Photographic silver halide emulsion containing contrast improving dopants

The present invention provides a photographic emulsion comprising a silver halide grains containing at least two dopants. The dopants comprise an osmium-based transition metal complex containing a nitrosyl or thionitrosyl ligand, and a transition metal complex containing a transition metal selected from Group 8 of the periodic table.

FIELD OF THE INVENTION 
This invention relates to photographic emulsions. In particular, it relates 
to photographic silver halide emulsions containing dopants and having 
improved contrast. 
BACKGROUND OF THE INVENTION 
In both color and black and white photography, there exists the desire for 
products which exhibit increased contrast upon exposure to light and 
subsequent development. This desire is based upon the realization that 
contrast is directly related to the appearance of sharpness; and, it 
follows, that products which exhibit increased contrast give the visual 
impression of enhanced sharpness. 
Traditionally, photographers have defined contrast by two methods, both of 
which are derived from the D-log E curve (also known as the 
"characteristic curve"; see James, The Theory of Photographic Properties, 
4th ed. pp 501-504). The first method is the determination of gamma 
(.gamma.), which is defined as the slope of the straight-line section of 
the D-log E curve. The second is the determination of the overall 
sharpness of the toe section of the D-log E curve. By sharpness of the toe 
section, it is usually meant the relative density of the toe section. For 
instance, a sharp toe corresponds to a relatively low (small) toe density, 
and a soft toe corresponds to a relatively high (large) toe density. 
Generally, the point at which toe density is measured corresponds to 0.3 
log E fast of the speed point, although toe density may properly be 
measured at any point prior to the curve's primary increase in slope. The 
speed point corresponds to the point on the D-log E curve where density 
equals 1.0. 
If either the value of .gamma. is high or the toe is sharp, then the image 
has a relatively high contrast. If the value of .gamma. is low or the toe 
is soft, the image has a relatively low contrast. 
It is known that in attempts to maximize the contrast of photographic 
elements based on silver halide emulsions (as well as other 
characteristics of the photographic element), the silver halide emulsions 
have been doped with various transition metal ions and compounds. Dopants 
are substances added to the emulsion during silver halide precipitation 
which become incorporated within the internal structure of the silver 
halide grains. Because they are internally incorporated, they are 
distinguished from substances added post-precipitation such as chemical or 
spectral sensitizers. These latter compounds are externally associated 
with the surface of the silver halide grains and are thus more properly 
referred to as addenda or grain surface modifiers. 
Depending on the level and location of dopants, they may modify the 
photographic properties of the grains. When the dopants are transition 
metals which form a part of a coordination complex, such as a 
hexacoordination complex or a tetracoordination complex, the ligands can 
also be occluded within the grains, and they too may modify the grain's 
photographic properties. 
Specific examples of doped silver halide emulsions can be found in U.S. 
Pat. No. 4,147,542, which discloses the use of iron complexes having 
cyanide ligands; U.S. Pat. Nos. 4,945,035 and 4,937,180 which disclose the 
use of hexacoordination complexes of rhenium, ruthenium and osmium with at 
least four cyanide ligands; and U.S. Pat. No. 4,828,962, which discloses 
the use of ruthenium and iridium ions to reduce high intensity reciprocity 
failure (HIRF). 
Recently, emulsion dopants have been described which comprise transition 
metal complexes having nitrosyl or thionitrosyl ligands. European Patent 
Applications 0325235 and 0457298 disclose the use of one such complex, 
namely potassium ferric pentacyanonitrosyl. A second type of dopant, 
rhenium nitrosyl or rhenium thionitrosyl is disclosed in U.S. Pat. No. 
4,835,093; and a third, dicesium pentachloronitrosyl osmate, is disclosed 
in U.S. Pat. No. 4,933,272. 
It has also been known to use combinations of dopants in silver halide 
emulsions. Such combinations of dopants can be found in U.S. Pat. No. 
3,901,713, which discloses the addition of both rhodium and iridium 
compounds during emulsification or the first ripening; and in U.S. Pat. 
No. 3,672,901, which teaches the combined use of iron compounds and 
iridium or rhodium salts. 
Methods of improving the photographic characteristics of silver halide 
emulsions have also consisted of adding transition metals to the emulsions 
during chemical or spectral sensitization. As mentioned, transition metals 
added in this manner, because they are added subsequent to silver halide 
precipitation, are referred to as grain surface modifiers rather than 
dopants. 
The most prevalent chemical sensitizers are the gold and sulfur 
sensitizers, both of which are thought to enhance emulsion speed by 
forming electron traps and/or photoholes on the silver halide crystal 
surface. Sensitization has also been accomplished by the addition of other 
transition metals. Specifically, platinum salts have been used, although 
sensitization with such salts is strongly retarded by gelatin. In 
addition, iridium salts and complex ions of rhodium, osmium, and ruthenium 
have been used as chemical sensitizers (and also as dopants). The overall 
effect of these metals on sensitivity appears to be dependent upon their 
valence state. 
Although it is known to employ transition metals, and combinations thereof, 
as either dopants or grain surface modifiers, prior applications of such 
transition metals have yielded emulsions exhibiting inferior contrast 
improvement. This has often been the result of one dopant or grain surface 
modifier exerting an insufficient effect; or the result of a combination 
of dopants or grain surface modifiers exerting opposing effects. 
Accordingly, it would be desirable to overcome these deficiencies by 
providing a high contrast silver halide emulsion exhibiting a high .gamma. 
and sharpened toe, wherein a combination of dopants imparts the high 
contrast characteristic. 
SUMMARY OF THE INVENTION 
The present invention provides a photographic silver halide emulsion 
comprising silver halide grains internally containing at least two 
dopants, wherein the first of said dopants is an osmium-based transition 
metal complex containing a nitrosyl or thionitrosyl ligand, and the second 
dopant is a transition metal complex containing a transition metal 
selected from Group 8 of the periodic table. 
The dopants utilized in accordance with the present invention are added to 
the emulsion during the precipitation of the silver halide crystals. Thus, 
they are incorporated into the internal structure of the crystalline 
grains where they unexpectedly improve the contrast of the silver halide 
emulsion. 
In one aspect of the invention, the dopants are incorporated into silver 
chloride grains that are substantially free of silver bromide or silver 
iodide. In another aspect, the emulsions contain a third transition metal 
as either a dopant or grain surface modifier. 
