Iodine-pentoxide method

Several quantitative procedures for concentrations above 0.1 vol % are available. Gas chromatographic analysis (78) is particularly useful because it is fast, accurate, and relatively inexpensive. The standard wet-chemical, analytical method (76) takes advantage of the reaction between iodine pentoxide and carbon monoxide at 423 K. 

According to H. W. Foote and L. H. Levy, soln. of the alkali chlorates in other molten salts gave f.p. indicating that the mol. wt. under those conditions are normal. A. Rosenheim and 0. Liebknecht48 found the mol. wt. of acid by the f.p. method depend on the concentration, and that the acid in dil. soln. is a monobasic acid, and in cone. soln. the acid is polymerized and exists as a dibasic acid, H2l206. E. Gro-schuff and P. Walden also showed that the electrical conductivity of iodic acid soln. corresponds with a monobasic acid, as is also the case with chloric and bromic acids. The monobasic acid, therefore, can be represented by A. Kekule s type of formula with iodine univalent or C. W. Blomstrand s type of formula, with iodine quinquevalent and iodic anhydride, i.e. iodine pentoxide will be represented ... 

Iodine pentoxide is a white solid substance that, at ordinary temperatures, is entirely stable. It cannot be prepared by direct synthesis from iodine and oxygen, because when cold the elements combine too slowly, and when heated the compound is unstable. It may be readily prepared by the direct oxidation of iodine by means of strong oxidizing agents, such as concentrated nitric acid or chlorine. One method for the oxidation of iodine has already been illustrated under the preparation of potassium iodate, but... 

Iodine pentoxide, I2O5, is the most stable oxide of the halogens [8]. It has found some practical application as a mild oxidant, especially useful in analytical chemistry. Iodine pentoxide is one of the few chemicals that can oxidize carbon monoxide rapidly and completely at room temperature. The reaction forms the basis of a useful analytical method for determining the concentration of CO in the atmosphere or in other gaseous mixtures [8]. 

Detector tubes A simple and relatively inexpensive measurement method involves the use of calibrated stain-length detector tubes such as those produced by Draeger, Kitagawa, Gastec, MSA-AUER, and others. CO detector tubes often rely on the reaction of CO with iodine pentoxide, which produces a purple colored iodine stain. The detector tube carries a scale calibrated in parts per million and the length of the color stain that develops after the required number of pump strokes corresponds to the concentration of CO in the sample ... 

In addition to the methods of preparation given in connection with the procedure for the acetylation of thiophene with acetyl chloride in the presence of stannic chloride, 2-acetothienone has been prepared from thiophene and either acetyl chloride or acetic anhydride in the presence of iodine, hydriodic acid, silica-metal oxides, zinc chloride, or inorganic oxyacids. It has also been prepared from thiophene and acetic acid in the presence of hydrogen fluoride or phosphorus pentoxide. The acylation in the presence of phosphorus pentoxide is particularly useful with higher aliphatic acids. ... 

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