CS209584B1 - Process for the production of ammonium dioxalate ethoxylate - Google Patents

Abstract

The invention relates to a method for producing ammonium dioxalatooxotitanate. Pure ammonium dioxalatopexotitanate has been proposed as a multipurpose primary standard. It can be prepared from titanium tetrachloride and oxalic acid, is chemically stable and has a high molecular weight. It is suitable not only as a titanium standard for the preparation of basic alkali-free solutions, but also as a St. avelate standard for oxidimetry. Another significant possibility of applying the oxalate complex is as a primary standard in permanganato- and cerimetry, where its high equivalent weight (.73.51) even surpasses the existing basic substances based on oxalate. It can also be a starting material for the preparation of highly pure titanium dioxide, or titanates of some divalent metals significantly used in electrical engineering for their dielectric and piezoelectric properties.

Description

The invention relates to a process for the production of ammonium dioxalatooxotitanate (ΝΗ ^) ₂ TiO (θ ₂ ° ^) ₂ · h ₂ °.

When studying the extraction equilibria of tetravalent titanium, it is advisable to work with a titanium salt basic solution in perchlorate. None of the prior art primary standards fully met the requirements for speed and reliability of preparation without the need for additional control of the titanium content of the solution, which in addition should not contain potassium ions. Consideration was therefore given to other compounds of tetravalent titanium characterized by a well defined composition of ^ niohž appeared promising as yet poorly understood dioxalatooxotitaničité acid ammonium salt in another only oxalatotitaničitó (NH ^) ₂ .Ti0 (C ₂ ^ 0) _{2 2} · h ° .

It is known that the complex oxalatotatin ion TiO (C ₂ O 4) ₂ - forms a number of salts, of which the alkali metal salts and the ammonium salt are water-soluble. So far, only potassium salt and ammonium salt have been isolated in crystalline form by dissolving titanium hydroxide in an equimolar mixture of the oxalate of the corresponding cation and oxalic acid by evaporating the solution.

Another method, however, suitable only for the preparation of the potassium salt, is based on potassium titanate which dissolves in oxalic acid.

These single methods described have a number of disadvantages. The titanium hydroxide required for the reaction can only be prepared by hydrolyzing the titanium salts at a pH lower than 5. It has been found that the deposit obtained at a higher pH no longer dissolves in an acidic solution of alkali or ammonium oxalate. The process for the preparation of reactive titanium hydroxide and its amorphous character clearly indicate the difficulties associated with its isolation, washing and later adherence to the correct stoichiometry in the reaction with oxalate. Both salts are very soluble in water and are only very slowly precipitated from the concentrated solutions in the form of large coarse crystals. Therefore, the cleaning efficiency is very low and a considerable part of the material used is lost. Release of crystals from the crystallization vessel is also very difficult. It has been found that the ammonium salt of the oxalate titanium complex has all the properties of the primary standard.

The aforementioned drawbacks have no process for the production of ammonium dioxalato-titanate starting from the readily available raw materials according to the invention, which comprises adding oxalic acid dihydrate to an aqueous solution of pure titanium tetrachloride and concentrated hydrochloric acid and heating the mixture in a water bath, after dissolution and by addition of the thymol blue indicator, the mixture is neutralized with concentrated ammonium hydroxide with vigorous stirring at the rate necessary to dissolve the white precipitate formed, and at the conclusion of the neutralization the ammonium hydroxide is added in a 1: 1 dilution to pink color. The indicator turns to yellow, after which the mixture is filtered hot after complete clarification and ethanol is added to the filtrate in an amount equal to 1/3 to 1/2 the volume of the filtrate, whereupon the solution cools and left to crystallize and precipitate crystals. After stirring, they are sucked off and washed with cold ethanol (2: 5 diluted with water) and allowed to air dry at normal temperature. Subsequently, ammonium dioxalatoate titanate of less than less than halide content is obtained by double crystallization in an equally diluted ethanol medium. 0.001%.

