Silver halides iodide

In another automated procedure utilizing ion exchange on preformed silver chloride (110), the irradiated uranyl nitrate (natural uranium) was dissolved in dilute nitric acid containing sulfur dioxide as reducing agent and Iodide carrier and inmedlately filtered through a bed of the silver halide. Iodide was reported to be essentially quantitatively adsorbed on the silver chloride. 

To determine which halogen is present, take 1-2 ml. of the filtrate from the sodium fusion, and add dilute sulphuric acid until just acid to litmus. Add about 1 ml. of benzene and then about 1 ml. of chlorine water and shake. A yellowish-brown colour in the benzene indicates bromine, and a violet colour iodine. If neither colour appears, the halogen is chlorine. The result may be confirmed by testing the solubility of the silver halide (free from cyanide) in dilute ammonia solution silver chloride is readily soluble, whereas the bromide dissolves with difficulty, and the iodide not at all. 

Iodides can also be determined by this method, and in this case too there is no need to filter off the silver halide, since silver iodide is very much less soluble than silver thiocyanate. In this determination the iodide solution must be very dilute in order to reduce adsorption effects. The dilute iodide solution (ca 300 mL), acidified with dilute nitric acid, is treated very slowly and with vigorous stirring or shaking with standard 0.1 M silver nitrate until the yellow precipitate coagulates and the supernatant liquid appears colourless. Silver nitrate is then present in excess. One millilitre of iron(III) indicator solution is added, and the residual silver nitrate is titrated with standard 0.1M ammonium or potassium thiocyanate. 

Determination of iodide as silver iodide Discussion. This anion is usually determined by precipitation as silver iodide, Agl. Silver iodide is the least soluble of the silver halides 1 litre of water dissolves 0.0035 mg at 21 °C. Co-precipitation and similar errors are more likely to occur with iodide than with the other halides. 

In i tltcrensc > from chloride to iodide for ionic halides in which the bonds are significantly covalent (such as the silver halides. ... 

The solubilities of the ionic halides are determined by a variety of factors, especially the lattice enthalpy and enthalpy of hydration. There is a delicate balance between the two factors, with the lattice enthalpy usually being the determining one. Lattice enthalpies decrease from chloride to iodide, so water molecules can more readily separate the ions in the latter. Less ionic halides, such as the silver halides, generally have a much lower solubility, and the trend in solubility is the reverse of the more ionic halides. For the less ionic halides, the covalent character of the bond allows the ion pairs to persist in water. The ions are not easily hydrated, making them less soluble. The polarizability of the halide ions and the covalency of their bonding increases down the group. 

Starting in the 1960s, many compounds with such properties were discovered (i.e., with high conductivities and low-temperature coefficients of conductivity). Some of them are double salts with silver iodide (uAgFmMX) or other silver halides where MX has either the cation or the anion in common with the silver halide. The best-known example is RbAgJj (= 4AgFRbI), where this sort of conduction arises at - 155°C and is preserved up to temperatures above 200°C. At 25°C this compound has a conductivity of 26 S/m (i.e., the same value as found for a 7% KOH solution). Another example is Ag3SI, which above 235°C forms an a-phase with a conductivity of 100 S/m. 

Shizuo [100] allowed the silver halide precipitate obtained in the co-precipitation process to stand in contact with the solution for more than 20 h to ensure quantitative collection of iodide on the precipitate. He then evaporated the oxidised iodate solution to 5-10 ml and again allowed the solution to stand for more than 12 h before the colorimetric determination. There was no interference from bromine compounds. The errors were then within 3%. 

Filtering and Drying the Silver Halide.—First heat the precipitate in the beaker on the boiling water bath. Heat silver iodide (and bromide) for two hours, since silver iodide forms with silver nitrate a solid compound which is only gradually decomposed by water. Further, when determining iodine, first reduce with sulphurous acid solution the silver iodate produced during the decomposition. 

An additional point worth mentioning is that the potentiometric method can monitor several partially soluble salts at once. For example, if a solution contains chloride, bromide and iodide ions, then a plot of emf against the volume of cation (e.g. Ag ) will contain three inflection points (see Figure 4.8), one for each of the three silver halides. for Agl is smaller than that for AgCl, while (AgBr) has an intermediate value, so the first inflection point represents the precipitation of Agl, the second represents formation of AgBr and the third represents the formation of insoluble AgCl. ... 

The construction and preparation of these electrodes were described in chapter 3.1. The modern version of this electrode, produced by Radelkis, Budapest, is a compromise between the original construction described by Pungor etal. [310,311, 313] and a system with a compact membrane. Electrodes with silver chloride, bromide and iodide are manufactured. According to the manufacturer these electrodes should be soaked before use for 1-2 hours in a dilute solution of the corresponding silver halide. They can be used in a pH region from 2 to 12 and the dFisE/d log [X ] value is approximately 56mV. These electrodes can be employed for various automatic analytical methods (see chapter 5). They can readily be used in mixtures of alcohol with water, for example up to 90% ethanol and methanol and up to 4% n-propanol and isopropanol [196]. In mixtures of acetone-water and dimethylformamide-water, they work reliably only in the presence of a large excess of water [197]. 

Other types of ISE with silver halides are based on homogeneous membranes [6, 383]. With silver chloride or bromide, a single crystal or membrane from a salt melt can be prepared, while silver iodide membranes are prepared from... 

