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Starch-iodine paper

A stirred soln of H-L-Phe(4-NH2)-OH (21 54 g, 300 mmol) in 4 M HC1 (600 mL) was cooled in a MeOH/ ice bath and treated slowly with aq NaN02 (20.7 g, 300 mmol). The mixture was kept for 1 h under vacuo (until negative to HN02 in the starch-iodine paper test). The soln of the diazonium salt was mixed slowly into 20% HC1 (400 mL) containing CuCl (10 g) and Cu powder (3g). After the cessation of gas release, the mixture was left overnight at 4 °C, the precipitate was filtered off (53 g of hydrochloride) and the filtrate was concentrated under vacuo and filtered again (9.2g) combined yield 61.2g (86%). [Pg.91]

The reaction then takes place and its progress is checked until the absence of nitrous ions. After 40 minutes, the presence or absence of nitrous ions is checked at regular intervals in the reaction medium. Starch-iodine paper, for example, is used, checking every 5 minutes. After about 60 minutes of reaction, the nitrous acid had been entirely consumed and no more N02" ions remained in the reaction medium. The pH was then adjusted to 7 with pure caustic soda, and the products of the reaction were recovered by the addition of 31 liters of pure ethanol (2 volumes). The precipitate formed was collected by centrifugation, washed with ethanol and dried at 60°C under vacuum. [Pg.1190]

A solution of AcOF (15 mmol) in 1 lOAc was added dropwlse lo a stirred solution of 1 (383 mg. 10 mmol) in CHCl, (100 niL) at 0 C. When no more AcOF was present (starch iodine paper) the mixture was poured into H,0 (500 mL). washed with NallCO, soln until neutral, dried (IVlgSO ), and conceniraied under reduced pressure. The residue was purified by flash chromaiography (5% ElOAe/pctrolcum elher) yield 132 mg (80%). [Pg.10]

Hydroperoxides in ethers can be detected by shaking a small amount of the ether with an acidified 10% aqueous solution of potassium iodide, KI, or by using starch iodine paper with a drop of acetic acid. Peroxides oxidize iodide ion to iodine, I2, which gives a yellow color to the solution. Hydroperoxides can be removed by treating them with a reducing agent. One effective procedure is to shake the hydroperoxide-contaminated ether with a solution of iron(ll) sulfate in dilute aqueous sulfuric acid. You should never use ethers past their expiration date, and you should properly dispose of them before then. [Pg.493]

Jod-saure, /, iodic acid, -schwefel, m. sulfur iodide, -serum, n. iodized serum, -silber, n. silver iodide, -silizium, n. silicon iodide. -stSrke, /. starch iodide, iodized starch. -stSrkepapier, n. starch iodide paper, -stick-stoff, m. nitrogen iodide, -thymol, n.iPhaTm.) thymol iodide, -tinktur,/. tincture of iodine, -toluol, n. iodotoluene. -iibertrilger, m. iodine carrier. [Pg.230]

Bromine (Br2> displaces iodine from a solution of potassium iodide and, as a consequence, the iodine turns starch blue-black. (Starch-iodide paper may also be used.)... [Pg.56]

In other words, the small excess of HN02 present at the end-point can be detected visually by employing either starch-iodide paper or paste as an external indicator. Thus, the liberated iodine reacts with starch to form a blue green colour which is a very sensitive reaction. Besides, the end-point may also be accomplished electrometrically by adopting the dead-stop end-point technique, using a pair of platinum electrodes immersed in the titration liquid. [Pg.208]

A commun means of detecting hypochlorites is the production of u blue color (caused by free iodine) with starch iodide paper by hypochlorites in weakly alkaline solution. Silver nitrate also precipitates part of the hypochlorite in solutions as white silver chloride. [Pg.815]

The corresponding sodium salts, which are cheaper, serve equally well. Excess of potassium bromide and hydrochloric acid is added to a solution of the substance to be estimated and the bromate, in the form of a volumetric solution (usually N/5), is run in. The end point (shown by the presence of free bromine) is detectable, quite sharply, by spotting on starch-iodide paper as external indicator. Alternatively the end point may be determined by adding a known amount of bromate in excess, then potassium iodide, and titrating the liberated iodine with thiosulphate. [Pg.500]

