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An example of back titration, the Volhard method, named after Jacob Volhard, involves the addition of excess silver nitrate to the analyte; the silver chloride is filtered, and the remaining silver nitrate is titrated against ammonium thiocyanate, [1] with ferric ammonium sulfate as an indicator which forms blood-red [Fe(OH 2) 5 (SCN)] 2+ at the end point:
Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated. A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions
Thus, one standard solution is needed (e.g. HCl) in the direct titration, while two are needed (e.g. HCl and NaOH) in the back-titration. One of the suitable indicators for these titration reactions is Tashiro's indicator. [3] In practice, this analysis is largely automated; specific catalysts accelerate the decomposition. Originally, the ...
Fig. 15. Titration plot of back-titration of excess EDTA with Cu(II) in NH 3 /NH 4 Cl buffered solution. Direct EDTA titrations with metal ions are possible when reaction kinetics are fast, for example zinc, copper, calcium and magnesium. However, with slower reaction kinetics such as those exhibited by cobalt and nickel, back-titrations are used.
The volumetric titration is based on the same principles as the coulometric titration, except that the anode solution above now is used as the titrant solution. The titrant consists of an alcohol (ROH), base (B), SO 2 and a known concentration of I 2. Pyridine has been used as the base in this case. One mole of I 2 is consumed for each mole of ...
The interplay of the intrinsic pK a values of a system with the electrostatic interaction energies between titratable groups can produce quite spectacular effects such as non-Henderson–Hasselbalch titration curves and even back-titration effects. [6] The image on the right shows a theoretical system consisting of three acidic residues.
An example of triglyceride occurring in the saponifiable fraction of oils with a saturated fatty acid residue, a monounsaturated fatty acid residue and a triple unsaturated (polyunsaturated) fatty acid residue. The triple esterified glycerol (marked black) can be seen in the center of the structure. Such a triglyceride has a high iodine value ...
A typical titration curve of a diprotic acid, oxalic acid, titrated with a strong base, sodium hydroxide.Both equivalence points are visible. Titrations are often recorded on graphs called titration curves, which generally contain the volume of the titrant as the independent variable and the pH of the solution as the dependent variable (because it changes depending on the composition of the ...