulation maxima appear. Two of them are identical with maxima that are found in absence of KNO₃, denoted with (II) and (IV) in fig. 1. The new maximum appears in the stability region of recharged sols (III). It is believed that this maximum is also—as maximum (IV)—caused by the coagulation of recharged silver halide sols by nitrate ions. Appearance of two nitrate coagulation maxima is explained by different charge densities on sol particles at various concentrations of Th(NO₃)₄ where they are formed. The new maximum indicates a lower charge density of sol particles. The possibility that the new maximum could have been caused by ionic complex species between thorium and nitrate ions has been rejected for data are available that the equilibrium constant for such complexes is small. In the presence of K₂SO₄ the coagulation effects of thorium nitrate on silver halide sols are markedly different. In acidified solutions only one coagulation maximum appears at rather high thorium nitrate concentrations [∼ 10⁻³ N Th (NO₃)₄] and the sol remains negatively charged [up to ∼ 10⁻² N Th (NO₃)₄] This is explained by complex formation of Th-ions and sulfate ions whereby ionic species of lower charge are formed, which exert a weaker coagulation effect. In neutral solutions another maximum at lower concentration of Th (NO₃)₄ is formed which appears to be the usual coagulation maximum produced by hydrolyzed thorium ions. The antagonistic effects of the salt pair Th (NO₃)₄-K₂SO₄ upon the coagulation of silver halides has been discussed and we have concluded that the large effects repeatedly reported can be explained not by simple electrostatic effects of ions in solution but rather by the formation of complexes between Th- and SO₄-ions.

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Zusammenfassung Die Koagulationseffekte des Thoriumnitrats in Anwesenheit von Kaliumnitrat und Kaliumsulfat an Silberhalogenid-Solenin statu nascendi wurden ausführlich untersucht. Wenn Silberhalogenid-Sole durch Thoriumnitrat-L?sungen koaguliert werden, bilden sich zwei Koagulationsmaxima (II und IV, Abb. 1). Bei sehr niedrigen Konzentrationen des Thoriumnitrats koaguliert das Thorium-Ion (oder Komplex) die negativen Silberhalogenid-Sole, w?hrend bei h?heren Thoriumnitrat-Konzentrationen die ungeladenen Sole durch die NitratIonen koaguliert werden. Zwischen den zwei Maxima besteht ein weites Gebiet der stabilen umgeladenen Sole (III). Unter dem Zusatz von konstanten Mengen des Kaliumnitrats wird in diesem Gebiet ein neues (drittes) Maximum gebildet (Abb. 2–5), das auch als Koagulationsmaximum identifiziert wurde. Es wird angenommen, da? dieses Maximum wieder eine Koagulation der umgeladenen Silberhalogenid-Sole durch Nitrat-Ionen darstellt. Das Auftreten von zwei Koagulationsmaxima, verursacht durch Nitrat-Ionen, wird durch die verschiedenen Ladungsdichten an Solteilchen in Gebieten der Thoriumnitrat-Konzentrationen, in denen Maxima erscheinen, erkl?rt. Die M?glichkeit eines Koagulationseffektes der komplexen Ionen zwischen Thorium und Nitrat wurde ausgeschlossen, da die Gleichgewichtskonstante solcher Komplexe ziemlich niedrig ist. In Anwesenheit von Kaliumsulfat sieht die Koagulationskurve für Silberhalogenid Sole sehr unterschiedlich aus (Abb. 6–8). In den mit Salpeters?ure (0,001N) versetzten Solen erscheint nur ein Maximum bei ziemlich hohen Thoriumnitrat-Konzentrationen [∼ 10⁻³ N Th (NO₃)₄], wobei die Solteilchen noch immer negativ sind. Da Thorium- und Sulfat-Ionen sehr stabile Ionen-Komplexe bilden, die eine niedrigere Valenz aufweisen, kann das Maximum als Folge der Koagulationseffekte solcher Komplexe an die Silberhalogenid-Sole angesehen werden. In neutralen L?sungen zeigt sich neben dem beschriebenen Maximum noch ein anderes Maximum bei niedrigerer Thoriumnitrat-Konzentration. Dieses Maximum, hervorgerufen durch die hydrolysierten Thorium-Ionen, scheint das „normale“ Koagulationsmaximum zu sein. Dieantagonistischen Effekte des Salzpaares Th (NO₃)₄-K₂SO₄ bei der Koagulation der Silberhalogenide wurden diskutiert, und es wurde geschlossen, da? die gro?en Effekte, die wiederholt ver?ffentlicht worden waren, sehr schwer nur durch die elektrostatischen Anziehungen zwischen den Ionen erkl?rt werden k?nnen. Die Komplexbildung zwischen Thorium- und Sulfat-Ionen wird für den sogenannten antagonistischen Effekt in diesem Falle als verantwortlich angesehen.

