US1602591A - Photographic light-sensitive material containing tellurium and process of making the same - Google Patents

Description

Patented Oct. 12, 1926 UNITED "STATES PATENT OFFICE,

SAMUEL E. SHEPPARD, OF ROCHESTER, iii'EW YORK, ASSIGNOR NEW YORK, A CORPORATION COMPANY, OF ROCHESTER,

OF NEW YORK.

PHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL CONTAINING TELLURIUM AND PROCESS OF MAKING THE, SAME.

Re Drawing. Original application filed June 6. 1824, Serial No. 718,411. filed January 21, 192a. Serial No. 82,846.

, This application is a division of iny prior application No. 718,411, filed June 6, 1924, for photographic light sensitive materials and processes of making the same, which has 6 matured into Patent 1,574,944, granted Mar.

This invention relates graphic materials.

One object of the invention is to rovide photographic emulsions, especially evelopmg-out ones, buying new or improved properties because of the use or presence therein of materials, the scnsitizin properties of which I have discovered; r ti 1 another object of m invention is to provide procassess in which such materials are used to improve photographic emulsions, especially developing-out ones, as regards li ht-sensitiveness, by whichte'rm I include their ability to give the earliest visible impressions or image with the minimum exposure or their ability to ive densit after a 'ven exposure or both, t e usual pliotograpl i m'e'nts, being used in preparing such impressicns or image or densi y. v further object of the invention is to provide colloid as gelatins, the usefulness of which for forminglight sensitive especiallydeveloping-out emulsions, greatlyincreased and controlled by my said sensitizing materials incorporated therewith. Another object of the invention is to revide processes for preparing said colloid products orintermedlates, herfobjects are,to increase the sensitiveness of photographic emulsions, especially develo ng-out emulsions, while wholly or partia 1y dispensing with expensive or ion and uncertain so-called ripening met ods; to enable the use of a type of gelatin having desirable physical qualities in making a photographic emulsion of eater light-sensitiveness than that norma y obtainable with said gelatin; to obtain more stable emulsions through the purity of the ingredients; to increase the light-sensitive ness of photographic emulsions, particularly developing-out ones, the grain characteristics' of which have already been determined to increase the general li ht-sensitiveness of such photographic emu ions throughout to the art of photoa0 is K products, such for instance photographic emulsions,

Divided and this application the spectral ranges to which they are nor-. mallv sensitive; to make such, photogra hic emu sions of standard light-sensitive c ar tellurium atom which is joined by a double metalloid atom (not one 4 bond to a single bond to one atom, different atom) to up of atoms i s iesirable that of atoms be such and the other bond to a which at least another the last mentioned group that it induces in the compound a chemical affinity for silver halids,

for instance the compound maycombine to an apreciable extent with silver halid to form a soluble complex salt when said atomic "roup is present. oreover, the metalloi atom to which the atom of tellurium is joined by a double bond is in many instances. but not necessarily, a carbon atom. I

For some of the preferred examples of my invention, I select from the above seriesthe following subseries tellurocarbamids. the corresponding carbimids are likewise usable in prefepred examples of my invenchanged into said cartion and are readil bamids, especially or instance in emulsions itwlll be of the alkaline or ammonia v understood that the correspon mg carbimids are included hereinafter when said carbamids are claimed. These subseries of carbamids and carhimids include many compounds containin one or more substltuent radicals, such as kyl, a l, acyl, alkyl-oxyi aryl-oxy, etc., groups. xamples are ally isotellurocyanate, allyl tellurourea. Not only can each compound of my 581168 of T0 nasmun xonnx is attached. Generally it I light-senstitzers be used alone to improve an emulsion (or colloid for an emulsion) but two or more of such compounds may be used together to obtain their mutual or cumulative effects.

