The action of organic divalent cation on the stability of negative silver iodide sol

Summary The action of organic divalent cations on negative silver iodide sol has been studied. The coagulation values of ethylene-, propylene-and hexamethylene-diammonium chlorides are found considerably less than those of corresponding n-alkylammonium chlorides, which shows the effect of the number of ionized groups. The action of hexamethylene-1,6-bis-trimethylammonium chloride is considered to be due to “adsorption” of the organic ions.

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Zusammenfassung Es wurde die Wirkung von organischen zweiwertigen Kationen auf die Stabilit?t vom negativen Silberjodid-Sol untersucht. Die Flockungswerte von ?thylen-, Propylen-, und Hexamethylen-diammoniumchlorid zeigen sich kleiner als die der entsprechenden n-Alkyl-ammoniumchloride. Es wird angenommen, da? die flockende Wirkung des Hexamethylen-1,6-bis-tri-methylammoniumchlorids auf Adsorption des organischen Ions beruht.

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The author wishes to express his hearty thanks to Prof. B. Tamamushi for his interest in this study and to Dr. K. Meguro and Dr. T. Kondo for their kind supply of sample.     

Stability of AQUO-organic silver iodide sol

Summary The coagulation concentration for silver iodide sol, both in presence of pyridine and dioxane, increases for mono- and bivalent coagulating electrolyte. In presence of a mixture of pyridine and dioxane in equal volume, the coagulation concentration assumes an intermediate value, which is nearer to dioxane. However, in presence of dioxane more bivalent electrolyte is needed than in presence of pyridine. If a bivalent coagulating electrolyte is added to a sol containing a mixture of pyridine and dioxane, the amount of electrolyte required to coagulate is less than pyridine and greater than dioxane. Thus silver iodide sol is more stable toward mono- and bivalent coagulating electrolytes. The degree of stabilization increases with the decrease of the dielectric constant of the dispersing medium. The intermediate values for dioxane pyridine mixture is accountable by the fact that dioxane acts as a solvent for pyridine. The PH value of the sol increases up to the coagulation point. Beyond this, there is an abrupt decrease. When the particles settle down completely a rise in PH is again noted on the further addition of electrolytes. The increase in the electrical conductance is more significant after coagulation. These changes have been explained by adsorption of the ions and due to the release of ions from the electrical double layer.

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Zusammenfassung Die Koagulationskonzentration für Silberjodidsol in Gegenwart von Pyridin und Dioxan steigt für ein- und zweiwertige Elektrolyte an. In Gegenwart einer Mischung zu gleichen Volumen erh?lt man mittlere Werte, n?her denen zu Dioxan. Für Koagulation in Gegenwart von Dioxan ist jedoch mehr zweiwertiger Elektrolyt notwendig als in Gegenwart von Pyridin. Bei Koagulation mit zweiwertigem Elektrolyt verbraucht ein Sol mit der Mischung von Pyridin und Dioxan weniger als für Pyridin und mehr als für Dioxan. Daher ist das Silbersol gegenüber ein- und zweiwertigen Elektrolyten stabiler. Der Grad der Stabilisierung w?chst mit abnehmender Dielektrizit?tskonstante des Dispersionsmediums. Die Zwischenwerte der Dioxan-Pyridin-Mischungen lassen sich verstehen durch die Tatsache, da? Dioxan als L?sungsmittel für Pyridin wirkt. Der PH-Wert des Sols w?chst bis zum Koagulationspunkt, darüberhinaus erfolgt ein steiler Abfall. Wenn die Teilchen vollst?ndig absetzen, ist bei weiterer Zugabe von Elektrolyt ein erneuter Anstieg im PH feststellbar. Der Anstieg der elektrolytischen Leitf?higkeit wird nach der Koagulation ausgepr?gter. Diese ?nderungen lassen sich durch Ionenadsorption und Freiwerden von Ionen aus der elektrischen Doppelschicht erkl?ren.

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Our thanks are due to Prof. R. C. Mehrotra for providing all the facilities for this work and to Prof. S. Ghosh of Allahabad University for helpful discussions. Thanks are also due to the University Grants Commission, Government of India, for the award of a research scholarship to one of us (V. K. S.).     

The effect of addition of polar molecules on the degree of dispersion of silver iodide sol

The objective of the present study was to investigate the changes in the degree of dispersion in a negative AgI sol under the influence of organic components introduced into the medium only after nucleation. It was found that the polar molecules of those components can stimulate the process of formation of individual colloidal particles from unstable metaphase clusters emerging as a result of embryo aggregation.     

