Tellurium salt fog inhibiting agents for silver halide photography

Radiation sensitive silver halide photographic elements are disclosed which are protected from fog by aromatic oxatellurazinium salts. The aromatic oxatellurazinium salts can be initially incorporated in the photographic element as manufactured or during processing.

FIELD OF THE INVENTION 
This invention relates to photography. It relates to silver halide 
photographic elements and to imaging processes. 
BACKGROUND OF THE INVENTION 
In the course of processing a photographic element containing an imagewise 
exposed silver halide emulsion layer reduced silver can be formed either 
as a direct or inverse function of exposure. At the same time, at least a 
low level of reduced silver formation also occurs independently of 
imagewise exposure. The term "fog" is herein employed to indicate the 
density of the processed photographic element attributable to the latter, 
usually measured in minimum density areas. In color photography fog is 
typically observed as image dye density rather than directly as silver 
density. 
Over the years a variety of differing materials have been introduced into 
silver halide emulsions to inhibit the formation of fog. Research 
Disclosure, Vol. 176, December 1978, Item 17643, Section VI, lists the 
more commonly employed fog inhibiting agents. Research Disclosure is 
published by Kenneth Mason Publications Limited; Emsworth; Hampshire P010 
7DD; England. From Section VI it is apparent that useful fog inhibiting 
agents are highly diverse in their structural forms, ranging from halide 
ions (e.g. bromide salts) to inorganic metal salts to specific polymers to 
selected acyclic organic compounds to specific heterocycles. These useful 
fog inhibiting agents have been selected from among a plethora of 
structurally similar, but relatively ineffective compounds. Useful fog 
inhibiting agents have been largely identified empirically. T. H. James, 
The Theory of the Photographic Process, 4th Ed., Macmillan, 1977, pp. 
393-399, in grouping and suggesting various performance mechanisms for fog 
inhibiting agents illustrates their diversity. 
Gunther et al U.S. Ser. No. 660,155, filed Oct. 12, 1984, titled 
PHOTOGRAPHICALLY USEFUL CHALCOGENAZOLES, CHALCOGENAZOLINES, AND 
CHALCOGENAZOLINIUM AND CHALCOGENAZOLIUM SALTS, commonly assigned, 
discloses to be useful as intermediates in synthesizing the title 
heterocycles compounds containing a 1,2,5-oxatellurazinium ring fused with 
an aromatic ring. A synthetic procedure for preparing these novel 
intermediates is also disclosed. 
SUMMARY OF THE INVENTION 
In one aspect this invention is directed to a photographic element 
containing a radiation sensitive silver halide emulsion and an effective 
amount of a fog inhibiting agent characterized in that the fog inhibiting 
agent is an aromatic oxatellurazinium salt. 
In another aspect this invention is directed to a process of producing a 
photographic image comprising processing a photographic element containing 
at least one imagewise exposed silver halide emulsion in the presence of 
an effective amount of a fog inhibiting agent characterized in that the 
fog inhibiting agent is an aromatic oxatellurazinium salt. 
The present invention permits the use of photographic elements containing 
radiation sensitive silver halide emulsions to produce photographic images 
exhibiting low levels of fog. The invention affords an alternative 
approach to fog reduction and in many instances fog reduction compares 
favorably with fog reduction achieved by other commonly employed and 
highly effective fog inhibiting agents. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention is based on the discovery that oxatellurazinium salts 
are effective in inhibiting fog. This invention has been necessarily 
predicated upon obtaining for investigation oxatellurazinium salts, a 
class of compounds not known to the art prior to this invention. Initial 
investigations have been conducted with oxatellurazinium salts containing 
a 1,2,5-oxatellurazinium ring fused with an aromatic ring. Although it is 
a synthetic convenience to have a fused aromatic ring present, fog 
inhibiting activity is attributed to the oxatellurazinium ring, which 
forms an inner salt. Substituents can take any form compatible with the 
oxatellurazinium ring structure. 