It is a common characteristic of the com ounds which I use, that said double bon ed tellurium atom is chemically held in the molecule with intermediate firmness. Such atom does not react on silver halids as readily asthe sulfur atom in sodium su'lfide for instance, but it separates out more readily than the sulfur atom in ethyl mercaptan for example. Consequently said double bonded sulfur-group atoms in my compounds correspond roughly in the firmness with which they are held to the firmness with which the sulfur atoms are held in the so-called potential mercaptans, although there is, of course, some range of difference in the firmness with which said double-bonded atoms are held in the different compounds of my series. The sensitiveness o' the grains of silver halid in emulsions has been shown to correspond to the presence in said grains of nuclei of unstated chemical composition. I, therefore, attribute the sensitizing action of my compounds to their formin in the emulsion grains small, mostly ultramicroscopic, nuclei which include silver combined with tellurium. The intermediate firmness with which said double-bonded atoms are held in my compounds facilitates this scattered formation or reaction without reacting on the whole of each grain. Since this deduction is not indispensable to the ractical using of my invention, I do not WlSll to be limited to it except as defined in the claims.

I have also found that the proportions in which my compounds are incorporated in the emulsions (or in the colloids for the emulsions) are important. If used in too high concentrations, they cause fog, and sometimes reversal. The largest proportions which can be effectively used vary somewhat with the particular sensitizin compound or com ounds which are use with the roportion of gelatin to silver hahd in the emulsion, with the type of emulsion as regards grain size characteristics and alkalinity, with the amount of natural sensitizer originating in the gelatin when the latter is manufactured, with the particular silver halid or halids employed, the standard as regards fog which it set by the emulsion maker, etc. This maximum proportion is in any specific case easily found, being about as readily determined by routine test as, for example, the proportion of sulfur permissible in steel for a particular purpose. It is, however, always surprisingly small. In general with gclatino-silver-halid developingout emulsions, it should be less than about 10 grains of active sensitizing compound, in 130 pounds of emulsion (the latter being computed as the weight of its non-aqueous ingredients in the dry state); or less that about10dgrains in 100 pounds of gelati (com ute as dry gelatin,)' when it is adde used in makin the emulsion. A quantity which causes immediate fogging tendency should not be used,that is, a quantity which causes more than the tolerated fog allowed in the particular type of emulsion in the trade after the customarily allowed period of storage. I have found 2 to 3 rains of sensitizing compound, to 100 pounds of gelatin (computed as dry) or 130 pounds of emulsion (computed as dry) is within the usefullimits and generally excellent,-say for instance with alkaline developin -out gelatino-silver-hali'd emulsions. 0 course, smaller amounts of sensitizers are employed when less sensitizing effects are desired; but it is important not to exceed the upper limits as stated above.

Because only very minute quantities of my sensitizing compounds are used, (often less than one three hundred thousandth of the weight of the emulsion) the addition of them does not appreciably dilute the emulsion or emulsion-forming colloid; nor does it affect their physical properties. Consequently, the use of my compounds provides a novel, dependable, and independent way for controlling the roperties of photographic emulsions in a dition to the customary expedients hitherto available. Gelatins, for instance, can be selected for their physical properties, such as setting ability, melting oint and viscosity, without regardvto w ether they can be made into sufiiciently li ht-sensitive emulsions, and any deficiency 1n sensitizing power can he made up by incorporating a little quantity of one or more of my independent compounds. Nor are the grain-size characteristics affected by such additions of my compounds, they being independently controlled I y the emulsion maker. In other words, I can establish a ratio of sensitizing compounds to silver halid in the emulsions which is independent of the ratio of gelatin to silver halid. Still differently stated, the sensitiz-er compounds can be added without adding any colloid, such as gelatin, and are, therefore, independent thereof.

My sensitizin compounds act as so-called chemical sensitizers instead of as optical sensitizers. In other words, they increase the eneral sensitiveness of photographic emulsions, notably developing-out ones, in which the are incorporated,that is to light of su stantially the same wave lengths as those to which the emulsion would be sensitive without the incorporation of my compounds; instead of merely increasing the to the gelatin before the latter is.

sensitiveness to some narrow group of wave lengths. Unlike the effects of dyes, the sensitiveuess is increased throughout the normal spectral range of the emulsion instead of at only those spectral points corresponding to the spectral absorption of the sensitiz ing compound. My compounds are effective in increasing the general light-sensitiveness of orthochromat-ic, panchromatic, X-ray, and all special emulsions, as well as the ordinary or non-color sensitized ones. They can be added without or with sensitizing dyes or before or after them. They do not specifically aii ect the dye action; but simply increase the general sensitiveness and thus in crease the ordinary sensitiveness to blue light to at least as great an extent as to light of a color corresponding to the dye.

