JPS6148403A - Manufacture of alkali iodide - Google Patents

Abstract

PURPOSE:To manufacture inexpensively high-purity alkali iodide in excellent yield by allowing alkali hydroxide or alkali (bi)carbonate to react with hydrazine and iodine. CONSTITUTION:After hydrazine is added to alkali hydroxide (e.g. KOH) or alkali (bi)carbonate (e.g. MgCO3) dissolved or suspended in water under stirring and mixed with each other, iodide is slowly added to the mixture and allowed to react with the soln. till the discharge of gaseous nitrogen or carbon dioxide is finished and the obtained soln. is concentrated to filter alkali iodide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing alkali iodide. More specifically, alkali hydroxide or alkali carbonate (including bicarbonate) (hereinafter collectively referred to as alkali hydroxide, etc.)
This relates to a method for producing alkali iodide, which involves reacting hydrazine with iodine. Alkali iodide is of course useful as a reagent for various chemical reactions or analyses, but sodium iodide and potassium iodide are also used as denaturing agents, expectorants, and diuretics. Potassium is a material for photographic emulsions, and recently, sodium iodide has been mixed with thallium iodide 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. As the number of useful applications for alkali iodide continues to increase, there is an extremely strong need 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 mole of alkali iodate is inevitably produced as a by-product. It is essential to convert the by-product alkali iodate into alkali iodide by mixing a reducing agent such as a carbon bed or sodium sulfite and heating it to several hundred degrees. This operation is complicated and unavoidable, and disadvantageous problems such as iodine being liberated and having an adverse effect on the reactor material are inevitable.

With the aim of obtaining highly pure alkali iodide using a highly productive, safe, inexpensive and easy manufacturing method, the present inventors have conducted extensive research and have successfully utilized the reducing properties of hydrazine in a skillful and extremely effective manner. Thus, the objective was achieved and the present invention was completed.

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. Add iodine gradually 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 present invention does not involve any by-products, there is no need to add any special purification treatment to the reaction wave. The desired high-purity alkali iodide can be obtained simply by concentrating and isolating the reaction solution.

Either hydrazine or iodine may be added in advance, but when starting from an alkali hydroxide or the like that is poorly soluble in water, it is easier to add hydrazine in advance.

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 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.

Alkali hydroxide, hydrazine, and iodine may be used in equivalent amounts, and there is no need to use an excess of any one of them. However, in order to make the primary effect of hydrazine effective, it is necessary to keep the pH at 1 alkaline and use a slight excess of alkali hydroxide or the like to the extent that the reaction is completed at the same alkaline level. Once the reaction is complete, add a small amount of raw material alkali hydroxide etc. to adjust the pH at the end of the reaction.
may be adjusted to alkaline.

Depending on the type of alkali hydroxide, the water used as the reaction medium may be used in an amount that completely dissolves it, or may be used in an amount that partially dissolves and most of it becomes cloudy. 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 large enough 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 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 hydride or its aqueous solution can be used as the easiest to handle. If you find it difficult to use a concentrated product, you can dilute it 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 the 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 111 kg of potassium hydroxide in pure water 2006,
Add a 30% aqueous solution of hydrazine Hitlerde 33 paste and mix well. Iodine 2 while stirring
Inject 50 Ky gradually.

Gas is released as the mixture is added, and stops when the reaction is completed. The pH after the reaction is alkaline (preferably pH 9-1)
0), and Hydrashinwo? - Confirm that they are not detected by 525 nm absorption quartz method using dimethylaminobenzaltehyde, convert iodic acid to sulfuric acid and assay at 420 nm, and then heat and concentrate. 245 kg of dry crystals were obtained in the first stage a condensation, and 65 kg of dried crystals in the second stage I condensed. The yield was 94%, and both reagent grade J
We confirmed that the quality passed the standards set by IS.

Example 2 Cesium carbonate 501 K9 was dissolved in pure water 5006, and 8
Add 48% hydrazine hydrazine powder, and while stirring, gradually add 390 Kq of iodine. In the same manner as in Example 1, add 598 K of cesium iodide crystals and 159 K of second crystal.
I got q. The yield was 95%, and both crystals exhibited quality comparable to special grade potassium iodide or sodium iodide reagents.

Examples 3 to 9, It was carried out in the same manner as in Example 1, as shown in the following table.

Note that in Examples 6 and 7, hydrazine was added after iodine was added. In all examples, the obtained dried crystals exhibited quality comparable to reagent grade potassium iodide or sodium iodide.

Patent applicant Monokoshi Kagaku Co., Ltd. Wako Pure Chemical Industries, Ltd.

Claims (1)

[Scope of 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.