Initial investigations have been conducted employing oxatellurazinium salts 
satisfying formula 
##STR1## 
prepared by reacting a compound according to formula 
##STR2## 
with TeX.sub.4 at an elevated temperature, wherein: H* is an activated 
hydrogen atom, 
G represents the atoms completing an aromatic nucleus, 
R represents an aliphatic or aromatic group comprised of a hydrocarbon 
moiety optionally linked through a divalent oxy, thio, or carbonyl 
linkage, an amino group, an amido group, a ureido group, a formamidine 
disulfide group, or a --C(O)M group, wherein M is chosen to complete an 
acid, ester, thioester, or salt, and 
X represents halogen or pseudohalogen. 
X in formula (I) is determined by the choice of the TeX.sub.4 compound 
employed in synthesis or in a post-sythesis conversion step. X can be 
halogen (employed here and elsewhere to designate generically chloride, 
bromide, or iodide) or a pseudohalogen (i.e., one of the recognized class 
of substituents known to approximate the substituent properties of 
halogen), such as a cyano, thiocyanate, or hydroxy substituent. In a 
specifically preferred form X is chloride or bromide. 
When the compound of formula (II) is melted or heated in a suitable solvent 
(e.g., acetonitrile, butyronitrile, or chloroform) with tellurium 
tetrabromide or, preferably, tellurium tetrachloride, the material of 
formula (I) in which X is chloride or bromide is produced. Heating to a 
temperature of at least 60.degree. C. up to about 140.degree. C. is 
contemplated, with temperatures of from about 110.degree. to 120.degree. 
C. being preferred. If desired, the chloride or bromide in the formula (I) 
compound can be displaced by iodide or a psuedohalogen by treatment with 
an iodide or pseudohalogen salt, thereby permitting the full range of 
values of X in formula (I) to be realized. In part the reaction to produce 
the material of formula (I) is accomplished by choosing G in formula (II) 
so that the aromatic nucleus which it completes is activated in the 
position ortho to the amido substituent. This can be accomplished by 
including in the aromatic nucleus one or more substituents capable of 
directing ring substitution in formula (II) to the ring position of the 
starred activated hydrogen atom. For carbocyclic aromatic rings, such as 
benzene and naphthene rings, useful substituents can be chosen from among 
aliphatic and aromatic groups comprised of hydro carbon moieties (e.g., 
alkyl, aryl, alkaryl, or alkaryl) optionally linked through a divalent 
oxygen or sulfur atom (e.g., an alkoxy, aryloxy, alkaryloxy, alkaryloxy, 
alkylthio, arylthio, alkarylthio, or alkarylthio group); an amino group, 
including primary, secondary and tertiary amines; an amido group (e.g., 
acetamido and butyramido); a sulfonamido group (e.g. an alkyl or 
arylsulfonamido group); a sulfamoyl group (e.g. an alkyl or arylsulfamoyl 
group); a ureido group (e.g., 1-ureido, 3-phenyl-1-ureido, and 
3-methyl-1-ureido); hydroxy; or a --C(O)M group or --S(O).sub.2 M group, 
wherein M is chosen to complete an acid, ester, thioester, or salt (e.g., 
--C(O)OH, --C(O)SCH.sub.3, --C(O)OCH.sub.3, --C(O)ONa, --S(O).sub.2 OH, 
--S(O).sub.2 OCH.sub.2 C.sub.6 H.sub.5, or --S(O).sub.2 OLi). 
The substituent R can take any synthetically convenient form. R can include 
an aliphatic or aromatic group comprised of a hydrocarbon moiety (e.g., 
alkyl, aryl, alkaryl, or aralkyl moiety) optionally linked through a 
divalent oxy, thio, or carbonyl linkage (e.g., an alkoxy, aryloxy, 
alkaryloxy, aralkyloxy, alkylthio, arylthio, alkarylthio, aralkylthio, or 
acyl moiety); an amino group, including primary, secondary and tertiary 
amines; an amido group (e.g., acetamido and butryamido); a ureido group 
(e.g., 1-ureido, 3-phenyl-1-ureido, and 3-methyl-1-ureido); a formamidine 
disulfide group (e.g., formamidine disulfide and 
N'-ethyl-N'-methyl-.alpha.,.alpha.'-dithiobisformamidine groups); or a 
--C(O)M group, wherein M is chosen to complete an acid, ester, thioester, 
or salt (e.g., --C(O)OH, --C(O)OCH.sub.3, --C(O)SCH.sub.3, or --C(O)ONa). 