My sensitizing compounds may be used in many ways. Broadly they may be incorporated in emulsions or in colloids for emulsions or both. The can also enter the emulsion mixed with other ingredients thereof whether organic or inorganic. They may be added at different stages of emulsion manufacture, even when the latter is otherwise completely ready for coating. Since their action is rapid when incorporated, the coating in such case need be delayed only long enough to mix in the sensitizing compounds. With the grain characteristics, such as size distribution. etc., already determined, and the other physical and photographic properties of the emulsion already taken care of at this stage, I can practically independently increase its light-sensitiveness without impairing said other properties by adding one or more of my compounds. The latter are especially effective in emulsions which are, at least slightly, alkaline.

Where difi'erent batches of emulsion, especially developing-out emulsions, fall below a required manufacturing standard of light sensitiveness, although they may be otherwise satisfactory, their sensitiveness can readily be brought up to standard by mixing in my sensitizing compounds, the proportion varying with the increase necessary to produce a uniform product. Emulsions having almost no practical light-sensitiveness but having enough other desirable qualities can be made usefully light-sensitive by m compounds. Thus the latter are useful in connection with emulsions having good initial light-sensitiveness and those having almost no initial sensitiveness. The increase in sensitiveness can be effected in one step by thoroughly stirring all of the sensitizing compound into the emulsion at one time; or it may be incorporated part at a time in successive ste s. When making new batches of emulsion rom the same materials which have yielded deficient emulsions, correctional quantities of my sensitizing compounds can be premixed with an ingredient; such as gelatin.

The following example illustrates how light-sensitwe photographuemulsions of the developing-out type may be prepared and improved by the aid of one or more of my sensitizing compounds. Of course, my inventionis not restricted to this illustration, except as indicated in the claims. The emulsion-forming operations hereinafter described are along the lines of known practice, see for instance Die lhotographie mit Bromsilber Gelatin by J. M. llder. published in Halle, Germany in 1903 by Wit helm Knapp as part III of Eders Ausfiihrliches Handbuch der Photographic."

The two following solutions are made up, the parts being by weight:

A. 900 parts of silver nitrate in 9,200 parts of water.

B. 690 parts of potassium bromide and 50 parts of potassium iodide in 0,100 parts of water along with 300 parts of gelatin.

In mixing B, the halid salts are first dissolved, the water and the gelatin then added to the salt solution. Solution B is then warmed, say to 140 F. or 150 F. for example and the silver nitrate solution A is gradually added to it with constant stirring. It is preferable to warm solution A before adding it to B, say to 150 F. or 160 F. for instance. lVhen solution A has been thoroughly incorporated in solution B, there are then added 43 parts of strong ammonia pre viously dissolved in 900 parts of water. The emulsion formed by these operations is allowed to stand for a short time, say 15 minutes to a half hour for example. Then 1050 parts of gelatin are dissolved in it with thorough mixing. The emulsion is next cooled, such as by keeping in a cool space, until it sets to a firm jelly. The latter is broken up, as by shredding for instance, and thoroughly washed to remove soluble salts, such as potassium nitrate and any excess potassium halids. The wash water is, of course, cool enough not to melt the pieces of emulsion jelly. The washed emulsion is next remelted to 100 F. and 1050 parts of water soaked gelatin are thoroughly mixed into it, the temperature then being raised, say between 120 F. and 150 F., for instance. for a short time, say a few minutes. It is then cooled and set. It is an example of the ammonia or alkaline type of developing-out emulsion.

