Note: Descriptions are shown in the official language in which they were submitted.
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P~OCE~SS _ _ RATUS FOR TREArr:cNG
WET FAT BIOI,OGICAL l'IS~.UE USING A
WArrER MISCIBI,E SOLVENT
Technical Field
This invention relates generally to processes for
separating fat from tissue and to apparatus utili~iny
such processes. In particular, it relates to processes
and apparatus for producing dried particles of defatted
tissue.
Background Art
It has long been recognized that there are many
substances, particularly of animal origin such as
glandular tissue, meat, and the like, which contain
valuable constituents, either for food or
pharmaceutical use. Such tissues however contain
relatively high percentages of water present either in
the form of intercellular fluid or intracellular
fluid. Removal of water from such tissues has proven
difficult, and without the removal of water, it has
been difficult to remove the fat of such tissues. Both
the fat and water of such tissues must be removed to
produce a stable product, and a product which may be
further processed.
Water has been removed from tissue by
evaporation, either at low temperature over a long
period of time, or at higher temperatures over a short
period of time, but such efforts have produ~ed products
of low food value with many biological values
completely destroyed.
Wet fat animal tissue has been successfully
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deciccatecl and cleEattecl by a process of comm:inutin~J
animal tissue, suspencling the tissue in a slu~ry with a
water lmmiscible solvent which forms an a~eotrope with
water, evaporating the solvent and water Erom the
sl~lrry as an azeotrope, condensing the azeotrope vapors
to separate the solvent and replenishing the organic
solvent used in the process with the recovered solvent,
as disclosed in United States Patent No. 2,503,312 of
Worsham and Levin entitled SIMULTANEOUS DEFATTING AND
DEHYDRATING OF FATTY SUBSTANCES, Patent No. 2t503,313
of Ezra Levin entitled PRODUCTION OF DRY DEFATTED
ENZYMATIC MATERIAL; and Patent No. 2,539,54~ of Levin
and Worsham entitled SIMULTANEOUS DEFATTING ~ND
DEHYDRATING FATTY SUBSTANCES.
The water immiscible fat solvent generally used
in the processes indicated above is a hydrocarbon
solvent, particularly, ethylene dichloride. Such
solvents must be removed from end products which are
intended to be used for human comsumption, and there is
a growing belief that the presence of more than mere
traces of such solvents in animal feed is
objectionable. The removal of all traces of a fat
solvent from the product is extremely difficult, and a
better solution would appear to be the use of a solvent
which is not considered to be injurious to the health
of individuals.
Traces of alcohol in a product are not considered
to be injurious to the health of an individual
consuming the product, or objectionable in animal
feed. Further, alcohol can generally be removed by the
application of heat to levels which are acceptable.
For this reason, alcohol is an attractive solvent for
the removal of fat and moisture from animal tissues.
The book, Fishery Byproducts Tec~ y by Julius
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srod~ AVI Publlshing Company, Inc., 1965, West Port,
Connecticu-t, descrlbes two processes for removing fat
and moisture from fish by the use of alcohol. The one
process uses three separate stages, the first of which
is to treat fish with acetone, and dry the product.
The second stage treats the product with 9~ ethyl
alcohol and heat, and thereafter dries the product.
The third stage treats the product with boiling 90%
ethyl alcohol and dries the product. This process is
more fully described in British Patent No. 727,072.
The second process described in Fishery
Byproducts Technology is attributed to A. Gutman and F.
A. Vandenhenvel and uses isopropanol to e~tract fat and
water from press-cake formed of fish offal. The
isopropanol is used hot, drained from the cake after
extraction, and the cake dried under vacuum.
Isopropanol is recovered by distillation from the fish
oil and reused in the process. Such plants have not
proven to be commercially successful. An economic
disadvantage of such plants i5 that the fish oil
produced by the process is difficult to separate from
the water removed from the fish and solvent.
Another process for dehydrating and defatting
animal tissue using a water miscible fat solvent is
disclosed by Thijssen in United States Patent No.