In these instances, the emulsions containing the combination of dopants 
according to this invention exhibit improved contrast. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is concerned with photographic emulsions comprising 
silver halide grains in which an osmium-based transition metal complex 
containing a nitrosyl ligand or a thionitrosyl ligand, and a transition 
metal complex containing a transition metal selected from Group 8 of the 
periodic table, serve as dopants which improve contrast by sharpening the 
emulsion's toe and increasing its .gamma.. To exert their contrast 
improving effect, the dopants of the present invention must be 
incorporated into the internal structure of the silver halide grains. 
Thus, they should be added during precipitation. Incorporation should 
preferably be done until 93% of the grain volume is formed. However, the 
advantages of the invention are achieved even when the dopants are added 
at an earlier or later time, so long as the dopants are positioned below 
the surface of the silver halide grain. 
The preferred osmium-based transition metal complexes which may be employed 
as dopants in accordance with the present invention can be generically 
defined by the formula: 
EQU [OsE.sub.4 (NZ)E'].sup.r 
where 
Z is oxygen or sulfur, and together with nitrogen forms the nitrosyl or 
thionitrosyl ligand; 
E and E' represent ligands additional to the nitrosyl or thionitrosyl 
ligand; and 
r is zero, -1, -2, or -3. 
As part of the osmium-based dopant, the nitrosyl or thionitrosyl ligand is 
incorporated into the internal structure of the silver halide grain where 
it serves to modify the emulsion's photographic properties. 
The additional ligands are also incorporated into the internal structure of 
the silver halide grains. The ligand defined above by E represents a 
bridging ligand which serves as a bridging group between two or more metal 
centers in the crystal grain. Specific examples of preferred bridging 
ligands include aquo ligands, halide ligands, cyanide ligands, cyanate 
ligands, thiocyanate ligands, selenocyanate ligands, tellurocyanate 
ligands, and azide ligands. The ligand defined above by E' represents 
either E, nitrosyl or thionitrosyl. 
The preferred osmium-based transition metal complexes include: 
______________________________________ 
TMC-1 [Os(NO)Cl.sub. ].sup.-2 
TMC-2 [Os(NO)(CN).sub.5 ].sup.-2 
TMC-3 [Os(NS)Br.sub.5 ].sup.-2 
TMC-4 [Os(NS)Cl.sub.4 (N.sub.3)].sup.-2 
TMC-5 [OS(NS)I.sub.4 (N.sub.3)].sup.-2 
TMC-6 [Os(NS)Br.sub.4 (CN)].sup.-2 
TMC-7 [Os(NS)I.sub.4 (SCN)].sup.-2 
TMC-8 [Os(NS)Br.sub.4 (SeCN)].sup.-2 
TMC-9 [Os(NS)Cl.sub.3 (N.sub.3).sub.2 ].sup.-2 
TMC-10 [Os(NS)Cl.sub.3 (SCN).sub.2 ].sup.-2 
TMC-11 [Os(NS)Br.sub.2 (SCN).sub.3 ].sup.-2 
TMC-12 [Os(NS)I.sub.2 (CN).sub.3 ].sup.-2 
TMC-13 [Os(NS)Cl.sub.2 (SeCN).sub.3 ].sup.-2 
TMC-14 [Os(NS)Cl.sub.2 (N.sub.3).sub.4 ].sup.-2 
TMC-15 [Os(NS)Cl(SeCN).sub.4 ].sup.-2 
TMC-16 [Os(NS)(SeCN).sub.5 ].sup.-2 
______________________________________ 
The most preferred osmium-based transition metal complex is [Os(NO)Cl.sub.5 
].sup.-2 ; and prior to its incorporation into a silver halide grain, it 
is associated with a cation, typically 2Cs.sup.+1. 
The Group 8 transition metals suitable in the second dopant are defined 
according to the format of the periodic table adopted by the American 
Chemical Society and published in the Chemical and Engineering News, Feb. 
4, 1985, p.26. Thus, these transition metals comprise iron, ruthenium and 
osmium. Preferably, the Group 8 transition metals are associated with 
cyanide ligands. More preferably, they are in the form of anions 
characterized by the formula: 
EQU [M(CN).sub.6-y L.sub.y ].sup.n 
wherein 
M is defined as a Group 8 transition metal; 
L is a bridging ligand which serves as a bridging group between two or more 
metal centers in the crystal grain (Preferably it is a halide, azide, or 
thiocyanate, although any ligand capable of functioning in a bridging 
capacity is also specifically contemplated.); 
y is zero, 1, 2, or 3; and 
n is -2, -3,or -4. 
