US1837050A - Colloidal diaphragm adapted for use in electrolytic apparatus for the manufacture ofhydrogen and oxygen - Google Patents

Description

Patented Dec. 15, 1931 UNITED STATES- PATENT OFFICE- GEORGE FRANCOIS J'AUBEBT, OF PARIS, FRANCE COLLOIDAL DIAPHRAGM ADAPTED FOR USE IN ELECTROLYTIC APPARATUS FOR THE IANUEACTURE OF HYDROGEN .AND OXYGEN No Drawing. Application filed November 22,1927, Serial No. 235,118, and in France December 1, 1926 I have already shown that it was feasible to employ as a diaphragm for the perfect separation of oxygen and hydro en gas at the time of their formation in tie electrolytic tank, a wire gauze member, a woven fabric, for instance of asbestos, or perforated sheet metal, but on the express condition that the cross-section of each of the innumerable orifices in this diaphragm shall be so small that the surface tension of the liquid contained in each of the minute orifices and formingthesurface of separation between the two fluids (such as liquid, gas or emulsion), contained in the anode and the cathode chambers, shall exceed the counter-pressure prevailing respectively in these two chambers, Which counter-pressure tends constantly to cause the mixing of the oxygen and hydrogen gases, thus forming a dangerous explosive 2o mixture.

If the above-mentioned conditions are strictly observed, a complete separation will be effected, and the oxygen and hydrogen.

gases will each be obtained in a very pure state. i

However, the manufacture of wire gauze, fabrics, or erforated sheet metal, having the necessary egree of fineness to comply with the said conditions, becomes a most expensive matter. In fact, when the holes are of a small size, their number will increase for a given surface, and the cost of manufacture is thus augmented.

A great advantage, and a considerable progress in manufacture, would be obtained by the use of sheet steel having larger holes, or of wire gauze sheets of the current sizes which are found in the market and inwhich the holes are much lar er than what theory prescribes. This would offer a great saving in cost, and would represent a considerable improvement in my said above process. It was however necessary to means for revent-ing the anode and the'cathode gases rom passing through these larger holes.

I have obtained this result by means of a colloidal diaphragm, the sub ect matter of the present invention, which diaphragm is so to speak superposed upon the diaphragm mentioned hereabove.

- I have observed that by the use of a diaphragm' consisting of perforated sheet metal or wire gauze, or even of a strong textile fabric, whose holes are too large to assure a sufficient separation between the anode and the cathode gases in the nascent state, it is simply necessary to coat this diaphragm with the hydrogel of a colloidal substance'which is unafi'ected by the electrolyte in the conditions of the operation, in order to-obtain at once a perfect separation of the gases, and without any appreciable reduction of the electric efficiency of the apparatus.

The term hydrogel refers. to all organic or inorganic bodies in a state of fine suspension in water or in an electrolyte or other solvent, the size of its parti les being between 1/ 1,000 and 1/ 1,000,000 millimeters diameter, which suspended particlw have the property of being transportable in the electric field by the action of the current.

The said colloidal diaphragm according to my invention can be variously manufactured as follows.

L The imperfect diaphragm, such as steef wire gauze N o. 30 to 50, is coated by a spatula with a hydrogel paste already prepared, for instance according to the list given below.

2.-The hydrogel is formed'in the holes of the diaphragm, i. e. the preparation is carried out in situ. Considering for example the wire gauze above mentioned, this is immer'sed in a soluble salt which is dissolved to the proper strength, and then without drying the diaphragm thus'moistened (each l mersed in a solution of another substance,

thus forming the hydrogel by double decomposition or coagulation, or the like.

As an example, I immerse a wire gauze sheet in an aqueous solution of magnesium sulphate or chloride, and then in an aqueuos solution of silicate of soda. There is at once formed in the holes of the wire gauze a hydrogel of magnesium silicate, otherwise known as colloidal asbestos, which is ex tremely porous and forms an excellent diaphra m, thus assuring the perfect separation etween the hydrogen and oxygen.

3.'-I may proceed in the following manner, making use of the fact that the colloidal substances will serve as electrolytes, taking part in the phenomenon of electrolysis and moving in the electric field.

