US2848330A

US2848330A - Photographic emulsions sensitized with sulfonium salts and alkylene oxide polymers

Info

Publication number: US2848330A
Application number: US550496A
Authority: US
Inventors: Chechak Jonas John; Jr John Sagal; Jr Albert C Smith
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1955-12-01
Filing date: 1955-12-01
Publication date: 1958-08-19
Anticipated expiration: 1975-08-19
Also published as: GB841536A; DE1048476B; BE553032A; FR1170224A

Description

United States Patent PHOTOGRAPHIC EMULSIONS SENSITIZED WITH SULFONIUM SALTS AND ALKYLENE OXIDE POLYNIERS Jonas John Chechak, John Saga], Jr., and Albert C. Smith, Jr., Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application December 1, 1955 Serial No. 550,496

14 Claims. (Cl. 96107) This application relates to photography and particular- 1y to sensitizing photographic emulsions.

It is well known that silver halide emulsions may be chemically sensitized with a variety of materials in order to increase the speed and generally the gamma of the emulsion, as opposed to optical sensitization in which the optical range of sensitivity is increased. Chemical sensitization usually results either from the formation of silver sulfide on the surface of the silver halide crystal, thus increasing sensitivity, or from the formation of small amounts of silver from the reduction of silver halide. Other classes of compounds, such as certain ethylene oxide condensation products and certain cationic surfaceactive salts increase sensitivity of silver halides without apparently entering into chemical combination with the silver halide.

Carroll and Allen U. S. Patent 2,275,727 describes the chemical sensitizing of silver halide emulsions containing sensitizing dyes, using cationic surface-active sulfonium salts. These sulfonium salts are incorporated in the emulsion before, simultaneously with, or after the optical sensitizing dye and increase the speed of the emulsion so sensitized.

We have now found that the sensitivity of silver halide emulsions which have been sensitized with alkylene oxide polymers, with or without optical sensitizing dyes, may be further increased by the use of certain cationic surfaceactive sulfonium salts and that this increase in speed is not accompanied by an increase in graininess. Fog in the emulsions so sensitized may be reduced by the use of fog inhibiting agents such as tetraazaindenes.

Sulfonium salts which we may use are trialkyl sulfonium salts in which one alkyl group contains more than 8 carbon atoms, preferably from 9 to 16 carbon atoms.

The anion of our compounds may be any acid radical not injurious to photographic emulsions, for example, ptoluene sulfonate, chloride, bromide, iodide, perchlorate or alkyl sulfate. The introduction of halide anions into photographic silver halide emulsions alters the halide concentration in the emulsion and compensating changes in the emulsion may be desirable if such salts are employed. For this reason, we ordinarily prefer to employ compounds containing anions other than halides. Perchlorates and p-toluene sulfonates are advantageously employed.

The sulfonium salts which we propose to use have the general structure:

where R and R represent alkyl groups, e. g., methyl, ethyl, propyl, butyl, etc., or aralkyl groups, e. g., benzyl,

R represents an alkyl group of more than 8 carbon atoms, e. g., nonyl, decyl, dodecyl, tetradecyl, cetyl, etc., and

X represents an anion, e. g., chloride, bromide, iodide, per-chlorate, p-toluene sulfonate, alkyl sulfate, etc.

Specific compounds which we may employ are:

Dimethyl n-nonyl sulfonium p-toluene sulfonate Dimethyl n-decyl sulfonium p-toluene sulfonate Dimethyl n-dodecyl sulfonium p-toluene sulfonate Dimethyl n-tetradecyl sulfonium p-toluene sulfonate Diethyl n-dodecyl sulfonium p-toluene sulfonate Benzyl ethyl n-dodecyl sulfonium ethosulfate The surface-active sulfonium salts used according to our invention may be made as described in U. S. Patents 2,090,890 and 2,121,823. This method involves, in general, the treatment of a dialkyl sulfide, such as methyl-ndodecyl sulfide, with an alkyl salt such as dimethyl sulfate or methyl bromide. The dialkyl sulfides are made by treating a higher alkyl mercaptan, e. g., n-dodecyl mercaptan, with an alkyl salt such as dimethyl sulfate or methyl bromide. The higher alkyl mercaptans may be made by treating an alkyl bromide such as lauryl bromide with thiourea (Drake, Organic Syntheses, vol. 21, page 36, 1941) or with sodium hydrosulfide (Organic Syntheses, Collective, vol. 2, page 547).