lWy sensitizing compounds may be usefully incorporated at any stage of the above described process of preparing the emulslon, even being premixed with solutions A or B or with ammonia or with the gelatin. at the initial stages. When the compounds are incorporated in either a partly or wholly prepared emulsion, they are most conveniently handled by dissolving them in a solvent which is inert with respect to the emulsion and simply acts as a vehicle to help in spreading the compounds throughout the emulsion. So long as an even distribution of the compounds throughout the emulsion is effected and the correct proportion of them is added, their particular concentration in the solvent or vehicle is not important. It is ood practice to keep the volume of the solution added to the emulsion under 2% of the volume of the emulsion; but this is not indispensable. For example, where 1 part of allyl tellurourea by weight is to be incorporated into 300,000 parts by weight of the above described emulsion (computed as the weight of its non-aqueous ingredients) the emulsion is melted, the sensitizer dissolved in ethyl alcohol or water or a mixture of them, the volume of said solvent being under approximately 1.5% of the volume of the melted emulsion, and then the solution is thoroughly mixed into the emulsion. When necessary to minimize dilution, the volume of solution can be kept even below a fraction of I may mention also as very useful potassium tellurocyanide.

With its light-sensitiveness increased by my compounds, the emulsion, being melted to the desired flowability, is coated on its support such as glass, film, paper, etc., in the well known way. It is convenient to control and check the process by coating samples of the emulsion before and after the addition of my sensitizing compounds, the coated specimens being tried out photographically by any well known sensitometric test, or even by comparative camera exposure on the same subject under like conditions. Of course, the usual precautions are observed during the emulsion making and coating processes, such as the use of non-actinic or safe light, cleanness of vessels and air, etc.

The different gelatines sold for photographic emulsion-making may be used in the example given above, hard ones being very useful. The temperatures given are, of course, adjusted if the particular gelatin employed has physical properties, such as meltmg and setting points, which deviate considerably from the usual ones, such adjustment being a matter of routine control.

Instead, however, of using gelatins which give emulsions of useful but lower sensitiveness even before the addition of m sensitizing material, an almost inert ge atin may be employed,-one which forms an emulsion which produces a developable image, if at all, only after impractically long exposures, and then does not yield an ima e of desirable density. A gelatin which orms such a practically inert emulsion may be prepared in the way described under the heading Preparation of ash-free gelatin in pages 1856 and 1859 of the Journal of the American Chemical Society, September, 1922, vol. XLIV, No. 9, bemgpart of an article by Sheppard, Sweet, and Benedict on Elasticity of purified gelatin jellies as a function of hydrogen-ion concentration. Emulsions of impractically low light-sensitiveness made by the above described process from such prepared gelatin, are transformed by my sensitizing compounds into emulsions which give developable ima es of excellent density after usfully brie exposures. have, for example, been able to increase the light-sensitiveness of some such low sensitive emulsions ten or even over twenty times, the exposures for a given subject in the latter case being cut to less than one twentieth of the original one and the image density being made excellent by a corresponding gain. Increases of the same general order of magnitude are made when my sensitizing compounds are added in similar proportions to emulsions which are made from normal photo raphic gelatins or mixtures of such norma gelatins with said almost inert gelatins, and already have useful, but lower initial sensitiveness. Difierent ercenta es of sensitizer produce correspondingl difi'erent increases. The increases in deve oping-out emulsions appjear upon the usual developing operations. ustomary pyro and metal-hydrochinon alkaline developers are suitable for example. An inert emulsion prepared as above described is a very useful medium or standard in which to test the sensitizing properties of different compounds, a sample containing the compound under test being tried out photographically along with a parallel sample of unsensitized emulsion.

Instead of the inert gelatin prepared according to the reference given in the preceding paragraph, I can prepare inert gelatins by treating active photographic gelatins with oxidizing agents. The latter oxidize the sulfur in the sensitizing substituted (allyl) thiocarbamide or corresponding carbimide, which occurs naturally in photographic elatins, thus converting it to a non-sensitizing compound and leaving the gelatins practically inert. Dilute aqueous solutions of a peroxide, such as sodium peroxide (say from 5 to 10% by weight) is intimately mixed into the gelatin and then washed out when the oxidation has occurred. The inert gelatin referred to in the preceding paragraph can be thus oxidized to make its inertness doubly sure.

