DE143347C

DE143347C -

Info

Publication number: DE143347C
Application number: DENDAT143347D
Authority: DE

Description

KAISERLICHESIMPERIAL

PATENTAMT.PATENT OFFICE.

Vorliegende Erfindung zeichnet sich ganz besonders dadurch aus, daß bei der Elektrolyse von Chloridlösurigen zum Zwecke der Darstellung von Alkalichloraten und -perchloraten, ganz gleichgültig ob die Lösungen Chromverbindungen enthalten oder nicht, der Elektrolyt einer ungleichen Einwirkung des Stromes an der Anode und der Kathode ausgesetzt wird, indem ein Teil des in die Lösung eintretenden Stromes zu einer Hülfskathode abgelenkt wird, welche sich in einer besonderen, von der ersten durch eine poröse Wand getrennten Zelle befindet. Diese Arbeitsweise gestattet, daß sich in der Lösung stets eine gewisse Menge unterchloriger Säure befindet, und dies ist deshalb von wesentlicher Bedeutung, als die Gegenwart von unterchloriger Säure in der Lösung zur schnellen Bildung von Chlorat beiträgt. Bekanntlich ist die freie unterchlorige Säure weniger beständig als ihre Salze und verwandelt sich schnell in Chlorsäure, die sich ihrerseits mit dem alkalischen Hypochlorit zu Chlorat umsetzt, wobei von neuem unterchlorige Säure frei wird, so daß der Kreislauf der Reaktionen wiederum eintritt.The present invention is particularly characterized in that during electrolysis of chloride solvents for the purpose of preparing alkali chlorates and perchlorates, Regardless of whether the solutions contain chromium compounds or not, the electrolyte is subject to unequal action Current at the anode and the cathode is exposed by adding some of the to the solution incoming current is deflected to an auxiliary cathode, which is in a special, from the first cell separated by a porous wall. This way of working allows that there is always a certain amount of hypochlorous acid in the solution, and this is therefore more essential than the presence of hypochlorite Acid in the solution contributes to the rapid formation of chlorate. It is well known that free hypochlorous acid is less stable than their salts and quickly turns into chloric acid, which in turn reacts with the alkaline Hypochlorite converts to chlorate, with hypochlorous acid being released again, see above that the cycle of reactions occurs again.

In der beiliegenden Zeichnung sind zwei Arten der hierbei zu benutzenden Zersetzungszellen dargestellt, und zwar ist in Fig. 1 die Hülfszelle α innerhalb des Hauptzersetzungsgefäßes b aufgestellt, während in Fig. 2 die Hülfszelle sich außerhalb vo"n b befindet, wobei ein Teil der Wandung c, ebenso wie der 35In the accompanying drawing, two types of the decomposition cells to be used are shown, namely in Fig. 1 the auxiliary cell α is set up inside the main decomposition vessel b , while in Fig. 2 the auxiliary cell is outside of b , with part of the wall c, as well as the 35

entsprechende Teil der Wand der Hülfszelle a, aus porösem Material hergestellt ist.corresponding part of the wall of the auxiliary cell a, is made of porous material.

Der bei der Anode d eintretende Strom wird in zwei Teile geteilt, wovon der größere Teil das Zersetzungsgefäß bei der Kathode e verläßt, wogegen der kleinere Teil durch die poröse Wand c nach der in der Hülfszelle befindlichen Kathode f hindurchtritt. Beispielsweise können bei d 1000 Ampere eintreten und nur 950 Ampere an der Kathode e und 50 Ampere bei f austreten, wodurch der in b befindliche Elektrolyt bei der Anode d einer größeren Einwirkung als bei der Kathode e unterworfen wird.The current entering at the anode d is divided into two parts, the larger part of which leaves the decomposition vessel at the cathode e , while the smaller part passes through the porous wall c to the cathode f located in the auxiliary cell. For example, 1000 amperes can enter at d and only 950 amperes can emerge at cathode e and 50 amps at f , whereby the electrolyte in b is subjected to a greater effect at anode d than at cathode e.

Das Zersetzungsgefäß b wird aus säurefestem Material und die Anoden und Kathoden aus solchem Material hergestellt, daß sie der Einwirkung des Elektrolyten widerstehen.The decomposition vessel b is made of acid-proof material and the anodes and cathodes are made of such a material that they withstand the action of the electrolyte.

