Sodium carbonate potentiometric titration

There are four basic sulfates that can be identified by potentiometric titration using sodium carbonate (39,40) langite [1318-78-17, CuSO -3Cu(OH)2 H2 i brochantite [12068-81 -4] CuSO -3Cu(OH)2 antedite [12019-54-4] CuSO -2Cu(OH)2 and CuS0 -Cu0-2Cu(0H)2-xH20. The basic copper(II) sulfate that is available commercially is known as the tribasic copper sulfate [12068-81 ] CuS04-3Cu(0H)2, which occurs as the green monoclinic mineral brochantite. This material is essentially insoluble in water, but dissolves readily in cold dilute mineral acids, warm acetic acid, and ammonia solutions. 

More straightforwardly, the sample may be titrated potentiometrically using hydrochloric acid to two points of inflexion. The first represents sodium hydroxide plus sodium carbonate the second sodium bicarbonate. Clearly there cannot be bicarbonate in the sample if there is sodium hydroxide present. Any second inflexion in this case can be used to determine the carbonate content. Should the titer from the first inflexion to the second be greater than that from start to the first inflexion, then the sample contains only carbonate and bicarbonate. The titer to the first inflexion can be used to estimate carbonate and the difference between twice this titer and the total titer to the second inflexion is a measure of bicarbonate. 

Potentiometric titration and colorimetric methods have been described for the determination of )5-chlorovinyldichloroarsine (Lewisite) . In the latter the organic arsenic is mineralized by refluxing with aqueous sodium hydrogen carbonate and then oxidized to... 

The acetic-acid content of household vinegar can be determined by potentiometric titration with sodium hydroxide. Mixtures of carbonate and bicarbonate can be analyzed by titration with HCl. 

Lisinoprii can be determined by potentiometric titration with aqueous sodium hydroxide and non-aqueous perchioric acid. The sodium hydroxide titration is carried out by titrating the iisinoprii potentiometrically with carbonate free 0.1 N NaOH to one endpoint using a combination eiectrode. Lisinoprii can aiso be determined by titration potentiometricaiiy with 0.1 N perchloric acid in acetic acid to one endpoint. The electrode system consists of a glass electrode (such as a Metrohm Model EA 107 vs. a silver/silver chloride reference electrode such as a Metrohm Model EA 432 filled with 0.1 N lithium perchlorate in glacial acetic acid. 

The total chlorine content of the diisocyanate can be determined by the standard analytical technique of decomposing the sample in an oxygen bomb and determining the ionic chloride formed by potentiometric titration with silver nitrate solution. Effectively, diisocyanate, as well as other organic materials, is oxidized by combustion in a bomb containing oxygen under pressure. The resultant chloride ion is absorbed in a 1% sodium carbonate solution and the concentration of chloride present is determined potentiometrically. 

The back titration method can be used to measure total alkalinity with simpler equipment than that required for the potentiometric titrations described above, but at the cost of a poorer precision. The method described is that of Gripenberg (1936) as modified by Koroleff (1972). The sample is acidified with hydrochloric acid to a pH of about 3.5, and the carbon dioxide is driven off by boiling. The solution is then back-titrated to pH 6 with sodium hydroxide solution using bromothymol blue as indicator. The alkalinity is estimated simply as the difference between the amounts of hydrochloric acid and sodium hydroxide added. 

Fusion with sodium carbonate is a very useful method for the fusion of polymers that, upon ignition, release acidic vapours, e.g., PE containing traces of chlorine or PVC, both of which, upon ignition, release anhydrous hydrogen chloride. To determine chlorine accurately in the polymer in amounts down to 5 ppm, hydrogen chloride must be trapped in a solid alkaline reagent (e.g., sodium carbonate). In this method, PE is mixed with pure sodium carbonate and ashed in a muffle furnace at 500 "C. The residual ash is dissolved in aqueous nitric acid, and then diluted with acetone. This solution is titrated potentiometrically with standard silver nitrate. 

Study of a system of sodium carbonate and Rm2 sodium silicate from a concentrated solution with 45% dry extract (2Si02, Na20). (We shall see in the section on silicates that the nature of the original silicate plays an important role.) The experimental study of the postreaction species obtained was carried out by filtration, potentiometric titration by specific electrode, and complexo-metric titration by EDTA. At equilibrium, the calcium is found in three different forms whose relative proportions vary considerably with the silicate/carbonate proportion ... 

In this method, polyethylene is mixed with pure sodium carbonate and ashed in muffle furnace at 500 °C. The residual ash is dissolved in aqueous nitric acid and then diluted with acetone. This solution is titrated potentiometrically with standard silver nitrate. 

Bodin has applied direct argentimetric potentiometric titration to phenobarbitone and its sodium salt in preparations containing a variety of standard diluents. He eliminates uncertainty in the end-point potential by determining the potential of a standard blank solution (saturated with silver carbonate) for each sample just prior to titration and using this as the end-point potential for titration of the sample. Stearates, halides and ammonium salts interfere and special consideration must be given to samples containing polyethylene glycols, alcohol, or hexamine. He includes a procedure for removal of stearates from tablets. 

Titrate potentiometrically with carbonate-free 0.2 M sodium hydroxide. There are end-points around pH 3 and 7.7. 

Alkyldimethylbetaine and free amine can be determined by potentiometric acid-base titration (12). For titration of the betaine, the sample is dissolved in a mixture of 10 1 methyl isobutyl ketone/isopropanol to which a little HCl has been added. Three breaks are observed on titration with ethanolic KOH, corresponding respectively to excess HCl, the betaine, and combined impurities amine, glycolic acid, and monochloracetic acid (see Fig. 1). Carbon dioxide must be excluded during the titration. Sodium chloride is insoluble in the solvent system and precipitates. The titration is very sensitive to water concentration (16)... 

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