3,649,294 entitled PROCESS FOR DEHYDRATING, DEFATTING
AND DEODORIZING ANIMAL TISSUE. In the Thijssen
process, vapors of a water miscible solvent such as
acetone, ethanol, and isopropanol contact comminuted
animal tissue in a countercurrent flow to dehydrate the
tissue, and the same or another solvent in liquid state
is utilized to defat the tissue. In the Thijssen
process, the fat solvent contains significant amounts
of water, such as isopropanol vapors having a water
~ss~
content of about ]5~ by weight.
l`here have been extensive efforts to develop
suitable solvent extraction mPthods for raw tissue,
particularly for the production of fish protein
concentrate. In December 1970, Roland Finch, Director
of the National Center for Fish Protein Concentrate,
Bureau of Commercial Fisheries, U.S. Department of
Interior, Washingtonr D.C., published "Pish Proteins
for Human Foods" in CRC riti¢al Reviews in Food
Technolo~y, and in Table 8 listed twenty solvent
extraction methods which had been applied to the
production of fish protein concentrate, including those
described above. Among the processes described is the
use of isopropyl alcohol by ~. E. Power~ as more fully
described in "Characteristics and Nutritional Value of
Various Fish Protein Concentrates", J Fish Res Bd.
Can., 21, 1486, 1964.
The known processes fsr extracting raw tissue
with isopropyl alcohol have resulted in the necessity
to separate ~he water, solvent and oil from the
extraction in order to recover the solvent for use.
This has proven to be a cost disadvantage of such
processes. Further, conventional extraction with
isopropyl alcohol requires the tissue to remain in
contact with isopropyl alcohol for longer periods than
desired, since it is desired to leave in ~he tissue
particles as large a proportion of protein and water
solubles as possible.
The azeotropic processes of ~evin for defatting
and dehydrating tissue particles achieve economical
separation of the solvent from the water and oil, and
retain the biological values in the tissue, but
requires the use of a water immiscible solvent, and
generally a toxic solvent.
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It is an object of the present invention to
provide a process for dehydrating and defatting animal
tissue in which the disadvantages of prior processes
are greatly reduced or eliminated.
It is a further object of tha presen~ invention
to provide a process for defatting and dehydrating wet
biological tissue utilizing a single solvent,
particularly alcohol.
It is a still further object of the pre~ent
invention to provide a process for dehydrating and
defatting wet biological tissue wherein the biological
values of the tissue are substantially preserved
therein.
It is a still further object of the present
invention to provide a process for defatting and
dehydrating biological tissue utilizing azeotropic
distillation of an alcohol solvent.
It is a still further object of the present
invention to provide apparatus for carxying out the
foregoing processes.
The foregoing objects of the invention are
achieved by the process of comminutiny the wet fat
biological tissue and thereafter introducing the
particles of tissue into a body of boiling water
miscible solvent to form a ~lurry of solvent, particles
and water, and maintaining the tissue in suspension in
the slurry for a period of time sufficient to reduce
the water content of the tissue to a desired nature.
The slurry is maintained under boiling conditions and
the particles are malntained suspended in the slurry.
Vapor of solvent and water is withdrawn from the
slurry, thereby reducing the content of water in the
tissue, and fresh
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solvent is introduced into the slurry to replace -the
solvent withdrawn in the vapor. The solvent water
cont.ent o~ the added solvent by volume is maintained at
least ~5~ alcohol duxing the period of time the tissue
particles remain in the slurry.
Brief Description o~ Dra~ s
Applicant's novel apparatus for carrying out the
process described above is illustrated in the attached
drawings, in which:
Figure 1 .is a schematic drawing of a plant for
commercial production of desiccated and defatted animal
tissue according to the present invention;
Figure 2 is a fragmentary view of the high purity
distillation system illustrated in Figure l; and
Figure 3 is a graph illustrating the results of
processing two samples under identical conditions
except for the water content of an isopropyl alcohol
solvent.
Best mode for Carrying Out the Inventio
The process of the present invention is an
improvement upon the processes described in the patent
of Worsham and Levin, No. 2,503,312, and the patent of
Levin, No. 2,503,313 referred to above in that a vessel
partially filled with a fat solvent is employed, and
comminuted particles of the tissue are introduced into
a boiling mass of solvent to form a slurry of solvent,
particles and water. The slurry only partially fills
the vessel, and vapors in the form of an azeotrope of
the solvent and water from the tissue particles develop
in the space above the level of the slurry. The
azeotropic vapors are withdrawn from the vessel, the
solvent separated from the water, and the solvent
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~eturnecl to the vessel to replerlish the level oE slurry
in the ve~sel. It :i9 not necessary in the inventor~s
proces~ to separa-te the water, fat and solvent from -the
separa-ted li~uid Eraction, since the water and ~olvent
are removed as vapor.
]n some respects, the pre~ent invention differs
materially from the process of Levin. The comminuted
particles do not tend to coagulate in the solvent as in
-the Levin process. The alcohol solvent prevents
coagulation. Further, wet fat partlcles are heavier
than the solvent, and sink in the body of solvent
rather than float on the surface as in the caee of an
ethylene dichloride solvent. The present invention
utilizes agitation or stirring to maximize the surface
contact of the solvent and the particles.
