US1224984A - Process of eliminating salts of the weak sulfur acids from fixed photographic media. - Google Patents

Description

S. H. WEINHANDLER & J. S. SIIVISOHN. PROCESS OF ELIMINATING SALTS OF THE WEAK SULFUR ACIDS FROM FIXED PHOTOGRAPHIC MEDIA.

APELICATION FILED SEPT. 9. 1916.

1,224,984; Patented May 8, 1917.

Wm Q3. GSA-Mm a QflZ- M WW SAMDSON H. WEINHANDLER, OF NEW YORK, N. Y., AND JULIAN S. SIMSOHN, OF PHILADELPHIA, PENNSYLVANIA.

PROCESS OF ELIMINATING SALTS OF THE WEAK SULFUR ACIDS FROM FIXED PHOTO- GRAPHIC Continuation of application Serial No. 22,352, filed AprillB, 1915.

Serial No.

I To all whom it may concern:

Be it known that We, SAMPSON H. WEIN- HANDLER, a citizen of the United States, and a resident of the borough of Manhattan, city, county, and State of New York, and JULIAN S. SIMSOHN, a citizen of the United States, and a resident of the city of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in the Process of Eliminating Salts of the Weak Sulfur Acids from Fixed Photographic Media, of which the following is a specification.

This invention relates to photography, and more particularly to that part of the photographic art which pertains to the removal of chemicals of fixing baths used in photography, as for instance, the removal of sodium thiosulfate. Heretofore various methods of removing sodium thiosulfate, sodium sulfite and other salts of the weak sulfur acids have been used, but these methods have been foundimperfect, due first to an additional action of the added chemical on the image, and secondly, because of their comparatively high cost. For this reason, the washing method is still largely employed. This washing method frees the medium, as the negative or positive, by washing it in running water or in fresh Water from onehalf an hour to an hour, such washing being necessary, as is well-known, because if the fixing chemicals are not removed, then the plate, film or print would deteriorate in a short time and would not be fit for further use.

Our invention overcomes these disadvantages, and provides a method whereby photographlc media, as plates, films 01' prints, may be treated in a very efiicient and timesaving manner, the use of our method rcquiring but a. short time to insure the removal of the sodium thiosulfate, sodium sulfite, or other salts of the weak sulfur acids, without injuring the photographic media treated.

In carrying out our invention, we develop the plate, film, or print in the usual manner well--known in the art. and tlldiiizlfiil fix the plate, film or print with sodium thiosulfatc, sodium sulfite or other salts of the weal: sul- Specification of Letters Patent.

MEDIA.

Patented May 8, 1917.

This application filed September 9, 1916. 119,785.

fur acids, to which in some cases alum or pochlorite, this being made intentionally strongly alkaline, so that the alkalinity causes the pores of the gelatin on the film or plate to be opened, whereby the sodium hypochlorite can act upon the material desired to be removed, before the medium is bleached or otherwise injured. A suitable solution is of such alkalinity that it requires 20 cc. of a 10% normal solution of sulfuric acid to neutralize 1 cc. of it. It is necessary to open the ports of the gelatin very rapidly, as before set forth, in order to remove the hypo for the sodium hvpochlorite bleaches the film, which is objectionable. A solution of the strength before described can accomplish the desired result in three minutes, in which time there is no bleaching of the films.

A suitable solution and a suitable relative concentration of the OH ions of the alkali with respect to the active ions of the sodium Conditions, of course, will vary with the character of the film, the degree of acidity of the hypo bath. etc, but from two to three minutes are sufiicient.

By means of the addition of the sodium carbonate to the bleach powder, sodium hypochlorite and an insoluble calcium carbonate are formed, which latter substance can be removed in any suitable way. The sodium hypochlorite thus produced is intentionally strongly alkaline, due to the formation of some sodium hydrate. This sodium hydrate is formed because commercial bleach powder contains calcium oxid, which when acted upon by sodium carbonate, produces sodium hydrate.

The resulting reaction produces a soluble substance (Glauber salt or sodium sulfate),

, which is readily soluble and quickly removed by dipping or washing in water. At the same time, the alkalinity has a favorable action upon the photographic medium, in that r it prevents it from becoming brittle.

A photographic medium treated by our improved process in the manner before described, when placed in an aqueous solution sulfur acid remain, then the pink coloring 1s changed to a brownish-yellow color.

Our process adapts itself especially to the treatment of the ordinary films for motion pictures, and for photographic processes where rapidity of manipulation is essential. A large amount of time is saved, and also a considerable expenditure due to the need oflarge quantities of water.

A second feature of our invention consists in producing sodium hypochlorite s1- multaneously with the immersion of the v films, plates, or other media, after they have been treated with the sodium thiosulfate, so-

dium white, or other salts of the weak.

sulfur acids. For this purpose, the plate, film, print or other medium is placed m a container of suitable proportions, in which non-attackablesuitably spaced electrodes are placed, and in which an aqueous solution of ordinary salt, (sodium chlorid) is placed.