The quantity of surface-active sulfonium salt which is most advantageously employed varies with the nature of the surface-active substance and-with the nature of the emulsion. Ordinarily, the most advantageous concentra: tion has been found to be between about 25 mgs. and 1000 mgs. of the surface-active sulfonium salt per gram mole of silver halide in the emulsion, although greater or smaller concentrations can be employed. We have found that excesses of the surface-active sulfonium salt are to be avoided since excesses produce fog in the emulsions. The optimum range of concentration for any particular sulfonium salt described herein is ordinarily fairly narrow and can best be determined by employing a series of concentrations of the sulfonium salt separately in several batches of the same emulsion and determining the sensitivity of the several batches before and after incorporation of the sulfonium salt, in the usual manner which is, of course, well known to those skilled in the art.

The alkylene oxide polymers used to sensitize the emulsions may be of various types. The alkylene oxides from which the polymers are derived contain from 2 to 4 carbon atoms, e. g., ethylene oxide, propylene oxide and butylene oxide. The preparation of polymers from these compounds is described in Ellis, The Chemistry of Synthetic Resins (1935), pages 990 to 994. These compounds are also referred to as polyalkylene glycols and their use as sensitizers for silver halide emulsions is described in U. S. Patents 2,423,549 and 2,441,389. The alkylene oxide derivatives may be prepared by condensing an organic compound containing an active hydrogen atom with an alkylene oxide polymer, or by condensing the active hydrogen compound with the alkylene oxide during the polymerization of the latter material.

Various derivatives of alkylene oxides may also be used! to sensitize the emulsions, e. g., condensation products of alkylene oxide with organic compounds containing an active hydrogen atom. Examples of active hydrogen, organic compounds, i. e., compounds in which a hydrogen atom may be replaced by reaction of the compound with metallic sodium, methylmagnesium iodide, etc., in clude alcohols, amines, mercaptans, acids, amides, hydrocarbons such as acetylene, and compounds having the active hydrogen in a methylene group such as dibenzoyl 3. methane. More specifically, we may employ condensation products otalkyleneoxide with glycols such as those having from 8 to 18 carbon atoms as described in U. S. Patent 2,240,472 and British Patent 443,559 as well as condensation products of alkylene oxides with aliphatic alcohols, condensation products of alkylene oxides with aliphatic acids, e. g., lauric acid and glycine, condensation productsof a-lkylene oxideswith aliphatic amines or amides, e. g., glycine and lauryl amide, and condensation products of alkylene oxides with phenols,- e. g., phenol. Thepreparation of these condensation products is described in U; S; Patent 1,970,578: Condensation products of alkylenemxideswith hexitol ring'dehydrationproducts as described in U. S. Patent 2,400,532 may also be employed.

In eachca sev the polyalkylene oxide or derivative of alkylene oxide should have a molecular weight of at least 300. Condensation products of et-hylene'oxide with long chain alcohols, acids, amines or amides should have a molecular, weight of about 700. In general the best results are obtained with the, condensation products of ethylene oxide with long chain compounds having a chain length of 112 or more carbon atoms and with ethyl-. ene oxide polymers having a molecularv weight of-l500 to 4000 or more.

When employing optically sensitized, emulsions the optical sensitizing dyes are advantageously employed in about their optimum concentration which ordinarily lies between about 10 mgs. and 40 mgs. of optical sensitizing dye per liter of emulsion containing about 0.25 gram mole of'silverhalide although concentrations above or below, the optimum concentration can be employed.

The alkylene, oxide derivatives used to sensitize the emulsions may be illustrated by the following specific examples, although our. invention is in no way limited to the use of these specific compounds.

HO CH CH O (CHgCH O ,CH,CH OH- Polyethylene oxide (CH2CH2O)CH2CHOH.

0(GHzCHgO)nOHgOHOH Di- (polyethylene-glycoxy) -decane HQCH CH O (CH CH O) CH2CH OC1qH33 Polyethylene oxide oleyl ether where n=an integer greater than about '10.

