Titration Flask

The end-point, which occurs with the complete conversion of iodide to iodine monochloride, is indicated by the disappearance of the violet iodine colour from a chloroform layer present in the titration flask. 

The experiment consists of weighing the primary standard on an analytical balance into the titration flask, dissolving, and then titrating it with the solution to be standardized. 

FIGURE 4.18 An automatic titrator. A pump draws the titrant from the reagent bottle on the left and fills the reservoir in the back of the unit. Pressing a key on the keypad in the foreground delivers titrant to the titration flask on the right as the solution is automatically stirred. The volume delivered is displayed on a digital readout. 

In order for a titrimetric analysis to be successful, the equivalence point must be easily and accurately detected, the reaction involved must be fast, and the reaction must be quantitative. If an equivalence point cannot be detected (i.e., if there is no acceptable indicator or other detection method), then the correct volume of titrant cannot be determined. If the reaction involved is not fast, the end point cannot be detected immediately upon adding the last fraction of a drop of titrant and there would be some doubt as to whether the end point had been reached. If the reaction is not quantitative—every trace of reactant in the titration flask is not consumed by the titrant at the end point—then again the correct volume of titrant cannot be determined. This latter point means that equilibrium reactions that do not go essentially to completion immediately are not acceptable reactions for this type of analysis. Thus, not all reactions are acceptable reactions. 

A graphic picture of what happens during an acid-base titration is easily produced in the laboratory. Consider again what is happening as a titration proceeds. Consider, specifically, NaOH as the titrant and HCI as the substance titrated. In the titration flask, the following reaction occurs when titrant is added ... 

Procedure Transfer 20 ml of the primary standard solution (Mohr s salt) to the titration flask and add 20 ml of 2 N sulphuric acid. Take the potassium dichromate solution in the burette. Put drops of freshly... 

Add 25ml of the above "sample solvent to titration flask of Fig Et 1 and titrate with Fischer reagent to orange-red end point. Add to the solvent, thus titrated, instead of the sample, 0.15 to 0.18g distd w from a weighing pipet. Complete the titration with Fischer reagent as described below under "Titration of Sample ... 

Introduce 10 to 25ml of the anhydrous "sample solvent (pyridine-glycol, 1 4) into the titration vessel (Fig Et 1), making sure, if an instrument end point apparatus is used, that the electrodes are covered by the amt of "sample solvent introduced. If the color end point is also to be used, introduce 10 to 25ml sample into the 2nd titration flask... 

Titration Flask, protected from atmosphere with provisions for electrodes and burets... 

Add 50—100ml of the solvent used to the titration flask and titrate to a 30 second end point... 

The 0.15N Ferric Alum soln shall be prepd as specified in Standard MIL-STD-286, method603.1 4.3 1.2.3 Procedure. An accurately weighed portion of approx O.lg of sample shall be transferred to a 500-nl titration flask. Twenty-five ml of distd w shall be added and shaken and heated until the sample is dissolved completely. The titration flask shall be placed with a magnetic stirrer and the contents shall be stirred for at least 10 mins. The air shall be swept out with a stream of carbon dioxide and the carbon dioxide atm shall be maintained thruout the detn. Exactly 50ml of 0.2N chromous chloride soln shall be added to the 500ml titration flask. The contents shall be stirred for 5 mins and 25mi of i5 percent HCi shall be added. Ten drops of 2% aq phenosafranin indicator shall be... 

Procedure. Transfer 0.6 to 0.8 g of the dry sample weighed to 0.1 mg to a 100 ml beaker. Add 50 ml of 25 percent acetic acid soln and stir to dissolve. Transfer to a 250 ml volumetric flask and dilute to the mark. Attach the cylinder of oxygen-free carbon dioxide to the titration flask as shown in Fig 1 and allow the gas to flow for 5 minutes thru gas humidifier (H) to displace the air. Continue the flow of gas during the-entire titration procedure, pipet a 25 ml aliquot of the solution of the sample into the titration flask (Fig 2). Add 30 ml of 20% Na acetate soln and 20.00 ml of 0.2N titanous chloride soln and swirl the flask for about 20 secs. 

Prepare and extract a 5g sample of proplnt as indicated in Vol 2 of Encycl, p Cl 31, but use for extraction the titration flask, shown in Fig, after plugging its inlet tube by the rubber stopper. After removing the solvent from extract by a stream of dry air, dissolve the residue... 

Titanous Chloride Buffer Method. Transfer quantitatively a 0.20 0.01g sample to a dry 500ml titration flask, add 40ml of glac Ac OH and connect with a C02 generator, similar to... 

For its standardization with TiClg soln, measure accurately 45 ml of the above prepd ferric ammonium sulfate into titration flask F of Fig 3j add 25 ml of 1555 hydrochloric acid and, while passing C02 thru rhe flask, titrate from buret C with 0.2N TiClg soln (already standardized by potassium dichromate) until near the end point. Then add 5 ml of 20% ammonium thiocyanate indicator and continue titrating until, the red color just disappears. 

Take the 250-mi volumetric flask contg material extracted by carbon tetrachloride as shown here under H- Analytical Procedures, step 1, and transfer from it 25 ml (using a calibrated pipet, previously rinsed with CC14 and dried, to the titration flask F, Evaporate the CC14 to dryness with a slow stream of air and then sweep the air off with a stream of C02 from a cylinder (or from a Kipp generator). While continuing to pass C02 thru the flask, introduce... 

P mg of sample is introduced into the titration flask and V2 is the precisely measured volume of Karl Fischer reagent added, corresponding to an excess. The excess is titrated as previously described by adding a volume F8 of methanol. Using these values, the amount of water p in P mg of sample is given by ... 

Dissolve approx O.lg of RDX, in a 500 ml titration flask, with a mixt of 25 ml of glac AcOH and 25 ml of coned. HC1. Stir the contents of the flask for at least 10 mins using a magnetic stirrer while the air is being replaced with COz. Maintain a C02 atm throughout the determination. Add exactly 100 ml of 0.2N chromous chloride soln and stir for another 15 mins. Add 15 drops of phenosafranine indicator and titrate with 0.15N ferric alum soln. The end-point is a sharp color change from green to blood-red. Determine a blank and caluclate as follows ... 

A 25.0cm sample of the iron(II) sulfate solution was measured into a conical titration flask. Solution A was run from a burette into the llask until an end-point was reached. Four titrations were done. The diagrams show parts of the burette before and after each titration. 

A titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask, burette fNled Titrations can be classified by the chemical 1 ase reaction involved or by the equipment used to determine the end-point of the titration. 

Method II (Sample Preparation) Transfer approximately 0.2 g of sample, accurately weighed, into the titration flask. The stoichiometric factor (Fs) for Allura Red is 8.06. Arsenic Determine as directed under Arsenic Limit Test, Appendix MIR, using a Sample Solution prepared as directed for organic compounds. 

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