For this purpose I place in an electrolytic tank of any type, the two electrodes, positive and negative, which are separated by an imperfect diaphragm, such as a No. 3050 steel wire gauze sheet. I then add the electrolytic bath (an aqueous solution of caustic soda or potash of 15 to 20 percent strength) holding in suspension the suitable hydrogel which ma be organic or inorganic, all that is require being thatit will be transported by the current, which gradually fixes it upon the diaphragm by an action of adsorption. It is obvious that this hydrogen must not be attacked by the electrolyteto any great degree, in the conditions of temperature and concentration in which the operation is performed with the said electrolyte consisting of water represented by the alkaline solution.

The best results are furnished by the following hydrogels whether or nic or inorganic, these being given sole y by way of example and without limitation-silicates of magnesia, silicates of iron, the kaolins, the ferric hydrates, yellow ochre natural or artificial, the limonites, the clays, hosphates of magnesia and of alumina car on in the form of raphite, carbon from blood, india rubber, t e hydrates ofthe alkaline earths or those ofthe series of rare earths, the flocculent metals such as copper and nickel, and the like. Wherever the use of the phrase colloid impervious to an attack by alkaline solution or alkali, is made in the specification andclaims, it is intended to include any of the above substances.

If the electrolyte consists of a solution of sodium or potassium carbonate, I obtain a good dia hragm b the use of a hydrogel of hydrocar onate of magnesia.

'The quantities of the said hydrogels to be added to the electrolyte are small, as a general rule. When the apparatus is put in operation, I add a quantity which is about 5 to 10 per cent-estimated as dry substancefor each liter of electrolyte.

. As soon as the hydrogel is fixed by electric transportation into the holes of the wire gauze in which it forms a gelatinous spongy substance pierced with extremely fine holes, the bath becomes clearer, due to the absence of the amount of the said substance which has been fixed upon the diaphragm, and-the gases are then perfectly pure.

I add at intervals a certain quantity of hydrogel, in case the portion fixed on the wire gauze should be accidentally detached, and shrogld fall to the bottom of the electrolytic ta' Should the electrolytic apparatus be taken apart, or its use discontinued for a long time, the diaphragm should not be dried, since it would lose its effectiveness; it should be simply washed with water to remove the eyectrolyte, and is then dipped in a 50 per cent glycerine solution and allowed to drain.

Obviously, the three methods of preparation herein specified by way of example may be combined together, or like methods may be devised with equal facility.

My said diaphragm according to the invention may be employed equally well with electrolytic apparatus of the tank type utilizing a diaphragm, or with electrolytic apparatus of the plate type represented by filter presses. My said method is advantageous for these latter, as I may employ if necessary a very inferior grade of asbestos cloth, with a consequent reduction in cost, whereas such material could not be used in the absence of the said layer of colloidal hydrogel. I

What I claim is 1. A process for the manufacture of diaphragms for electrolytic cells which comprises passing a current through an electrolyte containing a colloid impervious to an alkaline solution and depositing the colloid on a metal diaphragm during the electrolysis of the electrolyte while fixing the colloid on said metal diaphragm and maintaining the fiow of the current through the electrolyte.

2. A process for the manufacture of diaphragms for electrolytic cells which are permeable to the electrolyte but impermeable to the gaseous products evolved by the electrolysis which comprises forming a metal diaphragm, surrounding the diaphragm with an electrolyte solution containing a colloid impervious to attack by the electrolyte solution, passing an electric current through the electrolyte and causing disassociation of the elements of the electrolyte while causing the colloid to be deposited on the diaphragm so that hydrogen and oxygen which are bein evolved from the electrolyte will be separate from each other when the colloid has completelX covered the diaphragm.

3. process for the manufacture of diaphragms for electrolytic cells which are permeable to the electrolyte but impermeable to the gaseous products evolved by the electrolysis which comprises forming a metal diaphragm, surrounding the diaphragm with an electrolyte solution containing a colloid impervious to attack by the electrolyte solution, passing an electric current through the electrolyte and causing disassociation of the elements of the electrolyte while causing the.

colloid to be deposited on the diaphra so that hydrogen and oxygen which are a ing evolved from the electrolyte will beseparated from each other when the colloid has completely covered the diaphragm,

In testimony whereof I have hereunto set my hand.

GEORGE FRANCOIS JAUBERT.