Chloride Volhard titration

Chlorides, bromides, and iodides can be quantitatively determined by treatment with silver nitrate, and, with suitable precautions, the precipitated halide is washed, dried, and weighed. Chlorides in neutral soln. can be determined by F. Mohr s volumetric process 27 by titration with a standard soln. of silver nitrate with a little potassium chromate or sodium phosphate as indicator. When all the chloride has reacted with the silver nitrate, any further addition of this salt gives a yellow coloration with the phosphate, and a red coloration with the chromate. In J. Volhard s volumetric process, the chloride is treated with an excess of an acidified soln. of silver nitrate of known concentration. The excess of silver nitrate is filtered from the precipitated chloride, and titrated with a standard soln. of ammonium thiocyanate, NH4CN8—a little ferric alum is used as indicator. When the silver nitrate is all converted into thiocyanate AgN03-fNH4CNS=AgCNS +NH4NOS, the blood-red coloration of ferric thiocyanate appears. 

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. 

An accurately measured amount (about 0.2 g.) of S3N2CI2 is placed in a 250-ml. Erlenmeyer flask containing 5 g. of potassium hydroxide pellets, 50 ml. of distilled water, and 20 ml. of 3% hydrogen peroxide. A small short-stemmed funnel is placed in the mouth of the flask to prevent loss by spattering, and the flask is boiled gently on a hot plate for 1 hour. The solution is cooled, and the chloride is determined by a Volhard titration in the usual manner. 

Volhard titration, which involves the formation of a soluble coloured compound. This approach is exemplified by the quantitative analysis of chlorides, bromides and iodides by back titration. In this case, the halide is titrated with silver ... 

Chemical analysis Chemical analyses on suspension or powder samples were performed by a volumetric method (0.05 normal potassium dichromate) following dissolution in hydrochloric acid. The ferrous (Fe2+) content was determined directly. The ferric (Fe3+) content was analyzed via the Zimmermann-Reinhardt (SnCl2 reduction) technique, which gives the total iron. Subtraction of the Fe2+ gives the desired Fe3+ value. The Fe2+/Fe3+ ratio was determined with an accuracy of 0.01. The accuracy of the determination of the total iron was 0.5% of the result. Chloride content was determined by Volhard titration with an accuracy of 5% of the result. Nitrogen content was analyzed with the Nessler method with a relative accuracy of 15%. 

Explain the Volhard titration of chloride. The Fajan titration. Which is used for acid solutions Why ... 

This method of silver recovery can be applied to any silver precipitates from quantitative analysis, such as silver chloride, bromide, or thiocyanate. First wash the residues well with water by decantation and on the Buchner funnel, then spread out on paper to dry. A little nitrobenzene absorbed on the precipitate from the Volhard titration will not do any harm the greater part of the nitrobenzene will be removed by washing, in any case. 

The Fajans determination of chloride involves a direct titration, while a Volhard titration requires two standard solutions and a flitration step to remove AgCl before back titration... 

The purity of the crystallized product, determined volu-metrically by Volhard s method, exceeds 98%. In this procedure, 10 ml. of a 1% solution of methylisourea hydrochloride is acidified with a few drops of nitric acid and treated with 20 ml. of 0.1 N silver nitrate. After removal of the silver chloride by filtration, the excess of the silver nitrate is estimated with 0.1 TV thiocyanate solution, using ferric alum as indicator. Alternatively, 10-ml. portions of 0.1 N silver nitrate, acidified with nitric acid, may be titrated directly with the 1% methylisourea hydrochloride solution in the presence of tartrazine. 

Analysis of Bisphenol-A Carbonate Oligomers for Chloroformate Chlorine. Chloroformate chlorine end groups were determined by a modified Volhard procedure in which the bischloroformate first reacts with aqueous pyridine to convert chloroformate to chloride ion. The chloride ion is extracted into water and titrated by the Volhard procedure. 

Determination of Benzyl Bromide. The determination of this substance may be carried out by the method already described for benzyl chloride. However, according to Van der Laan, it is sometimes more convenient to decompose the substance directly with a measured volume of standardised alcoholic silver nitrate solution and to titrate the excess of the latter with ammonium thiocyanate solution by the Volhard method. 