Impedance measurements for pressed-pellet electrode membranes based on silver iodide and silver iodide/silver sulfide with solution contacts

Impedance characteristics of pressed pelletm membranes based on silver iodide, mixed $\text{AgI}\text{Ag}{}^2\text{S}$ with molar ratios of 10:1, 1:1 and 1:10, and silver sulfide are investigated by using solution contacts and a computer-controlled automatic measuring system. As membrane bulk impedances were commensurable with those of contacting solutions, special regression methods were necessary for evaluation. Typical resistivities were, in the order indicated above, as follows: 14, 2, 0.3, 0.1 and 0.1 kΩ cm, respectively. Thus, mixing of silver sulfide into the silver iodide matrix decreases dramatically the membrane resistance. These measured bulk membrane resistances are not affected by changes in composition and concentration of bathing solutions, and even the low-frequencies parts of impedance plots were not influenced by different stirring conditions, even in presence of corroding solutions such as thiosulfate or cyanide. Sorption also had no manifest effect on the impedance characteristics, but increasing pressure during membrane preparation or heat treatment significantly increased membrane resistances.     

The anodic dissolution of silver into silver rubidium iodide — Impedance measurements

A.c. impedance measurements have been made on the Ag/Ag₄RbI₅ interphase at anodic potentials less than 50 mV vs. Ag/Ag⁺, using an automatic frequency response analyser.At overpotentials between 10 and 35 mV a high frequency semicircle and a low frequency inductive shape were seen. Spectra at these low overpotentials can be interpreted in terms of rate determining two-dimensional nucleation and growth of holes in the metal surface. The number of atoms in the critical nucleus at various overpotentials have been calculated from both steady state and impedance measurements.     

Response of the cation-sensitive glass electrodes to alkyl-substituted ammonium ions

Summary The response of cation-sensitive glass electrodes to alkyl-substituted ammonium ions has been evaluated. Increasing ion size results in decreasing electrode selectivity, progressively greater deviations from the Nernst slope, and increasing equilibration times. Direct potentiometric measurements should be suited to the estimation of smaller alkyl-substituted ammonium ions in the presence of multivalent cations.

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Zusammenfassung In der vorliegenden Untersuchung wurde das Ansprechen von kation-empfindlichen Glaselektroden auf alkylsubstituierte Ammoniumionen geprüft. Mit steigender Größe des Ions konnte eine Abnahme der Selektivität der Elektrode, zunehmende Abweichungen von der Nernstschen Gleichung und eine wachsende Zeitdauer für die Einstellung des Gleichgewichts beobachtet werden. Es ergab sich, daß die kation-empfindliche Glaselektrode zur Bestimmung kleinerer alkylsubstituierter Ammoniumionen in Gegenwart mehrwertiger Kationen verwendet werden kann.

     

The electrical double layer on silver iodide in water+ethylene glycol mixtures II. Inner layer properties and their relation to sol stability

A discussion is given on the potentialities of combining double layer data with information derived from colloidal stability in order to gain insight into the composition of the Stern-layer. The method is applied to AgI-sols in water+ethylene glycol mixtures containing KNO₃ and Ba(NO₃)₂. On negative AgI-surfaces, K⁺ and Ba²⁺ ions adsorb specifically. The specific adsorption free energies of these ions are estimated, they are probably to a large extent entropically determined.     

Micellization of some amphiphilic quaternary ammonium chlorides

The micellization processes of N-dodecyl-N,N-dimethyl-N-[3-(β-methyl-β-nitrovinyl)-6-methoxybenzyl] ammonium chloride (I-A), N-dodecyl-N,N-dimethyl-N-benzylammonium chloride (I-B), N-dodecyl-N, N,N-trimethylammonium chloride (I-C), N-dodecyl-[3-(β-methyl-β-nitrovinyl)-4-methoxybenzyl] morpholinium chloride (IV-A), N-dodecyl-N-benzylmorpholinium chloride (IV-B), N-dodecyl-N-methylmorpholinium chloride (IV-C), and N-dodecyl-N-methylpiperidinium chloride (VI-C) were studied by means of the calorimetric titration method. The critical micelle concentrations and enthalpies of micellization were determined. It is suggested that the benzyl groups of I-B and IV-B and the nitrovinylbenzyl groups of I-A and IV-A behave as second chains during the micellization.     

The solubilization of Orange OT in aqueous solutions of alkyl-substituted ammonium salts of polystyrenesulfonic acid

Summary The solubilization of Orange OT in aqueous solutions of alkyl-substituted ammonium salts of polystyrenesulfonic acid has been studied. It has been found that the solubilizing power of polyelectrolytes increases with the increase of the carbon atom number of alkyl groups of counter-ions. It is suggested that the phenomenon originates from the increased hydrophobic nature of polyelectrolytes due to counter-ion binding.