When R is a primary amino group, it is in fact in one tautomeric form an 
imino group, which provides a convenient reaction site for further 
substitution. 
While the oxatellurazinium salts of formula (I) have been conveniently 
accessible for initial investigations based on the method for their 
preparation disclosed above, the synthetic method for preparing 
oxatellurazinium salts is not a part of the present invention. Thus, the 
present invention is considered to extend to oxatellurazinium salts 
generally without regard to the method by which they are prepared. 
The oxatellurazinium salt fog inhibiting agents are preferably incorporated 
in the photographic element to be protected prior to exposure and 
processing--e.g., at the time of manufacture. When the oxatellurazinium 
salt is being relied upon to reduce fog the origin of which antedates 
processing, it is essential that the oxatellurazinium salt be incorporated 
in the silver halide emulsion layer or layers to be protected. It is 
generally most convenient to introduce the oxatellurazinium salt into the 
silver halide emulsion after chemical ripening of the emulsion and before 
coating. 
When the oxatellurazinium salt is intended to become active at the time of 
processing, it can be incorporated within the photographic element at any 
location which permits permeation of one or more silver halide emulsion 
layers being imagewise developed. For example, the oxatellurazinium salt 
can be located in one or more silver halide emulsion layers or other 
hydrophilic colloid layers, such as in an overcoat, interlayer, or subbing 
layer. When the oxatellurazinium salt is intended to become active at the 
time of processing, it is generally most convenient to add the 
oxatellurazinium salt as a component of a processing solution, such as 
predevelopment bath or a developer, allowing it to permeate the silver 
halide emulsion layer or layers prior to or during development. 
Any amount of oxatellurazinium salt effective to reduce fog can be 
employed. Optimum amounts of fog inhibiting agents for specific 
applications are usually determined empirically by varying concentrations. 
Such investigations are typically relied upon to identify optimum fog 
reduction concentrations or an optimum balance between fog reduction and 
other effects, such as reduction in photographic speed. Based on the 
investigations reported below, when the oxatellurazinium salt is 
incorporated in a silver halide emulsion prior to coating, concentrations 
of from about 5.0 to 0.005 millimole per silver mole preferably 0.5 to 
0.01 millimole per silver mole, and optimally from 0.15 to 0.015 millimole 
per silver mole are contemplated. When the oxatellurazinium salt is 
incorporated in a processing solution, concentration ranges from minimum 
effective amounts--e.g., typically at least 0.05 millimole per liter--to 
up to about 0.5 millimole per liter are contemplated. 
It is, of course, recognized that conventional fog inhibiting agents, such 
as those illustrated by Research Disclosure, Item 17643, Section VI, cited 
above, can be employed in combination with oxatellurazinium salts in the 
practice of this invention. Since it is recognized that fog inhibiting 
agents operate by a variety of differing mechanisms, as illustrated by 
James, cited above, the effects produced by combinations of 
oxatellurazinium salts and conventional fog inhibiting agents will range 
from highly interdependent to independently additive, but in any case 
optimum concentrations are susceptible to empirical determination. 
In addition to the fog inhibiting agent this invention additionally 
requires a photographic element containing a radiation sensitive silver 
halide emulsion. These silver halide emulsions can be comprised of silver 
bromide, silver chloride, silver iodide, silver chlorobromide, silver 
chloroiodide, silver bromoiodide, silver chlorobromoiodide or mixtures 
thereof. The emulsions can include silver halide grains of any 
conventional shape or size. Specifically, the emulsions can include 
coarse, medium or fine silver halide grains of either regular (e.g., cubic 
or octahedral) or irregular (e.g., multiply twinned or tabular) 
crystallographic form. Recently developed high aspect ratio tabular grain 
emulsions, such as those disclosed by Wilgus et al U.S. Pat. No. 
4,434,226, Daubendiek et al U.S. Pat. No. 4,414,310, Wey U.S. Pat. No. 
4,399,215, Solberg et al U.S. Pat. No. 4,433,048, Mignot U.S. Pat. No. 
