Titration Volhard

The %w/w K in a 0.6712-g sample was determined by a Volhard titration. After adding 50.00 mb of 0.05619 M AgNOa and allowing the precipitate to form, the remaining silver was back titrated with 0.05322 M KSCN, requiring 35.14 mb to reach the end point. Report the %w/w K in the sample. 

DETERMINATION OF FLUORIDE PRECIPITATION AS LEAD CHL0R0FLU0RIDE COUPLED WITH VOLHARD TITRATION... 

Volcanic uranium deposits, 17 521 Volhard titration, 26 845 Voltage-dependent activation energy barrier, 9 571 Voltage... 

Volhard titration analychem Determination of the halogen content of a solution by titration with a standard thiocyanate solution. fol,hart tT tra-shan voltameter See coulometer. val tam-ad-ar ... 

Potassium thiocyanate is used in dyeing and printing textiles to make artificial mustard oil as a slimicide in paper production for controlling microbial growth in cooling water and in the preparation of organic thiocyanates. The salt also is used in analytical chemistry in Volhard titration. 

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. 

Elemental composition K 40.23%, S 33.00%, C 12.36%, N 14.41%. Potassium can be measured in an aqueous solution by flame photometry, AA, or ICP/AES (see Potassium). Thiocyanate anion can be measured by Volhard titration against a standard solution of silver nitrate in the presence of ferric ammonium sulfate. The color of the solution turns red at the end point. 

Volhard titration formation of a soluble, colored complex at the end point... 

The Volhard titration is a titration of Ag+ in HN03 solution. For Cl-, a back titration is necessary. First, Cl is precipitated by a known, excess quantity of standard AgN03. 

Applications of precipitation titrations are listed in Table 7-1. Whereas the Volhard method is an argentometric titration, the Fajans method has wider applications. Because the Volhard titration is carried out in acidic solution (typically 0.2 M HN03), it avoids certain interferences that affect other titrations. Silver salts of CO -, C20 -, and AsO " are soluble in acidic solution, so these anions do not interfere. 

In a spectrophotometric titration, absorbance of light is monitored as titrant is added. For many reactions, there is an abrupt change in absorbance when the equivalence point is reached. The Fajans titration is based on the adsorption of a charged indicator onto the charged surface of the precipitate after the equivalence point. The Volhard titration, used to measure Ag+, is based on the reaction of Fe3+ with SCN- after the precipitation of AgSCN is complete. 

Describe how to analyze a solution of Nal by using the Volhard titration. 

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. 

Of these methods the Volhard titration method was preferred... 

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 ... 

The indicator concentration is not critical in the Volhard titration. In fact, calculations similar to those shown in Feature 13-3 demonstrate that a titration error of one part in a thousand or less is possible if the iron(III) concentration is held between 0.002 M and 1.6 M. In practice, an indicator concentration greater than 0.2 M imparts sufficient color to the solution to make detection of the thiocyanate complex difficult because of the yellow color of Fe-. Therefore, lower concentrations (usually about 0.01 M) of iron(IIl) ion are employed. 

Table 13-3 lists some typical applications of precipitation titrations in which silver nitrate is the standard solution. In most of these methods, the analyte is precipitated with a measured excess of silver nitrate, and the excess is determined by a Volhard titration with standard potassium thiocyanate. 

Epoxide Volhard Titration of excess Cr following hydrohalogenation... 

The Association of Official Analytical Chemists recommends a Volhard titration for analysis of the insecticide heptachlor, C10H5CI7. The percentage of heptachlor is given by... 

After this reaction was complete, nitric acid was added to dissolve the AgaSOa but not the Ag2Se. The Ag+ from the dissolved AgaSeOs and the excess reagent required 16.74 mL of 0.01370 M KSCN in a Volhard titration. How many milligrams of Se were contained in each milliliter of sample ... 

Challenge Problem. The Volhard titration for Ag is being evaluated for use in determining silver in a thiosulfate photographic fixing bath. An independent analysis of the bath solution by atomic absorp-... 

EDVT Eschka digestion followed by Volhard titration... 

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%. 

A second example of this type of indicator is illustrated in the Volhard titration. This is an indirect titration procedure for determining anions that precipitate with silver (Cl , Br , SCN"), and it is performed in acid (HNO3) solution. In this procedure, we add a measured excess of AgNOa to precipitate the anion and then determine the excess Ag" " by back-titration with standard potassium thiocyanate solution ... 

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

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