Iodine vapour

L. J. M. Daguerre s photographic process (silver plate sensitized by exposure to iodine vapour)... 

The first permanent images were obtained by the French landowner . N. Niepce using bitumcn-coated pewter (bitumen hardens when expo.sed to light for several hours and the unexposed portions can then be dissolved away in oil of turpentine). He then helped the portrait painter, L. J. M. Daguerre, to perfect the daguerreotype process which utilized plates of copper coated with silver sensitized with iodine vapour. The announcement of this process in 1839 was greeted with enormous enthusiasm but it. suffered from the critical drawback that each picture was unique and could not be duplicated. 

Procedure Preparation of 0.05A/ iodine. Dissolve 20 g of iodate-free potassium iodide in 30-40 mL. of water in a glass-stoppered 1 L graduated flask. Weigh out about 12.7 g of resublimed iodine on a watchglass on a rough balance (never on an analytical balance on account of the iodine vapour), and transfer it by means of a small dry funnel into the concentrated potassium iodide solution. Insert the glass stopper into the flask, and shake in the cold until all the iodine has dissolved. Allow the solution to acquire room temperature, and make up to the mark with distilled water. 

Another reversal location method is to expose the TLC plate to iodine vapour in a closed chamber that contains some iodine crystals. Iodine is lipophilic and accumulates in hpophihc sample spots, showing a brown color on a pale yellow-brown background. The same result is obtained by spraying with an iodine solution (250 mg iodine dissolved in 100 ml of heptane). In nearly all cases, this iodine accumulation is totally reversible without altering the sample, because outside the closed chamber iodine evaporates quickly from the plate. Caution should be taken with this iodine treatment in the case of unsaturated compounds because iodine vapor can react with double bonds [16]. 

Alloys ranging from Al3Ti2 to Al4Ti have been described, which ignite or incandesce on heating in chlorine or bromine or iodine vapour (or hydrogen chloride) or oxygen. 

It bums brilliantly when cold in fluorine or chlorine, but must be warm before ignition occurs in bromine or iodine vapours. 

It ignites if moist and bums violently in fluorine, and ignites in moist or warm chlorine. It burns not very readily in bromine vapour and may ignite if finely divided on heating in iodine vapour. 

It ignites on heating in chlorine, or in bromine or iodine vapours at higher temperatures. Reaction with nitric acid causes incandescence. 

Ignition occurs in fluorine, chlorine and bromine or iodine vapours. Contact with liquid bromine would be expected to cause a violent explosion. 

Uranium powder ignites in fluorine at ambient temperature, in chlorine at 150-180°, in bromine vapour at 210-240° and in iodine vapour at 260°C. 

Figure 1 UV-visible spectra of a) AW-Ph-HMM after 1 hour contact with iodine vapours and outgassing at 293 and 373 K (curves a and b, respectively) and before adsorption of iodine (curve c) MCM-41 after 1 hour contact with iodine vapours and outgassing at 293 K (curve d) b) traces of iodine dissolved in the l,4-bis(triethoxysilyl)benzene precursor.

Figure 2 compares the UV-visible spectra of AW-Ph-HMM and CW-Ph-HMM (curves a and b, respectively), after contact with iodine vapours and outgassing at room temperature. As it concerns the material with crystal-like walls, no peaks related to I2 molecules are observed. Since surface specific areas of the two materials are comparable, this finding suggests a lower availability of phenyl rings for the crystal-like walls material, where, following the model reported in [7], the aromatic moieties lie perpendicularly with respect to the pore surface. 

Addition of concentrated sulphuric acid Steamy fumes of HCl(g) Steamy fumes of HBr(g) with some red-brown vapour of bromine Clouds of purple iodine vapour and black solid residue... 

Reagent iodine vapour phosphomolybdic acid fluorescein/bromine sulphuric acid ninhydrin or isotin 2,4 -dinitropheny lhy drazine H2S water, diphenylcarbazide or... 

The drug substance is visualized by reaction with iodine vapour. 

The compounds separated are visualized by uv at 254 and 366 nm, respectively, and by iodine vapour. Rf of bromocriptine is 0.27. The potential by-products yield spots at R 1.5 (2-bromo-a-ergocryptinine), and 0.55 (a-ergocryptine). 2-Bromo-lysergic acid remains at the starting point. 

The reaction was monitored by TLC (eluent petroleum ether-ether, 4 1). Olefin and diol spots, visualized by iodine vapour, have R values of 0.43 and zero respectively. 

In a bottle of iodine, the space above the solid I2 always shows a slight purple hue, indicating the presence of iodine vapour. 

The second difference is the gas inside the bulb. Inside a normal light bulb, the gas is usually argon, but the gas inside the quartz halogen bulb is iodine vapour at low pressure, which has the ability to combine chemically with tungsten vapour. When the temperature is sufficiently high, the halogen... 

A blank determination is always performed simultaneously to account for the losses caused by the bromine as well as iodine vapours due to the interaction of excess bromine on potassium iodide. 

Iodine vapour Place the dried plate in a sealed tank containing a few iodine crystals Dark yellow-brown spots appear within a few minutes where lipids have absorbed the iodine. Unsaturated lipids are more intensely stained. Glycolipids do not stain significantly... 

Equal amounts of hydrogen gas and iodine vapour are heated in a sealed flask. 

The mechanism for the decomposition of ethenal, CH3CHO, in the presence of iodine vapour is written as follows ... 

Attempts to subsequently oxidize the TTF network have given unstable phases. Iodine vapour oxidation occurs initially, but the hlms quickly revert back to the neutral donor form. In spite of the not-yet proven bifunctionality, this example represents a step towards the controlled preparahon of a dual-network LB him that is both conduchng and magnehc, showing the way to be followed. 

The vapour pressure ratio of actinides to noble metals is also the basis of the actinide metal preparation by thermal dissociation of intermetallic compounds. Such intermetallic compounds of An and noble metals can be prepared by hydrogen reduction of a mixture of an An oxide and a finely divided noble metal (Pt, Ir.. in the absence of noble metals, hydrogen reduction of An oxides is impossible. Am and Cm metals have been obtained by thermal dissociation of their intermetallic compounds with Pt and Ir High purity Th and Pa, the least volatile actinide metals, can be prepared by thermal dissociation of their iodides, which form readily by reaction of iodine vapour with car-... 

The iodine vapours act as transporting agent in this modified version of the van Arkel procedure ". By replacing the resistance heated dissociation wire by an induction heated metal sphere (W or Th, respectively) large samples of Th or Pa crystals can be... 

Atomie weight e 127. Mokeuhr weight 63264. Mateeuhr volume CD. 1 h>e of iodine vapour weighs 127 eriths, 8p. gr, 4 86. I ueee at 107 . Soils at 180 . 

Similar results have been observed with iodine, but the dissociation 9 is much more marked at even lower temp. The theoretical density for the two-atom molecule is 8758, air unity or 126-92 oxygen=16 and for the one-atom molecule the theoretical density is 4 379, air unity. When iodine vapour is heated above 700° its density diminishes steadily up to about 1700°, when it becomes constant at half its value at the lower temp. 

Without doubt, the iodine molecule, I2, dissociates into atoms I2=I+I. The state of the system in equilibrium will be represented by kCi2=k Ciz. If x denotes the proportion of iodine dissociated, and v the volume of the iodine vapour, then, Bince v volumes of iodine vapour become 2v volumes of dissociated iodine vapour, it follows that the concentration of the dissociated iodine will be xjv, and of the iindissociated iodine (1—x)/v. Hence for equilibrium... 

---