Iodometric titration technique

Head-to-head (H-H) PVC, prepared by adding chlorine to cis-polybutadiene, appears to be less stable than the ordinary head-to-tail polymer (26). The ordinary polymer itself is said to contain 3-3.5 H-H linkages per 1000 carbons (26), but these results were obtained with an iodometric titration technique (26) that needs to be corroborated. 

Chlorine gas may be identified readdy by its distinctive color and odor. Its odor is perceptible at 3 ppm concentration in air. Chlorine may be measured in water at low ppm by various titrimetry or colorimetric techniques (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington DC American Pubhc Health Association). In iodometric titrations aqueous samples are acidified with acetic acid followed by addition of potassium iodide. Dissolved chlorine liberates iodine which is titrated with a standard solution of sodium thiosulfate using starch indicator. At the endpoint of titration, the blue color of the starch solution disappears. Alternatively, a standardized solution of a reducing agent, such as thiosulfate or phenylarsine oxide, is added in excess to chlorinated water and the unreacted reductant is then back titrated against a standard solution of iodine or potassium iodate. In amperometric titration, which has a lower detection limit, the free chlorine is titrated against phenyl arsine oxide at a pH between 6.5 and 7.5. 

Analytical methods for measuring hydroperoxides in fats and oils can be classified as those determining the total amount of hydroperoxides and those based on chromatographic techniques giving detailed information on the structure and the amount of specific hydroperoxides present in a certain oil sample (8). The PV represents the total hydroperoxide content and is one of the most common quality indicators of fats and oils during production and storage (9, 18). A number of methods have been developed for determination of PV, among which the iodometric titration, ferric ion complex measurement spectrophotometry, and infrared spectroscopy are most frequently used (19). 

Traditional techniques to measure dissolved sulfur in marine porewaters are iodometric titrations and colorimetric methods based on methylene blue color development. However, these methods(17-] ) are not capable of measuring a wide variety of sulfur species or distinguishing between sulfur species. Major sulfur species are defined as those with concentrations typically greater than 10 uM. lodometric titrations can determine sulfur in -1 and -2 oxidation states as shown in equations (1) through (4). However, these titrations cannot distinguish between all of the various forms. 

One of the most convenient analytical techniques for the determination of purity of a polyhalide is the iodometric titration of the total reducible halogen. When the complex... 

The thermal decompositions are first order and usually unimolecular. A variety of experimental methods can. be used to follow the rates, which include direct chemiluminescence of the excited carbonyl product (A),14 50,93,96 activated chemiluminescence by energy transfer of the excited carbonyl to an efficient fluorescer (B),14c,l2a,94 9< dioxetane consumption or carbonyl product formation by NMR spectroscopy (C),l2M4b c iodometric titration of the cyclic peroxide (DVJ, Ub,c and infrared spectroscopy of a-peroxylactone consumption or carbonyl product formation (E).2,22,38 The method of choice depends on the particular system, but usually several techniques can be employed. 

The determination of intermediately formed peroxides in the oxidized polyolefins by, e.g., iodometric titration was very popular at the beginning of ninetieth of the last century. As the methodology requires the precise laboratory work, declination from this trend may be noticed today and the more preferred technique is deriva-tization of hydroperoxides by nitrogen dioxide or sulphur dioxide with a subsequent spectroscopical determination of derivatives received. 

One tried-and-tested technique is the volumetric method (iodometric titration) described in Section 3.2.6.1, involving the use of a known quantity of iodine and back titration of the iodine not consumed. 

Inductively coupled plasma atomic emission spectrometry (ICP AES) is a suitable method for determining crystal composition. It has replaced a routine of chemical titration methods (except maybe iodometric titration which is still widely used in the determination of the oxygen content in HTSC). This method is precise enough and it demands only a small amount of substance to be analyzed. Standard solutions as well as an automated measuring procedure are also available. Applications of this method to the analysis of HTSC crystal composition can easily be found in the literature (Yao and Shiohara 1997, Kuroda et al. 1997a,b, Tagami and Shiohara 1997), although some restrictions are evident the ICP technique is destructive and non-local, and it is very sensitive to the selection of the sample to be analyzed since even small flux inclusions in the crystal can affect the results drastically. 

The most convenient laboratory method for determining the strength of hypochlorite is iodometric titration. In one such technique (adapted firom Refs. 3 and 4), 5.00 mL of bleach is quantitatively diluted to 50.00 mL with distilled or deionized water free of dissolved CI2. Then, 5.00 mL of this prepared solution is pipetted into about 75 mL of the... 

Technique compared to iodometric titration C10 measured by subtraction of BrO in a ClO/BrO ... 

Technique compared to iodometric titration CIO" measured by subtraction of BrO" in a ClO/BrO"... 

The ferrous-ferric ion analytical technique was used to determine the ozone concentration of the stock solution. Enough ferrous ammonium sulfate was added to an aliquot of ozone to bring 100 ml. of the solution to about 0.005iV and the nonoxidized ferrous ions were then back-titrated with 0.1 A potassium permanganate. The chlorine concentration was determined iodometrically (2). 

Phosgene is an oxidising agent, and iodometric techniques, based upon equation (3.2), have been employed for its determination [425,1148,1255,1357,1604]. The reaction must be carried out under anhydrous conditions (commonly in propanone or methyl ethanoate [1604]), and the iodine determined by conventionai procedures, such as by titration with [S fi 3] Although the usual starch indicator cannot be used in propanone solution, the colour of the generated dliodlne affords a reasonably sharp end-point [1560]. In addition, indications of very smali quantities of phosgene are indicated by the reddish-yellow colour of the liberated diiodine, so that the method can be applied for the trace determination of the gas [1560],... 

Colour transitions of indicators Acid-alkali and iodometric/iodimetric titration Pipetting technique... 

There were many investigations to explain the mechanism of reduction. Since direct chemical measurements are out of question at carrier-free concentrations of Tc (10 M), carrier technetium ( Tc) in hydrochloric acid was used to determine the oxidation state of technetium in diethylene triamine pentaacetate (DTPA) and in citrate solution. Polaro-graphic and iodometric techniques were used to analyze for unreacted stannous ion and to perform direct potentiometric titrations of pertechnetate-99 with stannous chloride (Mtinze 1980 Steigman et al. 1975). No quantitative kinetic studies had been made, but qualitative conclusions have been drawn for the reduction mechanism. Most probably, the first step is the reduction to Tc(V). Reduction to Tc(III) proceeds in two successive complementary reactions, both of which should be rapid in the low concentrations at radiopharmaceutical level ... 

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