Zinc iodide test

Zinc Iodide Test. A Ger modification of Abel s Test or the K iodide—starch test (see Vol 1, A2-L) in which Zn iodide is used in place of K iodide, thus rendering the test more sensitive. The conditions of testing are given by Kast and Metz... 

Attempts were made at an early date to overcome the masking of the te.st by the use of other indicators in place of potassium iodide and starch. The zinc iodide test is, of course, open to the same criticisms. 

Apparently the role of methanol is to intercept unstable species which otherwise tend to polymerize or rearrange. The methoxy peroxide (72) can be isolated in crystalline form if desired, but it is preferable to treat the methylene dichloride solution at 0° with zinc dust and acetic acid until the mixture shows a negative potassium iodide test. The resulting crude seco-aldehyde (73) is then cyclized to (74) by stirring with neutral alumina in benzene at room temperature for 3 hr. ° Wechter has recently reported a number of transformations of a 5yS-hydroxy-6yS-formyl-B-norpregnane prepared in 8% yield by photolysis and hydrolysis of a 5a-hydroxy-6 -azidopregnane. 

Hess Test. In this test, a sample of an explosive was heated at 70° in a current of air which was then passed into a solution of zinc iodide and starch. The time taken to impart a blue color to the solution was noted (Ref 2)... 

Metz(Ref 3) compared Brunswig s Test method with other quantitative stability tests(such as Mayrhofer, Mayrhofer-Will, Hansen and the 85° 110° Hydrolysis Tests) and with qualitative tests(such as Abel the 134.5° Heat Tests). Brunswig s method is indicated to be applicable only to extremely stable powders. For example, if a powd is of moderate stability and just passes other quantitative tests, it might not pass Brunswig s Test. On the other hand, if a powd passes Btunswig s Test it usually passes other quantitative tests but may not pass qualitative tests, such as Abel s, Zinc-Iodide-Starch Test others... 

This is a German modification of the heat test. Zinc iodide is used in place of potassium iodide. This renders the test rather more... 

Test papers may be impregnated with zinc iodide and starch. 

Chlorine is more potent an oxidant than is bromine but less so than fluorine (Clifford, 1961a). Thus, chlorine is able to oxidize both bromide and iodide ions to Br2 and I2, respectively, whereas fluorine oxidizes chloride, bromide, and iodide to their corresponding halogens. The oxidizing ability of chlorine is the basis for the starch-iodide test for chlorine. Here, a mixture of potassium iodide, soluble starch, and zinc chloride produces a blue-violet color in the presence of chlorine. Unfortunately, and like many spot tests, this is a nonspecific test and gives a positive result with many oxidants, for example, bromine. 

Immediately determine the voltage of your galvanic cell by connecting the wires to the proper terminals of the voltmeter as indicated by your starch-potassium iodide test. Continue to read the voltmeter for several minutes to make sure that you observe the maximum voltage of your cell. Record the maximum voltage in TABLE 29.lA. Remove the zinc electrode, clean it, and return it to the reagent shelf. 

Halide exchange, sometimes call the Finkelstein reaction, is an equilibrium process, but it is often possible to shift the equilibrium." The reaction is most often applied to the preparation of iodides and fluorides. Iodides can be prepared from chlorides or bromides by taking advantage of the fact that sodium iodide, but not the bromide or chloride, is soluble in acetone. When an alkyl chloride or bromide is treated with a solution of sodium iodide in acetone, the equilibrium is shifted by the precipitation of sodium chloride or bromide. Since the mechanism is Sn2, the reaction is much more successful for primary halides than for secondary or tertiary halides sodium iodide in acetone can be used as a test for primary bromides or chlorides. Tertiary chlorides can be converted to iodides by treatment with excess Nal in CS2, with ZnCl2 as catalyst. " Vinylic bromides give vinylic iodides with retention of configuration when treated with KI and a nickel bromide-zinc catalyst," or with KI and Cul in hot HMPA." ... 

The effect of metal promoter species on the rate of carbonylation of [Ir(CO)2l3Me] was tested. Neutral ruthenium iodocarbonyl complexes such as [Ru(CO)3l2]2> [Ru(CO)4l2] or [Ru(CO)2l2]n were found to give substantial rate enhancements (by factors of 15-20 for a Ru Ir ratio of 1 13 at 93 °C, PhCl). Indium and gallium triiodides and zinc diiodide had comparable promotional effects. By contrast, addition of anionic ruthenium(II) species [Ru(CO)3I3] or [Ru(CO)2I4]2 did not lead to any appreciable promotion or inhibition. This behaviour indicates that the ability to accept an iodide ligand is a key property of the promoter. Indeed, it has been demonstrated that an iodide ligand can be transferred from [ Ir(C0)2l3Me] to neutral ruthenium or indium species [73,74],... 