Preferred examples of compounds incorporating Group 8 transition metals of 
the claimed invention include: 
______________________________________ 
TMC-17 [Ru(CN).sub.6 ].sup.-4 
TMC-18 [Os(CN).sub.6 ].sup.-4 
TMC-19 [Fe(CN).sub.6 ].sup.-4 
TMC-20 [RuF(CN).sub.5 ].sup.-4 
TMC-21 [OsF(CN).sub.5 ].sup.-4 
TMC-22 [FeF(CN).sub.5 ].sup.-4 
TMC-23 [RuCl(CN).sub.5 ].sup.-4 
TMC-24 [OsCl(CN).sub.5 ].sup.-4 
TMC-25 [FeCl(CN).sub.5 ].sup.-4 
TMC-26 [RuBr(CN).sub.5 ].sup.-4 
TMC-27 [OsBr(CN).sub.5 ].sup.-4 
TMC-28 [FeBr(CN).sub.5 ].sup.-4 
TMC-29 [RuI(CN).sub.5 ].sup.-4 
TMC-30 [OsI(CN).sub.5 ].sup.-4 
TMC-31 [FeI(CN).sub.5 ].sup.-4 
TMC-32 [RuF.sub.2 (CN).sub.4 ].sup.-4 
TMC-33 [OsF.sub.2 (CN).sub.4 ].sup.-4 
TMC-34 [FeF.sub.2 (CN).sub.4 ].sup.-4 
TMC-35 [RuCl.sub.2 (CN).sub.4 ].sup.-4 
TMC-36 [OsCl.sub.2 (CN).sub.4 ].sup.-4 
TMC-37 [FeCl.sub.2 (CN).sub.4 ].sup.-4 
TMC-38 [RuBr.sub.2 (CN).sub.4 ].sup.-4 
TMC-39 [OsBr.sub.2 (CN).sub.4 ].sup.-4 
TMC-40 [FeBr.sub.2 (CN).sub.4 ].sup.-4 
TMC-41 [RUI.sub.2 (CN).sub.4 ].sup.-4 
TMC-42 [OsI.sub.2 (CN).sub.4 ].sup.-4 
TMC-43 [FeI.sub.2 (CN).sub.4 ].sup.-4 
TMC-44 [Ru(CN).sub.5 (OCN)].sup.-4 
TMC-45 [Os(CN).sub.5 (OCN)].sup.-4 
TMC-46 [Fe(CN).sub.5 (OCN)].sup.-4 
TMC-47 [Ru(CN).sub.5 (SCN)].sup.-4 
TMC-48 [Os(CN).sub.5 (SCN)].sup.-4 
TMC-49 [Fe(CN).sub.5 (SCN)].sup.-4 
TMC-50 [Ru(CN).sub.5 (N.sub.3)].sup.-4 
TMC-51 [OS(CN).sub.5 (N.sub.3)].sup.-4 
TMC-52 [Fe(CN).sub.5 (N.sub.3)].sup.-4 
TMC-53 [Ru(CN).sub.5 (H.sub.2 O)].sup.-3 
TMC-54 [Os(CN).sub.5 (H.sub.2 O)].sup.-3 
TMC-55 [Fe(CN).sub.5 (H.sub.2 O)].sup.-3 
TMC-56 [Ru(SCN).sub.6 ].sup.-4 
TMC-57 [Os(SCN).sub.6 ].sup.-4 
TMC-58 [Fe(SCN).sub.6 ].sup.-4 
TMC-59 [Ru(OCN).sub.6 ].sup.-4 
TMC-60 [Os(OCN).sub.6 ].sup.-4 
TMC-61 [Fe(OCN).sub.6 ].sup.-4 
______________________________________ 
Most preferred are [Fe(CN).sub.6 ].sup.-4 and [Ru(CN).sub.6 ].sup.-4 ; and 
prior to incorporation, both are associated with an appropriate cation, 
typically 4K.sup.+1. [Fe(CN).sub.6 ].sup.-4 is also typically associated 
with three waters of crystallization (hydration). 
When [Os(NO)Cl.sub.5 ].sup.-2 is incorporated into a photographic emulsion 
in an amount between about 7.5.times.10.sup.-10 moles per mole of silver 
halide and about 4.5.times.10.sup.-9 moles per mole of silver halide; and 
[Fe(CN).sub.6 ].sup.-4 or [Ru(CN).sub.6 ].sup.-4 are incorporated in an 
amount between about 5.0.times.10.sup.-6 moles per mole of silver halide 
and about 2.0.times.10.sup.-5 moles per mole of silver halide, optimum 
contrast improvement is achieved. To obtain both improved contrast and a 
minimization of the dopants' impact on latent image keeping, it is 
contemplated to use an amount of the [Fe(CN).sub.6 ].sup.-4 or [Ru(CN) 
6].sup.-4 dopant less than the range previously specified. Specifically, 
an amount of dopant between about 1.0.times.10.sup.-9 and about 
5.0.times.10.sup.-6 moles per silver halide mole is contemplated. More 
preferred is an amount between about 5.0.times.10.sup.-8 and about 
5.0.times.10.sup.-6 moles per silver halide mole. 
In the preferred embodiment of the invention, an additional transition 
metal may be added to the emulsion as either a third dopant or as a grain 
surface modifier. This can be done without significantly detracting from 
effects of the other emulsion dopants. The additional transition metal is 
preferably added after precipitation so that it is incorporated onto the 
surfaces of the silver halide grains. However, it may also be added during 
silver halide precipitation so that it is banded from 93 percent to 95.5 
percent of the grain volumes at a level between about 4.1.times.10.sup.-8 
and 3.1.times.10.sup.-7 moles per mole of silver halide. By banding, it is 
meant that the additional transition metal is added to the emulsion after 
93 percent of the silver halide has precipitated, and until 95.5 percent 
of the silver halide has precipitated. It is most preferred that this 
third transition metal be iridium, which may be in the form of an anion. 
Silver halide grains in photographic emulsions can be formed of bromide 
ions as the sole halide, chloride ions as the sole halide, or any mixture 
of the two. It is also common practice to incorporate minor amounts of 
iodide ions in photographic silver halide grains. 
In photographic emulsions, iodide concentrations in silver halide grains 
seldom exceed 20 mole percent and are typically less than 10 mole percent, 
based on silver. However, specific applications differ widely in their use 
of iodide. In high speed (ASA 100 or greater) camera films, silver 
bromoiodide emulsions are employed since the presence of iodide allows 
higher speeds to be realized at any given level of granularity. In 
radiography, silver bromide emulsions or silver bromoiodide emulsions 
containing less than 5 mole percent iodide are customarily employed. 
Emulsions employed for the graphic arts and color paper, by contrast, 
typically contain greater than 50 mole percent chloride. Preferably they 
contain greater than 70 mole percent, and optimally greater than 85 mole 
percent, chloride. The remaining halide in such emulsions is preferably 
less than 5 mole percent, and optimally less than 2 mole percent, iodide, 
with any balance of halide not accounted for by chloride or iodide being 
bromide. 
The advantages of the invention would be present in any of the 
above-mentioned types of emulsions, although it is preferred that the 
emulsions comprise silver chloride grains which are substantially free of 
silver iodide and silver bromide. By substantially free, it is meant that 
such grains are greater than about 90 molar percent silver chloride. 
Preferably, silver chloride accounts for greater than about 99 molar 
percent of the silver halide in the emulsion. Optimally, silver chloride 
is the sole halide. 
Moreover, the invention may be practiced in black-and-white or color films 
utilizing any other type of silver halide grains. The grains may be 
conventional in form such as cubic, octahedral, dodecahedral, or 
octadecahedral, or they may have an irregular form such as spherical 
grains or tabular grains. Further, the grains of the present invention may 
be of the type having &lt;100&gt;, &lt;111&gt;, or other known orientation, planes on 
their outermost surfaces. 
The invention may further be practiced with any of the known techniques for 
emulsion preparation, specific examples of which are referenced in the 
patents discussed in Research Disclosure, December 1989, 308119, Sections 
I-IV at pages 993-1000. Such techniques include those which are normally 
utilized, for instance single jet or double jet precipitation; or they may 
include forming a silver halide emulsion by the nucleation of silver 
halide grains in a separate mixer or first container with later growth in 
a second container. Regardless of which method is used, the dopants of the 
invention should be added during silver halide precipitation so that they 
are internally incorporated into the silver halide grains. 
