JPH0470244B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing alkali iodide. More specifically, the present invention relates to a method for producing alkali iodide, which involves reacting alkali hydroxide or alkali carbonate (including bicarbonate) (hereinafter collectively referred to as alkali hydroxide, etc.), hydrazine, and iodine. Alkali iodide is of course useful as a reagent used in various chemical reactions or analyses, and sodium iodide and potassium iodide are used as pharmaceutical agents such as alterants, expectorants, and diuretics. is a material for photographic emulsions, and recently, sodium iodide has been mixed with a small amount of thallium iodide to be used as a material for single crystal lenses for scintillation counters, and cesium iodide has been used as a material for lenses for scintillation counters in nuclear reactors. The number of useful uses of alkali iodide, such as as a raw material, is increasing, and there is an extremely strong demand for an industrial supply of inexpensive and highly pure alkali iodide. Conventionally, alkali iodide has been produced by the reaction of alkali hydroxide and iodine, but in this method, along with 5 moles of alkali iodide, 1
Since a mole of alkali iodate is produced as a by-product, the by-product alkali iodate is converted into alkali iodide by mixing a reducing agent such as carbon powder or sodium sulfite with the resultant mixed crystal and heating it to several hundred degrees. is essential. This operation is complicated, and iodine is liberated, which adversely affects the reactor material.
Unfavorable problems are inevitable. With the aim of obtaining highly pure alkali iodide using a highly productive, safe, inexpensive and easy production method, the present inventors have conducted extensive research and have successfully improved the reducing properties of hydrazine in a skillful and extremely effective manner. The present invention was completed by utilizing the present invention. The general details of the method of the present invention are as follows. While stirring the alkali hydroxide etc. dissolved or suspended in water, hydrazine is added. Slowly add the iodine while continuing to stir. As the reaction progresses, nitrogen gas (contains carbon dioxide gas when carbonic acid (including bicarbonate) or alkali is used as the raw material) is released, and the release stops when the reaction is completed. After the reaction is completed, the solution is concentrated and the desired alkali iodide is filtered off. Since the reaction of the method of the invention does not involve any by-products,
There is no need to add any special purification treatment after the reaction. The desired high-purity alkali iodide can be obtained simply by concentrating and isolating the reaction solution. Hydrazine and iodine may be added in any order, but when starting from an alkali hydroxide or the like that is sparingly soluble in water, it is easier to add hydrazine first. Naturally, in order to prevent the inclusion of impurities, it is preferable to use highly pure raw materials and to use pure water or distilled water as the reaction medium. Before concentrating the reaction solution, it is also preferable to adjust the pH or perform filtration or decolorization filtration as usual. In order to eliminate any risks during concentration, it is also desirable to confirm by analysis that no hydrazine remains after the reaction is complete. What are alkali hydroxide, hydrazine, and iodine?
It is sufficient to use an equivalent amount, and there is no particular need to use an excess of either of them. However, in order to make the reduction effect of hydrazine effective, the pH should be kept alkaline and the reaction should be completed at the same alkaline level.
Alkali hydroxide etc. should be used in slight excess. Once the reaction is complete, a trace amount of raw material alkali hydroxide or the like may be added to adjust the pH to alkaline at the time the reaction is completed. The water used as the reaction medium may be used in an amount that will completely dissolve the alkali hydroxide, or may be used in an amount that will partially dissolve and most of the water will be suspended. Since alkali iodide is easily soluble in water, complete dissolution is achieved as the reaction progresses in the latter case as well, so there is no problem in applying the method of the present invention. If a large amount of water is used to completely dissolve the alkali hydroxide etc., it will be disadvantageous in concentration after the reaction. There is usually no need for particular heating or cooling during the reaction, but the reaction is somewhat exothermic and the temperature usually rises gradually. Here, the alkali of alkali iodide refers to alkali metals and alkaline earth metals. As the hydrazine, hydrazine hydrate or its aqueous solution can be used as it is the easiest to handle. If it is difficult to use a concentrated product, it may be diluted as appropriate. By the method of the present invention, highly pure alkali iodide can be obtained easily and inexpensively on an industrial scale, making a great contribution to this industry. The present invention will be further explained below with reference to Examples, but it goes without saying that these Examples do not limit the present invention. Example 1 Dissolve 111Kg of potassium hydroxide in 200% pure water, 80%
Add 33 kg of hydrazine hydrate diluted with a 30% aqueous solution and mix well. Iodine while stirring
Gradually introduce 250Kg. Gas is released as the mixture is added, and stops when the reaction is completed. After confirming that the pH after the reaction is alkaline (preferably PH 9 to 10), hydrazine is analyzed using p-dimethylaminobenzaldehyde at 525 nm spectrophotometry, and iodic acid is converted to sulfuric acid and analyzed at 420 nm. Confirm that it is not detected, then heat and concentrate. After the first stage concentration, 245 kg of dry crystals of potassium iodide were obtained, and after the second stage concentration, 65 kg of dry crystals of potassium iodide were obtained. The yield was 94%, and both products were of special reagent grade.
We confirmed that the quality passed the standards set by JIS. Example 2 Dissolve 501 kg of cesium carbonate in 500% pure water to 80%
48 kg of hydrazine hydrate was added, and while stirring, 390 kg of iodine was gradually added. In the same manner as in Example 1, 598 kg of first crystals of cesium iodide and 159 kg of second crystals were obtained. The yield was 95%, and both crystals showed quality comparable to special grade potassium iodide or sodium iodide reagents. Examples 3 to 9 The experiments were carried out in the same manner as in Example 1, as shown in the following table.

【table】

[Table] In Examples 6 and 7, hydrazine was added after iodine was added. All examples,
The dried crystals obtained showed a quality comparable to reagent grade potassium or sodium iodide.

Claims (1)

[Claims] 1. A method for producing alkali iodide, which comprises reacting an alkali hydroxide or an alkali carbonate (including bicarbonate) with hydrazine and iodine. 2. The method for producing alkali iodide according to claim 1, wherein the reaction medium is water. 3. The method for producing alkali iodide according to claim 1 or 2, wherein the reaction is carried out under alkalinity and completed under alkalinity.