Titrimetric determinations

Another line of analytical use is exemplified by the properties of l-(2-thiazolylazoi-2-naphthol (305), whose complexes with metals may be used for their spectrophotometric and titrimetric determination, as wel] as for their separation by solvent extraction (564, 568, 953-957, 1040). 

Phthaleins. Dyes of this class are usually considered to be triaryhnethane derivatives. Phenolphthalein [77-09-8] (23, R = CO) and phenol red [143-74-8] (23, R = SO2) are used extensively as indicators in colorimetric and titrimetric determinations (see Hydrogen-ION activity). These compounds are prepared by the condensation of phenol with phthaUc anhydride or i9-sulfoben2oic anhydride, respectively, in the presence of a dehydrating agent. 

The kinetics of alkaline hydrolysis of phenyl cinnamate were studied at 25°C, in solutions containing 0.8% acetonitrile ionic strength, 0.3 M initial ester, 8.19 X 10- M reaction followed spectrophotometrically in 5-cm cells at 295 nm. For studies at three pH values, these absorbance data were obtained. The pH was established with sodium hydroxide of the normality specified in the heading of the table (as titrimetrically determined). 

This reaction has also been used for the titrimetric determination of polysulfides [10, 11]. 

Hexa(hydroxyethyl)pararosaniline nitrile has been used in a chemical radiochromic dosimeter.130 Ferricyanide oxidation of leuco Crystal Violet to Crystal Violet dye finds use in detection of various heavy metals131 at trace quantities. Oxidation of leuco triphenylmethanes by chloramine-T is catalyzed by iodide and therefore is used for detection of iodide.132 On the other hand, the inhibition of the catalytic effect of iodide by some ions can be used for determining traces of Ag(I), Hg(II), Pd(II). In addition, the triphenylmethane leuco dyes, phenolphthalein or phenol red are used extensively as indicators in calorimetric and titrimetric determinations. 

Experimentally, the measurement of reaction rates consists in investigating the rate at which starting materials disappear and/or products appear at a particular (constant) temperature, and seeking to relate this to the concentration of one, or all, of the reactants. The reaction may be monitored by a variety of methods, e.g. directly by the removal of aliquots followed by their titrimetric determination, or indirectly by observation of colorimetric, conductimetric, spectroscopic, etc., changes. Whatever method is used the crucial step normally involves matching the crude kinetic data against variable possible functions of concentration, either graphically or by calculation, until a reasonable fit is obtained. Thus for the reaction,... 

In a method for titrimetric determination of manganese in pyrolusite ore, addition of the powdered ore to a cold 20% solution of the salt causes vigorous decomposition to occur. 

A feature of this analytical scheme is the marked reliance on infrared spectrometry and titrimetry. The former is particularly applicable to the qualitative characterization of unknown organic materials whilst titrimetry provides a rapid, precise and cheap means of quantitative analysis. The routine titrimetric determination of water, total acid (acid number) and total base (base number) forms a significant proportion of the work load in some analytical laboratories. It is instructive to consider how other techniques might have been applied to the solution of this particular problem, e.g. NMR spectrometry and chromatography. 

VI. Van Slyke, D. D., and Kirk, E., Comparison of gasometric, colorimetric, and titrimetric determinations of amino nitrogen in blood and urine. J. Biol. Chem. 102, 651-682 (1933). 

The titrimetric determination of soil constituents is most commonly applied to a limited number of soil analyses, namely, organic carbon, nitrogen compounds, carbonates, and chlorides. Determination of acid content by titration is generally not done because the titration curves are not amenable to typical titration analysis. Because of the color of soil and the fact that it is a suspension when stirred, it is often necessary to remove the constituent of interest before titration. In other cases, it is possible to do a direct titration using an appropriate indicator. However, even in these cases, detection of the end point is difficult. 

Sijderius, R. A Direct Titrimetric Determination of Barium with EDTA. 

Liu et al. prepared a procaine-sensitive FET transducer by coating a suitable electrode with sodium tetraphenylborate-procaine active material, 5% of poly(vinylchloride), and dibutyl phthalate in tetrahydrofliran [71]. The optimum operating pH was determined to be between 2 and 7. The transducer was applied in the potentiometric titrimetric determination of procaine in injection solution, where the recovery was 100.7% and the coefficient of variation (n = 2) was 1.4%. 

Since most technical products always contain the same constituents in approximately the same amounts it has been possible to develop numerous empirical methods which, for the most part, involve a combined procedure based on precipitation and titrimetric determinations. These are of practical use for particular purposes, e.g., in comparative determinations, but have no claims to general validity (4, 9, 68, 70, 71, 75, 87, 187, 236, 240, 352). 