The preparation .of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of theemplsion from aqueous soluble salts usually by washing, (3') the second. digestion or after-ripening to obtain increased sensitivity (Mees, The Theory of the Photographic Process, 1942, page 3). The sensitizing agents maybe added at any stage, preferably after the final dis st n- The photographicernnlsions which we use are of the developing-out type and best results have beenobtained with gelatino silver bromoiodide emulsions. However, emulsionsof varying halide, content may be used.

The emulsions may be chemically sensitizedby any of the acceptedprocedureain addition to or in combinationwith the sensitizing. with alkylene oxidepolymers. The emulsions may .bedigestedwith naturally active gelaw tin, or sulfur compounds may be added such,as those describedin Sheppard U, S. Patents 1,574,944 and 1,623,- 49 9, and Sheppard and Brigham U. S. Patent 2,410,689.

The emulsions mayalso be treated with salts of the no ble metals such, as ,ruthenium,rhodiumnpalladium, iridium andplatinum, all ofwhich belong togroup VIII of the periodic table of elements andhave an atomic weight greaterthan- 100., Representative compoundsare am,-

rnonium; chloropalladate, potassium, chloroplatinate. and.

sodium chloropalladite, which are used for sensitizing in '4 amounts below that which produces any substantial fog inhibition, as described'in Smith and Trivelli U. S; Pat ent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsions may also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, or stabilized withgold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzy and Leermakers U. S. Patent 2,597,915. Suitablecompounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride andZ-aurosulfobenzothiazole metho chloride.

The emulsions may also be chemically sensitizedwith reducing agents such as stannous' salts. (Carroll U. S. Patent 2,487,850), polyamines such as diethylenetriamine (Lowe andJones U. S. Patent 2,518,698), polyarnines such as spermine-(Lowe-and'Allen U. S. Patent 2,521,925), or bis-(,B-aminoethyl) sulfide and its watersoluble salts (Lowe-andl'ones U. S Patent 2,521,926).

The emulsions may also be stabilized withthemercury compounds of Allen, Byersand-Murray U. S.-.applicati0n.-

Serial No. 319,611, Carrolland Murray U. S. application Serial No. 319,612 andjLeubner and Murray U, .S. application Serial No. 319,613, all filed November 8, 1952.

Other stabilizing, agents may be. addedto. 'theemulsions containing thesulfoniumsalts-and alkylene oxide polymers, ,such. as-v cadmium .chloride, cadmium .nitrate,

cobalt nitrate, manganese chloride, manganese sulfate, zinc chloride, zinc nitrate and zinc sulfate.

When using the combination of the. sulfonium salt and the ethylene oxide polymer for. sensitizing photographic emulsions. thev fog was. found tobe. increased. on. both.

fresh andvincubated. samples-of the developedemulsion- This fog was-.reducedto normal levels byuseofan anti.- foggant such as a 4-hydroxy-6-alkyl-1,3,3a,7-tetraazain dene, specifically 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, or 5-carboxy-4-hydroxyl,3,3a,7-tetraazaindene..

The. following examples illustrate the methodwof staw bilizing emulsionsaccording to our invention:

EXAMPLE 1 A negative-speed gelatino-silver bromoiodide emulsion was. digested with a sulfur compound such'as disclosed in Sheppard U. S. Patent 1,574,944 and' potassium chloro-- aurate. Different portions of this emulsion were sensitized with varying amounts of the condensation product of 1 mole of'oleyl alcohol with approximately 15 moles ofethylene oxide (polyethylene glycol oleyl ether), the amounts usedbeing shown in the following tables. Portions of these'emulsionswere additionally sensitized with lowing composition:

Grams N-methyl-p-aminophenol sulfates -2 2.5 Hydroquinone 2.5 Sodium sulfite (desiccated) 30 Sodium metaborate 10 Potassium bromide 0.5

Water to 1 liter.

for speed, gamma and fog before and after incubationof each of the samples, speed. being read. as. 30/E where E is the exposure in meter candleseconds required .tocpro: duce. a density of 0.2 over fog, .were as. follows:

