Analysis, by titration

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. 

Hydroxyl number and molecular weight are normally determined by end-group analysis, by titration with acetic, phthaUc, or pyromellitic anhydride (264). Eor lower molecular weights (higher hydroxyl numbers), E- and C-nmr methods have been developed (265). Molecular weight deterrninations based on coUigative properties, eg, vapor-phase osmometry, or on molecular size, eg, size exclusion chromatography, are less useful because they do not measure the hydroxyl content. 

Titrier-analyse, /. analysis by titration, volu metric analysis, -apparat, m. titrating apparatus, volumetric apparatus, titrierbar, a. titratable. 

For analysis by titration with Fehling s solution, the sample is treated with lead acetate to precipitate protein and fat, filtered, and the filtrate titrated with alkaline CuS04, while heating. The reactions involved are summarized in Figure 2.37. 

ACIDIMETRY. An analytical method for determining the quantity of arid in a given sample by titration against a standard solution of a base, or, more broadly, a method of analysis by titration where the end point is recognized by a change in pH (hydrogen ion concentration). See also Analysis (Chemical) pH (Hydrogen Ion Concentration) Titration (Potentiometric) and Titration (Thermometric). 

Chlorine and bromine add vigorously, giving, with proper control, high yields of 1,2-dihaloethyl ethers. In the presence of an alcohol, halogens add as hypohalites, which give 2-haloacetals. With methanol and iodine, this is used as a method of quantitative analysis by titrating unconsumed iodine with standard thiosulfate solution. 

The analysis— by titration procedures and IR spectroscopy—of each of the separated phases showed that MAH becomes mostly grafted to EPR chains, and a small portion of the monomer combines with the PR No differences have been detected in the effect of peroxide initiators that show solubility values close to that of EPR or PR... 

Analysis by Titration Add, from a 10-mL btaret, 5 or 6 mL of standard 0.2 N H2SO4 solution to the ethereal Grignard solution. The resulting solution should be acidic and colorless. If not, add an additional portion of the acid. 

For analysis by titration, see Ref. Ic. Spectra available from the Aldrich Library. 

Crude oils contain carboxylic acids. These are analyzed by titration with potassium hydroxide and the result of the analysis is expressed in mg of KOH/g crude. 

IL Molecular Weight of Acids by Titration with Standard Alkali. III. Molecular Weight of Bases by Analysis of Chloroplatinates. 

In this experiment students standardize a solution of HGl by titration using several different indicators to signal the titration s end point. A statistical analysis of the data using f-tests and F-tests allows students to compare results obtained using the same indicator, with results obtained using different indicators. The results of this experiment can be used later when discussing the selection of appropriate indicators. 

The accuracy of a standardization depends on the quality of the reagents and glassware used to prepare standards. For example, in an acid-base titration, the amount of analyte is related to the absolute amount of titrant used in the analysis by the stoichiometry of the chemical reaction between the analyte and the titrant. The amount of titrant used is the product of the signal (which is the volume of titrant) and the titrant s concentration. Thus, the accuracy of a titrimetric analysis can be no better than the accuracy to which the titrant s concentration is known. 

Selecting and Standardizing a Titrant Most common acid-base titrants are not readily available as primary standards and must be standardized before they can be used in a quantitative analysis. Standardization is accomplished by titrating a known amount of an appropriate acidic or basic primary standard. 

CO2 is determined by titrating with a standard solution of NaOH to the phenolphthalein end point, or to a pH of 8.3, with results reported as milligrams CO2 per liter. This analysis is essentially the same as that for the determination of total acidity, and can only be applied to water samples that do not contain any strong acid acidity. 

A reagent used to reduce the analyte before its analysis by a redox titration. 

A quantitative analysis for NH3 in several household cleaning products is carried out by titrating with a standard solution of HGl. The titration s progress is followed thermometrically by monitoring the temperature of the titration mixture as a function of the volume of added titrant. Household cleaning products may contain other basic components, such as sodium citrate or sodium carbonate, that will also be titrated by HGl. By comparing titration curves for prepared samples of NH3 to titration curves for the samples, it is possible to determine that portion of the thermometric titration curve due to the neutralization of NH3. 

