Hydrochloric acid titration

A computer program has been used to calculate the magnitude of systematic errors incurred in the evaluation of equivalence points in hydrochloric acid titrations of total alkalinity and carbonate in seawater by means of Gran plots. Hansson [13] devised a modification of the Gran procedure that gives improved accuracy and precision. The procedure requires approximate knowledge of all stability constants in the titration. 

Procedure Weigh accurately about 0.4 g and dissolve in a mixture of 40 ml of alcohol and 10 ml of 0.01 N hydrochloric acid. Titrate the resulting mixture with 0.1 N iodine solution till a yellow colour that... 

Procedure Weigh accurately about 0.2 g of sodium metabisulphite and dissolve in 50.0 ml of 0.1 N iodine solution and add 1 ml hydrochloric acid. Titrate the excess of iodine with 0.1 N sodium thiosulphate employing freshly prepared starch solution, added towards the end of the titration, as indicator. Each ml of 0.1 N iodine is equivalent to 0.0047453 g of Na Oj. 

Nitrogen. — Dissolve 10 gm. of reduced iron in a mixture of 20 cc. of concentrated sulphuric acid (sp. gr. 1.84) and 200 cc. of water, with the aid of heat. Allow to cool, and when cold add 100 cc. of sodium hydroxide solution (sp. gr. 1.3), and distil off about 50 cc., collecting the distillate in a receiver containing about 20 cc. of water and 2 to 3 cc. of decinormal hydrochloric acid. Titrate the distillate with decinormal potassium hydroxide, using methyl orange as indicator. The ammonia should not have neutralized more than 0.2 cc. of the acid. 

Figure 14 Separation of the test mixture using a step voltage gradient and a short packed column. Capillary 75 mm i.d., 8 cm packed with Dionex AS9-HC (8.5 cm to detector, 34.5 cm total). Mobile phase 2.5 mM hydrochloric acid (titrated to pH 8.05 with Tris). Flow is a combination of 10-bar pressure and EOF with -30 kV added at 1.3 min. All other conditions as given in Figure 1. (Reprinted from Ref. 75, with permission.)...

Codeine is a strong mono-acid base and its solutions turn litmus blue, phenolphthalein pink, and helianthin yellow [65] it is incompletely precipitated from its salts by ammonia. The neutral point of a codeine-hydrochloric acid titration is at pH 4-93, so methyl red can be used as indicator [66-67] potentiometric titrations can also be used [68-72],... 

Cool and transfer quantitatively to a 100 ml beaker. Insert pH electrodes and add 1 M sodium hydroxide until the pH is about 3.5. Titrate potentiometrically with 0.1 M sodium hydroxide through two end-points to a pH of about 10. Determine the volume used between the end-points, which are around pH 4.5 and pH 9.2. Alternatively, transfer the acid solution to a conical flask, make just alkaline to phenolphthalein with c. 1 M sodium hydroxide and neutralise carefully with 0.1 M hydrochloric acid. Titrate to bromocresol green with the same acid. 

Pippette 25 cm 0.2 M di-n-butylamine solution into two dry stoppered 250 cm conical flasks (i.e., a sample and a blank flask). Allow a 15 s pipette draining time during these operations. Into one of the flasks pipette 25 cm of the ten-fold diluted phenyl isocyanate solution (sampled at 25 °C using a 15 s draining time) and into the blank flask pipette 25 cm of toluene. Leave both solutions for 15 minutes to react, then add to each 100 cm methanol and 5 drops bromophenol blue indicator. Using 0.1 M hydrochloric acid titrate the sample (Tj ml of normal hydrochloric acid) and the blank solutions (Tg ml of normal hydrochloric acid) to the yellow-green end point. 

The hydrochloric acid titration correction (Tp cm ) required to allow for the presence of Dabco catalyst in the portion of reaction solutions W (g) withdrawn for phenyl isocyanate determination is given by ... 

Immerse the 1 dm flask of stock solution of Dabco in a water bath thermostatted at 25 1°C and leave until the solution reaches this temperature. Pipette 25 cm of this solution (15 s draining time) into a 250 cm conical flask containing 100 cm methanol and 5 drops 1% aqueous bromophenol blue indicator. Using 0.1 M hydrochloric acid, titrate the sample solution (T cm of f M hydrochloric acid) to the yellow-green end point. The reaction which has occured at the bromophenol blue indicator end point is ... 

Two methods which are quite widely applicable to many local anaesthetics are non-aqueous titration (perchloric acid to crystal violet, p. 792) and titration with sodium nitrite (0 5 g in 75 ml water and 10 ml hydrochloric acid, titrating with O IM nitrite and determining the end-point using the dead-stop technique, p. 867). A few materials such as benzocaine may be determined by both methods but in most cases either one or the other is applicable. Lignocaine hydrochloride, for example, gives a satisfactory end-point by the non-aqueous method but cannot be determined by titration with nitrite procaine hydrochloride on the other hand is satisfactorily titrated wdth nitrite but gives rise to a precipitate during titration in non-aqueous medium which obscures the end-point. Certain compounds such as amethocaine hydrochloride cannot be determined by either method. 

Weigh about 0 5 g into a 250-ml beaker fitted with a magnetic stirrer and dissolve in 75 ml of water and 10 ml of concentrated hydrochloric acid. Titrate electrometrically with 01M sodium nitrite using the dead-stop technique (see p. 867). 

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