Iodine atmosphere

Summary Iodine was inserted into the voids of crystalline microporous materials built from pure SiOz (zeosils), namely UTD-1 (DON), SSZ-24 (AFI), CIT-5 (CFI), and ITQ-4 (IFR), by vapor phase loading. All these hosts possess large pores. Their iodine insertion compounds exhibit characteristic colors. The properties of these compounds were further studied by powder X-ray diffraction, UV-Vis and Raman spectroscopy. It turned out that the insertion compounds of the large-pore zeosils are unstable when removed from a saturated iodine atmosphere, a property in which they differ from the iodine insertion compounds of medium-pore zeosils. This instability hampered the characterization of these substances. 

As part of the biogeochemical cycle, the injection of iodine-containing gases into the atmosphere, and their subsequent chemical transformation therein, play a crucial role in environmental and health aspects associated with iodine - most importandy, in determining the quantity of the element available to the mammalian diet. This chapter focuses on these processes and the variety of gas- and aerosol-phase species that constitute the terrestrial iodine cycle, through discussion of the origin and measurement of atmospheric iodine in its various forms ( Sources and Measurements of Atmospheric Iodine ), the principal photo-chemical pathways in the gas phase ( Photolysis and Gas-Phase Iodine Chemistry ), and the role of aerosol uptake and chemistry and new particle production ( Aerosol Chemistry and Particle Formation ). Potential health and environmental issues related to atmospheric iodine are also reviewed ( Health and Environment Impacts ), along with discussion of the consequences of the release of radioactive iodine (1-131) into the air from nuclear reactor accidents and weapons tests that have occurred over the past half-century or so ( Radioactive Iodine Atmospheric Sources and Consequences ). 

Vikis and MacFarlane (1985) reported on reaction rates between I2 and O3 and the resultant formation of solid-phase iodine oxide aerosol. Coming from the opposite direction to the earlier work of Hamilton et al. (1963), this led the authors to suggest that the addition of O3 to nuclear reactor environments should be considered as a practical route for the removal of air-borne radioactive iodine species produced as fission by-products (see Radioactive Iodine Atmospheric Sources and Consequences ). 

The thin-layer chromatography (TLC) method was used for purifying the intermediary products obtained from the synthesis of the oligonucleotide dendrimers. The separations were performed on silica gel plates using various solvent mixtures as mobile phases, e.g., methanol-methylene chloride (1 9, v/v), methanol-chloroform (1 30, 1 9, v/v), hex-ane-dichloromethane (1 3, v/v), hexane-ethyl acetate (3 1, 1 1,4 1, v/v). The separated compounds were visualized in an iodine atmosphere. 

In general, the whole of the reactor unit, including joints and valves, must operate in an iodine atmosphere at temperatures above 230°C. Gaskets have been made of Teflon, lead and aluminium wire but, in practice, none are as satisfactory as gold wire. The cost is reduced by recovery after use, whereas gaskets of other materials are completely expendable. The type of joint employed is shown in Fig. 8.2. 

Place the TLC plate in an iodine atmosphere for 5-10 min to stain for the added PtdBnOH and mark this area with a pencil. The Retention factor (Rf) shonld be approximately 0.3-0.4. 

Fig. 163. Separation of novalgin (1), phenazone (2), aminop5rrine (S), ethenzamide (4), sahcylamide (5), phenylbutazone (5), mixture G). Layer silica gel H solvent cyclohexane-acetone (40 + 50) CS 10 cm run detection exposure to iodine atmosphere amounts applied 10 jxg of 1, 2, 3, 5 and 6 about 30 jig of 4...

Like RbAg I potassium silver iodide is a silver ion conductor. The working electrode was of the point type.An iodine atmosphere was maintained over the electrolyte. It was obtained by flushing an argon flow over thermostated so 1 id iodine. Iodine pressure varied from 10 to 10 " atm. 

Acetaldehyde condenses in the presence of a little sodium sulphite or sodium hydroxide solution to aldol. The latter ehminates water upon distUlation at atmospheric pressure, but more efficiently in the presence of a trace of iodine, which acts as a catalyst, to yield crotonaldehyde ... 