Perchlorates. These may be present in appreciable quantity in conversion-saltpetre. The following method gives very accurate results 20 g. of the sample is heated to 545 in a covered nickel crucible and maintained for an hour at this temperature in a Gilbert furnace or electric furnace, to reduce Ihe perchlorate to chloride, which is then titrated with silver nitrate by Mohr s or Volhard s method. The chloride present in an unheated sample is deducted. Any chlorate or iodate present must also be allowed for, Lenze recommended heating for half an hour in a porcelain crucible at 580 to 600 . The first quarter of an hour is occupied in raising the temperature to the required point. At higher temperatures losses of chloride occur. Methods involving the addition of iron... 

In what respect is the Fajans method superior to the Volhard method for the titration of chloride ion ... 

Wu and Lee 42 indicated that the free chloride ions on the active site (measured by Volhard analysis) were at only 50-70 i, of the amount of immobilized content (measured by element analysis). The results of the Volhard analysis method determined the free chloride ions in the bulk solution by the AgNOt titration method. Their results implicHl that the active site in the resin could not react completely w ith organic reactant in the duration of triphase reaction. According to the experimental results, this reaction is a two-zone model (or shell-core model), with the reaction (K-cuiring in the shell zone, and not in the core zone. Therefore, the triphasic reactitm mechanism and the swollen type of the resin can be given in Figure 4. This mechanism can help to understand the reaction phenomenon in the triphasc rcaciion. 

These experimental results demonstrate that tri- -butylamine could be immobilized completely with the active site on the resin for an immobilizion duration of 6 days. However, the immobilized content of tri-n-butylamine by the Volhard method was dependent on both the number of cross-linkages and the number of ring substitutions. The immobilized contents for the Volhard method are about 50-70% that for TGA (or EA). Since the analyzed results of the Volhard method determined the free chloride ions in the solution by the AgN03 titration method, the free chloride ion of the active site were only measured at 50-70% of the amount of immobilized content. The trend of the varied content for microresin is larger than that for macroresin. This result indicates that the analysis by the Volhard method may be influenced by the diffusion problem, and may be because the resin did not swell completely in the aqueous solution. On the other hand, if the resin is used as a TC to react in an actual reaction system, and the resin could not swell completely to release all free chloride ions, then the reaction environment would be influenced by the mass transfer of the reactant. 

Chloride may be determined by the Volhard method. The sample is acidified with concentrated nitric acid and silver nitrate is added, which reacts with the chloride, and then the mixture is boiled. After cooling, the pale yellow solution is diluted and the excess silver nitrate titrated with potassium thiocyanate solution using ammonium ferric sulfate as indicator. The ash may also be used for this determination. 

Sodium chloride levels are routinely determined in canned vegetables and legumes. Titrimetric methods are most commonly used with the sodium chloride first isolated by either ashing at 500-550°C, followed by aqueous dissolution of the ash and titration with silver nitrate solution (Mohr method), or by boiling the food in dilute nitric acid, adding excess silver nitrate and back-titration with potassium thiocyanate (Volhard method). Of these, the latter method is generally more accurate than the former method however, it is also more time-consuming. 

Gravimetric method such as AgCl or fire assay is used. Gay-Lussac method involves the titration of Ag with NaCl and/or KBr in acid solution. The endpoint is taken as the point at which no further precipitation of silver halide is observed upon the addition of more precipitant. Fajans method is based on the precipitation of Ag with chloride or bromide ions, using an adsorption indicator to detect the endpoint. Rhodamine 6G or dichlorofluorescein is used as the adsorption indicators. Volhard method is based on the titration of Ag with potassium or sodium thiocyanate to form insoluble silver thiocyanate. This titration is... 

In addition, the immobilized amount of the functional group of -N(C4H9)3 in the resin was determined from the mass fiaction of nitrogen by elemental analysis (EA) for C, H, and N, and from the chloride ion density titrated by the Volhard method. Table 1 lists the immobilized content of tri-n-butylamine in the resin determined by the TGA, EA and Volhard methods. The accuracy of our analytical techniques for TGA, EA and Volhard method were within 10%, 5% and 3%, respectively. The sequence of determining method for the immobilized content of tri- -butylamine in the resin was TGA > EA > Volhard. The analyzed residt of the TGA (or EA) method was based on the elemental weight, and it reveals the real immobilized content. 

However, the analyzed result of the Volhard method determined the See chloride ion in the solution by the AgJ 03 titration method. The immobilized content of tri-n-butylamine in the resin by the TGA (or EA) method was more 20 % larger than that determined by the Volhard method. 

At equilibrium both liquid and solid phases were analyzed. Chloride ion content was determined by the Volhard method. H2PO4 ions were precipitated as NH MgPO 6H2O, and the excess of Mg was titrated complex-ometrically (1). Ammonium ions were removed and the excess of base used was titrated with HCl. 

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