Iodide separation

This experiment describes the quantitative analysis of the asthma medication Quadrinal for the active ingredients theophylline, salicylic acid, phenobarbital, ephedrine HGl, and potassium iodide. Separations are carried out using a Gi8 column with a mobile phase of 19% v/v acetonitrile, 80% v/v water, and 1% acetic acid. A small amount of triethylamine (0.03% v/v) is included to ensure the elution of ephedrine HGl. A UV detector set to 254 nm is used to record the chromatogram. 

Experiments—Dissolve 0-02 g. of cholic acid in 0-5 c.c. of alcohol and add to the solution 1 c.c. of 0-1 A-iodine solution. On cautious dilution with water the blue crystalline iodine compound of cholic acid, comparable to starch iodide, separates. 

Ammino-cupric Iodides.—A solution of ammonia in water docs not dissolve cuprous iodide, but if air be allowed access to the mixture a blue solution is formed, and if the solution be cooled colourless crystals of diammino-cupric iodide separate. From the mother-liquor hydrated tetrammino-eupric iodide may be precipitated by means of alcohol. 

These compounds are all unstable and lose ammonia on heating. Silver iodide is readily soluble in liquid ammonia, and on evaporating the solution at —40° to —10° C. white lamellar crystals of monammino-silver iodide separate.1... 

Pyridino-bismuth Iodide, [Bi(CsHsN)]I3, is formed by treating a eold mixture of bismuth trichloride in pyridine with potassium iodide, when the pyridino-iodide separates as a dark red powder.1 The substance is soluble in alcohol and in aqueous potassium iodide, and separates from a saturated solution in red needle-shaped crystals which decompose on heating. The corresponding quinoline derivative, [Bi(C9H7N)]I3, is also a red crystalline substance, and is produced by boiling quinolino-. bismuth chloride with an aqueous solution of potassium iodide. 

Potassium iodide can also be obtained from the aq. extract of kelp or from the mother liquid remaining after the separation of sodium chloride and potassium sulphate from sea-water by evaporation. In E. Allary and J. Pellieux process,8 the liquid is evaporated to dryness and roasted in a special furnace so as to avoid a loss of iodine. The product is fractionally extracted with cold water, when a soln. is obtained which on evaporation gives a residue with 50 per cent, of alkali iodide. This product is extracted.in a special digester with 50 per cent, alcohol. The solvent dissolves little more than the iodides. The alcohol is distilled off, and on evaporation a residue containing about 34 per cent, of potassium iodide, and 66 per cent, of sodium iodide is obtained. To convert the latter into potassium iodide, the proper quantity of a soln. of potassium carbonate is added and carbon dioxide passed into the liquid whereby sodium bicarbonate is precipitated. The precipitate is separated by a filter press, and the small amount of sodium bicarbonate remaining in the soln. is separated by the addition of a little hydrochloric acid and the sodium chloride and potassium iodide separated by fractional crystallization. In E. Sonstadt s process, the mother liquid is treated with chlorine mixed with potassium chlorate or permanganate so as to convert the iodine into iodate. A soln. of a barium salt is added, and the barium iodate treated with potassium sulphate. Barium sulphate is precipitated, and the soln. of potassium iodate is evaporated to dryness and calcined to convert the iodate to iodide. The latter is purified by crystallization. 

This compound is formed by the interaction of silver thiocyanate and cyanogen iodide in ether solution, silver iodide separating out 5... 

Triethyl selenium iodide, (C2Hg)3SeI.—When diethyl selenide and ethyl iodide are mixed together in molecular proportions, combination slowly takes place at room temperatures. White crystals of the iodide separate out. These sublime completely between 80° and 126° C. without melting, undergoing dissociation into diethyl selenide and ethyl iodide, which, if collected in a receiver, recombine in twelve hours to re-form the iodide. The iodide is stable in air, non-hygroscopic, but readily soluble in water or alcohol, sparingly soluble in ether.4... 

Dibenzyl selenium di-iodide, (C6H5.CH2)2SeI2.—When dibenzyl selenide is heated with iodine in chloroform solution, dark violet crystals of the di-iodide separate, M.pt. 97° C. The halogen in this and the foregoing compound is removed by alkali, silver oxide or silver acetate. 

Chromium triphenyl iodide, (CeHg CrlXgHg.O.CaHg, is obtained by the interaction of potassium iodide or hydriodic acid and an aqueous solution of the base in the presence of chloroform. The aqueous layer is discarded, the chloroform solution dried, the bulk of the solvent removed at 40° to 50° C. in vacuo and the residue added dropwise to eight or ten volumes of dry ether. The iodide separates as an oil which gradually solidifies. The salt is hygroscopic, can be preserved for some time over concentrated sulphuric acid in a vacuum, but is unstable in air. It dissolves more readily in hot than cold water, and i also soluble... 

