Iodine solution, aqueous

Chlorine has a lower electrode potential and electronegativity than fluorine but will displace bromine and iodine from aqueous solutions of bromide and iodide ions respectively ... 

Iodine Solution. Cold saturated aqueous solution. (If a more concentrated solution is required, add i g. of powdered iodine to a solution of 2 g. of potassium iodide in a minimum of water, and dilute the solution to 100 ml.)... 

Hydrogen iodide (anhydrous) [10034-85-2] M 127.9, b -35.5°. After removal of free iodine from aqueous HI, the solution is frozen, then covered with P2O5 and allowed to melt under vacuum. The gas evolved is dried by passage through P2O5 on glass wool. It can be freed from iodine contamination by repeated fractional distillation at low temperatures. Fumes in moist air. HARMFUL VAPOURS. 

The filtrate was adjusted to a pH of 9 by adding concentrated ammonia, and than a 1 N aqueous iodine-potassium iodide solution was added dropwise, whereby the tetrahydro-pyrimido-[5,4-d] pyrimidine obtained by hydrogenation with zinc in formic acid was converted by oxidation into 2,6-bis-(diethanolamino)-8-piperidino-pyrimido-[5/4-d]-pyrimidine. The completion of the oxidation was checked by means of a starch solution. The major amount of the oxidation product already separated out as a deep yellow crystalline precipitate during the addition of the iodine solution. After the oxidation reaction was complete, the reaction mixture was allowed to stand for a short period of time, and than the precipitate was separated by vacuum filtration, washed with water and dried. It had a malting point of 157°C to 158°C. The yield was 8.0 g, which corresponds to 95% theory. 

A solution of iodine in aqueous iodide has an intense yellow to brown colour. One drop of 0.05M iodine solution imparts a perceptible pale yellow colour to 100 mL of water, so that in otherwise colourless solutions iodine can serve as its own indicator. The test is made much more sensitive by the use of a solution of starch as indicator. Starch reacts with iodine in the presence of iodide to form an intensely blue-coloured complex, which is visible at very low concentrations of iodine. The sensitivity of the colour reaction is such that a blue colour is visible when the iodine concentration is 2 x 10 " 5 M and the iodide concentration is greater than 4x 10 4M at 20 °C. The colour sensitivity decreases with increasing temperature of the solution thus at 50 °C it is about ten times less sensitive than at 25 °C. The sensitivity decreases upon the addition of solvents, such as ethanol no colour is obtained in solutions containing 50 per cent ethanol or more. It cannot be used in a strongly acid medium because hydrolysis of the starch occurs. 

Separately, another 25.0-ml. portion of the iodine solution was stirred in a 500-ml. Erlenmeyer flask and treated with 5.00 ml. of the 1 M aqueous sodium thiosulfate, 20 ml. of water, and 2 drops of acetic acid. 

Subsequently, Grovenstein and Aprahamian219 investigated the iodination of 4-nitrophenol and its 2,6-dideuterated derivative, by iodine in aqueous solution... 

The rate of formation of sulphoxides from sulphides and iodine in aqueous solution has been found to be relatively slow. It may be, however, accelerated by certain nucleophiles, such as phthalate ion S hydrogen phosphate ion and E(-cyclodextrin phosphate ion . The selective oxidation of JV-acetylmethionine and N-acetylmethionine methyl ester to the corresponding S-oxides was achieved using iodine in the presence of dicarboxylate ions. 

The explosion hazard associated with the usual laboratory preparation from white phosphorus and alkali may be avoided by an alternative method involving oxidation of phosphine with an aqueous iodine solution [1], The commercial 50% solution reacts violently with oxidants. On heating, it decomposes rapidly above 100°C evolving phosphine, which is liable to explode with air. It is recommended it... 

Walash et al. [14] described a kinetic spectrophotometric method for determination of several sulfur containing compounds including penicillamine. The method is based on the catalytic effect on the reaction between sodium azide and iodine in aqueous solution, and entails measuring the decrease in the absorbance of iodine at 348 nm by a fixed time method. Regression analysis of the Beer s law plot showed a linear graph over the range of 0.01 0.1 pg/mL for penicillamine with a detection limit of 0.0094 pg/mL. 

Modras (51) reported spot test reactions to differentiate hydralazine from closely related drugs. Reagents used were aqueous copper (I) chloride, aqueous ammonium molybdate, iodine in potassium iodide solution, aqueous cobalt (II) nitrate, alcoholic ninhydrin, and alcoholic bromophenol blue. The tests were performed on paper or on Silica Gel G. 

