Silver salts, analysis

In similar circumstances, silver salts leave a residue of metallic silver lead and copper salts usually leave a residue of the corresponding oxide calcium and barium salts leave a resirlne of the carbonate or oxide. Identify the metal in all such cases by the usual tests of qualitative inorganic analysis. Metals other than the above are seldom encountered in elementan qualitative analysis. 

I. Molecular Weight of Acids by Analysis of Silver Salts. 

The silver salts of most carboxylic acids are only sparingly soluble in cold water, and hence are readily prepared. Moreover they very rarely contain water of crystallisation, and therefore when dried can be analysed without further treatment. The analysis itself is simple, rapid and accurate, because gentle ignition of a weighed quantity of the silver salt in a crucible drives off the organic matter, leaving a residue of pure metallic silver. 

Benzyl cyanide, C Hj. CH.,CN, or phenyl-aceto-nitrile, is a constituent of cress oil, and probably of neroli oil. It is a strong smelling liquid boiling at 231 5°, and having a specific gravity 1 0146 at 18°. On boiling with alcoholic potash it yields phenyl-acetic acid, which can be identified by its melting-point, 77°, and by the analysis of its silver salt. 

The tests for metallic and acid radicals in chemical analysis are essentially tests for ions. For example, all soluble silver salts release silver ions in solution in water likewise, all... 

Often, greater accuracy may be obtained, as in Volhard type titration, by performing a back titration of the excess silver ions. In such a case, a measured amount of standard silver nitrate solution is added in excess to a measured amount of sample. The excess Ag+ that remains after it reacts with the analyte is then measured by back titration with standard potassium thiocyanate (KSCN). If the silver salt of the analyte ion is more soluble than silver thiocyanate (AgSCN), the former should be filtered off from the solution. Otherwise, a low value error can occur due to overconsumption of thiocyanate ion. Thus, for the determination of ions (such as cyanide, carbonate, chromate, chloride, oxalate, phosphate, and sulfide, the silver salts of which are all more soluble than AgSCN), remove the silver salts before the back titration of excess Ag.+ On the other hand, such removal of silver salt is not necesary in the Volhard titration for ions such as bromide, iodide, cyanate, thiocyanate, and arsenate, because the silver salts of these ions are less soluble than AgSCN, and will not cause ary error. In the determination of chloride by Volhard titration, the solution should be made strongly acidic to prevent interference from carbonate, oxalate, and arsenate, while for bromide and iodide analysis titration is carried out in neutral media. 

S.U. Hong, C.K. Kim and Y.S. Kang, Measurement and Analysis of Propylene Solubility in Polymer Electrolytes Containing Silver Salts, Macromolecules 33, 7918 (2000). 

The determination of the molecular weights of the chlorides, bromides, and iodides of sodium, potassium, and silver by analysis of the salts RXOa (R=metal, X=halogen), and induction from the ratios RX 30. 

The most important application of the Volhard method is the indirect determination of halide ions. A measured excess of standard silver nitrate solution is added to the sample, and the excess silver is determined by back-titration with a standard thiocyanate solution. The strong acidic environment required for the Volhard procedure represents a distinct advantage over other titrimetric methods of halide analysis because such ions as carbonate, oxalate, and arsenate (which form slightly soluble silver salts in neutral media but not in acidic media) do not interfere. 

Argentiometric procedures cut across the classification boundaries to some extent, in that volumetric, gravimetric or colorimetric methods may be applied to the analysis of particular silver salts. However, the argentiometric methods for the determination of phosgene are specific to the chloride ion, and as such are susceptible to other chloride impurities (especially dichlorine or hydrogen chloride). The details of these methods have been reviewed elsewhere [1255], and since they are neither specific to phosgene, nor in any obvious way amenable to automation, they will not be reviewed here. 

The LIS (Lanthanide Induced Shift) NMR technique is useful for such analysis and the separation of olefin enantiomers such as limonene, a-camphene and -pinene has been performed upon addition of silver salts such as Ag(fod) or Ag(hfc) to the commonly used lanthanide chiral salts such as Ln(tfc )3 or Ln(hfc)3, where fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctanedione, "hfc = heptafluoro-3-butyrylcam-phorato and tfc = tri 11 uoroacetylearnphorato. 

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