4,386,156, Evans et al U.S. Ser. No. 553,911, filed Nov. 21, 1983, 
commonly assigned, Maskasky U.S. Pat. No. 4,400,463, Wey et al U.S. Pat. 
No. 4,414,306, and Maskasky U.S. Pat. No. 4,435,501, are specifically 
contemplated. Sensitizing compounds, such as compounds of copper, 
thallium, lead, bismuth, cadmium and Group VIII noble metals, can be 
present during precipitation of the silver halide emulsion, as illustrated 
by Arnold et al U.S. Pat. No. 1,195,432, Hochstetter U.S. Pat. No. 
1,951,933, Trivelli et al U.S. Pat. No. 2,448,060, Overman U.S. Pat. No. 
2,628,167, Mueller et al U.S. Pat. No. 2,950,972, Sidebotham U.S. Pat. No. 
3,488,709 and Rosecrants et al U.S. Pat. No. 3,737,313. 
The silver halide emulsions can be either monodispersed or polydispersed as 
precipitated. The grain size distribution of the emulsions can be 
controlled by silver halide grain separation techniques or by blending 
silver halide emulsions of differing grain sizes. The emulsions can 
include Lippmann emulsions and ammoniacal emulsions, as illustrated by 
Glafkides, Photographic Chemistry, Vol. 1, Fountain Press, London, 1958, 
pp. 365-368 and pp. 301-304; excess halide ion ripened emulsions as 
described by G. F. Duffin, Photographic Emulsion Chemistry, Focal Press 
Ltd., London, 1966, pp. 60-72; thiocyanate ripened emulsions, as 
illustrated by Illingsworth U.S. Pat. No. 3,320,069; thioether ripened 
emulsions, as illustrated by McBride U.S. Pat. No. 3,271,157, Jones U.S. 
Pat. No. 3,574,628 and Rosecrants et al U.S. Pat. No. 3,737,313 or 
emulsions containing weak silver halide solvents, such as ammonium salts, 
as illustrated by Perignon U.S. Pat. No. 3,784,381 and Research 
Disclosure, Vol. 134, June 1975, Item 13452. 
The emulsions can be surface-sensitive emulsions--i.e., emulsions that form 
latent images primarily on the surfaces of the silver halide grains--or 
internal latent image-forming emulsions--i.e., emulsions that form latent 
images predominantly in the interior of the silver halide grains, as 
illustrated by Knott et al U.S. Pat. No. 2,456,953, Davey et al U.S. Pat. 
No. 2,592,250, Porter et al U.S. Pat. Nos. 3,206,313 and 3,317,322, Bacon 
et al U.S. Pat. No. 3,447,927, Evans U.S. Pat. No. 3,761,276, Morgan U.S. 
Pat. No. 3,917,485, Gilman et al U.S. Pat. No. 3,979,213 and Miller U.S. 
Pat. No. 3,767,413. 
The emulsions can be negative working emulsions, such as surface-sensitive 
emulsions or unfogged internal latent image-forming emulsions, or 
direct-positive emulsions of the unfogged, internal latent image-forming 
type, which are positive working when development is conducted with 
uniform light exposure or in the presence of a nucleating agent, as 
illustrated by Ives U.S. Pat. No. 2,563,785, Evans U.S. Pat. No. 
3,761,276, Knott et al U.S. Pat. No. 2,456,953 and Jouy U.S. Pat. No. 
3,511,662. 
Blends of surface sensitive emulsions and internally fogged, internal 
latent image-forming emulsions can be employed, as illustrated by Luckey 
et al U.S. Pat. Nos. 2,996,382, 3,397,987 and 3,705,858, Luckey U.S. Pat. 
No. 3,695,881, Research Disclosure, Vol. 134, June 1975, Item 13452, 
Millikan et al Defensive Publication T-904017, Apr. 21, 1972 and Kurz 
Research Disclosure, Vol. 122, June 1974, Item 12233. 
The oxatellurazinium salts are preferably employed to reduce fog in 
negative working silver halide emulsions and most preferably those that 
contain silver halide grains which form surface latent images on exposure. 