Ophardt, G. E. Acid Rain Analysis by Standard Addition Titration, /. Chem. Educ. 1985, 62, 257-258. 

This experiment describes a method for determining the acidity, reported as an equivalent molarity of H2SO4, of rain water. Because the volume of standard base needed to titrate a sample of rain water is small, the analysis is done by a standard addition. A 10.00-mL sample of nominally 0.005 M H2SO4 is diluted with 100.0 mL of distilled water and standardized by titrating with 0.0100 M NaOH. A second 10.00-mL sample of the sulfuric acid is mixed with 100.0 mL of rain water and titrated with the same solution of NaOH. The difference between the two equivalence point volumes... 

Tartaric acid, H2C4H4O6, is a diprotic weak acid with a pK i of 3.0 and a pK 2 of 4.4. Suppose you have a sample of impure tartaric acid (%purity > 80) and that you plan to determine its purity by titrating with a solution of 0.1 M NaOH using a visual indicator to signal the end point. Describe how you would carry out the analysis, paying particular attention to how much sample you would use, the desired pH range over which you would like the visual indicator to operate, and how you would calculate the %w/w tartaric acid. 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

Functional Group Analysis. The total hydroxyl content of lignin is determined by acetylation with an acetic anhydride—pyridine reagent followed by saponification of the acetate, and followed by titration of the resulting acetic acid with a standard 0.05 W sodium hydroxide solution. Either the Kuhn-Roth (35) or the modified Bethge-Liadstrom (36) procedure may be used to determine the total hydroxyl content. The aUphatic hydroxyl content is determined by the difference between the total and phenoHc hydroxyl contents. 

Titration Indicators. Concentrations of arsenic(III) as low as 2 x 10 M can be measured (272) by titration with iodine, using the chemiluminescent iodine oxidation of luminol to indicate the end point. Oxidation reactions have been titrated using siloxene the appearance of chemiluminescence indicates excess oxidant. Examples include titration of thallium (277) and lead (278) with dichromate and analysis of iron(II) by titration with cerium(IV) (279). 

Commercial Hquid sodium alumiaates are normally analyzed for total alumiaa and for sodium oxide by titration with ethylene diaminetetraacetic acid [60-00-4] (EDTA) or hydrochloric acid. Further analysis iacludes the determiaation of soluble alumiaa, soluble siHca, total iasoluble material, sodium oxide content, and carbon dioxide. Aluminum and sodium can also be determiaed by emission spectroscopy. The total iasoluble material is determiaed by weighing the ignited residue after extraction of the soluble material with sodium hydroxide. The sodium oxide content is determiaed ia a flame photometer by comparison to proper standards. Carbon dioxide is usually determiaed by the amount evolved, as ia the Underwood method. 

Descriptions of sulfuric acid analytical procedures not specified by ASTM are available (32,152). Federal specifications also describe the requited method of analysis. Concentrations of 78 wt % and 93 wt % H2SO4 are commonly measured indirectly by determining specific gravity. Higher acid concentrations are normally determined by titration with a base, or by sonic velocity or other physical property for plant control. Sonic velocity has been found to be quite accurate for strength analysis of both filming and nonfuming acid. 

Although the most sensitive line for cadmium in the arc or spark spectmm is at 228.8 nm, the line at 326.1 nm is more convenient to use for spectroscopic detection. The limit of detection at this wavelength amounts to 0.001% cadmium with ordinary techniques and 0.00001% using specialized methods. Determination in concentrations up to 10% is accompHshed by solubilization of the sample followed by atomic absorption measurement. The range can be extended to still higher cadmium levels provided that a relative error of 0.5% is acceptable. Another quantitative analysis method is by titration at pH 10 with a standard solution of ethylenediarninetetraacetic acid (EDTA) and Eriochrome Black T indicator. Zinc interferes and therefore must first be removed. 

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