Iodine in water

An aqueous solution of hydrogen iodide, up to 50% strength, may be prepared by passing hydrogen sulphide (or sulphur dioxide) into a suspension of iodine in water ... 

In view of the chromophoric character of the elemental iodine itself, many colorimetric methods have been proposed for the deterrnination of inorganic iodine (88—92). These methods use the visible portion of the spectmm in reading iodine concentrations. In the visible range the extinction coefficient for iodine is not high enough to be used for minute quantities of iodine in water and other solvents (93). Higher sensitivities have been reported for elemental iodine in potassium iodide solutions in the ultraviolet (93,94). 

From this solution, prepare 25.0 mL of a 0.00025 M solution of iodine in water. Pour this entire solution into a 125-mL separatory funnel. Stopper the funnel. 

G. N. Lewis proposed the term escaping tendency to give a strong kinetic-molecular flavor to the concept of the chemical potential. Let us consider two solutions of iodine, in water and carbon tetrachloride, which have reached equilibrium with each other at a flxed pressure and temperature (Fig. 9.2). In this system at equilibrium, let us carry out a transfer of an inflnitesimal quantity of iodine from the water phase to the carbon tetrachloride phase. On the basis of Equation (9.17), we can say that... 

Iodine in water also may be determined by the Leucocrystal violet colorimetric method. An aqueous sample is treated with mercuric chloride followed by Leucocrystal violet reagent [4,4 ,4 —methylidynetris(N,N-dimethylani-hne)] in the pH range 3.5 to 4.0. A violet color is produced. The absorbance or transmittance is measured at 592 nm by a spectrophotometer or filter photometer. Iodine concentration is calculated from a standard calibration curve. 

Oxidation of dithizone (414) with selenium dioxide or iodine in water gives the disulfide (417) which then disproportionates on standing, yielding dithizone (414) and dehydrodithizone (413, R = R = Ph). This is closely analogous to the disproportionation 254 251 + 253. 

There are some complications. As we know from Section 13.6, iron(III) ions tend to hydrolyze in aqueous solution unless the pH is very low. Accordingly, it is understood that, unless otherwise stated, E° values refer to measurements in 1.0 mold acid solution, even if the hydrogen ions do not explicitly appear in the balanced redox equation (e.g., reaction 15.12). Second, iodide ion actually reacts with iodine in water to give brown I3- ... 

Blandamer et al (1964) pointed out that the absorption spectrum of iodine ions (I ) in NH3 has its maximum at Jtv=4.0eV the difference from that for an electron in a cavity, 4.0-0.8= 3.2eV, corresponds well to the electron affinity of iodine. In water the maxima for both I and a solvated electron are shifted by 0.8 eV to higher frequencies we deduce that the energy of the bottom of the conduction band in water is about 0.8 eV. 

The solubility of iodine in water has not been so closely investigated as that of chlorine or bromine,4 and the determinations are not in close agreement. H. Hartley and N. P. Campbell found that water dissolves... 

Pour water into two test tubes and lower one crystal of the iodine prepared in the preceding experiments into each of them. Vigorously shake the contents of the tubes. What is the solubility of iodine in water Write the equation of the reaction of iodine with water. 

Decarboxylation of halofurancarboxylic acids is usually carried out with copper and quinoline at 150-230 °C and the product often distills from the reaction mixture (71BSF242). Heating chloromercuriofurans with iodine and potassium iodide in water yields iodofurans. Thus 3,4-bis(chloromercurio)-2,5-dimethylfuran yields the diiodo compound (41%), and tetrakis(chloromercurio)furan yields tetraiodofuran (67%). Boiling sodium furan-2,5-dicar-boxylate with potassium iodide and iodine in water yields the diiodofuran, and 2,5-dibromofuran (78%) is similarly available from sodium 5-bromofuran-2-carboxylate, potassium bromide and bromine (74ZOR1341). 