The silver halide emulsions can be surface sensitized. Noble metal (e.g., 
gold), middle chalcogen (e.g., sulfur, selenium, or tellurium), and 
reduction sensitizers, employed individually or in combination are 
specifically contemplated. Typical chemical sensitizers are listed in 
Research Disclosure, Item 17643, cited above, Section III. 
The silver halide emulsions can be spectrally sensitized with dyes from a 
variety of classes, including the polymethine dye class, which includes 
the cyanines, merocyanines, complex cyanines and merocyanines (i.e., tri-, 
tetra-, and polynuclear cyanines and merocyanines), oxonols, hemioxonols, 
styryls, merostyryls, and streptocyanines. Illustrative spectral 
sensitizing dyes are disclosed in Research Disclosure, Item 17643, cited 
above, Section IV. 
The silver halide emulsions as well as other layers of the photographic 
elements of this invention can contain as vehicles hydrophilic colloids, 
employed alone or in combination with other polymeric materials (e.g., 
latices). Suitable hydrophilic materials include both naturally occurring 
substances such as proteins, protein derivatives, cellulose 
derivatives--e.g., cellulose esters, gelatin--e.g., alkali treated gelatin 
(cattle, bone, or hide gelatin) or acid treated gelation (pigskin 
gelatin), gelatin derivatives--e.g., acetylated gelatin, phthalated 
gelatin, and the like, polysaccharides such as dextran, gum arabic, zein, 
caein, pectin, collagien derivatives, collodion, agar-agar, arrowroot, and 
albumin. The vehicles can be hardened by conventional procedures. Further 
details of the vehicles and hardeners are provided in Research Disclosure, 
Item 17643, cited above, Sections IX and X. 
The silver halide photographic elements of this invention can contain other 
addenda conventional in the photographic art. Useful addenda are 
described, for example, in Research Disclosure, Item 17643, cited above. 
Other conventional useful addenda include desensitizers, couplers (such as 
dye forming couplers, masking couplers and DIR couplers) DIR compounds, 
anti-stain agents, image dye stabilizers, absorbing materials such as 
filter dyes and UV absorbers, light scattering materials, antistatic 
agents, coating aids, plasticizers and lubricants, and the like. 
The photographic elements of the present invention can be simple 
black-and-white or monochrome elements comprising a support bearing a 
layer of the silver halide emulsion, or they can be multilayer and/or 
multicolor elements. The photographic elements produce images ranging from 
low contrast to very high contrast, such as those employed for producing 
half tone images in graphic arts. They can be designed for processing with 
separate solutions or for in-camera processing. In the latter instance the 
photographic elements can include conventional image transfer features, 
such as those illustrated by Research Disclosure, Item 17643, cited above, 
Section XXIII. Multicolor elements contain dye image forming units 
sensitive to each of the three primary regions of the spectrum. Each unit 
can be comprised of a single emulsion layer or of multiple emulsion layers 
sensitive to a given region of the spectrum. The layers of the element, 
including the layers of the image forming units, can be arranged in 
various orders as known in the art. In an alternative format, the emulsion 
or emulsions can be disposed as one or more segmented layers, e.g., as by 
the use of microvessels or microcells, as described in Whitmore U.S. Pat. 
No. 4,387,154. 
A preferred color photographic element according to this invention 
comprises a support bearing at least one blue sensitive silver halide 
emulsion layer having associated therewith a yellow dye forming coupler, 
at least one green sensitive silver halide emulsion layer having 
associated therewith a magenta dye forming coupler and at least one red 
sensitive silver halide emulsion layer having associated therewith a cyan 
dye forming coupler, at least one of the silver halide emulsion layers 
containing an oxatellurazinium salt fog inhibiting compound. 
The elements of the present invention can contain additional layers 
conventional in photographic elements, such as overcoat layers, spacer 
layers, filter layers, antihalation layers, scavenger layers and the like. 
The support can be any suitable support used with photographic elements. 
Typical supports include polymeric films, paper (including polymer-coated 
paper), glass and the like. Details regarding supports and other layers of 
the photographic elements of this invention are contained in Research 
Disclosure, Item 17643, cited above, Section XVII. 
