Excess Of Silver Ions Research Articles

Simulation of bromate-driven oscillations in the presence of excess silver ions using the Oregonator model

Simulation of bromate-driven oscillations in the presence of excess silver ions using the Oregonator model

The behaviour of the silver sulphide precipitate-based ion-selective electrode in the low concentration range

The anomalous behavior of the precipitate-based silver sulphide ion-selective electrode in the low concentration range of silver and sulphide ions is described. The excess of silver ion at the electrode surface, caused by adsorption or oxidation, is responsible for the deviations from the ideal Nernstian response. The adsorption/desorption processes were studied in a microcell by using combined potentiometric and atomic absorption measurements. The oxidation—reduction processes were studied by using polarized electrodes.

The mechanism of the photochemical oxidation of water to oxygen with silver chloride colloids

Photoexcitation of silver chloride colloids in the presence of excess silver ions, leads to the decomposition of water. Hydroxyl radicals were found to be intermediates in the decomposition process. Irradiation leads to hydroxyl radicals, which recombine to give hydrogen peroxide, on the colloidal particle surface. Subsequent decomposition of H 2 O 2 to give O 2 is catalyzed by silver ions. Addition of alcohols such as methanol and isopropanol reduce the oxygen yield, as they react with OH radicals and reduce the H 2 O 2 yield.

ChemInform Abstract: CHEMICAL OSCILLATIONS AND INSTABILITIES. PART 50. BROMATE‐DRIVEN OSCILLATORS IN THE PRESENCE OF EXCESS SILVER ION

Chemischer InformationsdienstVolume 14, Issue 13 Preparative Organic Chemistry ChemInform Abstract: CHEMICAL OSCILLATIONS AND INSTABILITIES. PART 50. BROMATE-DRIVEN OSCILLATORS IN THE PRESENCE OF EXCESS SILVER ION N. GANAPATHISUBRAMANIAN, N. GANAPATHISUBRAMANIANSearch for more papers by this authorR. M. NOYES, R. M. NOYESSearch for more papers by this author N. GANAPATHISUBRAMANIAN, N. GANAPATHISUBRAMANIANSearch for more papers by this authorR. M. NOYES, R. M. NOYESSearch for more papers by this author First published: March 29, 1983 https://doi.org/10.1002/chin.198313149AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue13March 29, 1983 RelatedInformation

Chemical oscillations and instabilities. Part 50. Bromate-driven oscillators in the presence of excess silver ion

Chemical oscillations and instabilities. Part 50. Bromate-driven oscillators in the presence of excess silver ion

A ’’photocurrent-inversion effect’’ of sintered AgBr microcrystals at room temperature

The photocurrent of sintered AgBr microcrystals of high dark conductivity has been measured at room temperature by using a polarization technique of mobile silver ions. Under the condition in which mobile silver ions were polarized, first, a negative photocurrent was observed and, consequently, this negative photocurrent was reversed to a positive one; that is, a ’’photocurrent-inversion effect’’ has been found. This negative photocurrent and the inversion effect of the current were explained by the theory of photographic sensitivity and the experimental estimation of the range of photoelectrons (?5×10−4 cm) in this sintered AgBr. It has been concluded that excess silver ions could be regarded not only as being significant for the electron traps in the surface region, but also as being the electron traps whose distribution could be varied by external voltage.

Reactions of silver ions with thiobenzamides in aqueous solution

In aqueous acid solution, in the presence of an excess of silver ions, thiobenzamides form 1 S-amide : 1 Ag+ complexes stoicheiometrically. For thiobenzamide the decomposition of the 1 : 1 complex leads to silver sulphide and benzonitrile and for N-cyclohexylthiobenzamide to silver sulphide and the O-amide. For both thiobenzamide and N-cyclohexylthiobenzamide the kinetic forms suggest mechanism of decomposition similar to those proposed for the corresponding decompositions of S-amide–Hg2+ complexes. These mechanisms involve the ionisation of the S-amides′N-hydrogen atoms.

ESR Study of Silver Chloride Crystals Doped with Sulphur Ions and Mercury Ions

Sulphur centers in silver chloride crystals are studied by ESR measurements and also observation of their kinetic behaviors. The paramagnetic centers produced by illumination have a symmetry axis of <100> and g values of g//=1.999 and g⊥=2.031. They are ascribed to AgS radicals substituting for AgCl molecules in the crystal. The activation energy of formation of the photoproduced ESR signals is 0.22–0.28 eV, and that of thermal bleaching is about 0.75 eV. These centers are considered as produced by trapping the holes and liberating the interstitial silver ions. The initial sulphur centers are guessed as AgS-Ag+ complexes formed under the condition of excess silver ions. The effects of hyperfine interaction by S33 isotopes are preliminarily described, in which the splitting constants are several gauss in both directions of the main axis of the g tensor.