While alcoho~ forms an azeotrope with water, and
the boiling point of the alcohol/water azeotrope is
somewhat lower than the boiling point of water or
alcohol, there is significantly less difference between
the boiling points of the solvent and the azeotrope.
Ethylene dichloride boils at 181 degrees F., while a
water/edc azeotrope boils at 160 degrees F. Isopropyl
alcohol on the other hand boils at approximately 178
degrees F. Accordingly, the sharp rise in temperature
signifying completion of the dehydration process in the
Levin apparatus is only an increase of approximately 3
degrees in the present invention. Accordingly,
completion of dehydration is more readily determined by
measurement of the concentration of isopropyl alcohol
in the vapor removed from the interior of the vessel,
or by determination of the specific gravity of the
alcohol and water portion of the slurry of particles,
alcohol and water in the vessel.
It is also critical to the present invention that
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the volumetric ratio oF isopropyL alcoho:l to water in
the solvent :introduc:ed into -the ve9sel be at least 95%
and preferclbly 99%. As the partic]es are dehydrated in
the vessel, the slurry formed of solvent an~l particles
becomes a slurry of solvent, water and particles. The
removal of solvent and water vapor from the vessel
gradually reduces the amount of water present in the
vessel, that water being divided between bound water
within the particles and the free water in solution
with the isopropyl alcohol solvent. It is critical to
the present invention that the free water in solution
with the isopropyl alcohol be less than 8% by volume.
The criticality of the ratio of water to
isopropyl alcohol cannot be explained based upon the
solubility oE protein, water solubles and fat in a
mixture of isopropyl alcohol and water under boiling
conditions. The solubility of both fat and protein
does not change appreciably until the percentage of
water in the mixture exceeds 20%. Further, the
solubility of water solubles in a mixture of water and
isopropyl alcohol increases gradually as the percentage
by volume of water increases from zero to approximately
20% when extracting fish muscle. Experiments have
shown that extraction according to the present
invention with isopropyl alcohol solvents containing
more than 5% water by volume results in a significantly
reduced extraction efficiency and it becomes
impractical to provide the heat necessary to remove the
water from the comminuted tissue. Figure 3 is a graph
comparing the deslccation and defatting of a laboratory
sample of spleen according to the present invention.
In each case, approximately 500 grams of raw spleen
were ground into fine particles and mixed into a slurry
in a beaker with approximately two liters of isopropyl
~SS;~
alcohol solvent. The beaker was heatcd, and the vapo.r
producecl ln the beaker withclrawn to a condense:r. The
colldenser was provlded wi-th a water cooled Jacket/ and
the specific grav.ity of the condensate was perio~ically
measured to determine the percentage of isopropyl
alcohol to water in the condensate. When water is no
longer present in large percen-taye in -the condensate,
the sample will be desiccated. In each case, the
sample was placed under vacuum, and boiling occurred at
approximately 33 degrees C.
The lower curve of Figure 3 sets forth the
results of processing a sample of sp,een with 91%
isopropyl alcohol. The percentage of isopropyl alcohol
in the distillate from a 500 gram sample of spleen is
set forth from the beginning of the process for a
period of five hours, and shows that the percentage of
isopropyl alcohol increased through this period from
the first measurement of 85.6% IPA taken approximately
1/2 hour after beginning the process to a final reading
of 89.02~ taken 5 1/2 hours after the process began.
The 500 grams of spleen yielded 98 grams of meat solids
and contained a moisture content of 6.3% and quick fat
of 2.44~. This product was achieved by utilizing three
washes of 99% IPA to water by volume of 500 millimeters
each at the end of the process in order to reduce the
moisture of the product sufficiently.
On the other hand, the upper graph of Figure 3
illustrates the results of processing a second sample
of spleen of approximately 505 grams under similar
conditions but utilizing a solvent of 99% isopropyl
alcohol to water by volume. Azeotroping was completed
in three hours and forty minutes, and the percentage of
isopropyl alcohol to water increased during this period
from 86.3% taken approximately 1/2 hour after
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commencing the process to 97.34 after three hours and
forty minutes. The end product received two washes of
500 millimeters each of fresh 99~ of isopropyl alcohol
and resulted in a yield of 89.5 grams of meat olids,
3.1% moisture, and 1.48% quick fat. The dramatic
improvement in extraction efficiency resultinq from use
of a. solvent containing 99% isopropyl alcohol to water
by volume over the same process using a solvent of 91~
isopropyl alcohol to water by volume is apparent from
Figure 3. By other experiments, the inventor has found
that the process described above can be carried out
efficiently using a solvent consisting of at least 95%
isopropyl alcohol to water, and that the efficiency of
the azeotropic extraction process is materially
degregated by use of a solvent having less than 95%
isopropyl alcohol to water.