The light-sensitive layer of the present-day photographic material consists essentially of a large number (e.g., 108 per square centimeter) of tiny crystals of silver halide embedded in a layer of gelatin. The tiny crystals, or grains as they are commonly called, of the most sensitive photographic materials are composed of silver bromide, a small percentage of iodide, and a very small but very important amount of silver sulfide (Sheppard, 1) or possibly silver (Carroll and Hubbard, la) or both. The halide in the less sensitive materials may be simply bromide, chloride, or mixtures of the two. 

In the method proposed by van Staden for the determination of three halides, these are separated in a short colunm packed with a strongly basic ion-exchange resin (Dowex i-X8) that is placed in an FI manifold. A laboratory-made tubular silver/silver halide ion-selective electrode is used as a potentiometric sensor. Van Staden compared the response capabilities of the halide-selective electrodes to a wide concentration range (20-5000 pg/mL) of individual and mixed halide solutions in the presence and absence of the ion-exchange column. By careful selection of appropriate concentrations of the potassixun nitrate carrier/eluent stream to satisfy the requirements of both the ion-exchange column and the halide-selective electrode, he succeeded in separating and determining chloride, bromide and iodide in mixed halide solutions with a detection limit of 5 /xg/mL [130]. 

Comparing the stability of the triammincs of silver halides, the chloride is more stable than the bromide, and the iodide cither does not exist or is very unstable. This is contrary to the usual observations in the ammines, where the stability of the ammine rises from chloride to iodide. In the case of the ammines of the oxy-halogen salts of silver the most unstable is the iodate, which is non-existent at ordinary pressure, then comes the bromate, and the most stable is the chlorate.3... 

The demethylation of the chloride salt A hot aqueous solution of N,N,N-trimethyltryptammonium iodide was treated with an excess of freshly precipitated AgCI, and all was boiled gently for 15 min. The mixed silver halides were removed by filtration, and the filtrate stripped of H20 as rapidly as possible. To the residue there was added a small amount... 

Silver Halides. Taking silver nitrate as a reactant, prepare silver chloride, bromide, and iodide, Wash the precipitates with water by decantation and test the action of light, an ammonia solution, and a sodium thiosulphate solution on them. Explain the observed phenomena. Write the equations of the reactions. Explain why silver iodide dissolves in sodium thiosulphate and does not dissolve in an aqueous solution of ammonia. 

A second area in which polarization effects show up is the solubility of salts in polar solvents such as water. For example, consider the silver halides, in which we have a polarizing cation and increasingly polarizable anions. Silver fluoride, which is quite ionic, is soluble in water, but the less ionic silver chloride is soluble only with the inducement ofcomplexing ammonia. Silver bromide is only slightly soluble and silver iodide is insoluble even with the addition of ammonia. Increasing covalency from fluoride to iodide is expected and decreased solubility in water is observed. 

Until recently, only two reports existed for 1 1 adducts of silver halides with amines, namely AgT piperidine57 and Agl-morpholine.381 The first had a tetrameric cubane structure whilst the second was described as a stair polymer adduct. The range has now been extended to include 2-and 3-methylpyridine, quinoline and triethylamine.382 In each case the adduct was obtained by recrystallization of silver(I) iodide from neat base. The colourless crystals were found to lose base readily on exposure to the atmosphere and structural data were collected from crystals mounted in argon-filled capillaries, containing mother liquor. 

High oxidation state silver halide complexes of chloride, bromide and iodide tend to be even more unstable with respect to reduction and have not been studied in detail.549... 

Silver halides employed in emulsions are the chloride, the bromide and the iodide. Negative emulsions are composed of silver bromide with a small amount of silver iodide. Positive emulsions for films and paper contain silver chloride, or mixtures of silver chloride and silver bromide in varying amounts, according to the tone, speed, and contrast desired. 

J. C. S., 67, 600.)—This method is used when an ester is not easily obtained by the usual methods owing to steric hindrance or some such cause. The silver salt and alkyl iodide are heated or shaken together with or without an inert solvent, benzene, etc. The precipitated silver halide is filtered off, and the ester separated from the filtrate by distillation or some other method. 

Silver Halides. Mixture with silver fluoride incandesces on grinding. Mixture with silver iodide reacts vigorously on heating.4... 

Silver halide includes silver bromide, silver chloride, and silver iodide. Film emulsions consist of silver bromide with small amounts of silver iodide. Paper emulsions can be either silver bromide, silver chloride, or a combination of the two, usually with small amounts of silver iodide. 

Allylic amination of allyl halides can also be achieved using lithium and potassium bis(trimethylsilyl)amides [34] and potassium 1,1,3,3-tetramethyldisilazide [35] as the nucleophiles. It has been found that for the reaction of alkyl-substituted allyl chlorides using lithium bis(trimethylsilyl)amides as the nucleophile the allylic amination proceeds smoothly in a SN2 fashion to give /V,Af-disilylamines in high yields when silver(I) iodide was used as an additive. Other metal complexes such as copper ) iodide and other silver(I) salts can also be used as additives for the reaction. 

Dimethyl Tellurium Dichloride4 Concentrated ammonia is added to dimethyl tellurium diiodide, and the grey paste that is formed is separated, and dissolved in water. A solution of silver nitrate is added until no more silver iodide precipitates. The silver halide is filtered off, hydrochloric acid is added to the filtrate, and the white precipitate of dimethyl tellurium dichloride is collected m.p. 95°. 

Dimethylaminophenyl 4-Ethoxypheny] Tellurium Dicyanide7 0.78 g (2 mmol) of 4-dimethylaminophenyl 4-ethoxyphenyl tellurium chloride iodide and 0.6 g (4 mmol) of silver cyanide in 30 ml of chloroform are stirred at 20°. The precipitated silver halides are filtered off and the filtrate is concentrated to give the product yield not given m.p. 192°. 

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