Table I.-Plyethylene glycol oleyl ether, 0.7 gram per molesilver halide Agent Fresh Test After Incubation Compound per mole,g

Speed Gamma Fog Speed Gamma Fog Dlmethyl dodecyl sulfonium p-toluene sulto 0 3, .91 .10 3,200 .72 .36 025 3,800 .95 .12 .77 050 4, .95 .14 Black .250 .70

Table Il.-Polyelhylene glycol oleyl ether, 0.7 gram per mole silver halide, +4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, 2 grams per mole silver halide Table IIL-Polyethylene glycol oleyl ether, 0.7 gram per mole silver halide, +4ehydroxy-6-methyl-l,3,3a,7- tetmazaindene, 2 grams per mole silver halide-l-panchromatic sensitizing dye Agent Fresh Test After Incubation Compound per mole, g.

Speed Gamma Fog Speed Gamma Fog Dimethyl dodecyl sulfonium p-toluene sulfonate 0 7, 900 97 18 7, 050 97 18 D 025 8, 050 1. 03 18 7, 200 90 17 050 9, 250 1. 12 18 7, 050 1. 0 17 250 11, 400 1.10 .21 10,400 .08 .24 1 0 10,900 1.12 .28 Black EXAMPLE 2 (Carbowax 1500 1s a polyethylene glycol having an aver- This example shows that various polyethylene glycols are useful in the emulsions of our invention.

A negative-speed gelatino-silver bromoioclide emulsion was digested with a sulfur compound such as disclosed in Sheppard U. S. Patent 1,574,944 and potassium chloroaurate. A portion of this emulsion was sensitized with dimethyl dodecyl sulfonium p-toluene sulfonate, 0.3 gram per mol of silver, and a separate portion was stabilized with 4-hydroxy 6 methyl 1,3,3a,7 tetraazaindene, 1.5 grams per mol of silver. Portions of these emulsions were mixed and additionally sensitized with various polyethylene glycols, and all of the emulsions were coated, exposed and developed as in Example 1. The results of tests for speed, gamma and fog (fresh tests) were as follows:

age molecular weight between 500 and 600. Carbowax 4000 is a hard, waxy polyethylene glycol resembling paraflin in appearance, but is water-soluble. Both are sold by Carbide and Carbon Chemicals Corp., New York city.)

EXAMPLE 3 This example shows the results of using various sulfonium salts.

A negative-speed gelatino-silver bromoiodide emulsion was digested with a sulfur compound such as disclosed in Sheppard U. S. Patent 1,574,944 and potassium chloroaurate, and was panchromatically sensitized. This emulsion was sensitized with the condensation product of 1 mole of oleyl alcohol with approximately 25 moles of ethylene oxide (polyethylene glycol oleyl ether), 0.75 gram per mol of silver, and stabilized with 4-hydroxy-6- methyl-1,3,3a,7-tetraazaindene, 4 grams per mol of silver. To portions of this emulsion there were added various amounts of several sulfonium p-toluene sulfonate salts as shown in the following table.

The emulsions were coated, exposed and developed as in Example 1, and results of tests for speed, gamma and fog (fresh tests) were as follows:

Agent Compound per Speed Gamma Fog mol, g.

Cheek (Polyethylene glycol and azainden 9, 500 1. 18

Dimethyl nonyl sulionium p-toluene sulfonate 0. 3 700 1. 01 18 Do 0.6 10.200 1. 00 .18 DO 1.2 10, 900 1.04 .19 Dimethyl decyl Sulfonium p-toluone sulionate 0.3 10, 900 1.03 18 Do... 0.6 11,400 1.06 .19 Do 1. 2 11, 900 1.06 .19

Dimethyl dodecyl sullonium p-toluene sulionate 0. 13, 100 1.05 .21 Do 0.3 13, 700 1. 25 22 D0 0. 6 14, 700 1. 31 25 Dlmethyl tetradeeyl sulionlum p' toluene snlfonate O. 06 11, 900 99 D0 0. 12 12, 200 1.08 22 D0 0. 32 13, 400 l. 15 .26

EXAMPLE 4 This example shows the results of using still other sulfonium salts.