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Supported in part by U.S. Atomic Energy Commission Contract No. AT (30-1)-1801.     

Flow injection analysis for calcium in serum,water and waste waters by spectrophotometry and by ion-selective electrode

The Flow Injection technique is shown to provide fast, reliable and sensitive methods for the determination of calcium in various aqueous as well as serum samples; spectrophotometric or potentiometric detection can be used. At sampling rates of 100–110 samples per hour, with 30-μl sample injections, high reproducibility of measurement and low reagent consumption are achieved in both methods. In the spectrophotometric method, the analytical readout is available within 12 s after sample injection at a total reagent consumption of 0.75 ml per analysis. The potentiometric measurement of the calcium activity in serum is placed on a reliable basis by alternating measurements of serum samples and aqueous standards without incurring any non-reproducible changes in potential between aqueous and serum solutions. This permits the simultaneous determination of pH and pCa, the analytical readout being available within XXX s of sample injection. The good agreement between the results obtained with the Flow Injection method and those attained by atomic absorption and EDTA titrations as well as pCa stat-measurements show that the new methods are potentially suitable for routine analysis.     

Hybridization in some macrocyclic polyacetylenes

The hybridization in several cyclic polyacetylene compounds has been calculated by the maximum overlap method, assuming planar and non-planar geometries of the molecules. In the planar configuration the hybrids describing the molecular skeleton deviate from the corresponding bond directions. We have a few “bent” bonds, but in contrast to the situation in small rings, here the deviation angles are negative, i.e., the hybrids point toward the inside of the ring. Non-planar structures in which acetylene groups are kept in a plane and CCH₂ or CH₂ groups are displaced out of the plane show less deviation from the bond directions of bent bonds. Furthermore, the deviation angles decrease with an increase in the out-of-plane displacement of methylene groups. Finally, when the angle of bending of the molecules approaches 50°, the deviation vanishes, predicting a puckered conformation for the molecules. Correlation between CC stretching vibration frequencies and the corresponding CC bond overlap is discussed.     

Über Reaktionen von Nitrosophenolen, 4. Mitt.: Reaktion von Nitrosonaphtholen mit Naphtholen

Zusammenfassung Die Reaktion von 1-Nitroso-2-naphthol mit 1-und 2-Naphthol sowie die Reaktion von 2-Nitroso-1-naphthol mit 2-Naphthol in Äthanol und in Äther bei Anwesenheit von HNO₃ gibt 5H-Dibenzo[a,j]phenoxazon-(5) (I), 5H-Dibenzo[a,j]phenoxazon-(5)-14-oxid (II), 5H-Dibenzo[a,h]phenoxazon-(5) (III) sowie 5H-Dibenzo[a,h]phenoxazon-(5)-14-oxid (IV). Es wurde ein Reaktionsmechanismus vorgeschlagen und die Konstitution der hergestellten Verbindungen spektrophotometrisch und potentiometrisch bestimmt.

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The reaction of 1-nitroso-2-naphthol with 2-and 2-naphthol and the reaction of 2-nitroso-1-naphthol with 2-naphthol in ethanol or ether in the presence of nitric acid have been studied. The main reaction products isolated were the dibenzophenoxazones I–IV. The reaction mechanism for their formation is proposed.

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Mit 4 Abbildungen     

Peroxides of higher aliphatic ethers

The oxidation of higher aliphatic ethers with oxygen at 50° yields two peroxides as the main oxidation products for each ether, namely a dihydroperoxy-dialkyl ether and a dihydroperoxy-dialkyl peroxide. The mass spectra of these compounds are recorded and the main fragmentation pattern is discussed.     