Immediately upon connecting the cell to a source of direct current, a deposit of gray metallic zinc appears on the surface of the cathode and bubbles of chlorine gas appear at the surface of the anode. A simple chemical test for chlorine may be made by leading this gas into an aqueous sodium iodide solution, whereupon the solution assumes a yellow color caused by displacement of iodine by chlorine. Accordingly, it is concluded that the products of the electrolysis of a zinc chloride solution are elemental zinc and elemental chlorine, and the next problem is that of explaining the mechanism by which these products may be produced. 

In a more recent study Co(dppe)I2 was used as a catalyst for reductive additions of primary, secondary, and tertiary alkyl bromides or iodides 249 to alkyl acrylates, acrylonitrile, methyl vinyl ketone, or vinylsulfone 248 in an acetonitrile/water mixture using zinc as a stoichiometric reducing agent [305]. The yields of the resulting esters 252 were mostly good. The authors tested radical probes, such as cyclopropylmethyl bromide or 6-bromo-1-hexene (cf. Part 1, Fig. 8). However, the latter did not cyclize, but isomerized during addition, while the former afforded complicated mixtures. On this basis the authors proposed a traditional two-electron mechanism to be operative the results do not, however, exclude a radical-based Co(I) catalytic cycle convincingly (Fig. 61). 

Procedure Transfer 50.0 mL of the Sample Solution into the generator flask, add 2 mL of a 15 100 solution of potassium iodide, and continue as directed in the Procedure under Arsenic Limit Test, Appendix IIIB, beginning with [add] 0.5 mL of Stannous Chloride Solution, and mix.. .. Modify the Procedure by using 5.0 g of Devarda s metal in place of the 3.0 g of 20-mesh granular zinc, and maintain the temperature of the reaction mixture in the generator flask between 25° and 21°. Treat 50.0 mL each of the Standard Solution and of the Blank Solution in the same manner and under the same conditions. Determine the absorbance at 525 nm produced by each solution as directed under Procedure. 

The iodide-treated paper samples were exposed for 88 h at 60° C and 60% relative humidity to the sunlamp and compared with the similarly exposed controls containing zinc oxide but no iodide. After exposure, the samples were conditioned and tested for MD fold endurance, with the results shown in Table III. 

If silver is found, the halogen with which the metal was originally combined is identified by melting another portion of the insoluble substance, immersing it in dilute sulphuric acid, placing a piece of zinc in contact with the acid and the fused mass, warming and allowing to stand for a few minutes. The silver salt is reduced to metallic silver, whilst the anions are present in solution in the presence of zinc ions, i.e. as zinc salts. Filter. The filtrate is tested for chloride, bromide, and iodide in the usual manner the tests for mixtures of these anions are described in Section IV.45, and in Section V.18, Table V.30. 

Nitrate in the presence of bromide and iodide The brown ring test for nitrates cannot be applied in the presence of bromides and iodides since the liberation of free halogen with concentrated sulphuric acid will obscure the brown ring due to the nitrate. The solution is therefore boiled with sodium hydroxide solution until ammonium salts, if present, are completely decomposed, and the solution is then cooled under the tap. Powdered Devarda s alloy or aluminium powder or zinc dust is then added and the mixture gently warmed. The evolution of ammonia, detected by its smell, its action upon red litmus paper and upon mercury(I) nitrate paper (see Section III38, reaction 1) indicates the presence of a nitrate. 

Preparation of Autocomplex Cadmium Iodide. Pour 20 ml of a 10% cadmium sulphate solution into a test tube and lower a plate of metallic zinc into it. What do you observe ... 

If Kdlliker s apparatus is used to determine phosgene in presence of hydrochloric acid, zinc dust cannot be used as it has too great a resistance. In this case the gas mixture to be tested is first passed through a wash bottle containing a sulphuric acid solution of silver sulphate (3 gm. in 100 ml. sulphuric acid of S.G. 1 84) and then through the acetone solution of sodium iodide. 

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