After formation of the silver halide grains, the emulsions containing the 
grains are washed to remove excess salt. They may then be chemically or 
spectrally sensitized by any conventional agent, and in any conventional 
manner, as disclosed in the above-referenced Research Disclosure 308119. 
Sensitizing dyes which can be used in accordance with the invention include 
the polymethine dye class, which further includes the cyanines, 
merocyanines, complex cyanines and merocyanines (i.e. tri-, tetra- and 
polynuclear cyanines and merocyanines), oxonols, hemioxonols, styryls, 
merostyryls, and streptocyanines. Specific dyes include 
3,3'-diethyl-9,11-trimethylene-thiacarbocyanine iodide, 
anhydro-3-ethyl-9,11-neopentylene-3'-(3-sulfopropyl)thiadicarbocyanine 
hydroxide, 
anhydro-9-ethyl-5,5'-diphenyl-3,3'-di(2-sulfoethyl)oxacarbocyanine 
hydroxide triethylammonium salt, 
anhydro-5-chloro-5'-phenyl-3,3'-bis(3-sulfopropyl)oxathiacyanine hydroxide 
triethylammonium salt, and anhydro-5-chloro-5'-pyrolylthiazolothiacyanine 
hydroxide tetrabutylammonium salt. Other dyes which can be used are 
disclosed Research Disclosure 308119. 
Chemical sensitizers which can be used in accordance with the invention 
include the gold and sulfur class sensitizers, such as aurous sulfide, 
aurous bis(1,4,5-trimethyl-1,2,4-triazolium-3-thiolate)tetra-fluoroborate, 
and sodium thiosulfate, or the transition metal sensitizers as discussed 
above. Further, they can be combined with any of the known antifoggants or 
stabilizers such as those disclosed in Research Disclosure 308119, Section 
VI. These may include halide ions, chloropalladates, and chloropalladites. 
Moreover, they may include thiosulfonates, quaternary ammonium salts, 
tellurazolines, and water soluble inorganic salts of transition metals 
such as magnesium, calcium, cadmium, cobalt, manganese, and zinc. 
After sensitizing, the emulsions can be combined with any suitable coupler 
(whether two or four equivalent) and/or coupler dispersants to make the 
desired color film or print photographic materials; or they can be used in 
black-and-white photographic films and print material. Couplers which can 
be used in accordance with the invention are described in Research 
Disclosure Vol. 176, 1978, Section 17643 VIII and Research Disclosure 
308119 Section VII, the entire disclosures of which are incorporated by 
reference. 
The emulsions of the invention may further be incorporated into a 
photographic element and processed, upon exposure, by any known method 
(such as those methods disclosed in U.S. Pat. No. 3,822,129). Typically, a 
color photographic element comprises a support, which can contain film or 
paper sized by any known sizing method, and at least three different color 
forming emulsion layers. The element also typically contains additional 
layers, such as filter layers, interlayers, overcoat layers, subbing 
layers, and the like. It may contain brighteners, antistain agents, 
hardeners, plasticizers and lubricants, as well as matting agents and 
development modifiers. Specific examples of each of these, and their 
manners of and sodium thiosulfate, application, are disclosed in the 
above-referenced Research Disclosure 308119, and Research Disclosure 17643 
.

The invention can be better appreciated by reference to the following 
specific examples. They are intended to be illustrative and not exhaustive 
of the emulsions of the present invention and their methods of formation. 
EXAMPLES 
Preferred sensitizing dyes, and those used in accordance with the examples 
below, are illustrated by the following structures: 
##STR1## 
The following examples also incorporated the addition of antifoggants and 
stabilizers into the emulsion making process. The specific antifoggants 
and stabilizers used are represented by the structures below: 
##STR2## 
Preferred image dye couplers, and those used in accordance with the 
following examples have the following structures: 
##STR3## 
______________________________________ 
Preparation of the emulsions 
Emulsion preparation for 
examples 1-25 
Solutions utilized for 
emulsion preparation: 
______________________________________ 
Solution A 
Gelatin 21.0 g 
1,8-dithiooctanediol 112.5 mg 
Water 532.0 ml 
Solution B 
Silver Nitrate 170.0 g 
Water 467.8 ml 
Solution C 
Sodium Chloride 58.0 g 
Water 480.0 ml 
Solution D 
Sodium Chloride 53.9 g 
Cs.sub.2 Os(NO)Cl.sub.5 
1.5 mg 
Water 446.4 ml 
Solution E 
Sodium Chloride 53.9 g 
K.sub.4 Fe(CN).sub.6 4.22 mg 
Water 446.4 ml 
______________________________________ 
Emulsion 1 was prepared by placing solution A in a reaction vessel and 
stirring at 46.degree. C. Solutions B and C were added simultaneously at 
constant flow rates of 0.05 moles/min while controlling the silver 
potential at 1.5 pCl. The emulsion was then washed to remove excess salts. 
The emulsion grains were cubic and had an edge length of 0.372 microns. 
Emulsion 2 was prepared by placing solution A in a reaction vessel and 
stirring at a temperature of 46.degree. C. Solutions B and E were added 
simultaneously at constant flow rates for 93% of the grain volume. The 
silver potential was controlled at 1.5 pCl. After 93% of the grain volume 
was achieved, solution C was used in place of solution E for the remainder 
of the reaction. The emulsion was washed to remove excess salts. The 
grains were cubic with an edge length of 0.358 microns. 
Emulsion 3 was prepared in a manner similar to emulsion 2 except that the 
amount of K.sub.4 Fe(CN).sub.6 was increased in solution E to 8.44 
milligrams. The cubic edge length of emulsion 3 was 0.327 microns. 
Emulsion 4 was prepared in a manner similar to emulsion 2 except that 
solution D was used in place of solution E. The cubic edge length of this 
emulsion was 0.342 microns. 
Emulsion 5 was prepared in a manner similar to emulsion 4 except that the 
amount of Cs.sub.2 Os(NO)Cl.sub.5 was increased to 3.0 micrograms. The 
emulsion had a cubic edge length of 0.361 microns. 