Delphinidin–Aluminum(III) Complexes in Aqueous and Non-Aqueous Media: Spectroscopic Characterization and Theoretical Study

Summary. The study of delphinidin complexation with trivalent aluminum in acidic aqueous buffered (pH 3.0 and 3.8) and methanolic solutions was performed utilizing electronic absorption spectroscopy and quantum chemical calculations. In its structure delphinidin possesses several chelating sites in competition towards aluminum(III). Molar ratio plots denoted the formation of only one aluminum(III):delphinidin complex of stoichiometry of 1:1 in both investigated media. Semiempirical calculations, performed at the restricted HF AM1 level, enabled the determination of the structural features of free delphinidin and structural modifications caused by chelation of aluminum(III). Considering the pigment molecular structure and the results of the theoretical calculations it is possible to equally implicate C3′–C4′ and C4′–C5′ hydroxyl groups as those with the predominant chelating power.     

Aromatic substitution

It is demonstrated that a previously developed topological expression for the total π-electron energy of aromatic molecules provides a good qualitative account of localization energies. The logarithm of the ratio of the algebraic structure counts for the ground state and the localized reaction intermediate is the principle energy determining factor. This expression fails for hydrocarbons with unusually small HOMO-LUMO separations. An alternative topological expression that includes a correction for this situation provides an excellent non-empirical explanation for the successful empirical use of Dewar reactivity numbers in correlating exact localization energies. The present analysis provides an explanation for the success of the traditional resonance structure counting technique in predicting relative rates of aromatic substitution. The analysis develop applied only to alternant hydrocarbons.     

Application of the ring oven method to the determination of dyestuffs

Summary The Weisz ring oven method has been applied to the semiquantitative determination of indigo carmine, erythrosin A, amaranth O, new coccine, Victoria blau B, tartrazine, azorubin S, alizarin S, eosin, light green SF, Guinea green B, fuchsin, eriochrome black T, saphranine, ponceau 3 R, cyanine, gelborange S, and methyl violet 6 B. The amount of dye needed ranges from 0.5 to 20g, and the error is generally less than 5%. The method has been used for the determination of azorubin S, methyl violet 6 B, tartrazine, and amaranth O in various materials.

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Zusammenfassung Die Ringofenmethode vonWeisz wurde für die semiquantitative Bestimmung folgender Farbstoffe angewendet: Indigocarmin, Erythrosin A, Amaranth O, Neucoccin, Viktoria blau B, Tartrazin, Azorubin S, Alizarin S, Eosin, Lichtgrün SF, Guineagrün B, Fuchsin, Eriochromschwarz T, Saphranin, Ponceau 3 R, Cyanin, Gelborange S und Methylviolett 6 B. Die dazu nötige Farbstoffmenge beträgt 0,5 bis 20g, der Fehler ist im allgemeinen geringer als 5%. Die Methode wurde für die Bestimmung von Azorubin S, Methylviolett 6 B, Tartrazin und Amaranth O in verschiedenen Materialien angewendet.

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Résumé On a appliqué la méthode du four annulaire deWeisz au dosage semi-quantitatif du carmin d'indigo, de l'érythrosine A, de l'amaranthe O, de la coccine nouvelle, du bleu Victoria B, de la tartrazine, de l'azorubine S, de l'alizarine S, de l'éosine, du vert lumière SF, du vert Guinée B, de la fuchsine, du noir ériochrome T, de la safranine, du ponceau 3 R, de l'orangé jaune, de la cyanine S et du violet de méthyle 6 B. La quantité de colorant nécessaire va de 0,5 à 20g et l'erreur est généralement inférieure à 5%. On a appliqué la méthode au dosage de l'azorubine S, du violet de méthyle 6 B, de la tartrazine et de l'amaranthe O dans diverses substances.

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We wish to thank Mrs.Lidija Pfendt of the Faculty of Sciences in the University of Belgrade for doing the spectrophotometric analyses.     