Iodine monochlorlde may be prepared as follows. Pass dry chlorine into 127 g. of iodine contained in a 125 ml. distilling flask until the weight has increased by 34-6 g. The chlorine should be led in at or below the surface of the iodine whilst the flask is gently shaken it is essential to have an excess of iodine. Distil the iodine chloride in an ordinary distillation apparatus use a filter flask, protected from atmospheric moisture by a calcium chloride (or cotton wool) guard tube, as a receiver. Collect the fraction b.p. 97-105° the jdeld is 140 g. Preserve the iodine monochloride in a dry, glass-stoppered bottle. 

The importance of ozone in the stratosphere has been stressed in Section 9.3.8. The fact that ozone can be decomposed by the halogen monoxides CIO, BrO and 10 means that their presence in the stratosphere contributes to the depletion of the ozone layer. For example, iodine, in the form of methyl iodide, is released into the atmosphere by marine algae and is readily photolysed, by radiation from the sun, to produce iodine atoms which can react with ozone to produce 10 ... 

CgH Cl, is produced commercially in the Hquid phase by passing chlorine gas into benzene in the presence of molybdenum chloride at 30—50°C and atmospheric pressure. This continuous process yields a 14 1 ratio of chlorobenzene to j -dicblorobenzene [106-46-7J, The reaction of iodine with... 

The mixture is cooled to room temperature, then filtered. The solvent is removed under reduced pressure, leaving the tribromide (47) as a foam. The foam is mixed with sodium iodide (9.55 g, 0.064 mole) and acetone (74 ml) and heated under reflux in a nitrogen atmosphere for 3.5 hr. The acetone is removed under reduced pressure and the residue is treated with chloroform and aqueous sodium thiosulfate solution. The chloroform layer is separated and washed with sodium thiosulfate solution until it is free from iodine, then dried over magnesium sulfate, filtered and evaporated to dryness under reduced pressure. The crude product (48) is obtained as a brown sohd (4.85 g) which is chromatographed over alumina (122 g, Merck acid-washed). The column is developed with hexane, benzene and ethyl acetate mixtures. The product (3.43 g) is eluted by benzene and benzene-ethyl acetate (10 1). Recrystallization from acetone yields purified 3jS-acetoxy-pregna-5,14,16-trien-20-one (48), 3.25 g, mp 158-159° 309 m/ (e 10,700). 

Alternative procedure. The following method utilises a trace of copper sulphate as a catalyst to increase the speed of the reaction in consequence, a weaker acid (acetic acid) may be employed and the extent of atmospheric oxidation of hydriodic acid reduced. Place 25.0 mL of 0.017M potassium dichromate in a 250 mL conical flask, add 5.0 mL of glacial acetic acid, 5 mL of 0.001M copper sulphate, and wash the sides of the flask with distilled water. Add 30 mL of 10 per cent potassium iodide solution, and titrate the iodine as liberated with the approximately 0.1M thiosulphate solution, introducing a little starch indicator towards the end. The titration may be completed in 3-4 minutes after the addition of the potassium iodide solution. Subtract 0.05 mL to allow for the iodine liberated by the copper sulphate catalyst. 

Procedure. The water sample should be collected by carefully filling a 200-250 mL bottle to the very top and stoppering it while it is below the water surface. This should eliminate any further dissolution of atmospheric oxygen. By using a dropping pipette placed below the surface of the water sample, add 1 mL of a 50 per cent manganese(II) solution (Note 1) and in a similar way add 1 mL of alkaline iodide-azide solution (Note 2). Re-stopper the water sample and shake the mixture well. The manganese(III) hydroxide forms as a brown precipitate. Allow the precipitate to settle completely for 15 minutes and add 2 mL of concentrated phosphoric(V) acid (85 per cent). Replace the stopper and turn the bottle upside-down two or three times in order to mix the contents. The brown precipitate will dissolve and release iodine in the solution (Note 3). 

The solubility of iodine in many organic vapors behaves similarly at moderate pressures, but at pressures below atmospheric the concentration of iodine is much less than in the pure saturated vapor. Jepson and Rowlinson38 suggested that this is due to strong absorption of the vapors on the surface of the iodine. The effect is most marked with vapors of substances such as pyridine which are known to form strong electron-transfer complexes with iodine. 

Bromine is a dark-red liquid with high specific gravity. Iodine is a black solid which sublimes at atmospheric pressure producing a violet vapor. Both are used in CVD but to a lesser degree than either fluorine or chlorine. 

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