The advantage of the process according to the invention is that the ammonium dioxalatooxo-titanate is particularly suitable for the preparation of basic solutions of pure titanium salts, which are used both in the study of equilibria in solutions and in various titanium determination methods (photometry, volumetric analysis). The solutions are free of alkaline salts, do not contain unnecessary excess acid and, due to the guaranteed stoichiometry of salt ejection, do not require additional control of the titanium content by other methods. Another significant possibility of using oxalatocomplex is as a primary standard in permanganato- and cerimetry, where its high equivalent weight (73.51) even surpasses the existing oxalate base substances.

The absence of alkali and complete thermal decomposition as early as 300 ° C suggest another possibility of using this oxalatocomplex, for example for the very simple preparation of highly pure titanium dioxide, respectively. titanates of certain divalent metals (Ba, Sr and the like), whose monocrystals have remarkable dielectric and piezoelectric properties and are used in the electric furnace and high temperature measurement.

Example

The procedure for the production of ammonium dioxalatooxititanate can be expressed by the equation of H ₂ TiCl ₆ + 2H ₂ C ₂ Q 4 + 8 NH 4 OH = (HH 2 g TiCl 2) 6 NH 4 Cl + 7H ₂ O

To 120 ml of a solution containing 38 g of pure titanium tetrachloride (0.2 mol) and 50 ml. of concentrated hydrochloric acid (= 1.19), 53 g of oxalic acid dihydrate (0.42 mol) are added and the mixture is heated on a water bath. After dissolution, a small amount of thymol blue indicator is added to the solution and neutralized with about 110 ml of 25% ammonia with vigorous stirring. Ammonia is added as quickly as the white deposit formed can dissolve; the last 10 to 15 ml is best added dropwise and diluted 1: 1 with water. Neutralize the solution until the pink indicator turns yellow. The mixture is then further heated until complete clarification, filtered while hot and 1/3 to 1/2 volume of ethanol added to the filtrate. The amount of alcohol should be selected such that a second liquid phase is not formed. If it is formed, it is removed by a few drops of water. The solution is then cooled and allowed to crystallize. The precipitated small crystals are filtered off with suction and washed with cold ethanol diluted with water 2: 5 and allowed to air dry at normal temperature. The crude ammonium dioxaoxo-titanate is purified by dissolving hotly in the same amount of water by weight and, after filtration if necessary, adding as much ethanol to the hot solution as possible until a second liquid phase is formed (approximately half the volume of water used to dissolve). The mixture is then again homogenized with a few drops of water, cooled and the salt crystallized to disturbed. The aspirated monohydrate crystals were washed twice with cold dilute ethanol (2: 5) and air dried at normal temperature. The yield of pure salt (ΝΗ ^) ₂ Τχ0 (0 ₂ 0 ^) ₂ · Η ₂ 0 is 65% (calculated on the titanium tetrachloride) after two recrystallizations; by evaporation of the mother liquors, addition of alcohol and re-crystallization, the total yield of the pure product can be increased up to 85%.

Claims (1)

SUBJECT OF THE INVENTION A process for the production of ammonium dioxalate oxititanate (NH4JgTiOCCgO4Jg.HgO) by adding oxalic acid dihydrate to an aqueous solution of pure titanium tetrachloride and concentrated hydrochloric acid and heating the mixture in a water bath. neutralized with concentrated ammonium hydroxide added at a rate necessary to dissolve the white precipitate formed, with the final neutralization adding ammonium hydroxide in a 1: 1 dilution with water until the pink color of the indicator turns yellow, after which complete clarification by hot filtration and ethanol is added to the filtrate in an amount equal to 1/3 to 1/2 the volume of the filtrate, then the solution is cooled and left to crystallize disturbed and the precipitated crystals are suction filtered and washed with cold ethanol diluted with water a 2: 5 and allowed to dry for vzduohu normální.teploty and then recrystallized twice from dilute ethanol environment anyway.