Interactions of silver halide sols with hydrolyzed hafnium species

Summary Coagulation and reversal of charge effects of freshly prepared and heated solutions of hafnium tetrachloride have been studied as a function of the p_H using aged silver halide sols and solsin statu nascendi. It was shown that the critical coagulation concentration and the critical stabilization concentration (due to charge reversal) increased with increasing p_H. These observations have been related to the hydrolysis of the hafnium ion. At p_H values above 4 essentially the entire amount of hafnium is present in the form of the neutral soluble, species Hf(OH)₄. This accounts for the inability of the hafnium solutions to reverse the charge of the sols at higher p_H values. The adsorption measurements carried out with the aid of the radioactive isotope¹⁸¹Hf showed that the neutral hydrolyzed species are strongly adsorbed on negatively charged silver iodide particles. The adsorbed amounts of hafnium on a AgI sol are considerably larger than in the case of charged hydrolyzed ions (such as hydrolyzed thorium ions) on a similar sol. This is explained by the ability of the neutral hafnium species, Hf(OH)₄. to form a close-packed adsorbed layer. The results confirm previous findings that the enhanced adsorption of hydrolyzed ions is caused by the presence of the hydroxyl group, whereas the ionic charge plays a negligible role in this case.

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Zusammenfassung Die Koagulations- und Umladungserscheinungen von frisch dargestellten und durch Erwärmung gealterten Lösungen von Hafniumchlorid wurden an Silberhalogenid-Solen in der Abhängigkeit vom p_H untersucht. Es wurde festgestellt, daß die kritische Koagulationskonzentration und die kritische Stabilisationskonzentration (die Umladungsgrenze) mit steigendem p_H höher werden. Diese Beobachtungen wurden durch die Hydrolyse des Hafnium-Ions erklärt. Wenn p_H>4 ist, bestcht nahezu die ganze Menge von Hafnium als neutrale, gelöste Hf(OH)₄ Moleküle. Damit wird es erklärt, daß die Silberhalogenid-Teilchen bei höheren p_H-Werten durch Hafniumsalze nicht umgeladen werden können. Die mittels des radioaktiven Isotopen¹⁸¹Hf durchgeführten Messungen zeigten, daß die neutralen Hf(OH)₄ — Moleküle stark an den negativ geladenen Silberjodid-Teilchen adsorbiert sind. Die adsorbierte Menge per Mol von AgI ist beträchtlich größer als die Menge der geladenen, hydrolysierten Ionen (wie z. B. ThOH³⁺), die an dem gleichen Sol bestimmt wurde. Dieser Effekt ist leicht erklärt, da man mit den neutralen adsorbierten Molekülen eine fest gepackte Adsorptionsschicht bilden kann. Diese Resultate bestätigen die früheren Befindungen, daß die höhere Adsorptionsfähigkeit der hydrolysierten Ionen durch die Hydroxylgruppe verursacht wird, während die Ionenladung eine zu vernachlässigende Rolle spielt.

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Supported by the U.S. Army Research Office (Durham), Grant No. DA-ARO (D)-31-124-G 656.

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Part of a PhD Thesis byL. J. Stryker, supported by a NASA Traineeship.     

Influence of medium on the kinetics of oxidation of iron(II) ion with t-butyl hydroperoxide

The oxidation of iron(II) with tert-butyl hydroperoxide was investigated in the absence of oxygen in water, methanol, and the dichloromethane—methanol solvent mixture (φ_r = 2:1). The oxidation rate depends on solvent polarity; measured in the presence of SCN⁻ at constant 0.8 mmol dm⁻³ HCl, the rate constant increases with the polarity decrease passing from water and methanol to the dichloromethane—methanol solvent mixture. Further, in non-aqueous solutions at this acid concentration the rate constant was higher than the rate constant in the presence of Cl⁻ only. The oxidation rate measured in the [FeCl]²⁺ complex in dichloromethane—methanol was slow in acidic medium and increased by decreasing the acid concentration. Approaching the physiological pH conditions the rate constant attained the value of an order of magnitude of 10³ dm³ mol⁻¹ s⁻¹, while very little alteration of stoichiometry of the oxidation reaction was observed. The rate constant measured in the presence of Cl⁻ strongly depends on electrolyte concentration at concentrations less than 0.5 mmol dm⁻³ HCl, both in MeOH and the solvent mixture. Based on these results, a possible mechanism of the influence of solvent, acidity, and ligand type on the rate constant is discussed. We assume that the oxidation proceeds by an inner-sphere mechanism considering that the breakdown of the successor inner-sphere complex forming reactive alkoxyl radicals is probably the rate-limiting step. Presented at the 20th International Conference on the Coordination and Bioinorganic Chemistry organized by the Slovak Chemical Society, Slovak University of Technology, Comenius University, and the Slovak Academy of Sciences, Smolenice Castle, 5–10 June 2005.