Fi~ure 1 illustrates schematically a suitable
plant constructed according to the present invention.
A vessel 10 is provided with a port 12 to receive raw
material, the port 12 being located above the level 14
of a slurry 16 which partially fills the vessel 10.
The vessel 10 is provided with a heater 18 in the form
of a jacket, and the heater 18 provides heat to
maintain the slurry 16 under boiling conditions.
The raw material is in the form of small
particles of raw fat biological tissue, and those
particles and an alcohol solvent comprise the slurry
16. In addition, the alcohol solvent forms a solution
with water extracted from the tissue parti~les. The
boiling condition of the slurry 16 causes vapor to form
in the portion of the vessel 10 above the level 14 of
the slurry, ~his region being designated 20. The
vapors formed by the slurry are in the form of an
azeotrope of alcohol and water, and the vessel is
1~; '3
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provide~ with an upper port 22 for removal of the
vapors. A stirring device 24 extends down i.n the
slurry 16 and is driven by a motor 26 locat~d
externally of the vessel lO.
The upper port 22 is connected to a condenser 28
which is provided with a cold water jacket not shown.
The condenser has the function of converting the
azeotropic vapors withdrawn from the vessel lO through
the upper port 22 to liquid form, and the condenser is
connected to a used solvent tank 30. The used solvent
tank 30 is connected to a high purity distillation
system 32 which will be described in more detail
hereinafter, and the distillation system 32 is
effective to remove the water through an exit port 34
and to provide solvent through a second exit port 36.
The solvent exiting through the port 36 consists of
alcohol with no more than 5~ water by volume, and this
exit port 36 is connected to a clean solvent reservoir
38. The clean solvent reservoir 38 is in turn
connected to an upper inlet port 40 of the vessel 10 to
replenish the solvent withdrawn from the slurry 16 by
the vapors.
The apparatus of Figure 1 is a batch system/ and
the apparatus thus far described is required for
processing the raw material through the azeotropic
cycle. When the vapors passing through the upper port
22 cease to contain significant amounts of water vapor,
the moisture from the raw material mixed in the slurry
16 has been substantially removed, and the material
uncler treatment is ready for the next step. The vessel.
lO is provided with a lower opening 42, which has a
valve not shown, and is connected to an
extractor/desolventizer 44. When the a~.eotroping
process is completed, the heater 18 is turned off, and
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the slurry 1.6 ls dumped throu~h -the lower opening 42
into the e.YtractorJdesolventizer 44 through a p:roduct
opening 46. The extractor/desolventizer ~4 also has an
upper solvent opening 48, and this is connected to the
clean solvent tank 38. The extractor/desolventizer
also has a drain opening 50 for removal of liqulds from
the extractor/desolventizer, and a lower product
opening 52 for removal of processed tissue solids.
After the slurry 16 is dumped into the
extractorJdesolventizer 44, the liquid portion thereof
is drained through the drain 50 to the evaporator 54.
Also, clean solvent is introduced through the solvent
opening 48 to wash the solids from the slurry now
located in the extractor/desolventizer 44. The solvent
from the clean solvent tank 38 also is drained through
the drain 50 and conducted to the evaporator 54. Heat
is applied in the extractor/desolventizer 44 to dry the
solid particles, and when the particles are dry they
are removed through the Einished product opening 52.
The evaporator 54 receives from the
extractor/desolventizer 44 a liquid flow of fat and
solvent, the water having been removed as an azeotrope
by the cooker 10. The evaporator applies heat to
evaporate the solvent from the fat, and the evaporator
has a drain 56 to remove the fat. Likewise, the
evaporator 54 has an upper opening 58 through which
solvent vapors flow to a condenser 60. The condenser
60 transforms the solvent vapors to liquid state, and
the condenser 60 is connected to the clean solvent tank
38.
When heat is applied to the solid particles in
the extractor/desolventizer 44 in the final drying
stages, the solvent associated with the solid particles
is evaporated, and conducted from the
:
1~55~3~
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extractor/desolventizer throu~h an exlt port 62 to a
con~enser 6~. The condenser 6~ -transforms the vapors
to liqllid form, and the Iiquid solvent is conducted to
the clean solvent tank 38.