Emulsion 6 was prepared by decreasing the amount of water in solutions D 
and E to 223.2 ml. Solution A was placed in a reaction vessel and stirred 
at 46.degree. C. Solutions D and E were then run in simultaneously with 
solution B at constant flow rates for 93% of the grain volume. The silver 
potential was controlled at 1.5 pCl. After 93% of the grain volume was 
achieved, solution C replaced solutions D and E for the remainder of the 
precipitation. The emulsion was then washed to remove excess salts. The 
emulsion was cubic with an edge length of 0.335 microns. 
Emulsion 7 was prepared in a manner similar to emulsion 6 except that the 
amount of K.sub.4 Fe(CN).sub.6 was increased in solution E to 8.44 
milligrams. The cubic edge length of emulsion 7 was 0.351 microns. 
Emulsion 8 was prepared in a manner similar to emulsion 6 except that the 
amount of Cs.sub.2 Os(NO)Cl.sub.5 was increased to 3.0 micrograms. The 
emulsion had a cubic edge length of 0.336 microns. 
Emulsion 9 was prepared in a manner similar to emulsion 8 except that the 
amount of K.sub.4 Fe(CN).sub.6 was increased in solution E to 8.44 
milligrams. The cubic edge length of emulsion 9 was 0.345 microns. 
The above emulsions are described in Table I. 
TABLE I 
______________________________________ 
K.sub.4 Fe(CN).sub.6 
Cs.sub.2 Os(NO)Cl.sub.5 
Edge length 
Emulsion (milligrams) 
(micrograms) (microns) 
______________________________________ 
1 control 
0 0 0.372 
2 control 
4.22 0 0.358 
3 control 
8.44 0 0.327 
4 control 
0 1.5 0.342 
5 control 
0 3.0 0.361 
6 invention 
4.22 1.5 0.335 
7 invention 
8.44 1.5 0.351 
8 invention 
4.22 3.0 0.336 
9 invention 
8.44 3.0 0.345 
______________________________________ 
Examples 1-9 
Each of the emulsions described above was heated to 40.degree. C. To each 
emulsion, 17.8 milligrams of a gold sensitizing compound as disclosed in 
U.S. Pat. No. 2,642,361 was added. The emulsions were then digested at 
65.degree. C. In addition, 297 milligrams of Compound 1 and 1306 
milligrams KBr was added along with 20 mg sensitizing dye A. The emulsions 
were coated on a paper support at 183 mg/m.sup.2 silver along with 448 
mg/m.sup.2 cyan dye forming coupler A. A 1076 mg/m.sup.2 gel overcoat was 
applied as a protective layer along with a vinylsulfone hardener. The 
coatings were exposed for 0.1 second with a Wratten.TM. WR12 filter 
through a step tablet and were processed at 35.degree. C. as follows: 
______________________________________ 
Color development 45 sec 
Bleach-fix (FeEDTA) 45 sec 
Wash 90 sec 
Developer composition: 
Water 800 ml 
Triethanolamine 100% 11 ml 
Lithium Polystyrene Sulfonate 30% 
0.25 ml 
Potassium Sulfite, 45% 0.5 ml 
N,N-Diethylhydroxylamine 85% 
6 ml 
PHORWITE REUa 2.3 g 
Lithium Sulfate 2.7 g 
1-Hydroxyethyl-1,1-diphosphoric acid 60% 
0.8 ml 
Potassium Chloride 1.8 g 
Potassium Bromide 0.02 g 
Methanesulfonamide,N-(2-((4-amino-3- 
4.55 g 
methylphenyl)ethylamino)ethyl)-, sulfate 
(2:3) 
Potassium Carbonate 23 g 
Water to make 1.0 ltr 
pH 10.12 
______________________________________ 
The results are shown in Table IIA and correspond to sensitometric data 
points on each emulsion's D-log E curve. To assist in understanding these 
results, and hence the invention, particular attention is drawn to 
Examples 1, 3, 5, and 9. Example corresponds to an emulsion having no 
dopants. Its toe value is 0.352 and its gamma is 2.763. When a single 
dopant is added to this emulsion, as in Examples 3 or 5, toe value and 
gamma are changed. If 8.44 milligrams of K.sub.4 Fe(CN).sub.6 per mole of 
silver halide are added (Example 3), contrast decreases as toe softens 
(larger value) and gamma decreases. If, on the other hand, 3.0 micrograms 
of Cs.sub.2 Os(NO)Cl.sub.5 are added to the emulsion instead of K.sub.4 
Fe(CN).sub.6 (Example 5), contrast increases as toe sharpens (smaller 
value) and gamma increases. 
The invention resides in an emulsion containing the combination of dopants. 
As can be seen from Example 9, such an emulsion exhibits a very large 
contrast increase. Toe density, for instance, is much sharper with the 
combination of dopants than with either dopant alone, or even additive 
effects of each dopant. Similarly, gamma is much higher with the 
combination of dopants. 
This analysis may be used to understand the remaining results in Table IIA, 
as well as the results in the following Examples. Further understanding of 
the invention may be garnered by reference to the columns labeled "% Toe 
change". The values in these columns correspond to the change in toe from 
an undoped emulsion (i.e., Example 1). For Table IIA, doping with only 
K.sub.4 Fe(CN).sub.6 results in a positive toe change (softening); and 
doping with only Cs.sub.2 Os(NO)Cl.sub.5 results in a negative toe change 
(sharpening). Doping with a combination of these two dopants, by contrast, 
results in a very large negative toe change (sharpening). 
TABLE IIA 
______________________________________ 
Ex- Dopants % Toe 
ample Fe.sup.1 
Os(NO).sub.2 
Speed.sup.3 
0.3Toe.sup.4 
Gamma.sup.5 
change 
______________________________________ 
1 0 0 138 0.352 2.763 -- 
control 
2 4.22 0 152 0.353 2.753 +0.3% 
control 
3 8.44 0 143 0.375 2.686 +6.5% 
control 
4 0 1.5 133 0.347 2.776 -1.4% 
control 
5 0 3.0 133 0.305 2.915 -13.4% 
control 
6 in- 4.22 1.5 132 0.318 2.900 -9.7% 
vention 
7 in- 8.44 1.5 137 0.306 2.929 -13.4% 
vention 
8 in- 4.22 3.0 131 0.283 2.709 -19.6% 
vention 
9 in- 8.44 3.0 129 0.248 3.139 -30.5% 
vention 
______________________________________ 
.sup.1 milligrams K.sub.4 Fe(CN).sub.6 /mole silver halide; Fe(CN).sub.6 
.sup.-4 incorporated throughout 93.0% of the grain (by volume) 
.sup.2 micrograms Cs.sub.2 Os(NO)Cl.sub.5 /mole silver halide; 
Os(NO)Cl.sub.5 .sup.-2 incorporated throughout 93% of the grain (by 
volume) 
.sup.3 The reciprocal of the relative amount of light in LogE .times. 100 
to produce 1.0 density. 