The photographic elements can be imagewise exposed with various forms of 
energy, which encompass the ultraviolet, visible, and infrared regions of 
the electromagnetic spectrum as well as electron beam and beta radiation, 
gamma ray, X ray, alpha particle, neutron radiation, and other forms of 
corpuscular and wave-like radiant energy in either noncoherent (random 
phase) forms or coherent (in phase) forms, as produced by lasers. When the 
photographic elements are intended to be exposed by X rays, they can 
include features found in conventional radiographic elements, such as 
those illustrated by Research Disclosure, Vol. 184, August 1979, Item 
18431. 
Processing of the imagewise exposed photographic elements in the presence 
of the oxatellurazinium salt need not differ from conventional processing. 
Processing procedures, developing agents, and development modifiers are 
illustrated by Research Disclosure, Item 17643, cited above, Sections XIX, 
XX, and XXI, respectively. In its preferred application the invention 
relates to silver halide photographic elements which are processed in 
aqueous alkaline developers in the presence of the oxatellurazinium salt.

The following examples further illustrate the invention: 
PREATIONS OF OXATELLURAZINIUM SALTS 
The preparation of representative oxatellurazinium salts is illustrated by 
the preparation of five 1,1,1-trihalo (substituted) 
2,1,4-benzoxatellurazinium, inner salts. 
##STR3## 
3-Methoxyacetanilide, (34 g=0.2 mole) and tellurium tetrachloride (54 g=0.2 
mole) were jointly stirred into chloroform (100 ml) in a 500 ml Erlenmeyer 
flask. After an initial solution had been formed, the mass set solid with 
a fine yellow precipitate. The mixture was immersed in an oil bath kept at 
115.degree. C. The mixture was manually stirred until all solids had 
redissolved or melted. After most of the chloroform had evaporated, there 
resulted a clear yellow melt that rapidly became opaque while gaseous HCl 
was being emitted. The temperature was raised to 120.degree. C. and 
heating continued with occasional manual stirring until the entire mass 
had set to a brittle solid. The reaction was terminated after 2 hours. 
Ethanol was added to the still hot reaction mixture to disperse the 
product. Recrystallization from ethanol (1300 ml) yielded colorless 
needles (47.1 g, 59% of theory), m.p. 245.degree.-246.degree. C. 
C, Cl, H, N and Te elemental analyses were in agreement with those 
calculated for the structural formula. 
##STR4## 
3-Methylacetanilide (m-acetotoluidide) (82 g=0.55 mole) and tellurium 
tetrachloride (148 g, 0.55 mole) were combined with chloroform (300 ml) 
and the mixture heated for 20 hours in an oil bath kept at 115.degree. C. 
with continuous removal of HCl. The hot reaction product was dispersed in 
ethanol (200 ml) and the product collected by filtration to give a yield 
of 149 g, 71% of theory, colorless prisms, m.p. &gt;300.degree. C. For 
analyses the compound was recrystallized from boiling acetonitrile. 
The elemental analyses were in agreement with those expected for the 
structural formula: 
##STR5## 
3,4-Dimethylacetanilide (56 g=0.37 mole) was combined with TeCl.sub.4 (100 
g, 0.37 mole) in acetonitrile (100 ml) and immersed in an oil bath, first 
for one hour at 120.degree. C. and then for 3 more hours at 130.degree. C. 
Additional acetonitrile was added, and the partial solution was chilled. 
The product was collected by filtration to give 74.7 g, 52% of theory, 
colorless crystals, m.p. &gt;300.degree. C. after darkening at &gt;280.degree. 
