A-silver iodide

A silver iodide sol can be positively as well as negatively charged, dependent on whether there is an excess of positive or negative silver iodide ions present (figure 5.7). 

In many colloidal systems, the double layer is created by the adsorption of potential-determining ions for example, the potential 0o the surface of a /Silver iodide particle depends on the concentration of silver (and iodide) ions in solution. Addition of inert electrolyte increases k and results in a corresponding increase of surface charge density caused by the adsorption of sufficient potential-determining silver (or iodide) ions to keep 0O approximately constant. In contrast, however, the charge density at an ionogenic surface remains constant on addition of inert electrolyte (provided that the extent of ionisation is unaffected) and 0O decreases. 

Silver iodide (Agl) is used in place of silver chloride for the fastest photographic film because it is more sensitive to light and can therefore form an image in a very short exposure time. A silver iodide emulsion is prepared by adding 6.60 L of 0.10 M Nal solution to 1.50 L of 0.080 M AgN03 solution at 25°C. Calculate the concentration of silver ion remaining in solution when the mixture comes to equilibrium and its chemical amount relative to the amount present initially. 

The surface charge on a solid surface can be obtained by determining the adsorption of potential-determining ions at various potentials of the interface [1]. For example, in the case of a silver iodide sol the adsorption of Ag+ and I ions is determined at various concentrations of Ag" " and I" ions in bulk solution. Similarly, for an oxide the adsorption of H" " and OH" ions Fand respectively) is determined as... 

For salt formation by salt exchange, the salt of the drug substance is combined with a salt containing the desired counterion in specific molar ratios in a suitable solvent system. As described above, there must be adequate solubility of each reactant in the solvent system. If the desired salt of the drug substance is less soluble than the starting materials, it will precipitate out and can be isolated by filtration. If no precipitate is obtained, other isolation methods can be employed. A method that was described for iodide salts (19) involved precipitation of the unwanted counterion first. In this case silver salts were used for the counterions (silver sulfate, silver orf/tophosphate, silver lactate) and a silver iodide precipitate was isolated first by filtration. The desired salt of the drug substance was then precipitated from the filtrate by addition of an antisolvent. 

Mix equal amounts of 0.020 mol din sodium bromide solution and 0.018 mol dm silver nitrate solution. A colloidal dispersion of silver bromide is formed immediately. A silver iodide sol maybe prepared in a similar manner. 

Figure 1. Plateau values for the adsorption of human plasma albumin on polystyrene latex (A), silver iodide (x), polyoxymethylene ( ) and hematite ( ).

Thus Bryant et al. (i960) find that a supersaturation of 12 per cent with respect to ice is required to nucleate ice crystals directly from the vapour on a silver iodide substrate. Since for a vapour pressure/)... 

Reversible Electrodeposition of a silver iodide complex from a solution of 0.3 M Agl and KI or Rbl, and Ij in DMSO or diethyl malonate is an example for the third class of wet non-emissive electro-optic displays . As long as the silver content of the solution is high enough the solvent did not deteriorate when pulses of 50 V were passed through. The addition of AljOj, for preventing TiOj from agglomeration, and the use of RbAg4lj in DMSO as the solid ion-conductor established a cell which survive more than 10 cycles when operated at <2V drive, the realized response times were < 10 ms. 

A silver iodide crystal has a surface pattern that closely resembles that of an ice crystal it was this resemblance that led Langmuir to try silver iodide as a seeding material. The silver atoms and iodine atoms occupy the positions of alternate oxygen atoms in the ice structure (Figure 9-8), and the silver-iodine distance, 280 pm, is only 1.5 percent greater than the oxygen-oxygen distance in ice. 

In addition to the use of the standard potential ( ), reaction potentials may also be reported with the convention of electromotive force (emfor S [V]). The convention of emf was adopted to make the calculation of cell potentials, from the combination of two half-reactions, more straightforward. For a reduction reaction, the standard potential and the cm/have the same value, while for the same reaction written in the direction of oxidation (e.g the reverse reaction), their signs are opposite. Using the example of a silver iodide cell, consider the complete cell schematic ... 

S. V. Shevkunov, Structure of water in microscopic fractures of a silver iodide crystal, Russ. J. Phys. Chem. A, 88,313-319 (2014). 

Recall that silver chloride is soluble in an excess of chloride ions by the formation of the ion complex chlorosilver(I) (see Chap. 25). Bromide ions give a clear yellow color of silver bromide that dissolves in the same reagents as the chloride ion but with more difficulty. Iodide ions give a silver iodide precipitate insoluble in ammonia but soluble in potassium cyanide and sodium thiosulfate. From another standpoint, Ag+ ions give silver dithizonate with dithizone. The... 

A. Tube abcdg was filled with a silver iodide sol, and e and / were closed by semipermeable membranes. As the electrodialyas proceeded, one could observe a boundaiy between the sol and the solvent being formed at the top of c and slowly moving downward. Similarly, an increased concentration could be seen in b. The final concentration distribution obtained is shown in Fig. 17B the original concentration still remained in d and... 

Figure 5. Ag 3dsy2 XPS spectra from a silver iodide sample placed on a fine copper mesh. Spectra (1) no bias, (2) -4 V dc bias, and (3) -10 V dc bias. (From Ref. 27.)...

The original AMEC method was to leach the sample before a selective volatilisation and capture of iodine in a separate solution. Following this was a silver nitrate precipitation to form a silver iodide solid which was then analysed by liquid scintillation counting. Although the selective volatilisation of iodine from chlorine separates the two elements, as Cl is not oxidised to CI2 in nitric acid (whereas I is oxidised to I2), some Cl... 

Fig. 10. Electron micrographs of colloidal silver iodide (diameter 100 - 800 A) and of colloidal silver (diameter of primary particles about 150 A), a. Silver iodide Pt shadowed 10,000 x. b. Silver 32,000 x.

Nagel using an abrasion electrode in which periodically the surface of a silver iodide electrode is scratched away, also found a zero point of charge near pAg =" 6, This method, which for solid substances should be equivalent to the direct determination of the charge with the dropping mercury electrode (see 5 b, p, 149), seems to be difficult to handle and has often led to false or uncontrollable conclusions. For literature, see Nagel, /,c. 

Fig, 40. Exchange of monovalent for divalent electrolyte as a function of the composition of the solution and of the surface potential Oo Circles describe exchange of HNO3 against Ba(N03)2 in a silver iodide sol. 

In most cases of ion exchange, specific influences play a much more prominent part than in the cases treated in the foregoing subsection. Even in the exchange of monovalent cations at a silver iodide surface (Van Os, Z.c.) a slight specificity can be detected, the preference for the double layer being in the order Rb+, K, Na+, Li , H Usually the specific influences are much larger as is illustrated for instance in Fig. 45 taken from Jenny s work on the cation exchange in zeolites. 

Van Laar used the sol concentration effect in order to determine the zero point of charge of Agl. He determined the pAg for which there was no difference in E.M.F. between a salt bridge in a silver iodide suspension and a salt bridge in the equilibrium solution. At this pAg there is no diffuse double layer and when specific adsorption is absent the zero point of charge is reached Sec also 6a, p 161 ... 

Fig. 9. Extinction-time curves for a silver iodide sol (0.4 m mol litre) flocculated with KNO3. The concentration of KNO3 in m mol/litre is indicated beside the curves.

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