Precipitation chloride ions

In the late 1970s and early 1980s there was a flurry of interest in precipitation techniques as a method of keeping ions in their in vivo locations, and thus avoid the problems mentioned in Subheading 3.1. The idea was simply to add a precipitant to the fixative, which reacted with the ion in question, and hopefully kept it where it was in the tissue. The most popular technique was to use a silver salt to precipitate chloride ions (35). Two problems emerged loss of ions was not totally prevented (36) and quantification was not possible. This led to the almost complete... 

Conductivity detection is preferred when water is used as eluent then ionizable analytes are readily detected. However, in the case where HCl is used as the eluent, the analytical column is followed by a suppressor column, packed with a cation-exchange resin in the silver form. The hydrogen ions of the eluent are exchanged for silver ions, which then precipitate chloride ions, thus removing the ions contributed by the eluent and enhancing the analyte s signal. 

Mercury(I) compounds in solution give a white precipitate with chloride ion. blackened by ammonia (p. 437) alkalis and reducing agents generally produce black or grey mercury from mercury(I) compounds. 

Silver Chloride. Silver chloride, AgCl, is a white precipitate that forms when chloride ion is added to a silver nitrate solution. The order of solubility of the three silver halides is Cl" > Br" > I. Because of the formation of complexes, silver chloride is soluble in solutions containing excess chloride and in solutions of cyanide, thiosulfate, and ammonia. Silver chloride is insoluble in nitric and dilute sulfuric acid. Treatment with concentrated sulfuric acid gives silver sulfate. 

Qualitative. The classic method for the quaUtative determination of silver ia solution is precipitation as silver chloride with dilute nitric acid and chloride ion. The silver chloride can be differentiated from lead or mercurous chlorides, which also may precipitate, by the fact that lead chloride is soluble ia hot water but not ia ammonium hydroxide, whereas mercurous chloride turns black ia ammonium hydroxide. Silver chloride dissolves ia ammonium hydroxide because of the formation of soluble silver—ammonia complexes. A number of selective spot tests (24) iaclude reactions with /)-dimethy1amino-henz1idenerhodanine, ceric ammonium nitrate, or bromopyrogaHol red [16574-43-9]. Silver is detected by x-ray fluorescence and arc-emission spectrometry. Two sensitive arc-emission lines for silver occur at 328.1 and 338.3 nm. 

The primary constituents to be measured are the pH of precipitation, sulfates, nitrates, ammonia, chloride ions, metal ions, phosphates, and specific conductivity. The pH measurements help to establish reliable longterm trends in patterns of acidic precipitation. The sulfate and nitrate information is related to anthropogenic sources where possible. The measurements of chloride ions, metal ions, and phosphates are related to sea spray and wind-blown dust sources. Specific conductivity is related to the level of dissolved salts in precipitation. 

Remove traces of ethanol and dissolve precipitate in a minimum (10 ml) of distilled water. Molecular sieving on a Sephadex G25 fine column (1300 ml, 0 5 cm). Assay fraction for /3-poly(L-malate) and chloride ions. Use only salt-free fractions. 

The chloride ion resulting from the reduction of HCIO is precipitated as AgCl. When 50.0 mL of laundry bleach (d = 1.02 g/cm3) is treated as described above, 4.95 g of AgCl is obtained. What is the mass percent of NaClO in tiie bleach ... 

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 small amount of mercury(I) chloride in suspension has no appreciable effect upon the oxidising agent used in the subsequent titration, but if a heavy precipitate forms, or a grey or black precipitate is obtained, too much tin(II) solution has been used the results are inaccurate and the reduction must be repeated. Finely divided mercury reduces permanganate or dichromate ions and also slowly reduces Fe3+ ions in the presence of chloride ion. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Figure 6. Bipolar precipitates consisting of an inner anion-selective layer and an outer cation-selective layer.19 When the electrode is polarized to the more noble side, protons and chloride ions are kept from permeating through the film, so that anodic dissolution of the substrate metal is blocked. (Reproduced from N. Sato, Corrosion, 45 354, 1989, Fig. 24 with permission of NACE International.)...

Self-Tfst 11.14B Chloride ion is added to a solution containing the following concentrations of soluble salts 0.020 mol-L 1 Pb(NO,)2(aq) and 0.0010 mol-L 1 AgN03(aq). (a) Use the information in Table 11.4 to determine the order in which each ion precipitates as the concentration of chloride ion is increased and give the concentration of Cl when precipitation of each begins, (b) Calculate the concentration of the first ion to precipitate that remains in solution when the second ion precipitates. 

Suppose we have a solution that contains lead(II), mercury(I), silver, copper(II), and zinc ions. The method is outlined in Fig. 11.20, which includes additional cations, and is illustrated in Fig. 11.21. Most chlorides are soluble so, when hydrochloric acid is added to a mixture of salts, only certain chlorides precipitate (see Table 11.4). Silver and mercury(I) chlorides have such small values of Ksp that, even with low concentrations of Cl ions, the chlorides precipitate. Lead(II) chloride, which is slightly soluble, will precipitate if the chloride ion concentration is... 

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