Silbermercaptide und ‐mercaptokomplexe

AbstractThe complex formation of silver(I) has been studied with the anions of simple mercaptans RSH which have been rendered soluble by replacing some H in the substituent R by OH. All equilibria constants refer to a solvent of ionic strength μ = 0,1 and 20°C.Monothioglycol HOCH2CH2SH (pK = 9.48) forms an amorphous insoluble mercaptide {AgSR} (s), ionic product [Ag+] [SR−] = 10−19.7. The solution in equilibrium with the solid contains the molecule AgSR at a constant concentration of 10−6.7 M which furnishes the formation constant of the 1:1‐complex: K1 = 1013. 0. The solid is soluble in excess of mercaptide (AgSR+SR− → Ag(SR)2−: K2 = 104. 8) as well as in an excess of silver ion (AgSR + Ag+ → Ag2SR+K ≈︁ 106).With the bulky monothiopentaerythrite (HOCH2)3CCH2SH (pK = 9.89) no precipitation occurs with silver when the mercaptan concentration is below 10−3. 2M. A single polynuclear Ag10(SR)9+ (β10.9 = 10175) is formed in acidic solutions which breaks up with the formation of Ag2SR+ (β2.1 = 1019.0) when an excess of silver ion is added. Below the mononuclear wall ([RS]total &lt; 10−6) Ag2SR+ is formed via the mononuclear AgSR (K1 = 1013). At higher mercaptan concentrations ([RS]tot &gt; 10−3.2) an amorphous precipitate is formed which has almost the same solubility product as silver thioglycolate ([Ag+] [SR−] = 10−19.1).Apparently silver(I) forms with mercaptans always the complexes Ag2SR+, AgSR and Ag(SR)2−. Above the mononuclear wall, these species condense to chain‐like polynuclears which are cations Ag(SRAg)n+ in presence of an excess of Ag+, and anions SR (AgSR)n− when the concentration [RS−] is larger than [Ag+]. Usually n becomes rapidly very large as soon as the condensation starts (n → ∞: precipitate). The decanuclear Ag(SRAg)9+ formed with thiopentaerythrit is somewhat more stable than the shorter chains (n &lt; 9) and larger chains (n &gt; 9), because it can tangle up to a ball by coordination of bridging mercapto‐sulfur to the terminal silver ions (figure 12, page 2179). This ball seems to be further stabilized by hydrogen bonds between the many alcoholic OH groups of the substituent R = (HOCH2)3CCH2. The stability of the bonds AgS, however, is little influenced by the substituent R which carries the mercaptide sulfure.

Reaction of hypohalous acids with 2-halogenopropenes. Exchange of halogen atoms. Part II

2-Chloropropene reacts with [36Cl]hypochlorous acid in the presence of excess of silver ion to form chloroacetone (85%) and 2,3-dichloropropene (15%) both with a much reduced specific activity. The radioactivity in the 2,3-dichloropropene was shown to be exclusively in the 3-chloro-substituent. The loss of activity was decreased as the initial silver-ion concentration was increased. Similar exchange occurred in the reaction of 2-bromopropene with [82Br]hypobromous acid and the reaction of hypochlorous acid with 2-bromopropene produced bromoacetone as well as chloroacetone. Addition of halide ion to [36Cl]hypochlorous acid containing excess of silver ion showed the expected variation with silver ion of the radioactivity formed in solution which also decreased in the order Cl– > Br– > l–.

Exchange of chlorine atoms during the reaction of hypochlorous acid with 2,3-dichloropropene

2,3-Dichloropropene reacts with [36Cl]hypochlorous acid in water in the presence of mineral acid and an excess of silver ions to give 1,3-dichloroacetone (major product) and 1,2,3-trichloropropene, both with specific activity only ca. 65% of that of the [36Cl]hypochlorous acid. 2,3-[2-36Cl]Dichloropropene reacted with inactive hypochlorous acid to give 1,3-dichloroacetone, with specific activity ca. 35% of that of the olefin. Addition of potassium [36Cl]chloride solution during the reaction with inactive substrates resulted in appreciable radioactivity in the product, whereas in the presence of freshly precipitated silver [36Cl]chloride negligible activity appeared in the product. Addition of sodium [36Cl]chloride to hypochlorous acid containing an excess of silver nitrate immediately produced radioactivity in solution. The extent of this activity depended markedly on the silver ion concentration and hardly at all on the acidity of the medium. The results are interpreted in terms of an exchange reaction involving silver chloride ion-pair aggregates.