The solution contains part of the base in the form of its iodate, and is therefore first treated with sulphur dioxide, and then with excess of potassium iodide solution, when the iodide separates out completely. It is recrystallised from alcohol. 

Silver iodide sol. Mix equal volumes of aqueous solutions (10 3 to 10 2 mol dm-3) of silver nitrate and potassium iodide. Separate the sol from larger particles by decantation or filtration. By arranging for the silver nitrate or the potassium iodide to be in very slight excess, positively or negatively charged particles, respectively, of silver iodide can be formed. 

Iridium Tri-iodide, Irl3.—This salt is stated to occur 3 when potassium iodiridate and ammonium chloride solutions are mixed, iodine and the tri-iodide separating out. The former is removed by treating with alcohol, the tri-iodide being left as a greenish powder. 

Reagent. Dissolve 1 g of bismuth subnitrate in 3 ml of lOM hydrochloric acid with the aid of heat, dilute to 20ml with water, and dissolve in the mixture 1 g of potassium iodide. If black bismuth tri-iodide separates, add 2M hydrochloric acid and more potassium iodide to dissolve it. 

Methylsulfanyl)quinazoline (17.6 g, 0.1 mol) and anhyd Mel (17.6 mL) were mixed and heated under reflux on a water bath for 4 h. The orange-yellow l-methyl-4-(methylsulfanyl)quinazolinium iodide separated rapidly as a hard mass yield 28.8 g (90%), It was ground with anhyd EtjO and anhyd acetone and recrystallized from EtOH (1 g in 50mL) mp2l7-219°C. 

These mercurated naphthylamine sulphonic acids react immediately with halogen halides, the mercury being freed, and in the case of potassium iodide solution mercuric iodide separates. 

Lead triphenyl iodide. —If the mother-liquors of the above bromide be treated with potassium iodide, and the product obtained crystallised from water, the iodide separates in pale yellow prisms, which sinter at 189 C. and melt sharply at 142 C. to a canary yellow liquid, which soon deposits lead iodide. It is difficultly soluble in liot methyl alcohol, and insoluble in water, and is distinguished from all the other lead aryl or alkyl iodides by its stability. It does not appear to yield an oxide with alcoholic sodium or potassium hydroxide, but a white precipitate is thrown down, this yielding lead triphenyl chloride with 50 per cent, hydrochloric acid. 

This compound is formed by oxidation of p-diamidodiphenyl-amine, or of a mixture of equal molecules of paraphenylenediamine and aniline. It is the simplest member of the indamine series, and its salts are greenish blue and are mostly soluble in water. Acids turn the solutions green, and rapid decomposition, with formation of quinone, sets in. The iodide separates in long brilliant green crystals from a mixture of the hydrochloride and potassium iodide. Indamine, on reduction, yields paradiamido-diphenylamine. On heating with a solution of an aniline-salt, phenosaffranine is formed. 

This precursor of dimethylsulfonium methylide is prepared in almost quantitative yield by mixing dimethyl sulfide (6 g.) and methyl iodide (14 g.). The sulfonium iodide separates as a solid cake and after 24 hrs. it is collected, crystallized from ethanol, and washed with ether. 

Fig. 3-69. Dependence of the net retention volume of various inorganic anions on the concentration of a) phthalate, b) trimesate, c) o-sulfobenzoate, and d) iodide. - Separator column 250 mm X 2.8 mm I.D. SAR-40-0.6 (taken from [81]).

We exemplify the preparation of a higher alkoxybenzaldehyde by that of /7-octyloxybenzal-dehyde / -Hydroxybenzaldehyde (6.1 g, 0.05 mole) and potassium hydroxide (4 g) are dissolved in cyclohexanol (50 ml) and mixed with a solution of octyl iodide (14.4 g, 20% excess) in cyclohexanol (50 ml). The mixture is then stirred vigorously for 4 h in an oil-bath at 120-130° potassium iodide separates. After cooling, the mixture is taken up in ether, washed with water and with dilute hydrochloric acid, dried over sodium sulfate, freed from ether, and fractionated in a vacuum. The mixed ether distils at 162-163°/4 mm (7.6 g, 65 %). 

Metalation of A-acetyl-2-naphthylamine requires a somewhat higher temperature. For preparation of. /V-methyl-2-naphthylamine486 the acetyl amine is boiled with the calculated amount of sodium in toluene. An equimolar amount of methyl iodide is added without isolation of the sodium salt sodium iodide separates and is filtered off. The toluene solution is then boiled with dilute hydrochloric acid the toluene is then extracted with ether, and the aqueous solution is made alkaline. The oil that separates distils in a vacuum at 165-170°/ 12 mm (yield 55%). 

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