US637638A - Composition for sensitizing paper or other surfaces. - Google Patents

Description

mfA W NITED STATES Fries,

PATENT J OHANNES MEYER, OF NEW YORK, N. Y., ASSIGNOR OF TI-IREE-EIGIITHS TO GOTTFRIED PIEL, OF SAME PLACE.

COMPOSITION FOR SENSITIZING PAPER OR OTHER SURFACES.

SPECIFICATION forming part of Letters Patent N 0. 637,638, dated November 21, 1899.

7 Application filed September 5, 1899. Serial No. 729,522. (No specimens.)

To all whom it 'n'tay concern.-

Be it known that I, J OHANNES MEYER, doctor of medicine, of the city of New York, in the borough of Brooklyn and State ofNew York, have invented certain new and useful Improvements in Compositions for Sensitizing Paper or other Surfaces; and I do hereby declare that the following is a full, clear, and exact description of the same.

This invention is based upon the discovery of the valuable properties of the silver phosphates when combined with organic acids, such as acetic, tartaric, citric, and succinic acids. The silver phosphates have so farnot been employed for photographic or other purposes, and the only mention for any application made of them is to be found in Hardwichs llfamtal of Photographic Chemistry. He writes: Other insoluble salts, such as the phosphate and citrate, render the paper more sensitive than when it has been treated with a soluble salt of silver only. The great value of the silver phosphates consists in their property of forming emulsions with suitable organic acids which behave in all respects like the well-known emulsions of the silver haloid salts with albumen, gelatine, or collodion. I have discovered that the silver phosphate, aside from being soluble in am monia, phosphoric-acid and nitric-acid solutions, as was well known, form solutions with a number of organic acids-as, for instance, acetic, tartaric, citric, and succinic acids; but under certain conditions silver phosphates will form in conjunction with an organic acid a true emulsion. I have studied the behavior of silver phosphate toward tartaric acid in this direction most carefully and, as the tartaric-acid-silver-phosphate emulsion is chiefly employed, I will now proceed to give directions how to prepare and how to use it.

To an aqueous solution of one dram of silver nitrate a well-diluted solution of sodium phosphate is added. The resulting silver phosphate is well washed by decantation and brought to the volume of one fluid ounce. To this silver phosphate held in suspension I add five drams of tartaric acid dissolved in five drams of water, at the same time imparting to the containing vessel a quick rotary motion. In this way is obtained a white jelly-like mass of a volume of two ounces con taining a quantity of silver phosphate equiv-- alent to the dram of nitrate we started from.

It is essential that all the chemicals, including the water, be chemically pure. To render this emulsion more fluid, it is either slightly heated or agitated with a glass rod or by shaking the bottles. In this state it is used for coating the paper or other surfaces on which it is desired to print.

The proportions given above are the best for practical use. The preparation of the emulsion is, however, easier for one not experienced in this special line of work by mixing a fluid ounce of silver phosphate with a smaller quantity of tartaric acid-for instance, two drams of acid in two drams of water-when the emulsion will set more readily. Vhen the emulsion is left in its jellylike state, crystallization will set in after some time, while a portion of the silver is retained in the solution. Citric acid seems to have the greatest aflinity for silver phosphate. Twelve drams of citric acid mixed with one fluid ounce of silver phosphate will produce a clear transparent solution which has remarkable sensitiveness and qualities. The emulsion or solution of silver phosphate in organic acid thus obtained is then applied in any suitable manner to the surface to be sensitized. It may be applied by means of a soft flat caInels-hair brush to paper, after which it is permitted to dry. When this sensitized photographic paper is exposed underanegative to direct or shaded sunlight, a positive picture of great accuracy and agreeable tone is obtained. When the paper is first coated with albumen or gelatine or any similar substance, a photographic print can be produced 0 in less time than by the silver haloids heretofore employed, and not only sunlight but also artificial light can be used for producing a direct print. The photographic print thus obtained can be toned by any of the well- 5 known toning solutions and finally fixed by means of sodium hyposulfite. The print is then washed until no traceof the hyposulfite is left in the same. In place of paper any other material such as wood, celluloid, litho- I00 I graphic stone, silk, cotton, or other textile fabric, and other materials-can be coated with the composition and pictures of great delicacy and beauty, not inferior to prints on paper, he produced thereon.

The advantages of these compositions are to remove the unchanged silver and render the prints permanent.

When the prints are left in the fixing-bath for a longer time than a minute, the sulfuration of the prints will commence, which is induced by the organic acid and which will be completed to blackness of the picture in a few minutes more. Though sulfurtoningis believed to have many objectionable features, the prints made by the process described do not suffer in appearance if the sulfuration is not too long continued. The use of albumen will prevent the prints which have been toned by sulfur from becoming yellow and faded by atmospheric oxidation. were obtained by a number of tests continued through a considerable period of time. The dominant colorof the prints made by the silver-phosphate emulsion or solution is a brown or auburn shade, which darkens considerably with the drying of the prints. Toning may therefore be dispensed with in many applications in the arts. When the prints are made on textile fabrics, they are generally'brown in tone; but this can be changed in the case of cotton to black by passing a hot fiat-iron over the same, while prints on silk will not undergo this change. Though the predominating color of the silver-phosphate prints is brown, many of them show various other tones, and it must be assumed that certain negatives act as media for the transferring of color qualities and influencethe production of the tone to a certain degree under conditions not yet known. When a silver-bromide emulsion is added to a silver-phosphate emulsion, the sensitiveness of the emulsion is so increased that even the light of a common petroleum-lamp is sufficient to produce a direct print. The sensi- These results the addition of a small quantity of citric acid. Thesolution of silver phosphatein citric acid whenapplied to aplain piece of paper and exposed under the negative to direct sunlight produces a print of a very agreeable bluish tone, which will compare favorably with other prints in accuracy, in the high lights, and in the depths of the shadows. I

Paper coated with albumen andsensitized with a silver-phosphate emulsion or solution has great durability and will not deteriorate under climatic influences. It can be used, therefore, at any time for printing without impairing the quality of the print.

By my improved silver-phosphate emulsion or solution positive pictures can be made with but little trouble and in a very short time. The print is removed from the printing-frame directly to the fixing-bath, to which sodium bicarbonate is added when the original color of the print is to be preserved. The print re= mains in the fixing-bath for a short time and is then freed from any adhering traces of sodium hyposulfite by washing it in hot or cold water for about five minutes.

I do not claim in'this application the process of sensitizing paper and other surfaces, as aseparate application for Letters Patent has been filed for the same,dated July 22, 1899, Serial No. 724,792.

Having thus described my invention,- I

claim as new and desire to secure by Letters Patent-- 1. A composition for sensitizing paper and other surfaces, consisting of silver phosphate combined with an organic acid, substantially as set forth.

2. A composition for sensitizing paper and other surfaces, consisting of silver phosphate combinedwith tartaric acid, substantially as set forth. I

3. A composition for sensitizing paper and other surfaces, consisting of silver phosphate combined with tartaric and citric acids, substantially as set forth.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscribing witnesses.

JOHANNES MEYER.

Witnesses:

PAUL GOEPEL, M. H. WURTZEL.