The Karl Fisher titration is one of the most common and most sensitive methods used in the analytical laboratory. The titrimetric determination of water is based on the quantitative reaction of water with an anhydrous solution of sulfur dioxide and iodine in the presence of a buffer that reacts with hydrogen ions. This titration is a two-stage process ... 

Diols and polyols can participate in equilibria with boric acid in aqueous solution. The stability of polyolborates is determined by the number of OH groups in cis positions. Complexes with polyols are more stable than with diols, and 1,2-diol complexes are more stable than their 1,3-diol counterparts (Table 10) since the resulting five-membered chelate ring is unstrained.75120 In the case of 1,3,5-triols stable cage-like structures (5) and (6) are favored. Open-chain or five-membered cyclic polyols form more stable chelate complexes than their six-membered counterparts.120 Thus, chelates from alditols and ketohexoses are more stable than the corresponding aldose chelates (Table 10). Many polyols allow quantitative titrimetric determination of boric acid. Of these, mannitol remains the most widely used reagent on the basis of availability, cost and ease of handling.75... 

Phthaleins. Dyes of Uiis class are usually considered to be tnaryl-methane derivatives. Phenolphthalein and phenol red are used extensively as indicators in colorimetric and titrimetric determinations. See also Hydrogen-Ion Activity. 

Vanadium(II) reacted with SCN- and diphenylguanidine (L) to form a ternary complex with a V SCN L ratio of 1 2 2.176 Other ternary complexes like phenylguanidine iron(II) cyanide are being exploited in titrimetric determination of cyanide ions, for example. 

Basic Protocol 1 Titrimetric Determination of Lipase Activity Basic Protocol 2 Colorimetric Assay of Lipase Activity Using the Copper Soap Method... 

Certain azo dyes of this type, in particular pyridineazo-2-naphthol (PAN) and pyridineazore-sorcinol (PAR), have been used in the spectrophotometric and titrimetric determination of metal... 

The shape of the dissociation curve makes it possible to reject the other possibility of formation of the tropyl alcohol, i.e. direct nucleophilic attack of hydroxide ions. By means of equation (19) and titrimetrically determined value of dissociation constants, the rate constants i = 2 106 1 mole-1 sec-1 and ft i = 50 sec-1 can be calculated (55). Similarly, it is possible to treat the system (21) ... 

Argentometric titration involves the titrimetric determination of an analyte using silver nitrate solution as titrant. Its application in environmental analysis is limited to the determination of chloride and cyanide in aqueous samples. The principle of the method is described below. 

The iodometric assay for moxalactam involves the hydrolysis of moxalactam in aqueous base which results in the cleavage of the 3-lactam ring. This is followed by oxidation of the hydrolysis products with iodine, and the titrimetric determination of the iodine consumed. Since the unhydrolyzed drug does not react with iodine, an unreacted sample is used as a blank to compensate for iodine consuming impurities. 

Based on the fact that mefenamic acid reacts quantitatively with tV-bromosuccinimide (NBS) in an acidic medium, Hassib et al. [8] reported the titrimetric determination of mefenamic acid. A solution of mefenamic acid in acetic acid (0.02% m/V) was prepared. A volume of this solution containing 1.5-3.5 mg of mefenamic acid was allowed to react with 40 mL of 0.05 M NBS solution for 10 min in the dark (temperature of 25 2°C). Potassium iodide solution (10 mL) was added, and the solution was titrated with 0.01 N sodium thiosulfate to the starch end-point. A blank determination was carried out. For the determination of mefenamic acid in the capsules, the contents of 20 Ponstan capsules were mixed thoroughly and an accurately weighed portion of the mixed powder (nominally containing 25 mg of mefenamic acid) was extracted with diethyl ether (3 x 10 mL). The residue remaining after evaporation of diethyl ether was dissolved in acetic acid, and the procedure was continued as described for the determination of mefenamic acid. 

Assay and test results are determined on the basis of comparison of the test sample with the reference standard that has been freed from or corrected for volatile residues or water content as instructed on the reference standard label. If a reference standard is required to be dried before use, transfer a sufficient amount to a clean, dry vessel. Do not use the original container as the drying vessel, and do not dry a reference standard repeatedly at temperatures above 25°. Where the titrimetric determination of water is required at the time a reference standard is to be used, proceed as directed in the Karl Fischer Titrimetric Method under Water Determination, Appendix IIB. 

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