When preparing inert elatin on a considerable scale, it is far preamble to introduce the oxidizing step during the regular manufaeturing operations, say the liming and /or deliming treatments. The oxidizing agents should be efi'ective as desensitizers and yet not be present in quantities capable of materially reducing the yield of gelatin or harming its quality especially its physical pro erties. Nor s ould they leave 0 jectiona le products from the oxidation reaction. For example, the regular liming solution of the usual gelatin manufacturing process can be saturated with as much calcium hypochlorite as will dissolve therein; or it can obtain about 5 to 10% of sodium peroxide. Subsequent operations then proceed as usual.

My sensitizing compounds ma be incorporated into gelatin from which p iotographic emulsions are to be made. This strengthened gelatin then constitutes a valuable intermediate in emulsion manufacture. While any good gelatin may be thus treated, that which has been rendered inert by the above described oxidation treatment during liming or deliming is articularly adapted to this strengthening. ltmulsions made from the mixture have markedly increased lightsensitiveness as compared with those made from corresponding unstrengthened gelatins. The proportion of sensitizing material is, of course, adjusted to give the desired control of the sensitiveness of emulsions made from the gelatin, the total sensitizing material in the strengthened gelatin being thus brought to, or even above, normal.

When working on a considerable scale, this activating of gelatin, such, for instance, as said inert gelatin, is one of the most desirable ways of employing my sensitizing compounds. In fact, premixing of one or more of my sensitizers with gelatin is my preferred system. During manufacture of the gelatin, say for instance when the concentrated gelatin solution comes from the evaporator before setting and drying, the sensitizing compound or compounds are added and thoroughly mixed to obtain effectively uniform distribution. For example 2 or 3 grains of any of the hereinabove listed compounds or mixtures of them is carefully mixed with each fraction of gelatin solution containing 100 pounds of gelatin (calculated as dry). The compound is taken up, preferably in as little aqueous-alcohol mixture as is practicable, and. then this concentrated solution added to the gelatin solution. In this Way undesirable dilution of the latter is avoided.

On a large scale, the sensitized solution may be accurately and continually dosed into a regulated stream of elatin solution with continuous mixing. Alternately dried or set gelatin may be allowed to swell in an aqueous solution of the sensitizing compound. The nearly uniform distribution or diffusion of the compound in the gelatin thus effected can be made even more nearly uniform by melting and agitating the swollen gelatin.

In the examples given above, the steps of treating with ammonia and warming of the emulsion just before its final setting improve the photographic properties of the emulsion, especially when the latter is made from hard gelatins. But one or both of them may be omitted. In other words, my sensitizing compounds act by themselves to increase the light-sensitiveness, whether ripening steps be employed or not, and so can wholly or partially replace them. llut I prefer to use them because the effect of either or both of them is to help increase the light-sensitiveness of the emulsions and thus gives a stronger initial sensitized condition which is multiplied or increased by using my sensitizing compounds. When using any of the inert gelatins mentioned above in making very sensitive emuls ons, these steps can sometimes be shortened and made more certain in effect by reason of the use of my powerful and dependable sensitizing compounds.

1 have described gelatin emulsions and emphasized the developing-out and alkaline types because at the present time they are the ones which have the widest practical use. Moreover they form the best medium for testing new sensitizing-compounds. .llut other organic colloids and mixtures of them with each other or with gelatin, where their nature admits such mixtures, may be used in making light-sensitive emulsions which can be improved by adding my sensitizing material. Albumens, agar-agar, gums, such as gum-arabic, cellulosic derivatives such as collodion are instanced. While I have illustrated the use of my sensitizer in connection with such sensitive substances as silver bromide and silver iodide, other lightscnsitive substances can be employed, such as silver chlorid, alone or mixed with one or more of the others.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A photographic developing-out emulsion comprising a colloid, particles of photographic silver salt suspended therein, and an added compound therein upon WhlCll at least part of the light-sensitiveness of the emulsion depends, said compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the proportion of said compound being substantially independent of the proportion of said colloid.

