US1487136A - Electrolytic refining of tin - Google Patents

Description

Patented Mar. l8, 1924.

NIT

HARRY n. ALEXANDER, or WESTFIELD SMELTING- AN D BEFININ G COMPANY, NEW J ELECTROLYTIC REFINING OF Tm.

No Drawing. Application filed December 30 -1920, Serial No. 434,124. Renewed October 26,1923. I

To all whom it may concern: 7 Be it known that I, HARRY H. ALEXANDER,

a citizen of the. United States, and resident of \Vestfield, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Electroing is a'specification.

The invention relates to certain new and useful improvements in the production of an electrolytically refined tin from impure tinanodes and the present disclosure constitutes an improvement over the disclosure in the patent to R. L. \Vhitehead, #1,157,- 830, October 26, 1915.

It is suggested in this patent that in the lytic Refining of Tin, of which the followelectrolytic refining. of tin containing lead,

an 'amount of sulphuric acid be added to the electrolyte, which contains'metallic tin dissolved in hydrofluosilicic acid, in an amount sufiicient to convert the lead present into lead sulfatewhiclris insoluble in the electrolyte. The patentee suggests the employment in a twenty-per cent solutiou'of hydrofluosilicic acid to insure the continued maintenance of the electrolytic decom'positiomof the tin during the refining operation.

Under some conditions this electrolyte did not prove entirely satisfactory especially when an addition agent, such as glue was added. For instance, ipolariaation would occur, necessitating the re uent removal of the cathode plates, silica iO would deposit on the anodes and when attempts were made to heat this electrolyte as suggested in the application of Stack Serial N 0. 434,114, filed under even date there would result a loss of acid as silicon fluoride (SiF,,) It was a usual practice in using the patented electrolyte to line the tanks with tar pape'rand pitch which rapidly deteriorated especially when cresylic acid wasused as one of the addition agents in the nianner suggested in.

the application of Frank C. Mathers, Serial No. 257,700, filed Octoberll, 1918. I

,The primary object of the present invention is to provide anelectrolyte which will effectively and continuously dissolve the tin,

which will precipitate-the lead'from the anode, which will prevent the formation of the basicsalts of tin, will render the anode entirely soluble, prevent polarization and permit the use of a tank linin which will be substantially unaffected by t e contents of the tank.

Incidentally other objects of the invention n-nw JERSEY, As'smiron To amnnronn or NEW YORK, N. Y., a oonronarroiv or is to attain high current efliciency and to obtain a smooth, dense, tinof high purity.

I attain this invention broadly simply by adherent deposit of changing the character of the electrolyte de fined in the \Vhitehead patent, above identified, from a hydrofluosilicic acid basis to a sulphuric acid basis. Instead of using merely sufiicient sulphuric acid to unite with the lead present in the electrolyte a materially excessive amount of sulphuric acid is used. Further'and mainly for the purpose of featuring economy in the use of the relatively expensive hydrofluosilicic acid, the contents of this acid in theelectrolyte is reduced with beneficial effect. While it is within the scope of this disclosure to suggest any amount of sulphuric acid in excess of the amountnecessary to precipitate the lead it has been found in practice that six to eight per cent of free sulphuric acid gives the best conductivity and anode corrosion,

but-this proportion is only suggestive of ranged preferably in batteries with the impure tin usually .cast in anodes and each operatively associated in a lead lined'tank with a cathode usually formed of tin. A directv current of suitable voltage and of about eight amperes per square foot of cathode surface is passed from the impure tin as anodes to the cathodes through the sulphuric hydrofluosilicic acid electrolyte as is well known in the racticing of such processes.- The tin is dissolved from the anodes into the electrolyte and deposited out of the "electrolyte upon the cathode plates.

The impurities usually found in such tin will not dissolve from the anode in the presence of the large .excess of tin present and the lead which dissolve'sis precipitated as sulfate and appears as a' slime which is later subjected to other treatments in order a to retain itsvalues.

With this sulphuric acid electrolyte a was possible to use lead lined tanks without anger of destruction from the electrolyte.

The presence of the large excess of sulphuric acid prevents any solvent action of the sulphurous acid on the lead and the resence of the hydrofluosilicic acid even in t 1e reduced 1 proportions herein suggested prevented the formation of basic salts of tin, rendered the anode soluble and prevented polarization.

, of suitable voltage and amperage from the impure tin as an anode to a cathode through an electrolyte which is a solvent of tin and lead and protecting the electrolyte from contamination by lead, by incorporating with the electrolyte an agent which will combine with the lead to form an insoluble compound, said agent being present in an amount materially in excess of the amount necessary to unite with all the lead present in the elec-.

trolyte.

2. In the electrolytic refining of impure tin containing lead, the method of refining tinwhich consists in passing an electrolytic 4 current of" suitable voltage and amperage from the impure tin as an anode to a cathode through a solution of hydrofluosilicic ac d containing an amount of sulphuric acid greatly in excess "of ,the amount sufli-' cient to combine with the lead in the electro- I lyte to form lead sulphate.

3. In the electrolytic refining of impure tin, the method of preventing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin All in hydrofluosilicic acid together with a quan tity of sulphuric acid in excess of the amount suflicient-to convert thelead of the dissolving anode into-lead sulphate thereby to leave some free sulphuric acid in the electrolyte. I v

4:. The process for the refining of impure tin, which comprises passing an electrolytic current of suitable voltage and amperage from a tin anode to a; cathode through a solution of hydrofluosilicic acid contained in a lead lined tank and addin'gto the solution an agent which will protect the tank lining from the solvent action of the hydrofluosilicic acid.

5. An electrolyte for the deposition of tin free from lead, comprising an electrolytic solution of tin in hydrofluosilicic acid containing a large amount of sulphuric acid, whereby, upon the passage of a current therethrough from an impure tin anode containing lead to a cathode, the tin will be dissolved from ,the anode and deposited on the cathode without contamination with lead and in the presence of an excess of the sulphuric acid.

6. In the electrolytic refining of impure tin containing lead, the method of refining tin which consists in passing an electrolytic current of suitable voltage and amperage t'roln the impure tin as'an anode to a cathode through a solution of hydro-.'

fluosilicic acid three-to five per cent and free sulphuric acid six to eight per cent.

7. In the electrolytic refining of impure tin containing lead,the method of refining tin which consists in passing an electrolytic current of suitable voltage and amperage from the impure tin as an anode to a cathode through a solution of hydrofiuosilicic acid three to five per cent and free sulphuric acid six to eight per 'cent and in the presc ence' of an addition agent.

8. In the electrolytic refining of impure tin containing lead, the method of refining tin which consists in passing an electrolytic current of suitable voltage and amperage I from the'impure tin as an anode to a cathode through a solution of hydrofluosilicic acid threeatqfive per cent and free sulphuric acid six to eight per cent and in the presence of .cresylic acid and glue.

SIgned at Maurer, in the county of Middlesex and State of New Jersey this twentvsecond day of December, A. I); 1920. i

. HARRY II. ALEXANDER.