C. Recrystallization from acetonitrile required 400 ml solvent for 15 g of 
the substance. C, H, Cl, N and Te elemental analyses were in agreement 
with those expected for the structural formula: 
##STR6## 
3-Methylthioacetanilide (68 g=0.37 mole), prepared by acetylation of 
commercial 3-methylthioaniline, was combined with TeCl.sub.4 (100 g=0.37 
mole) in chloroform (100 ml). The mixture was heated for 3 hours in an oil 
bath kept at 130.degree. C., then introduced hot into acetonitrile (300 
ml), chilled, and filtered. A crystalline solid yielding 68 g, 49% of 
theory was obtained. For analysis the material was recrystallized from 
boiling acetonitrile (100 ml dissolves .perspectiveto.4 g) with the aid of 
decolorizing charcoal and was recovered as lustrous, pale yellow prisms, 
m.p. 251.degree.-253.degree. C. The elemental analyses were in agreement 
with those expected for the structural formula: 
##STR7## 
3-Hydroxyacetanilide (60 g=0.4 mole) and TeCl.sub.4 (107.6 g=0.4 mole) were 
combined in acetonitrile (80 ml) and the mixture immersed for 2 hours in 
an oil bath maintained at 120.degree. C. To the hot melt was then added 
enough acetonitrile to make a paste. The mixture chilled overnight and 
filtered with suction to give 86.5 g, 56% of theory, colorless crystalline 
solid. For analysis this was recrystallized from hot acetonitrile, where 
25 g required 150 ml of solvent and gave a recovery of 10 g colorless 
needles, m.p. 247.degree.-248.degree. C. The elemental analyses were in 
agreement with that expected for the structural formula: 
EXAMPLES 1 THROUGH 5 
The five oxatellurazinium compounds prepared above as well as a control 
compound C 6 were evaluated in a sulfur and gold sensitized silver 
bromoiodide emulsion. C 6 was chosen as a control since it is a well-known 
effective antifoggant and there are no sulfur or selenium analogues of the 
oxatellurazinium compounds. The compounds were added at the levels 
indicated and coated on cellulose acetate support to achieve a silver 
coverage of 4.9 g/m.sup.2 and a gelatin coverage of 11.1 g/m.sup.2. To 
show the characteristics of the emulsion without an intentionally added 
fog reducing agent, a coating was also prepared to which none of the above 
compounds was added. Samples of the coatings were exposed to a tungsten 
light source in an Eastman 1B sensitometer through a wedge spectrograph. 
The coatings were developed for five minutes in a hydroquinone-Elon.RTM. 
(p-N-methylaminophenol hemisulfate) developer, fixed, washed, and dried. 
Samples of each of the coatings were incubated for two weeks at 49.degree. 
C. under 50 percent relative humidity before being exposed and processed 
as described above. A characteristic (density vs log exposure) curve was 
plotted for each coating. The sensitivity and fog (Dmin) data were 
determined from these curves. The results are reported in the Table I. The 
structure of compound C 6 is set forth below: 
##STR8## 
TABLE I 
______________________________________ 
Level Fresh After Incubation 
(mmole/mole 
Sensi- Sensi- 
Compound Ag) tivity Fog tivity Fog 
______________________________________ 
Te 5 0.015 102 0.12 55 0.44 
0.15 95 0.09 73 0.19 
Te 1 0.015 91 0.10 63 0.44 
0.15 95 0.10 91 0.19 
Te 4 0.015 95 0.09 53 0.45 
0.15 95 0.09 95 0.19 
Te 2 0.015 95 0.09 53 0.46 
0.15 91 0.09 94 0.23 
Te 3 0.015 97 0.10 55 0.46 
0.15 95 0.09 83 0.28 
C 6 0.015 67 0.07 82 0.33 
0.15 68 0.07 80 0.26 
None -- 100 0.10 25 0.79 
______________________________________ 
EXAMPLES 6 THROUGH 10 
Examples 1 through 5 were repeated, except that control compound C 6 was 
replaced with 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, sodium salt, 
Compound C 7. A summary of this data is presented in Table II. 
TABLE II 
______________________________________ 
Level Fresh After Incubation 
(mmole/mole 
Sensi- Sensi- 
Compound Ag) tivity Fog tivity Fog 
______________________________________ 
Te 5 0.15 112 0.16 94 0.23 
Te 1 0.15 110 0.15 85 0.30 
Te 4 0.15 107 0.15 87 0.29 
Te 2 0.15 100 0.15 91 0.35 
Te 3 0.15 105 0.14 85 0.29 
C 7 0.15 105 0.14 53 0.57 
1.50 105 0.14 95 0.29 
None -- 100 0.18 19.5 1.03 
______________________________________ 
This data illustrates that Compound C 7, a common antifoggant, is clearly 
not as active as the oxatellurazinium compounds, all of which were highly 
effective. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.