Sulfurous acid titration with sodium hydroxide

Various workers have discussed the determination of total alkalinity and carbonate [ 10-12], and the carbonate bicarbonate ratio [ 12] in seawater. A typical method utilises an autoanalyser. Total alkalinity (T milliequivelents per litre) is found by adding a known (excess) amount of hydrochloric acid and back titrating with sodium hydroxide solution a pH meter records directly and after differentiation is used to indicate the end-point. Total carbon dioxide (C milliequivelents per litre of HCO3 per litre) is determined by mixing the sample with dilute sulfuric acid and segmenting it with carbon dioxide-free air, so that the carbon dioxide in the sample is expelled into the air segments. The air... 

A weighed sample is boiled in concentrated sulfuric acid, which quantitatively produces ammonia that reacts with the excess sulfuric acid to produce ammonium sulfate. An excess of sodium hydroxide is then added and the liberated ammonia is distilled into an excess of a standard acid solution, which is then titrated with sodium hydroxide. 

Sodium Oxide Disperse 500 mg of sample, accurately weighed, in 150 mL of water, and heat to ensure its dissolution. Add 2 to 3 drops of phenolphthalein TS and 100.0 mL of 0.1 N sulfuric acid. Titrate with 0.1 N sodium hydroxide until a permanent pink color first appears. Subtract the volume of 0.1 N sodium hydroxide from the volume of 0.1 N sulfuric acid. Each milliliter of 0.1 N sulfuric acid is equivalent to 3.099 mg of sodium oxide. 

You will extract 10 mL of Ipecac with 125 mL of diethyl ether for about 2 hours. The ether will be evaporated from the sample, and the sample redissolved in ethanol. The alkaloids will be back titrated using both standard sulfuric acid and standard sodium hydroxide. Methyl red is the indicator. 

The balanced equation for a titration reaction is the key to calculating the unknown molarity. For example, sulfuric acid is titrated with sodium hydroxide according to this equation. 

When the colloidal suspension is titrated with sodium hydroxide (NaOH), its conductivity decreases and reaches a minimum when the surface acid groups have all been neutralized. From material balances it is possible to calculate the total number of acid head groups initially present, and eventually the area per head group, which is seen to vary from 3 to 4 nm /group. When there are two acid groups present (sulfuric and carboxylate), the conductivity plots show a feamre similar to having two minima. These steps are often required to prepare well-characterized colloids to perform controlled experiments. 

The comprehensive method determines the nitrogen content for all forms of nitrogen compounds (nitrite, nitrate, urea, organic nitrogen, and ammonia), which upon distillation can be collected in a known amount of sulfuric acid and titrated with sodium hydroxide. A great deal of time is consumed in performing this classical nitrogen method. Note Boric acid may be used for collection of ammonia in the distillation step rather than sulfuric acid. 

The Kjeldahl digestion method is used to determine only the ammonia nitrogen content. Sodium hydroxide or magnesium oxide is used to raise the pH to above 12 to liberate the ammonia upon distillation, which is collected in a known amount of sulfuric acid. The excess sulfuric acid is titrated with sodium hydroxide and the percentage ammonia nitrogen is determined. Only ammonia-based fertilizer material should be analyzed using this method. 

Equations 9.41 and 9.42 represent the reactions that occur when solutions of nitric and sulfuric acid are titrated with sodium hydroxide ... 

Repeat problem 3, but compare the titration curves of 0.10 M sulfuric acid and 0.10 M phosphoric acid titrated with 0.10 M sodium hydroxide. 

Assay Transfer about 1 g of sample, accurately weighed, into a 1000-mL flask containing 20 mL of water, and dilute to volume with water. Place 10 mL of this solution into a glass-stoppered flask, add 25 mL of sodium hydroxide TS, and allow the mixture to stand for 5 min. Add 25 mL of 0.1 A iodine, stopper the flask, allow the contents to stand in a cold, dark place for 10 min, and add 30 mL of 1 A sulfuric acid. Titrate the excess iodine with 0.1 A sodium thiosulfate, using starch TS as the indicator. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1 A iodine is equivalent to 0.9675 mg of... 

Kjeldahl test. An analytical method for determination of nitrogen in certain organic compounds. It involves addition of a small amount of anhydrous potassium sulfate to the test compound, followed by heating the mixture with concentrated sulfuric acid, often with a catalyst such as copper sulfate. As a result ammonia is formed. After alkalyzing the mixture with sodium hydroxide, the ammonia is separated by distillation, collected in standard acid, and the nitrogen determined by back-titration. 

The equivalence point in a titration is a theoretical point reached when the amount of added titrant is chemically equivalent to the amount of analyte in the sample. For example, the equivalence point in the titration of sodium chloride with silver nitrate occurs after exactly 1 mol of silver ion has been added for each mole of chloride ion in the sample. The equivalence point in the titration of sulfuric acid with sodium hydroxide is reached after introduction of 2 mol of base for each mole of acid. 

The most stable oxidation state is +3, which is yellow, but +2 (green) and +6 (easily reduced) also exist. Solutions of iron(II) ions give a green precipitate with sodium hydroxide solution, whereas iron(III) ions give a brown precipitate. The concentration of iron(II) ions can be estimated in acid solution by titration with standard potassium manganate(VII) solution. Iron(III) ions must first be reduced to iron(II) ions with sulfur(IV) oxide (sulfur dioxide). 

Fig. 81 Titration diagram of sulfuric acid (lo C ifuric acid — —P ai — —3, p fa2 — 1-99 with sodium hydroxide...