.sup.4 The density value of the point 0.3 log E fast of the speed point. 
.sup.5 The slope of the line between a point 0.3 log E fast of the speed 
point and a point 0.3 Log E slow of the speed point. 
The effect of a third transition metal, iridium, on the activity of the 
dopants is illustrated by adding to the emulsions corresponding to 
Examples 1-9, post-precipitation, 0.05 mgs K.sub.3 IrCl.sub.6, and 
processing such emulsions as stated above. The results are set out below 
in Table IIB. They indicate that the effect of the combination of dopants 
remains even in the presence of a third transition metal. 
TABLE IIB 
______________________________________ 
Ex- Dopants % Toe 
ample Fe.sup.1 
Os(NO).sub.2 
Speed.sup.3 
0.3Toe.sup.4 
Gamma.sup.5 
change 
______________________________________ 
1' 0 0 139 0.354 2.668 -- 
control 
2' 4.22 0 143 0.364 2.640 +2.8% 
control 
3' 8.44 0 134 0.382 2.392 +7.9% 
control 
4' 0 1.5 127 0.357 2.591 +0.8% 
control 
5' 0 3.0 128 0.298 2.858 -15.8% 
control 
6' in- 
4.22 1.5 128 0.313 2.718 -11.6% 
vention 
7' in- 
8.44 1.5 131 0.308 2.853 -13.0% 
vention 
8' in- 
4.22 3.0 121 0.263 2.907 -25.7% 
vention 
9' in- 
8.44 3.0 127 0.247 3.004 -30.2% 
vention 
______________________________________ 
.sup.1 milligrams K.sub.4 Fe(CN).sub.6 /mole silver halide; Fe(CN).sub.6 
.sup.-4 incorporated throughout 93.0% of the grain (by volume) 
.sup.2 micrograms Cs.sub.2 Os(NO)Cl.sub.5 /mole silver halide; 
Os(NO)Cl.sub.5 .sup.-2 incorporated throughout 93% of the grain (by 
volume) 
.sup.3 The reciprocal of the relative amount of light in LogE .times. 100 
to produce 1.0 density. 
.sup.4 The density value of the point 0.3 log E fast of the speed point. 
.sup.5 The slope of the line between a point 0.3 log E fast of the speed 
point and a point 0.3 Log E slow of the speed point. 
Examples 10-21 
Emulsions 1, 5 and 9 as described in Table I were chemically sensitized by 
adding 330 mg sensitizing dye B per mole silver and 22 mg of a gold 
sensitizing compound per mole silver, as described in U.S. Pat. No. 
2,642,361. The emulsions were then digested at 70.degree.. After 
digestion, compounds 1, 2 or 3, or combinations thereof, were added to the 
emulsions. When compounds 2 or 3 were used, they were always combined with 
compound 4 in a 1:10 ratio. Compound 1 was added at 380 mg/mole, compound 
2 at 400 mg/mole and compound 3 at 240 mg/mole. KBr was added to the 
emulsions at 612 mg/mole. The emulsions were coated at 280 mg/m.sup.2 
silver along with 448 mg/m.sup.2 magenta dye forming coupler B, or at 172 
mg/m.sup.2 with 350 mg/m.sup.2 of magenta dye forming coupler C. The 
emulsion plus dye forming coupler was coated on a paper support that had 
been sized using conventional sizing methods or a paper support prepared 
according to the special procedure described in U.S. Pat. No. 4,994,147. 
The results after a 0.1 second exposure and the aforementioned process are 
listed in Table III below and show that the effect on toe sharpening due 
to the combination of dopants in the emulsion exists under a wide variety 
of coating preparation conditions. 
TABLE III 
__________________________________________________________________________ 
EMULSION.sup.4 
EMULSION.sup.5 
EMULSION.sup.3 
5 9 
1 % Toe % Toe 
Example 
Support Coupler 
Antifoggant 
Speed.sup.(1) 
Toe.sup.(2) 
Speed.sup.(1) 
Toe.sup.(2) 
Change 
Speed.sup.(1) 
Toe.sup.(2) 
Change 
__________________________________________________________________________ 
10 conventional 
B 1 133 0.345 
124 0.295 
-15.5 
116 0.227 
-34.2 
11 " B 1 + (2 + 4) 
134 0.340 
123 0.295 
13.2 116 0.230 
-32.4 
12 " B 1 + (3 + 4) 
134 0.345 
123 0.296 
14.2 116 0.227 
-34.2 
13 " C 1 134 0.380 
124 0.337 
-11.3 
117 0.260 
-31.6 
14 " C 1 + (2 + 4) 
133 0.381 
124 0.330 
13.4 117 0.258 
-32.1 
15 " C 1 + (3 + 4) 
134 0.380 
123 0.337 
11.3 117 0.264 
-30.5 
16 special procedure 
B 1 134 0.326 
123 0.287 
-12.0 
114 0.218 
-33.1 
17 " B 1 + (2 + 4) 
134 0.324 
122 0.291 
10.2 114 0.220 
-32.1 
18 " B 1 + (3 + 4) 
134 0.330 
122 0.291 
11.8 114 0.224 
-32.1 
19 " C 1 135 0.386 
123 0.340 
-11.9 
116 0.256 
-33.7 
20 " C 1 + (2 + 4) 
134 0.378 
123 0,328 
13.2 115 0.258 
-31.7 
21 " C 1 + (3 + 4) 
135 0.384 
123 0.337 
12.2 116 0.257 
-33.1 
__________________________________________________________________________ 
.sup.1 The reciprocal of the relative amount of light in LogE .times. 100 
to produce 1.0 density 
.sup.2 The density value of the point 0.3 logE fast of the speed point 
.sup.3 Emulsion 1 contained no K.sub.4 Fe(CN).sub.6 and no Cs.sub.2 
Os(NO)Cl.sub.5 (control) 
.sup.4 Emulsion 5 contained no K.sub.4 Fe(CN).sub.6 and 3.0 micrograms of 
Cs.sub.2 Os(NO)Cl.sub.5 (control) 
.sup.5 Emulsion 9 contained 8.44 milligrams of K.sub.4 Fe(CN).sub.6 and 
3.0 micrograms of Cs.sub.2 Os(NO)Cl.sub.5 (invention) 
______________________________________ 
Emulsion Preparation for examples 22-29 
______________________________________ 
Solution A 
Gelatin 20.1 g 
1,8-dithiooctanediol 190.0 mg 
Water 715.5 ml 
Solution B 
Silver Nitrate 170.0 g 
Water 230.3 ml 
Solution C 
Sodium Chloride 58.0 g 
Water 242.6 ml 
Solution D 
Sodium Chloride 53.9 g 
Cs.sub.2 Os(NO)Cl.sub.5 
0.5 mg 
Water 225.6 ml 
Solution E 
Sodium Chloride 53.9 g 
K.sub.4 Fe(CN).sub.6 2.11 mg 
Water 225.6 ml 
______________________________________ 
Solution A was placed in a reaction vessel and stirred at 68.3.degree. C. 
