Iodin sublimes

Iodine sublimes more readily than ice because its triple-point pressure, 90 mm Hg, is much higher. Sublimation occurs on heating (Figure 9.6) below the triple-point temperature, 114°C. If the triple point is exceeded, the solid melts. Solid carbon dioxide (dry ice) has a triple-point pressure above 1 atm (5.2 atm at — 57°C). Liquid carbon dioxide cannot exist at 1 atm pressure regardless of temperature. Solid C02 always passes directly to vapor if allowed to warm up in an open cantainer. 

Elemental iodine, I2, is a purphsh solid. Like solid carbon dioxide (dry ice), iodine sublimes. That is, it goes directly from the sohd to the gas phase without ever becoming liquid. So a bottle of iodine has a nice purple haze above the solid element. 

In the case of an iodine/salt mixture the iodine sublimes but salt does not. Iodine can be separated by heating the mixture in a fume cupboard as shown in Figure 2.25. The iodine sublimes and re-forms on the cool inverted funnel. 

The resulting solution is evaporated to dryness and heated further, whereupon the iodine sublimates and thus may be separated from the other products of the reaction. 

At normal temperatures and pressures, iodine is a shiny, purplish-black or gray solid. Near room temperature, iodine sublimes (i.e., it does not melt to form a liquid but goes directly from the solid to the gas phase). It is found at a level of about 60 parts per billion (ppb) by weight in seawater but its concentration is enhanced in marine organisms. 

Like liquids, solids have vapor pressures. Figure 16.49 shows iodine vapor in equilibrium with solid iodine. At 25°C and 1 atm iodine sublimes that is, it goes directly from the solid to the gaseous state without passing through the liquid state. Sublimation also occurs with dry ice (solid carbon dioxide) under these conditions. 

Fortunately the method is not limited to colored substances. Any organic compound capable of being eluted from alumina will form a spot, which soon becomes visible when the solvent is let evaporate and the plate let stand in a stoppered 4-oz bottle containing a few crystals of iodine. Iodine vapor is adsorbed by the organic compound to form a brown spot. A spot should be outlined at once with a pencil because it will soon disappear as the iodine sublimes away brief return to the iodine chamber will regenerate the spot. The order of elution and the elution power for solvents are the same as for column chromatography. 

Iodine sublimes even at room temperature. Molecules escape from the solid and go into the gas phase, which is in equilibrium with the solid. 

Iodine sublimes from the bottom of the beaker and condenses on the bottom of the chilled round-bottom flask. 

Iodine sublimes at room temperature and pressure water does not. Explain the differences you would expect to observe at room temperature if 5.0 grams of iodine crystals were sealed in a 10.-mL container and 5.0 mL of water were sealed in a similar container. 

Iodine is removed from a solution of iodine and potassium iodide. The material can be dried at a relatively high temperature without the appearance of iodine vapors. However, if the iodine-ash mixture is heated strongly in a closed flask, the iodine sublimes, but later upon cooling the ash readsorbs the iodine vapors. 

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SYNONYMS iodine crystals, iodine sublimed, molecular iodine. 

Why does solid iodine sublime readily Use your knowledge of intermolecular forces to explain. 

They are volatile elements fluorine and chlorine are gases at room temperature, whereas bromine and iodine are a liquid and volatile solid respectively. Solid iodine sublimes when warmed. 

The iodine method When heated, iodine sublimes and its vapor reacts with the carbon-carbon double bonds in fats and oils, turning the ridge pattern to a yellow-brown color. This method is particularly well suited for fingerprints on porous objects like papers and cardboard. Write an equation showing the reaction of I2 with fats and oils. 

In all the procedures, the chromatographic bands became visible as white spots on a yellow background or as white spots on a violet-gray background when starch was used. The spots appear because of the induction effect of the C-S, C=S, P-S, or P=S bonds. However, after some time, the background starts to disappear owing to iodine sublimation. 

The spots become visible after a time lag on account of the induction time (i.e., time required for the induction reaction to complete) conditioned by induction properties of the particular compound. The induction time should not be too long because it may cause disappearance of the background owing to iodine sublimation. 

Densitometric analysis coupled with iodine-azide reaction as a detection system is relatively difficult to conduct owing to background disappearance. There are two processes behind this iodine sublimation from a plate area and uninduced iodine-azide reaction proceeding outside a spot. Addition of potassium iodide to the spray solution lowers... 

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