Neuere Forschungsergebnisse über die nach dem Säure-Base-Prinzip funktionierenden Adsorptionsindicatoren

In order to confirm the function of adsorption indicators on acid-base principle the following procedures have been applied: measurement of the donation or acceptance of protons and detection of a change of the dissociation constant of the adsorbed dye originated by excess of own ions. This methods can be completed by the measurement of starting adsorption, when in acid medium in the presence of excess of silver ions the adsorbent is titrated with indicator solution, and by the determination of the adsorbed dyes during 30 min in six varieties of charge distribution. Moreover, the advantageous effect of organic solvents is discussed. In conclusion new statements are reported for the adsorption indicators on acid-base principle.

A Potentiometric Study of The Silver Complexes of N,N'‐Bis (2‐Hydroxyethyl) Dithio‐Oxamide

AbstractIt has been proved that N,N'‐Bis (2‐hydroxyethyl) dithio‐oxamide forms with silver different complexes, dependent from the pH of the solutions and the excess of the metal ion.With an excess of ligand an insoluble yellow complex Ag3H5X4 is formed in the pH range 2,5 to 3,5. The solubility product in strong buffered solution was found to be Ks=10–61,31In the pH range 4 to 6 a more stable yellow complex AgHX is formed with a solubility product Ks=10–19,27.With an excess of silver ion a very unstable white complex Ag2X is formed.

The liesegang phenomenon II. Addition of protecting agents

The present work demonstrates that the formation of clearly defined rhythmicity is intimately related to the stability of the sol prior to precipitation. The various factors affecting this stability have been analyzed for their effect on the periodicity. It is shown that excess silver ion causes rapid flocculation and blurred precipitation zones. On the other hand, the spacing coefficient is shown to increase in the presence of peptizers for the precipitated substance. The periodicity observed in gels may be used as a method for investigating the stability of colloidal sols.

The liesegang phenomenon II. Addition of protecting agents

The present work demonstrates that the formation of clearly defined rhythmicity is intimately related to the stability of the sol prior to precipitation. The various factors affecting this stability have been analyzed for their effect on the periodicity. It is shown that excess silver ion causes rapid flocculation and blurred precipitation zones. On the other hand, the spacing coefficient is shown to increase in the presence of peptizers for the precipitated substance. The periodicity observed in gels may be used as a method for investigating the stability of colloidal sols.

Radiometric analysis for chloride ion

In this experiment the chloride-ion concentration in an unknown solution is determined by the addition of excess silver ion containing radioactive silver.

On the role of crystal imperfections in photographic sensitivity

The role of crystal imperfections in the formation of the latent image in large crystals of silver bromide has now been established by experimental work. The internal latent image is formed by the separation of silver along dislocation lines associated with strained regions of the crystal and with the boundaries of the polyhedral substructure. Chemical sensitizing agents are adsorbed and react preferentially at the surfaces of regions of strain and imperfection in the crystals. Non-reacting sensitizing molecules are also adsorbed in the same regions because of the higher density of kink sites associated with them. This means that the chemical sensitizers are concentrated at the surfaces of strained and imperfect parts of the crystal where positive holes and electrons liberated during exposure are most likely to be trapped. It is postulated that the trapping of the holes occurs before that of the electrons and leaves the surface with a positive charge due to an excess of silver ions. The bromine atoms formed by the trapping of the holes by bromide ions occupying kink sites combine with atoms or molecules of sensitizers. The silver ions ultimately attach themselves to nuclei consisting of one or two metallic atoms and these positively charged aggregates then combine with the electrons. In this way larger aggregates are formed which may become positively charged in equilibrium with the silver ions of the crystal and act as development centres. With some molecular sensitizers, it is possible that a surface latent image is produced by the internal rearrangement of the molecule without the actual liberation of electrons.

The electrophoresis of silver bromide sols. Part 1.—The establishment of reproducible electrophoretic mobilities in presence of excess silver ion

The first page of this article is displayed as the abstract.