Preparation of Purified Iodine

Preparation of Purified Iodine. Dissolve 32 g of potassium iodide in 100 ml of water and 25 g of copper sulphate pentahydrate in 80 ml of water. Pour the solutions together into a 200-ml glass beaker and let the solution settle. Separate the precipitate from the 

Assemble an apparatus for distillation with steam (Fig. 59a). Transfer the aqueous solution of iodine into flask 4. Distil off the iodine. For this purpose, open the clamp on tee-piece 3 and heat the water in steam boiler 1 until it boils. Next regulate the rate of steam flow with the aid of the clamp and carefully heat flask 4. After the main part of the iodine gathers in glass tube 5, open the clamp and stop heating steam boiler 1 and flask 4. 

Remove the iodine crystals from tube 5. Transfer them onto a glass plate, dry them with filter paper, and then put them in a desiccator over a concentrated sulphuric acid solution overnight. 

Perform final purification of the iodine in the apparatus shown in Fig, 596. Put the iodine in vessel 4. Cool it with liquid nitrogen. Connect the apparatus to a fore pump. Evacuate the apparatus with cock 2 open (40 min), then close the cock, fill tube 1 with cold water, remove the liquid nitrogen so that vessel 4 acquires room temperature, and carefully heat it with the flame of a burner. When sublimation of the iodine is completed, cool the apparatus, carefully open cock 2, 

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Fig. 59. Preparation of purified iodine a—apparatus for distillation with steam 6—apparatus for purifying dry iodine by sublimation...

Preparation of Plutonium Metal from Fluorides. Plutonium fluoride, PuF or PuF, is reduced to the metal with calcium (31). Although the reactions of Ca with both fluorides are exothermic, iodine is added to provide additional heat. The thermodynamics of the process have been described (133). The purity of production-grade Pu metal by this method is ca 99.87 wt % (134). Metal of greater than 99.99 wt % purity can be produced by electrorefining, which is appHcable for Pu alloys as well as to purify Pu metal. The electrorefining has been conducted at 740°C in a NaCl—KCl electrolyte containing PuCl [13569-62-5], PuF, or PuF. Processing was done routinely on a 4-kg Pu batch basis (135). 

A purified fatty acid is recommended for the preparation of a pure a-sulfo acid. Purified palmitic acid (m.p. 60.8-61.4°, neutralization equivalent 256.2) is prepared by twice recrystallizing a good commercial grade of palmitic acid from acetone at 0°, using a solvent ratio of 10 ml. to 1 g. However, the reaction may be applied to commercial saturated higher fatty acids, if the iodine number is sufficiently low. The checkers obtained similar results with recrystaUized Neo-Fat 1-56 (Armour and Company, Chicago, 111.) or Eastman white label palmitic acid. 

Preparation of Crystalline Silicon. Pure crystalline silicon is prepared in a quartz ampoule (Fig. 110). Put 2.5 g of amorphous silicon and 0.5 g of iodine preliminarily purified by sublimation... 

Pure concentrated hydriodic acid for use in this preparation is synthesized directly from purified iodine and hydrogen as described in synthesis 54. Potassium bicarbonate is purified by repeated crystallization from water at 70°C., in an atmosphere of carbon dioxide. 

The preparation of anhydrous aluminum iodide by methods described previously1 2 involves direct union under conditions that invariably yield products contaminated with elemental iodine. Attempts to purify these products by sublimation under a variety of conditions (including sublimation in vacuo or in an atmosphere of carbon dioxide or helium) result in at least partial decomposition of the iodide and a final product that is colored, owing to the presence of iodine. The method described below also provides for direct union of the elements, but under conditions that eliminate contamination with elemental iodine and yield an initial product of exceptionally high purity. 

The most thorough investigation in this area was that of Harrison and Royle43 on astatination of rabbit immunoglobulin (IgG) which could be used in animal experiments. PAtBA was produced with > 90% radiochemical yield, and a reproducible overall yield of > 30% for labelled protein was obtained with negligible deastatination of the latter in vivo. These favourable results could be achieved most probably due to the fact that the PAtBA was prepared without an iodine carrier and that the micro amounts of the product were purified from the macro amounts of contaminates by HPLC. To bind PAtBA to the protein, acylation with mixed anhydride was used. Preparation of the mixed anhydride 7 (equation 5) could be carried out in about 20 minutes at ca 0 °C. For astatination rabbit IgG protein is dissolved in borate buffer (pH = 9.3) and then added to 7 (see equation 6) the procedure takes about 1 hour at ca 15 °C. The astatinated protein is separated from non-conjugated materials by gel filtration and eluted from the column by phosphate-buffered saline. 

Iodine can be purified by sublimation from potassium iodide and calcium oxide and weighed as a primary standard. Because of the limited solubility and volatility of iodine, it must be dissolved in concentrated potassium iodide solution and diluted to volume. Air oxidation of iodide should be minimized by preparing the solution with water free of heavy-metal ions and storing it in a cool, dark place. Because of the inconvenience of weighing iodine accurately, its solutions are commonly standardized against arsenic(III) oxide (primary standard) or thiosulfate. ... 

In conclusion, therefore, several groups of investigators have produced antisera which they find useful for the work which they propose to undertake. No systematic experiments have yet been carried out with these antisera to determine whether the specificity of radioimmunoassays for FSH and LH changes when hormones purified by different procedures are employed for the label. As shown in Section 2 there is a large variety of methods in current use for the preparation of the pituitary hormones, and there is evidence that the final products are not identical (see Tables 3 and 4). Accordingly, it is likely that different iodinated preparations will yield different results. In this connection Ryan (R24) found that several human pituitary LH preparations, all made by the same method, showed different cross-reactions with HCG in the presence of the one antiserum. 

Preparation of m-nitrophenol from m-nitroaniline 557 A cold mixture of water (450 ml and concentrated sulfuric acid (330 ml) is poured, with stirring, over finely powdered ra-nitro-aniline (210 g), and ice (800 g) is added. When the mixture has become homogeneous, a solution of sodium nitrite (105 g) in water (250 ml) is run in during 8-10 min from a dropping funnel until the starch-iodine reaction remains positive. The temperature is kept between 0° and 5° and the mixture is stirred for a further 5-10 min. Then the m-nitrobenzenediazonium sulfate is allowed to settle, the supernatant liquid is poured off and the solid washed, if necessary, with water by decantation in order to purify the salt filtration is necessary only when gross impurity is present. 

Iodoform, CHI3, tri-iodomethane, is formed when alcohol and certain other compounds (66) are treated with iodine in the presence of an alkali. It can be prepared by adding iodine to a warm aqueous solution of alcohol or acetone which contains sodium carbonate. The iodoform, which separates as a yellow precipitate, is purified by crystallization from dilute alcohol. It crystallizes in yellow, lustrous, six-sided plates, which melt at 119 , and have a peculiar, very characteristic odor. The reactions by which alcohol is converted into iodoform are analogous to those as the result of which chloroform is obtained from alcohol. The formation of iodoform is often used as a test for ethyl alcohol, but as other substances, such as acetone, isopropyl alcohol, and aldehyde yield iodoform when warmed in alkaline solution with iodine, the test is not reliable unless it is known that the other substances which respond to it are absent. Most of the compounds which yield iodoform when treated in this way contain the group CH3.C linked to oxygen. 

Since even the purest commercial KI to be used for the preparation of specially purified iodine may still contain such impurities as Cl, Br, ICN, alkali sulfate, carbonate and sulfide, as well as traces of organic material, special purification is necessary. 

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