To produce emulsion 10, solutions B and C were added simultaneously with 
flow rates increasing from 0.193 moles/minute to 0.332 moles/minute. The 
silver potential was controlled at 1.5 pCl. The emulsion was then washed 
to remove excess salts. The cubic emulsion grains had an edge length of 
0.784 microns. 
Emulsion 11 was prepared in a manner similar to emulsion 10 except that 
solution D was used for 93% of the grain volume. After 93% of the grain 
volume had been achieved, solution C was used for the remainder of the 
precipitation. The cubic edge length of this emulsion was 0.780 microns. 
Emulsion 12 was prepared in a manner similar to emulsion 11 except that 
solution E was used in place of solution D. The emulsion grains were cubic 
and had an edge length of 0.788 microns. 
Emulsion 13 was prepared by decreasing the amount of water in both 
solutions D and E to 112.8 ml, mixing the two solutions together and using 
this solution for 93% of the grain volume as described for emulsion 11. 
After 93% of the grain volume, solution C was used for the remainder of 
the precipitation. The cubic emulsion grains had an edge length of 0.774 
microns. 
The above emulsions are listed in Table IV. 
TABLE IV 
______________________________________ 
K.sub.4 Fe(CN).sub.6 
Cs.sub.2 Os(NO)Cl.sub.5 
edge length 
Emulsion mg/mol AgX .mu.m/mol AgX (microns) 
______________________________________ 
10 control 
none none 0.784 
11 control 
none 0.5 0.780 
12 control 
2.11 none 0.788 
13 invention 
2.11 0.5 0.774 
______________________________________ 
Examples 22-29 
The above emulsions were melted at 40.degree. C. To each emulsion a gold 
sensitizing compound as described in U.S. Pat. No. 2,642,361 was added. 
The emulsions were heated and digested at 60.degree. C. To each emulsion, 
280 mg of dye C was added, along with 104 mg of compound 1 and 547 mg of 
potassium bromide. These emulsions were used in examples 22-25. Examples 
26-29 were prepared the same way except that 0.15 milligrams of K.sub.3 
IrCl.sub.6 were added to each emulsion subsequent to the addition of 
compound 1. The emulsions were coated at 280 mg/m.sup.2 silver along with 
1076 mg/m.sup.2 of yellow dye forming coupler D on a paper support 
prepared by conventional sizing methods. The coated material was exposed 
for 0.1 second or 100 seconds and processed as in the previous examples. 
The results are shown in Table V below. These data illustrate that 
improved contrast due to the combination of dopants is found in the 
presence of a third transition metal, namely iridium, and that this 
advantage is present even at long exposure times. 
TABLE V 
__________________________________________________________________________ 
0.1 sec exposure 
Cs.sub.2 Os(NO)Cl.sub.5 
K.sub.4 Fe(CN).sub.6 
K.sub.3 IrCl.sub.6 % Toe 
Example 
Emulsion 
.mu.g/mole 
mg/mole 
mg/mole 
Speed.sup.(1) 
Toe.sup.(2) 
Gamma.sup.(3) 
Change 
__________________________________________________________________________ 
22 10 control 
none none none 104 0.345 
2.652 
-- 
23 11 control 
0.5 none " 117 0.363 
2.473 
+5.2 
24 12 control 
none 2.11 " 131 0.327 
2.501 
-5.2 
25 13 invention 
0.5 2.11 " 128 0.229 
2.764 
-33.6 
26 10 control 
none none 0.14 111 0.347 
2.662 
-- 
27 11 control 
0.5 none " 120 0.345 
2.536 
-0.3 
28 12 control 
none 2.11 " 141 0.302 
2.550 
-13.0 
29 13 invention 
0.5 2.11 " 133 0.218 
2.837 
-37.2 
__________________________________________________________________________ 
100 sec exposure 
Cs.sub.2 Os(NO)Cl.sub.5 
K.sub.4 Fe(CN).sub.6 
K.sub.3 IrCl.sub.6 % Toe 
Example 
Emulsion 
mg/mole mg/mole 
mg/mole 
Speed.sup.(1) 
Toe.sup.(2) 
Gamma.sup.(3) 
Change 
__________________________________________________________________________ 
22 10 control 
none none none 122 0.240 
2.953 
-- 
23 11 control 
0.5 none " 129 0.2444 
2.960 
+0.2 
24 12 control 
none 2.11 " 138 0.280 
2.902 
+16.7 
25 13 invention 
0.5 2.11 " 131 0.153 
3.362 
-36.3 
26 10 control 
none none 0.15 124 0.239 
3.126 
-- 
27 11 control 
0.5 none " 130 0.240 
3.112 
+0.1 
28 12 control 
none 2.11 " 143 0.295 
3.039 
+23.4 
29 13 invention 
0.5 2.11 " 133 0.169 
3.399 
-29.3 
__________________________________________________________________________ 
.sup.1 The reciprocal of the relative amount of light in LogE .times. 100 
to produce 1.0 density 
.sup.2 The density value of the point 0.3 logE fast of the speed point 
.sup.3 The slope of the line between a point 0.3 log E fast of the speed 
point and a point 0.3 logE slow of the speed point 
Examples 30-49 
A series of emulsions were prepared according to the procedures used for 
preparing Emulsions 10-13, except that the dopants were incorporated 
throughout 0-25% (core), 25-75% (band) or 75%-98% (band) of the volume of 
the silver halide grains, and the dopant levels were increased to 1.5 
.mu.g of Cs.sub.2 Os(NO)Cl.sub.5 per mole silver chloride and 4.22 mg of 
K.sub.4 Fe(CN).sub.6 per mole silver chloride. 
