Silver -thiocyanate AgSCN

Silver Thiocyanate. Silver thiocyanate, AgSCN, is formed by the reaction of stoichiometric amounts of silver ion and a soluble thiocyanate. 

The reactions of potassium thiocyanate in aqueous solution are essentially those of the thiocyanate anion. Its reaction with ferric ammonium sulfate, apphed in Volhard titration, results in the formation of ferric thiocyanate, Fe(SCN)3. Similarly, in titration against shver nitrate, it forms insoluble silver thiocyanate, AgSCN. 

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. 

Silver nitrate solution white, curdy precipitate of silver thiocyanate, AgSCN, soluble in ammonia solution but insoluble in dilute nitric acid. 

If either Fe " or SCN is removed from solution, the equilibrium will shift to the left, and the solution will become lighter in color. When Ag is added to the solution, a white precipitate of silver thiocyanate (AgSCN) is formed, thus removing SCN ion from the equilibrium ... 

An electrode is prepared by dipping a silver strip into a solution saturated with silver thiocyanate, AgSCN, and containing 0.10 M SCN. The emf of the voltaic cell constructed by connecting this electrode as the cathode to the standard hydrogen half-cell as the anode is 0.45 V. What is the solubility product of silver thiocyanate ... 

Silver(I) thiocyanate AgSCN -61.8 Thallium(I) bromide TlBr -63.9... 

Magnesium carbonate MgCOj 5HjO 3.79 10-3 Silver(I) thiocyanate AgSCN 1.03 10-33... 

The nature of thiocyanate complexes of silver in non aqueous solvents has recently been reassessed. IR and Raman spectra were used to show that when Ag was complexed by SCN , the species present and the equilibrium steps involved were solvent specific. Characteristic absorption bands are summarized in Table 24. In pyridine, complexation passed through [Ag2(SCN)] and AgSCN to [Ag(SCN)2], such that even when the [SCN ]T/[Ag ]r ratio was 0.059, 50% was present as the hnear [Ag(SCN)2] ion. 

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