In the classical Kjeldahl method, the proteins are digested (wet oxidized) in sulfuric acid with a catalyst (mercury and selenium tablets now succeed by the much safer potassium and copper sulfate tablets). An acid solution of ammonium sulfate is formed which is then diluted in water. The solution is made alkaline with sodium hydroxide and heated to distil off ammonia into excess standard acid sulfuric acid. The excess acid is back-titrated with standard sodium hydroxide to determine the amount of ammonia. It is more usual now to use boric acid in which to collect the ammonia and titrate with standard hydrochloric acid. The Kjeldahl procedure has been partially automated in systems such as the Kjeltec Analyzer. Total protein can be calculated as nitrogen content x 6.38. 

The most popular device for fluoride analysis is the ion-selective electrode (see Electro analytical techniques). Analysis usiag the electrode is rapid and this is especially useful for dilute solutions and water analysis. Because the electrode responds only to free fluoride ion, care must be taken to convert complexed fluoride ions to free fluoride to obtain the total fluoride value (8). The fluoride electrode also can be used as an end poiat detector ia titration of fluoride usiag lanthanum nitrate [10099-59-9]. Often volumetric analysis by titration with thorium nitrate [13823-29-5] or lanthanum nitrate is the method of choice. The fluoride is preferably steam distilled from perchloric or sulfuric acid to prevent iaterference (9,10). Fusion with a sodium carbonate—sodium hydroxide mixture or sodium maybe required if the samples are covalent or iasoluble. 

Assay of beryUium metal and beryUium compounds is usuaUy accompHshed by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryUium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryUium content of the sample is calculated from the titration volume. Standards containing known beryUium concentrations must be analyzed along with the samples, as complexation of beryUium by fluoride is not quantitative. Titration rate and hold times ate critical therefore use of an automatic titrator is recommended. Other fluotide-complexing elements such as aluminum, sUicon, zirconium, hafnium, uranium, thorium, and rate earth elements must be absent, or must be corrected for if present in smaU amounts. Copper-beryUium and nickel—beryUium aUoys can be analyzed by titration if the beryUium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

The phosphorodichloridate was hydrolyzed by adding to a stirred solution of sodium carbonate (253 grams) in water (2.9 liters). After 1 hour the solution was cooled and acidified with a solution of concentrated sulfuric acid (30 ml) in water (150 ml) and then extracted with a mixture of tetrahydrofuran and chloroform (2.3/1 3 x 1 liter). The tetrahydro-furan/chloroform liquors were bulked and evaporated to dryness to give a light brown oil. This was dissolved in water (1 liter) and titrated with 2N sodium hydroxide solution to a pH of 4.05 (volume required 930 ml). The aqueous solution was clarified by filtration through kieselguhr and then evaporated under reduced pressure to a syrup (737 grams). 

A second major use of sulfuric acid of commerce is in reactions with bases. In laboratory use it is diluted to a much lower concentration and can be used as a standard acid. A typical problem would be the titration of a base solution of unknown concentration using a sulfuric acid solution of known concentration. For example, What is the concentration of a sodium hydroxide solution if 25.43 ml of the NaOH solution just reacts with 18.51 ml of 0.1250 M HiSOt (to produce a neutral solution) ... 

A 10-0 cm3 volume of a liquid drain cleaner containing sodium hydroxide was diluted to 250 cm3 g standard flask. Samples of this diluted solution with volumes of 25-0 cm3 ere pipetted into a conical flask and titrated against a 0-220 mol h sulfuric acid solution. The average of the concordant titres was 17-8 cm3. Calculate the mass of sodium hydroxide in one litre of the drain cleaner. 

Elemental composition Na 58.93%, N 35.90%, H 5.17%. The compound may he decomposed cautiously with water (reaction is violent) under cooling to yield sodium hydroxide and ammonia. (Or it may he decomposed with anhyrous alcohol to form ammonia and sodium alcoholate. The alcoholate then may he treated with water to form sodium hydroxide). Ammonia liberated is dissolved in water and the solution is measured using an ammonia-selective electrode. Alternatively, ammonia is collected over horic acid solution containing a small quantity of methyl red indicator. The solution is titrated with a standard solution of sulfuric acid. Sodium hydroxide is measured hy titration with a standard solution of hydrochloric or sulfuric acid. 

Weigh accurately about 400 mg of analyte, previously dried at 105°C for 3 h, and dissolve in 15 mL of water in a glass-stoppered conical flask. Add 40 mL of 0.1 N-sodium hydroxide VS, and heat on a steam bath for 30 min. Insert the stopper, allow to cool, add phenolphthalein TS, and titrate the excess alkali with 0.1 N sulfuric acid VS. Determine the exact normality of the 0.1 N sodium hydroxide by titrating an aliquot of 40.0 mL after it has been treated in the same manner as in the test. Each milliliter of 0.1 N sodium hydroxide is equivalent to 4.30 mg of CH3CO. Between 23.2 and 24% of CH3CO is found. 

Assay Place about 10 mL of water in a weighing bottle, tare the bottle and its contents, add about 2 g of sample, and accurately weigh. Transfer the contents of the bottle to a 250-mL flask, and while mixing, slowly add 50.0 mL of 1 A sulfuric acid, allowing for the release of carbon dioxide. When solution has been effected, wash down the sides of the flask with a few milliliters of water, add a few drops of methyl orange TS, and titrate the excess acid with 1 A sodium hydroxide. Each milliliter of 1 A sulfuric acid is equivalent to 17.03 mg of NH3. 

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