2. A photographic developing-out emulsion comprising gelatin, particles of silver halid suspended therein and telluro carbamid upon which at least part of the lightsensitiveness of the emulsion depends.

3. A photographic developing-out emu]- sion comprising gelatin, particles of silver halid suspended therein and allyl tellurourea upon which at least part of the lightsensitiveness of the emulsion depends.

4. A photographic developing-out gelatino-silver-halid emulsion of the alkaline type of relatively high light-sensitiveness, comprising a mixture of the contituents ot a gelatino-silver-halid emulsion of lower light-sensitiveness and an added sensitizing compound upon which depends the difference between said lower and said high light sensitiveness, said compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

5. A photographic emulsion comprising a colloid, particles of silver halid suspended therein and an added compound therein upon which at least part of the light-sensitiveness of the emulsion depends, said compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the proportion of said compound being substantially independent of the proportion of gelatin, and said emulsion being substantially free from sensitizing dye.

6. A photographic developing-out emulsion comprising a colloid, particles of photographic silver salt suspended therein, and an added compound therein upon which at least part of the light-sensitiveness of the emulsion depends, said compound containing a divalent tellurium atom di rectly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of added compound being less than the order of 10 grains per 130 pounds of emulsion and insufiieient to cause immediate fogging tendency.

7. In a process of preparing a developing-out gelatino-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituents thereof a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached. 4 8. In the process of preparing a developing-out gelatino-silver-halid emulsion, in creasing the light-sensitiveness thereof by incorporating a telluro carbamid with the other constituents thereof.

9. In the process of preparing a developing-out gelatino-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating allyl tellurourea with the other constituents thereof.

10. In the process of preparing a developmlg-out gelatino-silver-halid emulsion of the al alme type of relatively high light-sensit veness, combining constituents of a gelatmo-silver-halid emulsion of said type but of lower light-sensitiveness with an independent sensitizing compound, said compound containing a divalent tellurium atom of the sulfur group directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

11. In the process of preparing a developing-out colloid sensitive-silver-salt emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituents thereof, which are substantially free from sensitizing dye, a sensitizing compound, which is also substantially free from sensitizing dye. said compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

12. In the process of preparing a developing-out gelatino-silver-halid emulsion, increasing the light-sensitiveness thereof by incorporating with the other constituents thereof a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of said added compounds being less than the order of 10 grains per 130 pounds of emulsion and insufiicient to cause immediate fogging tendency.

13. An intermediate for use in making photographic emulsions, comprising an en-iulsion-forming colloid having incorporated therein a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

14. An intermediate for use in making photographic emulsions, comprising gelatin having incorporated therein telluro carbamid. I

15. An intermediate for use in making photographic emulsions, comprising gelatin having incorporated therein allyl tellurourea.

16. An intermediate for use in making photographic emulsions, comprising an emulsion-forming colloid having incorporated therein a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another oup of atoms is attached, the amount 0? said added compound being less than the order of 10 grains in 100 pounds of gelatin.

17 The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid an independent sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a sin le metalloid atom to which 'at least anot or group of atoms is attached.

18. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid telluro carbamid.

19. The process of making an intermediate for use in the pre aration of photographic emulsions, whic comprises incorporating in an emulsion-forming colloid allyl tellurourea. I

20. The process of making an intermediate for use in the preparation of photographic emulsions, Which comprises incorporating in an emulsion-forming colloid an independent sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry colloid), and being insufficient to cause immediate fogging tendency.

21. lhe process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid telluro carbamid, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry as colloid) and being insufficient to cause immediate fogging tendency 22. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid allyl tellurourea, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry colloid) and being insufficient to cause immediate fogging tendency.

23. The process of making an intermediate for use in the preparation of hotographic gelatino-silver-halid emu sions, which comprises substantially freeing gelatin from sensitizing compounds, and incorporating therein a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

24. The process of making an intermediate for use in the preparation of photographic gelatino-silver-halid emulsions, which comprises substantially freezing gelatin from sensitizin compounds, and incorportaing therein te luro carbamid.