Bei Einleitung des Prozesses besteht der in den Gefäßen α und b befindliche Elektrolyt aus einer Chloridlösung, aus welcher man vorteilhaft zuerst Kalk-, Magnesium- und Eisensalze ausfällt, indem man die Chloridlösung mit Alkalikarbonat oder einer Mischung von Alkalikarbonat und Alkalihydrat kocht. Hierfür ist die in der Hülfszelle α entstehende alkalische Lösung sehr geeignet, besonders dann, wenn sie ganz oder teilweise in Karbonat umgewandelt wird.When the process is initiated, the electrolyte in vessels α and b consists of a chloride solution, from which it is advantageous to first precipitate lime, magnesium and iron salts by boiling the chloride solution with alkali carbonate or a mixture of alkali carbonate and alkali hydrate. The alkaline solution formed in the auxiliary cell α is very suitable for this, especially when it is completely or partially converted into carbonate.

Durch den eintretenden Strom wird an der Anode d Chlor frei gemacht, und zwar in einer mit der im Gefäß α abgeschiedenen Menge Alkali äquivalenten Menge. DiesesThe incoming current releases chlorine at the anode d in an amount equivalent to the amount of alkali deposited in the vessel α. This

Claims

Chlorine acts on the hypochlorous alkali, which is always present in the bulk of the liquid during the formation of chlorate. A reaction is likely taking place here, represented by the following equation, where R denotes an atom of an alkali metal: R Cl O + H ^ O + 2 Cl = R Cl +2 HCl O. ίο Whether this equation represents the process in progress correctly , is immaterial. However, practical experiments have shown that the presence of free hypochlorous acid in the electrolyte promotes the formation of chlorate. The magnitude and duration of the current passing between electrodes d and f is controlled by determining the amount of hypochlorite oxygen in the main decomposition vessel b in the usual manner by means of sodium arsenite. This hypochlorite oxygen must be kept below 1 g per liter and this can be done quite well without any noticeable evolution of chlorine, if only the liquid is always kept in sufficient agitation. The control can also be carried out in such a way that the acidity of the liquids is determined after conversion of the hypochlorous acid by means of neutral hydrogen peroxide into hydrochloric acid, using phenolphthalene as an indicator. The correct acidity of the liquid is about 2 g H Cl O per liter. The cathode f is connected to the line emanating from the cathode e through a rheostat g and off switch h serving to regulate the current intensity, whereby the activity of the cell α can be regulated or completely interrupted as required. Of course, the electrolyte is saturated with fresh chloride from time to time after the chlorate or perchlorate formed has been removed and the solution in the auxiliary cell α is replaced by fresh liquid as often as necessary. Example: 238 liters of a sodium chloride solution saturated at 150 ° C. and heated to about 700 ° C. were poured into vessel b, and 290 g of sodium dichromate were added to this. The average amperage between anode d and cathode e was 880.8 amps for 236.2 hours and between anode d and cathode f was 46.03 amps for 28.33 hours, while the mean voltage between anode d and cathode e was 4.596 volts. During the experiment the electrolyte had a temperature of 720 C. and at the end 124.3 kg of sodium chlorate were detected in the solution, i.e. H. 90 percent of the theoretical yield corresponding to the electricity consumed. Patent-A ν Proverbs:

1. Process for the electrolytic preparation of alkali chlorates and perchlorates, characterized in that the electrolyte used for the decomposition has a greater electrochemical effect at the anode of the current is exposed than at the cathode, for the purpose of being in the electrolyte to generate a small amount of free chlorine.

2. Embodiment of the method protected by claim ι, characterized characterized in that one part of the current from the anode to one in one special one filled with a second electrolyte and with the main decomposition vessel Auxiliary cathode contained in conductive connected vessels deflects.

3. Apparatus for carrying out the method protected by claims 1 and 2, characterized in that in addition to the main decomposition vessel (b) an auxiliary cell (a) is provided which is separated from this by a diaphragm (c) and contains a second cathode (f) , the auxiliary cell having separate and independent supply and discharge tubes for the electrolyte.

1 sheet of drawings.