Detection is made in UV light. The yellow fluorescence of tetracyclines and their epimers in UV light is greatly enhanced by exposing the paper to ammonia vapours. They may also be detected by Ehrlich s reagent or by starch-iodine following N-chlorination (137). [Pg.629]

The iodine which separates may be recognised either by the reddish-violet colouration which it imparts to chloroform or to carbon disulphide, or by the blue colouration which is produced with starch solution. This latter reaction can be adapted in practice by employing starch-iodide paper, which when exposed even for a short period to an atmosphere containing chlorine assumes a blue colour more or less intense according to the concentration of chlorine present. According to the experiments of Smolczyk a content of 14 mgm. chlorine per cu. m. of air produces a change in the colour of starch-iodide paper within 3-5 seconds. [Pg.41]

If the base is slightly soluble in acid, as in the case of those arylamines which have very feeble basic properties, a large excess of acid is used, or a suspension of the finely divided base is diazo-tized. The base dissolves as fast as that portion which is in solution is diazotized. The aminosulfonic and aminocarboxylic acids are diazotized by first dissolving in alkali to form the sodium salt and then adding the calculated amount of nitrite. The mixture is cooled and added slowly to a solution of acid. The end of all diazotizations is recognized by the presence of,free nitrous acid in the solution. As a test of this, a drop of the solution of the diazonium salt placed on starch-iodide paper produces a dark blue stain immediately, due to the oxidation of iodide by nitrous acid to iodine and action of the latter on starch. [Pg.272]

Add dropwise 1 % NaNO with constant stirring at 4 C. Large excess of NaNO should be avoided. This can be checked with starch-iodide paper or, alternatively, with 1% starch and 50 mM KI on a white tile. Free nitrous acid oxidizes iodide to iodine which reacts with starch to give a blue-black color. [Pg.286]

Starch Test Paper. From a cold decoction of starch free iodine turns it blue. [Pg.277]

Observation Behavior of aqueous iodine toward starch-KI paper... [Pg.522]

Chlorine (Cl"). A dark blue color of starch-potassium iodide paper, due to the formation of a starch-iodine complex, indicates the presence of CI2. Be careful reddish-brown NO2 gas and Br2 gas may cause a faint test. [Pg.563]

Iodine-metal alginate compound... Sodium alginate reacts with iodine and under acid gives a blue stained adduct like a starch-iodine inclusion complex. In this paper results for film form metal alginate are presented. The effect of pH on the formation of a blue stained adduct is shown in Figure 4A. At about pH 1 the formation reaches the maximum. The amount of the adduct shows an increase with iodine concentration and... [Pg.404]

What was the purpose of testing the reaction mixture with starch/iodide paper Illustrate your answer by showing the chemical reaction that transforms iodide ion into iodine in this test. [Pg.545]

If carried out on filter paper containing a little starch, even minimal quantities of the resulting blue starch-iodine are easily seen because of fixation on the surface of the paper, and through contrast with the white background. Most spot papers already contain sufficient starch. Oxidizing agents that liberate iodine from iodides in acid solution must be absent. [Pg.366]

Quantitative Determination of Free Chlorine. The gas mixture can be shaken with a potassium iodide solution, and the liberated iodine can be then determined by titration. Chlorine in alkaline solution can be reduced to chloride by potassium or sodium arsenite, and the arsenite can be then oxidized to arsenate. The end point is detected by spot tests with starch-iodide paper. Excess arsenite is back-titrated with acidified potassium bromate solution. Small amounts of chlorine, e.g. in drinking water, can be determined by photometric measurement of the yellow color produced by the reaction with o-tolidine in hydrochloric acid solution [281]. [Pg.158]


See other pages where Starch-iodine paper is mentioned: [Pg.102]    [Pg.1189]    [Pg.55]    [Pg.263]    [Pg.55]    [Pg.55]    [Pg.263]    [Pg.102]    [Pg.1189]    [Pg.55]    [Pg.263]    [Pg.55]    [Pg.55]    [Pg.263]    [Pg.464]    [Pg.154]    [Pg.264]    [Pg.268]    [Pg.296]    [Pg.298]    [Pg.384]    [Pg.396]    [Pg.84]    [Pg.372]    [Pg.63]    [Pg.176]    [Pg.373]    [Pg.417]    [Pg.641]    [Pg.566]    [Pg.143]    [Pg.351]    [Pg.355]    [Pg.591]   


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