Theory Iodine in aqueous solution acts as an oxidizing agent which forms the basis of assay methods involving direct titration with iodine. Thus, we have ... 

Thus, potassium iodide plays dual role, viz., in iodimetry—to solubilize iodine in aqueous KI solution, and in iodometry—as reducing agent, the excess KI helps in retaining liberated I2 in solution through interaction with KI. 

Ohno, T., Saito, S., Fujihara, K., Matsumura, M. 1996. Photocatalyzed production of hydrogen and iodine from aqueous solutions of iodide using platinum-loaded TiOj powder. Bull Chem Soc Jpn 69 3059-3064. 

A sample of organolithium compound solution is added to an excess of standardized iodine solution in Et20 the excess iodine is extracted with aqueous KI and titrated with standard thiosulfate solution. Evaluation of the organometallic compound is made according to equation. A possible interference can be expected from the couphng reaction in equation 20. This was shown to be neghgible, as demonstrated spectrofluorometrically for phenyllithium , whereas a low titer was found for n-BuLi, attributable to this side... 

By oxidation of phosphine with an aqueous iodine solution ... 

Iodine in aqueous solution may be measured quantitatively by acidifying the solution, diluting it, and titrating against a standard solution of sodium thiosulfate, sodium arsenite or phenyl arsine oxide using starch indicator. The blue color of the starch decolorizes at the end point. The indicator must be added towards the end of titration when the color of the solution turns pale yellow. Prior to titration, iodine in the dilute acidic solution is oxidized to iodate by adding bromine water or potassium permanganate solution. Excess potassium iodide is then added. The liberated iodine is then titrated as above. 

Sodium iodide is an iodine supplement in food, an expectorant, cloud seed to cause rain, and solubilizes iodine in aqueous solution for analytical work. The radioactive iodide salt of sodium, Na(I-131) is used to diagnose thyroid function. 

Cool the contents of the flasks to approx O t, and set aside two of the flasks for blank determinations. Using a 50-ml graduate cooled by rinsing with portions of die cooled sample, pour 50ml of the sample into each of the other two flasks. Swirl the contents of the flasks to effect soln. Allow the four flasks to stand, at room temp, for at least 10 mins but not more than 30 mins with occasional swirling. Add 10ml of water previously cooled in an ice bath to each flask. Immediately titrate the contents of each of the flasks with 0.1N iodine solution until the yellow color begins to persist, add 5ml of freshly prepared 1.035 aqueous starch indicator, and continue the titration to the first permanent blue end point. Calculate as follows ... 

Various microchemical tests are available for the detection of minute quantities of sulphur, both free and combined. The substance under examination may be treated with a little sodium hydroxide solution, the extract evaporated just to dryness, a few drops of aqueous sodium cyanide (0-1 per cent.) added and the evaporation repeated. The residue, moistened with dilute sulphuric acid and a drop of ferric chloride, gives the characteristic ferric thiocyanate colour if sulphur is present.6 In the ease of minerals, traces of sulphur dioxide produced on heating may be detected 6 by the colour change of an alkaline solution of Bromocrcsol Green or by the deeolorisation of starch-iodine solution. 

W. Gottardi, Redox-Potentiometric/Titrimetric Analysis of Aqueous Iodine Solutions, Fresenius J. Anal. Chem. 1998, 362, 263. 

Thiazolidine-4-carboxylic acid is not stable in the presence of reducing agents, e.g. sodium in liquid ammonia 193 and, in contrast to N-protected Thz, the N-unprotected forms are unstable under oxidizing conditions, e.g. slow ring opening occurs in air at pH 10 in the presence of traces of ferric chloride, or, more rapidly, with hydrogen peroxide, bromine, or iodine in aqueous solution. 190 ... 

The PVA-Iodine complexes formed in PVA films soaked in iodine-KI aqueous solutions without boric acid are studied from the structural point of view. First, iodine soaking at comparatively low iodine concentrations is studied where iodine sorption takes place mostly in the amorphous phase. There, our interest is concentrated on the following problems What happens in PVA films during iodine soaking How does the solid structure of PVA films affect the formation and properties of the complex How does the chain extension affect the complex formation and properties What is the structure of the complex formed in the amorphous phase Then iodine soaking at high iodine concentrations is studied where iodine sorption takes place in the crystal phase as well as in the amorphous phase. 

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