Silver chloride iodide

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

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. 

The attenuated total reflectance (ATR) technique is used commonly in the near-infrared for obtaining absorption spectra of thin Aims and opaque materials. The sample, of refractive index i, is placed in direct contact with a material which is transparent in the region of interest, such as thallium bromide/thallium iodide (known as KRS-5), silver chloride or germanium, of relatively high refractive index so that Then, as Figure 3.f8... 

Halide Complexes. Silver hahdes form soluble complex ions, AgX and AgX , with excess chloride, bromide, and iodide. The relative stabihty of these complexes is 1 > Br > Cl. Complex formation affects solubihty greatiy. The solubihty of silver chloride in 1 A/ HCl is 100 times greater than in pure water. 

Analysis. The abiUty of silver ion to form sparingly soluble precipitates with many anions has been appHed to their quantitative deterrnination. Bromide, chloride, iodide, thiocyanate, and borate are determined by the titration of solutions containing these anions using standardized silver nitrate solutions in the presence of a suitable indicator. These titrations use fluorescein, tartrazine, rhodamine 6-G, and phenosafranine as indicators (50). 

The base boiled in methyl alcoholic solution with methyl iodide and potassium hydroxide, forms a gelatinous methiodide, which was converted by silver chloride into the methochloride. The latter when boiled with 20 per cent, solution of sodium hydroxide, produced a mixture of methine bases, which were separated as the methiodides into 0-methylbebeerine-methine methiodide B, m.p. 237° (cf. p. 375), and a lasvorotatory form, m.p. 190°, which proved to be the lasvo-enantiomorph of d-O-methyl-bebeerinemethine methiodide (form C, p. 375). Chondrofoline therefore belongs to the bebeerine type represented by formula (III). In it R = H, the single phenolic hydroxyl is at ORj or OR4 and the remaining groups, OR2, OR 3, OR or alternatively ORj, OR2, OR 3 are methoxyl groups (King,i 1940). 

It has been prepared synthetically by Ewins in the following manner Meta-oxybenzoic acid is converted with the aid of dimethyl sulphate into m-methoxybenzoic acid, which is then nitrated, and from the nitration products 2-nitro-3-methoxybenzoic acid is separated. This is reduced to 2-amino-3-methoxybenzoic acid which on heating with methyl iodide, yields 2-methylamino-3-methoxybenzoic acid. On warming this with freshly precipitated silver chloride it yields damascenine hydrochloride. 

Similar measurements were made for the heat of precipitation of silver iodide,5 which is even less soluble in water than silver chloride. As shown in Table 33 in Sec. 102, a saturated solution of Agl at 25°C contains only 9.08 X 10-9 molcs/liter, as compared with 1.34 X 10-6 for AgCl. By calorimetric measurement the heat of precipitation of Agl at 25°C was found to be 1.16 electron-volts per ion pair, or 20,710 cal/mole. 

We have seen in Experiment 8 that silver chloride has low solubility in water. This is also true for silver bromide and silver iodide. In fact, these low solubilities provide a sensitive test for the presence of chloride ions, bromide ions, and iodide ions in aqueous solutions. If silver nitrate... 

That some silver does dissolve to form Ag+ can be verified experimentally by adding a little KI to the solution. Silver iodide has an even lower solubility than does silver chloride. The experiment shows that the amount of silver that dissolves is sufficient to cause a visible precipitate of Agl but not of AgCl. This places the Ag+ ion concentration below 10-10 M but above 10-17 M. Either of these concentrations is so small that we can consider our prediction for the standard state to be applicable here too—silver metal does not dissolve appreciably in 1 M HC1. In general, the question of whether a prediction based upon the standard state will apply to other conditions depends upon how large is the magnitude of °. If ° for the overall reaction is only one- or two-tenths volt (either positive or negative), then deviations from standard conditions may invalidate predictions that do not take into account these deviations. 

It is evident that silver iodide, being less soluble, will be precipitated first since its solubility product will be first exceeded. Silver chloride will be precipitated when the Ag+ ion concentration is greater than... 

Hence when the concentration of the iodide ion is about one-millionth part of the chloride ion concentration, silver chloride will be precipitated. If the initial concentration of both chloride and iodide ions is 0.1M, then silver chloride will be precipitated when... 

