DE382924C - Process for the simultaneous production of lead chromates (chrome yellow, chrome orange, chrome red) in one operation directly by electrolysis - Google Patents

Description

Process for the simultaneous production of lead chromates (chrome yellow, Chrome orange, chrome red) in one operation directly through electrolysis. the Invention relates to the electrowinning of chrome yellow, chrome orange and chrome red.

It is already known to use sodium chromate using anodes from lead and a so-called solution salt (chlorate) from electrolytic decomposition subject to a neutral or a more or less alkaline bath Texture to give in this way to the depending on its composition different colored lead chromates (British patent r48or from the year 1895, especially p. 4., lines a3 ff). According to the invention is for the simultaneous Obtaining such products occurs during electrolysis and is gradual Increasing alkalinity of the bath made usable by the fact that the Electrolytes in uninterrupted operations, after respective clarification and separation from the precipitate, in other connected cells or rows of cells accordingly exceed the number of desired products and after regeneration the cycle lets start all over again.

According to the manufacture of the three products mentioned, there is the whole system of three rows of cells (baths) separated from one another: I. Chrome yellow, II. Chrome orange and III. Chrome red. For the electric 1vse, the cells and rows preferably connected in series.

The bath containers are practical boxes made of wood with funnel-shaped or funnel-like bottom insert and a bottom opening along with adjustable, (controllable) Drainage device.

The electrodes usually hang on the edges of the box. The anodes are plates made of soft lead, the cathodes either, especially if the direction of the current should change in certain intermediate times, or made of perforated hard lead or z. B. perforated, well leaded, nickel-plated or tinned iron sheets. On red cathodes there are either no protective measures against sponge formation as a result of a reduction in what remains Product, or they are made of wooden frames for a suitable filter cloth envelope edged or provided with flat, box-like coverings made of thin wooden boards, such as are used, for example, in electrical collectors.

In electrolysis, the current density is on average about 5o to roo amps on the square meter of anode immersion surface. The bath tensions fluctuate depending on the current density, the density, reaction, temperature and movement or the Circulation of the electrolyte, the spacing of the electrodes from one another by volts below the prerequisite for bright aluminum immersion surfaces.

The direction of the current either remains diesel, or it changes in certain Periods, e.g. B. with the help of so-called comers; in the latter hall Of course, the cathodes are similar to the anodes and lack any protective measures against sponge formation. The electrolyte exists in series, for example I from sodium chlorate Na Cl O ;, or sodium perchlorate Na Cl O. "(95 parts) and N atrium chromate NazCr O4 -f - i o H, O (r o parts), in row II from sodium chlorate or sodium perchlorate (95 parts), sodium chromate (around 8 to 9 parts) and caustic soda NaOH (around 1 to 2 parts), in row III from sodium chlorate or sodium perchlorate (95 parts), sodium chromate (around 7 to 8 parts) and caustic soda (around 2 to 3 parts), everything in a very dilute, about 1 to 2 percent aqueous solution.

The reaction of the electrolyte is almost neutral in row I, in row II weakly alkaline and in row III alkaline.

The temperature of the electrolyte can be any reasonable Moving boundaries is usually a moderate one; during the winter months is therefore the electrolyte has to be heated to the bath voltages and accordingly the power consumption favorable to influence.

Each of the rows I, II and III has a lower one like this one larger collection tub (deep tanks I, 1I and III) and one higher up like that one smaller collecting tank (elevated tanks I, 1I and 11I); the containers are best made of wood. The deep tanks are partially and as required with that of the corresponding series of corresponding electrolytes charged. During electrolysis flows to them continuously or intermittently from the individual cells (baths) each Row as evenly as possible the precipitation together with a certain limited part of the electrolyte, as far as this is adapted to its current density Circulation is necessary on dense, smooth wooden channels finite with a sufficient slope to.

A few minutes after the start of the electrolysis, the circulation of the electrolvte, which serves to balance its composition, density and reaction, is allowed to take place by partially opening the shut-off or adjustment devices on the bottom of the box and regulating the outflow as evenly as possible, cell by cell, appropriate to the circulation Shoot through any product a1> and to that accumulates on the bottom of the box by fully opening the shut-off devices. At the same time, an amount of electrolyte that comes as close as possible to the entire process of row II is pumped from deep tank I after previous clarification and separation from the precipitate by means of appropriate measures and devices (filters) into elevated tank II, from where the electrolyte is pumped to the individual cells of row 1I as far as possible flows in evenly, which is achieved by means of a suitable pipe or hose oil channel stone and control devices for the individual cells. Likewise, the clarified or filtered electrolyte is pumped from the deep tank II into the elevated tank III and from there fed to the individual cells of row III in the same way according to their electrolyte flow. The clarified or filtered electrolyte is also pumped from deep tank III into high tank I, which also serves as a common regenerator for the electrolytes of series I, 1I and III; the here by gradual, according to the demand regulated supply of aqueous chromic acid H_ Cr 04, which, however, usually has a certain content of sodium dichromate Na, Cr, 07 +: 2 HZ O, washing water of the products from series 1, 1I and III as well as temporarily Replacement of the relatively small amounts of sodium chlorate or sodium perchlorate, which are mainly lost in the product, refreshed (regenerated) electrolyte flows after thorough mixing from the elevated tank I in the same way to the individual baths of row I according to their electrolyte flow. Depending on a lower or higher content of sodium dichromate in the chromic acid, it will be necessary in the course of operation to eliminate or neutralize a gradually increasing and more and more disturbing t% of the electrolyte of sodium chromate or free sodium hydroxide solution as required to be able to gradually add the electrolyte in the elevated tank serving as a regenerator I, if necessary, for. B. acetic acid C; H., 0., so that then, in addition to the sodium chlorate or sodium perchlorate content of the electrolyte, a sodium acetate content Na C2 H; O- + 3 H_ O arises. The electrolyte in elevated tank I is kept slightly acidic in chromium, as a result of which the sodium chromate is completely or partially converted into sodium dichromate.

At the same time you can, as far as the operation requires, clarified or filtered electrolyte also from the deep tank I into the elevated tank I, from the deep tank 1I into the elevated tank II, from your deep tank III in the elevated tank III, from <learn deep tank II into the elevated tank I, from the Deep tank II into the elevated tank and from the deep tank I into the elevated tank III pumps, whereby the inlet and outlet of the electrolyte in the relevant rows is reinforced accordingly.

Claims (1)

PATENT CLAIMS: Process for the simultaneous production of lead chromates in the Order chrome yellow, chrome orange and chrome red immediately by the electrolytic decomposition of alkali chromate using anodes Lead and a solution salt in one operation, characterized in that for the simultaneous recovery of these dyes occurs during the electrolysis and gradually increasing alkalinity of the bath is made usable in such a way that one the electrolyte in uninterrupted operation, after respective clarification and separation of counterfeit product, in connected additional cells or rows of cells accordingly the three products and after regeneration the cycle again lets begin.