US656982A - Electrolytically treating scrap-tin. - Google Patents

Description

' irnn STAT PATENT ()FFICTE.

EDIVARD D. KENDALL, OF NEW YORK, N. Y.

l ELECTROLYTlCALLY TREATING SCRAP-TIN.

SPECIFICATION forming part of Letters Patent No. 656,982, dated August 28, 1900.

Application filed November 20, 1899. Serial No. 737,676. (No specimens.)

To all whom it may concern;

Be it known that I, EDWARD D. KENDALL, of the city and State of New York, have invented certain Improvements in Processes of Electrolytically Treating Scrap-Tin for the Separate Recovery of Pure Iron and Tin Therefrom, of which the following isa specification.

In the processes for recovering the tin from so-called scrap tin-plate heretofore commonl y employed the iron residuum. is of comparatively small value,because itis not wholly freed from tin.

The principal objects of the electrolytic process herein described are to effect the complete dissociation and separate recovery of the iron and tin present in scrap tin-plate and, incidentally, to secure in commercial quanti ties as a by-product a nitrate of the alkali metal or alkalineearth metal the nitrate of which forms the base of the electrolyte employed. Commercial nitrate of sodium, commonly called Chili saltpeter is preferably employed because of its comparatively small cost; but there may be employed nitrate of potassium or ammonium or calcium or any other suitable nitrate, it being understood that a nitrate which in aqueous solution, under the influence of the electric current, would deposit on thecathode any metal other than tin would not be a suitable nitrate for the present purpose.

In carrying the invention into practice there is prepared an electrolyte consisting of an aqueous solution containing five per cent, more or less, by weight, of the nitrate selected. The solution is usually filtered and is then introduced into an electrolytic vat,which may have any desired form or size and may be made of iron or steel or of wood. The inner surface of the vat, which is exposed to contact with the solution, may, if desired, be lined with metal or coated with asphalt or suitable paint or other chemical-resisting material. In appropriate relation to the electrolyte and in any d esired position or positions there may be arranged a plate or plates of carbon or of tin or other metal coated with tin to serve as the cathode. It will be understood that if the vat be made of metal or lined with metal such metal may in some instances be advan 'tageously made to serve as the cathode, particularly if the surfaces in contact with the electrolyte be coated with tin. The scrap tinplate to be operated upon, which may or may not have been passed through corrugatingrolls, is loosely packed to form a mass, which is submerged in the electrolyte and made to serve as the anode by connection in the usual manner with one terminal of acharged electric circuit,the cathode being electrically connected with the other terminal of said circuit. Of course a plurality of so-prepared electrolytic vats, preferably arranged in series, may be operated together. The ensuing chemical action is as follows: Sn-I-NaNO,-l-H,O=Sn0 +NaNO +H The results are the formation of stannic oxid in the form of a solid precipitate, a portion of which on coming in contact with the cathode will be reduced to metallic tin. A further result is the reduction to a nitrite of the sodium nitrate or other nitrate originally contained in the electrolyte. After using the electrolyte until it ceases to act with the desired energy I add enough of the nitrate (say sodium nitrate) to restore efficiency to the solution. By such repeated. addition the solution finally becomes heavily charged with sodium nitrite and usually contains a small proportionate quantity of unchanged nitrate and also some ammonia resulting from the electrolytic decomposition of the nitrite. It may also contain traces of tin, which may be recovered by electrolysis when deemed expedient. This strong solution of sodium nitrite is conducted to any suitable evaporating plant in which the water present is driven off, leaving as a residuum the salts from the solution in a solid form available for use as asource of nitrogen in the preparation of agricultural fertilizers.

Should the electrolytic operation have been carried so far as to have generated in the solution a material quantity of ammonia, this may be neutralized with an equivalent quantity of sulfuric acid, in which case the saline mass recovered from the solution will contain some ammonia sulfate, also useful for fertilizing purposes.

The stannic oxid, which forms a precipitate in the electrolyte, and any metallic tin which may have been produced may be from time to time collected and utilized in any of the usual Ways for the production of sodium stannate or metallic tin.

It will be understood that the treatment is more or less prolonged according to the greater or less size of the mass of scrap-tin submerged in the electrolyte, until the tin and iron present are completely dissociated. The sodium nitrate employed as herein set forth is so effective an electrolytic agent that the component metals of scrap tinplate can be completely separated within thirty minutes by the use of a six-volt electric current of adequate amperage.

The advantages of the described electrolytic treatment of scrap tin-plate are threefold-to wit: first, the complete separation of the tin and the production of a pure iron having the same commercial value as like grades of iron uncontaminated with tin;

secondly, the absence of any evolution from' the electrolyte of any noxious or deleterious gases, and, finally, the opportunity afforded for the recovery of a valuable by-p'roduc't to wit, the described nitrite available in the manufacture of agricultural fertilizers. What is claimed as the invention is 1. The improvement in the art tr elefctrolytically dissociating the iron and tin of socalled scrap tin-plate, which consists in the preparation of an electrolyte composed of an aqueous solution of a nitrate of an alkali metal, or a nitrate of an alkaline-earth metal the introduction into said electrolyte of an anode 'consistin g of .a mass'of scrap tin-plate;

the electrical connection of said mass with one terminal of a charged electric circuit and i the establishment in contact with said elec- I trolyte, of a suitable cathodeelectricallyconnected with the other terminal'of'said charged electric circuit.

2. The improvement in the electrolytic treatment of scrap tin-plate, which consists in the preparation of an electrolyte composed of an aqueous solution of a nitrate of an alkali metal, or a nitrate of an alkaline-earth metal; the introduction into said electrolyte 3 of an anode consisting of a mass of scrap tinwhich consists in submerging an anode composed of said scrap tin-plate in an electrolyte composed of an aqueous solution of a nitrate of an alkali metal or anitrate of an alkalineearth metal 5 the electrical connection of said anode with one terminal of acharged electric circuit; the establishment of a suitable cathode electrically connected with the other terminal of said charged electric circuit Whereby the nitrate originally present is transformed into a nitrite; the addition of sodium or other nitrate to the solution from time to time as required, and finally, the collection I and evaporation of the resulting strong solutioP for the recovery of the salt therefrom in a solid form.

4. In the electrolytic treatment of scrap tinplate, consisting in the submergence of an anode composed of scrap tin-plate in an electrolyte composed of an aqueous solution of sodium or other suitable nitrate, and in contact with a suitable cathode, the said anode and cathode electrically connected respectivel'y with the opposite terminals of a charged 'electric circuit; the introduction into the said electrolyte from time to time, as required, of additional quantities of said sodium or other hitrate, ah'd the concentration by evaporation of the resulting'strong solution for the recovery of the nitrite therefrom.

EDWAR D. KENDALL. Witnesses:

' A. M. JONES,

E. GATTERER.