The supporting electrolyte may be 0.5 M potassium nitrate for bromide and iodide for chloride, 0.5 M potassium nitrate in 25-50 per cent ethanol must be used because of the appreciable solubility of silver chloride in water. 

If the pellet contains a mixture of silver sulphide and silver chloride (or bromide or iodide), the electrode acquires a potential which is determined by the activity of the appropriate halide ion in the test solution. Likewise, if the pellet contains silver sulphide together with the insoluble sulphide of copper(II), cadmium) II), or lead) II), we produce electrodes which respond to the activity of the appropriate metal ion in a test solution. 

An interesting extension of the above experiment is the titration of a mixture of halides (chloride/iodide) with silver nitrate solution. Prepare a solution (100 mL) containing both potassium chloride and potassium iodide weigh each substance accurately and arrange for the solution to be about 0.025 M with respect to each salt. A silver nitrate solution of known concentration (about 0.05 M) will also be required. 

In the Koenigs-Knorr method and in the Helferich or Zemplen modifications thereof, a glycosyl halide (bromide or chloride iodides can be produced in situ by the addition of tetraalkylammonium iodide) is allowed to react with a hydrox-ylic compound in the presence of a heavy-metal promoter such as silver oxide, carbonate, perchlorate, or mercuric bromide and/or oxide,19-21 or by silver triflu-oromethanesulfonate22 (AgOTf). Related to this is the use of glycosyl fluoride donors,23 which normally are prepared from thioglycosides.24... 

Silver bromide Silver chloride Silver perchlorate Silver cyanide Silver fluoride Silver iodide Silver permar>gate Silver nitrate Silver carbonate Silver oxide Silver sulphate Silver sulphide Silver phosphate... 

Tsunogai [7] carried out a similar coprecipitation allowing a 20-hour standing period to ensure that iodide is fully recovered in the silver chloride coprecipitate. Again, the iodide is oxidised to iodate prior to spectrophotometric determination of the latter. This procedure also includes a step designed to prevent interference by bromine compounds. 

Silver chloride is white silver bromide is pale yellow and silver iodide has a rich yellow colour. We might first think that the change in colour was due to Agl incorporating the iodide anion, yet Nal or HI are both colourless, so the colour does not come from the iodide ions on their own. We need to find a different explanation. 

Out of the three compounds, silver chloride is the most soluble and silver iodide is the least soluble. (You can compare the solubilities of the compounds based on their solubility products because they are all the same type. Each formula unit contains two ions.)... 

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 complexation of anionic species by tetra-bridged phosphorylated cavitands concerns mainly the work of Puddephatt et al. who described the selective complexation of halides by the tetra-copper and tetra-silver complexes of 2 (see Scheme 17). The complexes are size selective hosts for halide anions and it was demonstrated that in the copper complex, iodide is preferred over chloride. Iodide is large enough to bridge the four copper atoms but chloride is too small and can coordinate only to three of them to form the [2-Cu4(yU-Cl)4(yU3-Cl)] complex so that in a mixed iodide-chloride complex, iodide is preferentially encapsulated inside the cavity. In the [2-Ag4(//-Cl)4(yU4-Cl)] silver complex, the larger size of the Ag(I) atom allowed the inner chloride atom to bind with the four silver atoms. The X-ray crystal structure of the complexes revealed that one Y halide ion is encapsulated in the center of the cavity and bound to 3 copper atoms in [2-Cu4(//-Cl)4(//3-Cl)] (Y=C1) [45] or to 4 copper atoms in [2-Cu4(/U-Cl)4(/U4-I)] (Y=I) and to 4 silver atoms in [2-Ag4(/i-Cl)4(/i4-Cl)] [47]. NMR studies in solution of the inclusion process showed that multiple coordination types take place in the supramolecular complexes. 

Silver(I) halide complexes of oA could not be prepared. The phosphine ap, however, reacts with silver iodide to give a colourless, unstable, non-conducting compound of empirical formula Agl(ap). This compound reacts with excess ap to give the stable 2 1 adduct Agl(ap)2- Silver bromide and silver chloride react directly with the ligand to give similar 2 1 adducts. These complexes are essentially monomeric, contain three-coordinate silver (I) and uncoordinated olefinic groups. The structure of the 1 1 adduct is unknown. 

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