The emulsions were sensitized, coated, exposed, processed and tested as 
described for Examples 22-25. The sensitometric results are shown in Table 
VI below, where Speed, Toe, Gamma and % Toe Change are as shown in Table 
V. 
TABLE VI 
__________________________________________________________________________ 
Location (0.1 sec exposure) 
Example 
Emulsion 
Cs.sub.2 Os(NO)Cl.sub.5 
K.sub.4 Fe(CN).sub.6 
Speed 
Toe 
Gamma 
% Toe Change 
__________________________________________________________________________ 
30 control 
-- -- 160 0.386 
2.86 -- 
31 " 0-25% -- 148 0.398 
3.03 +3.1 
32 " -- 0-25% 
175 0.390 
2.71 +1.0 
33 invention 
0-25% 0-25% 
132 0.216 
5.33 -44.0 
34 control 
-- -- 160 0.386 
2.86 -- 
35 " 0-25% -- 148 0.398 
3.03 +3.1 
36 " -- 75-98% 
180 0.400 
2.70 +3.6 
37 invention 
0-25% 75-98% 
140 0.269 
4.32 -30.3 
38 control 
-- -- 160 0.386 
2.86 -- 
39 " 25-75% -- 163 0.377 
3.03 -2.3 
40 " -- 25-75% 
176 0.394 
2.79 +2.1 
41 invention 
25-75% 25-75% 
139 0.221 
4.74 -42.8 
42 control 
-- -- 160 0.386 
2.86 -- 
43 " 75-98% -- 158 0.358 
3.05 -7.5 
44 " -- 0-25% 
175 0.390 
2.71 +1.0 
45 invention 
75-98% 0-25% 
147 0.51 
3.10 -9.1 
46 control 
-- -- 160 0.386 
2.86 -- 
47 " 75-98% -- 158 0.368 
3.08 -7.3 
48 " -- 75-98% 
180 0.40 
2.70 +3.6 
49 invention 
75-98% 75-98% 
159 0.305 
3.63 -21.0 
__________________________________________________________________________ 
The data from Table VI demonstrates that the advantages of the present 
invention are obtained when the dopants are incorporated at different 
locations within the silver halide grains. 
Emulsion Preparation for Examples 50-55 
Emulsions were prepared similar to those described for examples 22-29, 
except that the amount of K.sub.4 Fe(CN).sub.6 was kept constant and the 
amount of the Cs.sub.2 Os(NO)Cl.sub.5 was varied from 0 to 2 
micrograms/mole. Additional emulsions were prepared by varying the amount 
of Cs.sub.2 Os(NO)Cl.sub.5 over the same range, and substituting K.sub.4 
Ru(CN).sub.6 for the K.sub.4 Fe(CN).sub.6 at a level of 2.07 
milligrams/mole. The emulsions are described below in Table VII. 
TABLE VII 
______________________________________ 
Cs.sub.2 Os(NO)Cl.sub.5 
K.sub.4 Fe(CN).sub.6 
K.sub.4 Ru(CN).sub.6 
Emulsion (.mu.g/mole) (mg/mole) (mg/mole) 
______________________________________ 
14 control 
none 2.11 none 
15 invention 
1 2.11 " 
16 invention 
2 2.11 " 
17 control 
none none 2.07 
18 invention 
1 " 2.07 
19 invention 
2 " 2.07 
______________________________________ 
Examples 50-55 
Emulsions 14-19 were finished, coated, exposed and processed in a manner 
similar to examples 22-25. The sensitometric results are given in Table 
VIII and show that the increased toe sharpening according to the present 
invention can be obtained with K.sub.4 Ru(CN).sub.6 in place of K.sub.4 
Fe(CN).sub.6. 
TABLE VIIII 
______________________________________ 
Example Emulsion Speed.sup.1 
Toe.sup.2 
______________________________________ 
50 14 153 0.316 
51 15 151 0.232 
52 16 134 0.155 
53 17 154 0.269 
54 18 146 0.142 
55 19 127 0.132 
______________________________________ 
.sup.1 The reciprocal of the relative amount of light in Log E .times. 10 
to produce a density of 1.0 
.sup.2 The density of a point 0.3 Log E faster than the speed point 
Examples 56-63 
In the following examples, as set forth in Table IX, the ability of the 
present invention's combination of dopants to improve contrast without 
deleteriously impacting an emulsion's stability is shown. 
The emulsions for Examples 56-63 were prepared according to the procedures 
used for preparing Emulsions 10-13, except that the Cs.sub.2 
Os(NO)Cl.sub.5 dopant was incorporated throughout 0-70% of the volume of 
the silver halide grains, and the K.sub.4 Ru(CN).sub.6 dopant was 
incorporated throughout 75-93% of the volume of the silver halide grains. 
Also, the levels of dopants utilized were as described in Table IX, 
measured in terms of moles per mole of silver halide. The emulsions were 
sensitized, coated, and tested as described for Examples 22-25. LIK was 
taken as a measure of the emulsion's latent image stability. Specifically, 
it was measured as the speed change resulting from a delay of 24 hours 
from time of exposure to processing. Speed, Toe, and Gamma were as shown 
in Table V. 
TABLE IX 
______________________________________ 
Ex- 
am- Gam- 
ple Cs.sub.2 Os(NO)Cl.sub.5 
K.sub.4 Ru(CN).sub.6 
Speed Toe ma LIK 
______________________________________ 
56 -- -- 160 0.39 2.7 0 
57 3.9 .times. 10.sup.-9 
-- 130 0.30 3.4 0 
58 3.9 .times. 10.sup.-9 
3.8 .times. 10.sup.-5 
120 0.13 6.9 2 
59 3.9 .times. 10.sup.-9 
3.8 .times. 10.sup.-6 
117 0.14 6.3 2 
60 3.9 .times. 10.sup.-9 
1.2 .times. 10.sup.-6 
125 0.18 5.0 1 
61 3.9 .times. 10.sup.-9 
3.8 .times. 10.sup.-7 
125 0.25 4.2 0 
62 3.9 .times. 10.sup.-9 
1.2 .times. 10.sup.-7 
132 0.29 3.6 0 
63 3.9 .times. 10.sup.-9 
3.8 .times. 10.sup.-8 
133 0.30 3.5 0 
______________________________________ 
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.