Hydrochloric acid titration with

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. 

The determination of tin in metals containing over 75 wt % tin (eg, ingot tin) requites a special procedure (17). A 5-g sample is dissolved in hydrochloric acid, reduced with nickel, and cooled in CO2. A calculated weight of pure potassium iodate (dried at 100°C) and an excess of potassium iodide (1 3) are dissolved in water and added to the reduced solution to oxidize 96—98 wt % of the stannous chloride present. The reaction is completed by titration with 0.1 Af KIO —KI solution to a blue color using starch as the indicator. 

Reduction. Triaryknethane dyes are reduced readily to leuco bases with a variety of reagents, including sodium hydrosulfite, 2inc and acid (hydrochloric, acetic), 2inc dust and ammonia, and titanous chloride in concentrated hydrochloric acid. Reduction with titanium trichloride (Knecht method) is used for rapidly assaying triaryknethane dyes. The TiCl titration is carried out to a colorless end point which is usually very sharp (see Titanium COMPOUNDS, inorganic). 

The preparation of cyclohexylmagnesium bromide is described on p. 22. The solution may be standardized by titrating against 0.5 N hydrochloric acid, and exactly one mole equivalent is used in the preparation. Five cubic centimeters of cyclohexylmagnesium bromide solution is slowly added to 20 cc. of water, an excess of the standard acid is added, and the excess acid titrated with sodium hydroxide. If 85 g. (3.5 moles) of magnesium, one liter of dry ether, and 571 g. of cyclohexyl bromide (3.5 moles) are used, a solution results which is about 2 molar. 

Titrations curves for polyprotic acids have an inflection point for each hydrogen in the formula if the dissociation constant (Ka) for each hydrogen is very different from the others and if any dissociation constant is not too small. The titration curves of the polyprotic acids H2S04 and H3P04 are shown in Figures 5.6 and 5.7. Sulfuric acid has essentially one inflection point (like hydrochloric acid—compare with Figure 5.1(a)), while phosphoric acid has two apparent inflection points. Both hydrogens on the... 

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. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

A method involving electrometric titration depends on the volumetric reduction of selenious acid to selenium by means of titanium sulphate. The method is rapid and accurate5 if the solution is in cold concentrated hydrochloric acid saturated with sodium chloride. The presence of the latter is important, for it ensures rapid and uniform coagulation of the selenium hydrosol and increases the sharpness in the change of voltage at the end-point. The use of the hydrochloric acid in the cold eliminates the otherwise almost inevitable loss of selenium by volatilisation. Under these conditions any tellurium which may be present is unreduced and only has the effect of modifying the nature of the end-point.6... 

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. 

Dissolve 0.10 to 0.15 gm. of dried potassium iodate in 20 cc. of water, add 3 gm. of potassium iodide and 5 cc. of hydrochloric acid. Dilute with 50 cc. of water, and titrate the liberated iodine with decinormal sodium thiosulphate. 

One of the most common titrations of this type is the titration of hydrochloric acid, HC1, with sodium hydroxide, NaOH. If you remember from earlier, this is a neutralization reaction. However, you should also remember from earlier that in order for a complete neutralization to occur, the reaction must use appropriate stoichiometric ratios. When we first look at the process, we will do so with two solutions of known concentration, but you will see that this process can be used to determine the concentration of one of the solutions. 

Available from Ventron Corporation, Alfa Products, Beverly, MA 01915. t The molarity of the butyllithium solution may be checked before use by the procedure devised by Gilman.3 This involves careful hydrolysis of a measured sample using excess distilled water, followed by titration against standard hydrochloric acid solution with phenolphthalein as indicator. Since the butyllithium solution may contain some lithium hydroxide, it is necessary to carry out an identical titration of a sample which has undergone complete reaction with benzyl chloride in order to determine the lithium hydroxide present. From the difference between the two titrations, the molarity of the butyllithium may be calculated. 

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.)...

The analysis of mixtures of these two acids is very simple. The mixture is first titrated with nitrite to determine the total of the two acids, and then the 2,5,7 acid is titrated with sodium hypobromite. The 2,5,7 add reacts smoothly in hydrochloric acid solution with sodium hypobromite, taking up two atoms of bromine, while the 2,6,8 acid is entirely unreactive. This behavior is surprisingly similar to that of Schaeffer salt and R salt. 

Pure ferric oxide is recommended for the standardising of permanganate solutions for volumetric analysis. It is dissolved in hydrochloric acid, reduced with stannous chloride, and titrated with permanganate.11... 

Calcium Carbonate. Ten g. of nitrocellulose, 100 c.c. of N hydrochloric acid and too c.c. water are put into a stoppered cylinder, shaken for an hour, and the excess of acid titrated with N o sodium carbonate, using methyl orange as indicator. 

A bromination method has been described116 based on amperometric titration at 0.3 V of the =Si-H groups in the presence of double bonds in 4 m hydrochloric acid medium with 0.1 M-methanolic bromine saturated with sodium bromide with a rotating platinum micro-electrode, then analogous titration of the double bonds after treatment with methanolic potassium hydroxide to destroy the silidyne groups. The content of silidyne groups is then found by difference. 

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