An emulsion was made and tested as in Example 3; except that 3 grams per mol of silver of 4-hydroxy-6- methyl-l,3,3a,7-tetraazaindene was used and no poly ethylene glycol was added initially. Tests forspeed, gamma and fog (fresh tests) gave the following results:

The increase in speed according to our invention may also be obtained by adding the sulfonium salt to the developer. ratherthan: to* the emu'lsion..- The? present examplesh'ows the improvement-obtained in this'way.

An emulsion was-made: as in Example 3,, except that no azaindene was added to the-emulsion-initially. To a portion of. this-emulsion-before testing. there 'wasadded one gram of 4-hydroxy-6-methyl-l,3,3a,7-tetraazaindene per mol of silver.

Each of the emuisionswas. exposed and developed for 12 minutes in a developerofExample 1, and in this developer to which had been added various quantities of dim'ethyl dodecyl sulfoniu'ntp toluene' sulfonate. Speeds were measured as 100( l-log E), where 1 is the exposure in metercandle secondsi-requiredto produce-a density of 8 0.3 above 'fog, and the results of tests for speed and fog were tabulated as follows:

Coating Coating polyeth. polyeth. glycol glycol azaindene Speed Fog Speed Fog DeveloperofExamplel u... 339 .as 347 .40 361 .50 379 .51

0 gave the results shown in the following table:

v Coating Coating Develpolyeth'. poiyeth opulent glycol glycol time, azaindene minutes Speed Fog Speed Fog 3 293 .31 298 .31 Developer of Example 1 5 315 33 319 .35 8 327 .35 337 .36 Developer mg. per liter 3 315 .32 319 .33 dimethyl n-decyl sulionlum 6. 332 34' 338 36 p. t; s... 8, 343 39 349 .43 Developer mg. per liter 3 312 .33 317 .34 dimethyl n-decyl sulionlum 5 330 .34 335 .35 p. t. s 8, 337 .38, 339 .42 Developer 50 mg. per liter 3' 324 .34 331 .34 diethyl lauryl sulfonium 5 339 .37 345 .40 p. t. s 8 346 .45 352 .48

Improved results may also be obtained by bathing the exposed emulsion in a solution of the sulfonium salt, preferably containing potassium bromide, prior to developme'iit.

EXAMPLE 6' The increase in speed according to our invention may be obtained by adding the sulfonium salt to the emulsion and the polyethylene glycol to thedeveloper. The present example shows the improvement obtained in this way.

An emulsion was made and tested as in Example 3, except that no polyethylene glycol was added to the emulsion, and the amount of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was 1.5 grams per mol of silver. To portions of this emulsion: dimethyl dodecyl sulfonium p-toluene s ulfonate was added in the concentrations shown in the following table.

Each of the emulsions was developed after exposure, in the developer of Example 1 and in this developer to which had been added 2 grams poi-liter of polyethylene glycol oleyl ether. The results of tests for speed and fog aeeasso 9 EXAMPLE 7 sulfonate, 0.3 gram per mole of silver. To portions of the emulsion containing both the polyethylene glycol and the sulfonium salt there were added various amounts of cadmium chloride, as shown in the following table. The various emulsions were coated, exposed and developed as in Example 1, and records made of the speed (SO/E), gamma and fog as follows:

Agent Fresh Test Compound per mole Speed Gamma Fo lPolyethylene glycol (I) 7,200 .74 .20 }6,700 .90 .58 .75

The chemical sensitizing agents and other addenda which we have described may be used in various kinds of photographic emulsions. In addition to being useful in non-optically sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. They may be added to the emulsion before or after any sensitizing dyes which are used. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride or mixed silver halides such as silver chlorobromide or silver bromoiodide. The agents may be used in emulsions intended for color photography, for example, emulsions containing colorforming couplers or emulsions to be developed by solutions containing couplers.

The dispersing agent for the silver halide may be gelatin or other colloidal material such as collodion, albumin, cellulose derivatives or synthetic resins.

It will be understood that we contemplate as included within our invention all modifications and equivalents falling within the scope of the appended claims.