The chemical basis for the phosphite triester approach is the observation, that dialkyl phos-phorochloridites such as (CjHjOJjPCI react very rapidly at the 3 -OH of nucleosides in pyridine even at low temperatures. In contrast, the reactions of analogous chloridates, e.g. (C2HjO)2POCIi require several hours at room temperature. It was later found that phosphite esters can be oxidized quantitatively to the phosphates by using iodine in water and that clean condensation of phosphorochloridites with nucleosides can be achieved in THF at -78 °C. To develop this chemistry into a useful synthetic procedure it was necessary to establish which... 

Vinylsilanes can be desilylated stereoselectively upon treatment with iodine in water (equation 3)36,37. Under basic conditions, TBAF-mediated stereoselective desilylation proceeds smoothly38. Although desilylation of a vinylsilane can readily be achieved by treatment with hydroiodic acid, selective destannation is observed when a substrate contains both stannyl and silyl groups at the olelinic carbons (equation 4)39. 

Potassium iodide also enhances the solubility of iodine in water. 

A saturated solution of iodine in water contains 0.33 g I2 per liter. More than this can dissolve in a KI solution because of the following equilibrium ... 

Problem 9 At 25°C, the distribution coefficient of iodine between CCl4 and water is 85. If at 25 °C, the solubility of iodine in water is 0.33 g/litre, determine the solubility of iodine in CCI4. 

On the other hand, the reactivity of the anions (obtained in the acid dissociations of imidazole and pyrazole) is, of course, very much higher. On iodination in water, the reactivity of the pyrazole anion C3H3N2- has been estimated to be greater than that of the neutral molecule by a factor in the range of 3 x 109 to 7 x 1012, or perhaps even larger.105... 

The solubility of iodine in water is 0.00134 moles per liter. The apparent solubility of iodine in 0.007 molar KI (as determined from the concentration of titratable iodine) is 0.0048 molar. Calculate the apparent solubility of iodine in 0.10 molar KI. 

I. 45 THE DISTRIBUTION OR PARTITION LAW It is a well-known fact that certain substances are more soluble in some solvents than in others. Thus iodine is very much more soluble in carbon disulphide, chloroform, or carbon tetrachloride than it is in water. Furthermore, when certain liquids such as carbon disulphide and water, and also ether and water, are shaken together in a vessel and the mixture allowed to stand, the two liquids separate out into two layers. Such liquids are said to be immiscible (carbon disulphide and water) or partially miscible (ether and water), according as to whether they are almost insoluble or partially soluble in one another. If iodine is shaken with a mixture of carbon disulphide and water and then allowed to settle, the iodine will be found to be distributed between the two solvents. A state of equilibrium exists between the solution of iodine in carbon disulphide and the solution of iodine in water. It has been found that when the amount of iodine is varied, the ratio of the concentrations is constant at any given temperature. That is ... 

The calcium salt is soluble in water, unlike that of phosphite or phosphate the free acid can be made from it or obtained by oxidation of phosphine with iodine in water. Both the add and its salts are powerful reducing agents, being oxidized to orthophosphate. The pure white crystalline solid is a monobasic acid (pK = 1.2). The more correct name of this acid, phosphinic acid, is rarely used, but when the... 

In a similar way, 3-phenyl-4-pentenoic acid (3) is lactonized in almost quantitative yield and a cis/trans ratio of 94 6 when treated with iodine in water/chloroform in the presence of sodium hydrogen carbonate183. 

The Partition of a Solute between Two Solvents. If a solution of iodine in water is shaken with chloroform, most of the iodine is transferred to the chloroform. The ratio of concentrations of iodine in the two phases, called the distribution ratio, is a constant in the range of small concentrations of the solute in each solution. For iodine in chloroform and water the value of this ratio at room temperature is 250 hence whenever a solution of iodine in chloroform is shaken with water or a solution in water is shaken with chloroform until equilibrium is reached the iodine concentration in the chloroform phase is 250 times that in the water phase. 

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