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Zusammenfassung Es wurde die Solubilisation von Orange OT in wässerigen Lösungen alkylsubstituierter Ammoniumsalze von Polystyrolsulfonsäure untersucht. Es wurde gefunden, daß die Wirksamkeit zur Solubilisation von Polyelektrolyten mit der Zunahme der Kohlenstoffatomzahl der Alkylketten der Gegenionen steigt. Die experimentellen Ergebnisse deuten darauf hin, daß die Erscheinung durch die zunehmende hydrophobe Eigenschaft von Polyelektrolyten infolge der Gegenionenbindung verständlich ist.

     

Role of ammonium ions on the stability of TiO2 sol

In this paper, the role of the trace ammonium ions on the stability of TiO₂ sol prepared by peroxo titanic acid (PTA) sol was investigated. The results showed that the removal of ammonium ions in PTA sol is beneficial to reduce agglomeration and increase the negative charge on the surface of TiO₂ colloidal particles, contributing to the higher stability and longer storage time of the TiO₂ sol. It was also approved by the increase of interaction energy calculated by classical DLVO theory. In addition, the photocatalytic performance of TiO₂ sol was improved due to the decrease of aggregation of TiO₂ colloidal particles.     

Crystal lattice energy of ammonium and methanaminium chlorides

The fraction of crystal lattice energy of ammonium and methanaminium chlorides caused by electrostatic interactions has been evaluated on the basis of modified Coulomb equation for infinite number of interacting charges using available crystallographic information and estimating charge distribution for cations by MNDO and INDO methods. The evaluated characteristics compare well with experimentally derived crystal lattice energies particularly with respect to the observed trends of both quantities on the degree of substitution.

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Zusammenfassung Unter Verwendung zugänglicher kristallographischer Informationen und einer Schätzung des Ladungsbeitrages von Kationen (MNDO, INDO) wurde auf der Basis einer modifizierten Coulomb-Gleichung für eine unendliche Zahl von beteiligten Ladungen derjenige Anteil der Kristallgitterenergie von Ammonium- und Methanaminiumchloriden geschätzt, der auf elektrostatischen Wechselbeziehungen beruht. Die geschätzten Angaben stimmen gut mit experimentell ermittelten Kristallgitterenergien überein, besonders im Hinblick auf die beobachtete Tendenz beider Größen in Abhängigkeit vom Substitutionsgrad.

     

Time-dependent SERS of pseudoisocyanine on silver particles generated in silver bromide sol by laser illumination

SERS spectra of pseudoisocyanine dye (PIC) in silver bromide sols show a strong time-dependence. The enhancement factor, in general, follows the formation (and destruction) of SERS-active colloidal silver in the silver halide sols by laser illumination during the Raman measurement. Changes in the relative intensities within a characteristic fine triplet of the SERS spectrum show that the surface potential which is “seen” by the dye molecules shifts to more positive values with longer times. In particular, the values of the potential hint at the existence of Ag₁ and Ag₄ … Ag₆ clusters as SERS-active adsorption sites of the dye molecules in AgBr sols.     

Surface enhanced Raman spectra of isomeric acetylpyridines adsorbed on silver sol

Raman spectra of 2-, 3- and 4-acetylpyridines (AP) are obtained in bulk phase, in aqueous solution and in the adsorbed state on colloidal silver particles. Addition of the acetylpyridines on the Ag-sol results in aggregation of the silver particles showing characteristic charge transfer (CT) bands. Significant surface enhancement of the Raman bands are observed. Both the estimated enhancement factor and the absorption maxima of the CT bands are in inverse parallel relationship with the electron density on the nitrogen atom as reflected by the Hammett σ values of the substituents. It is inferred that the charge transfer interactions between the adsorbates and the metal particles contribute to the enhancement mechanism. This is further substantiated by the concentration dependence of enhancement. A classical electromagnetic contribution is demonstrated by the Raman excitation frequency dependence of SERS. The results further show that the molecules are adsorbed on the metal surface through the nitrogen atom. Appearance of some out-of-plane modes in the SERS spectra suggests that the pyridyl ring planes are not perpendicular to the metal surface, but are tilted.     

Investigations of fundamental properties of the silver/silver iodide film electrode

A study is presented of the basic physicochemical properties of vacuum deposited silver/silver iodide film electrodes. X-ray analysis and electron microscopy yield information on the crystal structure and morphology of these films. The AgI was predominantly present in the γ modification. On the AgI surface irregularities are observed with diameters of 100 nm and lower. Aged surfaces show smaller irregularities than non-aged surfaces. The total roughness factor is estimated at 1.5 with an uncertainty of at least 10%. Methods are presented to determine the average film thickness and the conductivity of the film. The films used have a thickness of about 350 nm. The specific conductivity of the AgI film is approximately 10^?4 Ω^?1 cm^?1.