We claim:

1. A light-sensitive silver halide emulsion sensitized with a mixture of an alkylene oxide polymer selected from the class consisting of (1) polyalkylene glycols and (2) condensation products of alkylene oxide with organic compounds containing an active hydrogen atom, said alkylene oxide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular weight of at least 300, and a sulfonium salt having the general formula:

in which R and R are selected from the class consisting of alkyl and aralkyl groups, R represents an alkyl group of more than 8 carbon atoms, and X represents an anion.

2. The light-sensitive emulsion of claim 1 containing as a fog inhibiting agent a 4-hydroxy-6-alkyl-1,3,3a,7-tetraazaindene.

3. The light-sensitive emulsion of claim 1 in which the alkylene oxide polymer is an ethylene oxide polymer.

4. The light-sensitive emulsion of claim 1 in which the alkylene oxide polymer is polyethyleneglycol oleyl ether.

5 The light-sensitive emulsion of claim 1 in which the sulfonium salt is n-dodecyldirnethyl sulfonium-p-toluene sulfonate.

6. The light-sensitive emulsion of claim 1 in which the alkylene oxide polymer is polyethylene glycol oleyl ether and the sulfonium salt is n-dodecyl dimethyl sulfoniump-toluene sulfonate.

7. A light-sensitive silver halide emulsion sensitized with a mixture of polyethyleneglycol oleyl ether and ndodecyldimethyl sulfonium-p-toluene sulfonate and containing as a fog inhibiting agent 4-hydroxy-6-methyl-1,- 3,3a,7-tetraazaindene.

8. The method of increasing the sensitivity of a silver halide emulsion, which comprises exposing said emulsion and developing it in the presence of an alkylene oxide polymer selected from the class consisting of (1) polyalkylene glycols and (2) condensation products of alkylene oxide with organic compounds containing an active hydrogen atom, said alkylene oxide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular weight of at least 300, and a sulfonium salt having the general formula:

in which R and R are selected from the class consisting of alkyl and aralkyl groups, R represents an alkyl group of more than 8 carbon atoms, and X represents an anion, at least one of said alkylene oxide polymer and said sulfonium salt being incorporated in said emulsion prior to exposure.

9. The method of claim 8 in which the alkylene oxide polymer is an ethylene oxide polymer and the sulfonium salt is a di-lower alkyl sulfonium salt containing a third alkyl group of more than 8 carbon atoms.

10. The method of claim 8, in which the alkylene oxide polymer is a polyethylene glycol and the sulfonium salt is dimethyl alkyl p-toluene sulfonate in which the alkyl group contains more than 8 carbon atoms.

11. The method of claim 8, in which the alkylene oxide polymer is polyethylene glycol oleyl ether, and the sulfonium salt is n-dodecyl dimethyl p-toluene sulfonate.

12. The method of claim 8, in which the alkylene oxide polymer is an ethylene oxide polymer and is in the solution used to develop said emulsion, and the sulfonium salt is a di-lower alkyl sulfonium salt containing a third alkyl group of more than 8 carbon atoms and is incorporated in said emulsion prior to exposure.

13. The method of claim 8, in which the alkylene oxide polymer is an ethylene oxide polymer and is incorporated in said emulsion prior to exposure, and the sulfonium salt is a di-lower alkyl sulfonium salt containing a third alkyl group of more than 8 carbon atoms and is in the solution used to develop said emulsion.

14. The method of claim 8, in which the alkylene oxide polymer is polyethylene glycol oleyl ether and 1s 1ncorporated in said emulsion prior to exposure, and the sulfonium salt is a di-methyl alkyl sulfonium p-toluene sulfonate in which the alkyl group contains more than 8 carbon atoms, and is in the solution used to develop said emulsion.

References Cited in the file of this patent UNITED STATES PATENTS 2,275,727 Carroll et al. Mar. 10, 1942 2,288,226 Carroll et al. June 20, 1942 2,410,690 Smith et a1. -2 Nov. 5, 1946 2,716,062 Carroll et al. Aug. 23, 1955 UNITED STATES PATENT DJFFICE CERTIFICATE OF CORRECTION Patent No. 2,848,330 August 19, 1.958

Jonas John Chechak 'et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column '7, line 59, aift'er "Where", for "1" read E Signed and sealed this 18th day of November 1958a (SEAL) Attest:

KARL H. AXLINE Attesting Oflicer ROBERT c. WATSON Commissioner of Patents