An apparatus suitable for carrying out this part of our invention is shown in the drawing, in which 1 represents an ordinary tank for electrolysis, containing the solution 2, this tank having the electrodes 3 and 4.. Current can be admitted by means of the switch 5 which makes contact with the mains 6 and 7. A resistance 8 is provided, as

also an ammeter A and a voltmeter -B. More solution can be admitted from an upper tank 18 and a pipe 9 having the valve 10. By the electrolysis produced by the passage of the electric current, sodium hypochlorite can be produced, the amount thereof depending upon the current, which can be regulated so as to produce just such a quantity of sodium hypochlorite as is necessary to combine with the sodium thiosulfate or the like, and form the soluble sodium sulfate. The strong alkalinity of the solution will at the same time give the advantages before described, to wit, the rapid opening of the pores of the gelatin of the photographic medium. In the formation of sodium hypochlorite as described, by electrolysis, a small amount of chlorin escapes as the gas is formed, leaving an excess of sodium hydrate (NaQH), thus producing the alkalinity of the solution, this being due to the fact that there is only a reasonable mixing of the products from the anode or cathode. This is different from the known process of making sodium hypochlorite, in

which large quantities are produced with constant agitation, whereas in our process no agitation is allowed to take place.

After the photographic medium has been subjected to the action of the sodium hypochlorite, it is removed to a water bath, water spraying device, or other suitable means for the purpose of washing out of the solution the sodium sulfate. This washing only takes a few minutes, as dipping in water for sixty to one hundred andtwenty seconds, whereby the complete removal of the sodium thiosulfate or the like is assured.

Gelatin has been spoken of, but it is clear that the invention can be applied to other media usuable in the photographic arts and processes. I Similarly, instead of sodium hypochlorite, we have found that sodium hypobromite, which can also be obtained by the electrolysis of sodium bromid, may be used, and we have found further that any electrolysis carried out. as above described, using an aqueous solution or one of an alkali, produces the desired result.

Similarly, the alkali and the sodium hypochlorlte need not be combined in one solutlon as is obvious, since the medium can be lmmersed in an alkaline solution having the desired degree of alkalinity until the pores of the gelatin are thoroughly opened, and it can then be immersed into a solution of the sodium hypochlorite.-

We have described an effective embodiment of our invention, but it is clear that nuinerous changes may be made 'in the de* tails thereof, such as in the strength andproportions of solutions and the meet various conditions, and we do to be limited thereto.

We claim z- 1. The process herein described of treatng a photographic medium, which consists 1n subjectin the thiosulfate held in the gelatln of the lms, to the action of a strongly alkaline solution of sodium hypochlorite for producin a soluble substance, saidsolution like, to not wish being su cientlyalkaline to rapidly open the pores of said gelatin before said film is bleached, and washing out this soluble substance.

2. Theprocess herein described of treating developed and fixed photographic medium containing salts of the weak sulfur aclds, which consists in subjecting said medium to the action of a, strongly alkaline solution of sodium hypochlorite for the urpose of opening the pores of the ge atin rapldly, said solution of sodium hypochlorite forming a soluble substance of said salts, and

.then removing said soluble substance, said alkaline solution being so strongly alkaline as to open the pores of the gelatin before said film is bleached;

3. The hereindescribed process of treatmg a developed and fixed photographic medium containing a salt of weak sulfur acids to a solution of a halogen salt, which is being subjected to the action of a controlled electric current, whereby the salt of a hypo halogen acid is produced in a quantity proportional to the quantity of said Weak sulfur acid and said medium, for forming a soluble substance therewith, and thereafter removing said soluble substance, said solution being maintained in a state of substantial quiescence, an alkaline hydrate being formed by the action of said electric current, so as to make said solution strongly alkaline as to open the pores of said gelatin, before said medium is bleached.

1. The herein described process of treating fixed and developed photographic media containing salts of the weak sulfur acids, which consists in subjecting them to the action of an aqueous solution of common salt which is being decomposed by a controlled electric current, to produce quantities of sodium hypochlorite for forminga soluble substance with the said salt of the weak sulfur acid, washing out said soluble substance with water, said solution being maintained substantially quiescent during the electrolysis, and being always maintained so strongly alkaline as to rapidly open the pores of the gelatin of said medium, before said medium is bleached.

5. The process herein described of treating fixed and developed photographic medium containing a salt of the weak sulfur acids, which consists in treating said medium with a strongly alkaline solution of salt of a hypo halogen acid for producing a soluble substance, and washing out said soluble substance, said solution being so strongly alkaline as to produce the said soluble substance before said film is bleached.

In testimony, that we claim the foregoing as our invention, we have signed our names in presence of two subscribing witnesses.

SAMPSON H. WEINHANDLER. JULIAN s. SIMSOHN.

Witnesses:

MURRAY R. LAzAnUs, A. Y. CONGAN.

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