25; The process of making an intermediate for use in the preparation of photographic gelatino-silver-halid emulsions, which comprises substantially freeing gelatin from sensitizing compounds, and incorporating therein a sensitizing compound containin a divalent tellurium atom directly joined y a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains for 100 pounds of gelatin (calculated as dry gelatin), and being insufficient to cause immediate fogging tendency in emulsions made from said mtermediate.

Signed at Rochester, New York, this 18th day of January, 1926.

SAMUEL E. SHEPPARD.

graphic emulsions, which comprises incorporating in an emulsion-forming colloid telluro carbamid.

19. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid allyl tellurourea.

20. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises lIICOI" porating in an emulsion-forming colloid an independent sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another grou of atoms is attached, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry colloid), and being insufiicient to cause immediate fogging tendency.

21. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid telluro carbamid, the amount of said added compound being less than the order of 10 .grains per 100 pounds of said colloid (calculated as dry as colloid) and being insufficient to cause immediate fogging tendency 22. The process of making an intermediate for use in the preparation of photographic emulsions, which comprises incorporating in an emulsion-forming colloid allyl tellurourea, the amount of said added compound being less than the order of 10 grains per 100 pounds of said colloid (calculated as dry colloid) and being insufficient to cause immediate fogging tendency.

23. The process of making an intermediate for use in the preparation of hotographic gelatino-silver-halid emu sions, which comprises substantially freeing gelatin from sensitizing compounds, and incorporating therein a sensitizing compound containing a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached.

24. The process of making an intermediate for use in the preparation of photographic gelatino-silver-halid emulsions, which comprises substantially freezing gelatin from sensitizin compounds, and incorportaing therein te luro carbamid.

25. The process of making an intermediate for use in the preparation of photographic gelatino-silver-halid emulsions, which comprises substantially freeing gelatin from sensitizing compounds, and incorporating therein a sensitizing compound containin a divalent tellurium atom directly joined by a double bond to a single metalloid atom to which at least another group of atoms is attached, the amount of said added compound being less than the order of 10 grains for 100 pounds of gelatin (calculated as dry gelatin), and being insufficient to cause immediate fogging tendency in emulsions made from said 1ntermedi ate.

Signed at Rochester, New York, this 18th day of January, 1926.

SAMUEL E. SHEPPARD.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,602,591,

granted October 12,

1926, upon the application of Samuel E. Sheppard, of Rochester, New York,l for an improvement in Photogra hic Light-Sensitive Material (/ontammg Ie lurlum and Processes of Making t 0 Same, errors appear inthe printed spec fication requiring correction as follows: Page 1, line 43, after the word making insert the word such;

page 3, line 22, for the article The, first occurrence, read They; page 5, line rd for the word sensitized read sem'ibizingf' same pa e, line 53, for the W0 Alternately read Alternatively; page 6,

page 2, line 56, after the word which insert the word is,

inc 39, claim 7, for the article a,

first occurrence, read the; page 7, line 29Tclaim 21, strike out the word as; same page, line 53, claim 24, for the Word eezing read racing; and that the said Letters Patent should be read with these corrections t erein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of December, A. D. 1926.

M. J. MOORE, Acting Commissioner of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,602,591, granted October 12, 1926, upon the application of Samuel E. Sheppard, of Rochester, New York, for an improvement in Photographic Light-Sensitive Material Containing Tellurium and Processes of Making the Same, errors appear in the printed specification requiring correction as follows: Page 1, line 43, after the word making insert word such,- page 2, line 56, after the word which insert the word is; page 3, line 22, for the article The, first occurrence, read They; page 5, line 50 for the word sensitized read semrim'zing' same page, line 53, for the W0 Alternately read Alternatively; page 6, inc 39, claim 7, for the article a first occurrence, read the; page 7, line 29 claim 21, strike out the word as; same age, line 53, claim 24, for the word freezing read freeing; and that the said tters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and. sealed this 28th day of December, A. D. 1926.

[emu] M. J. MOORE,

Acting Uommissiomr of Patents.