When defattin~ and dehydrating certain tissues
such as pancreas for food or pharmaceutical values, it
is desirable to limit the temperature of the pancreas
particles during the process. Accorclingly, a vacuum
pump 66 is connected to the region 20 of the vessel 10
through the condenser 28. The vacuum pump 66 exhausts
gases present in the condenser 28 to the atmosphere to
reduce the pressure of the region 20 and to permit
boiling to occur in the slurry 16 at a temperature
lower than the atmospheric boiling point.
The vapors developed through boiling of the
slurry 16 contains a fixed proportion oE solvent vapors
and water vapors according to the alcohol/water
vapor-liquid equilibrium curve. In the case of
isopropyl alcohol, more than 87% of the vapors are it
is necessary to employ some system other than
distillation, since the water solvent mixture will
always come off as an azeotrope with the same
proportion of solvent to water. Figure 2 illustrates
the high purity distillation system 32 for achieving
this purification.
The water solvent solution from the used solvent
tank 30 is introduced into a distillation column 67
through a port 68. The distillation column 67
reconverts the vapors from the cooker or vessel 10 from
liquid form to vapor form, and the vapors from the
distillation column pass thxough a molecular sieve 70
which traps and removes water vapor while passing
solvent vapors. Molecular sieves are commercially
available and can be utilized to purify isopropyl
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alcohol to approximately 99% isopropyl alcohol and 1
water. Other processes for purification also exist,
such as saltincJ out wlth sodium chloride, sodium
sulfate, sodium hydroxide. The purified water vapors
are thereafter condensed in a condenser 72 and
delivered through the port 36 to the clean solvent
reservoir 38. Because ofthe fact that the sieve 70
will become saturated with water vapor, it is provided
with valves 74 and 76 to remove it from the system, and
a second molecular sieve 78 is connected in parallel
with the sieve 70 through valves 80 and 82. The
saturated molecular sieve may be re~uvenated and
returned to service.
The used solvent tank 30 functions to isolate the
portion of the system operated at subatmospheric
pressures, namely the cooker or vessel 10 and condenser
28, from the high purity distillation system. It is
possible to eliminate the used solvent tank 30 and the
distillation column 67, and directly impress the vapors
from the region 20 of the vessel 10 on the molecular
sieve 70 or 78.
As an example, 4,000 lbs. of raw bovine pancreas
was desiccated and dehydrated with a solvent consisting
of 99% isopropyl alcohol and 1% water under vacuum to
produce a desiccated and defatted ground meal
containing approximately 5% moisture and 2% Eat. Raw
beef pancreas was obtained frozen in 60 lb. boxes at 0
degrees F. The pancreas was allowed adequate time to
thaw just enough that it could be removed easily from
the boxes in block form and was thereafter ground
through a prebreaker equipped with a coarse grinding
plate. The meat was then ground a second time to make
a puree of the frozen meat, and thereafter mixed until
it warmed enough to be easily pumped into the apparatus
a
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illustratad in F~gure 1.
The vessel 10 was filled in the level 14 with 750
gallons of solvent consistincJ of 99~ isopropyl alcohol
and 1~ water. The water jacket on the condencer 2~ was
placed in operation and the vacuum pump 66 was u~sed to
xeduce the pressure within the regivn 20 of the vessel
to approximately 54 degrees C. The heater was
activated, and when the solvent in the vessel 10
commenced boiling, the entire 4,000 lbs. of beef
pancreas was pumped through the port 12 into the vessel
10 .
As soon as the slurry 16 of the pancreas
particles, solvent and water reached boiling,
azeotropic vapors were withdrawn from the region 20
above the level of the slurry 16 through the upper port
22 and condensed to liquid form in the condenser 28.
The condensate from the condenser 28 was collected in
the used solvent tank 30. Fresh solvent was withdrawn
from the clean solvent tank 38 and introduced through
the port 40 to maintain the level 14 of slurry lS in
the vessel 10 at the same level. Azeotroping continued
until approximately 3,000 gals. of solvent had been
distilled and condensed by the condenser 28, at which
time the product in the slurry 16 contained
approximately 10% moisture~ Thereafter, the heater 18
was deactivated, and the vacuum released. The entire
slurry 16 was dropped through the lower opening 42 by
opening a valve to the extractor/desolventizer 44. The
liquid fraction of the slurry 16 containing principally
isopropyl alcohol and fat was then drained off of the
solid fraction in extractor/desolventizer 44, and the
drained fraction transported through the drain 50 to
the evaporator 54. The evaporator 54 heater coils were
energized, and the evaporator evapo.rated the solvent
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from the fat. The condenser 60 was placed in operation
on actuation o the ev~porator heater, and condensed
the vapor solvent, which is relatively pure i~opropyl
alcohol, and returned it to the clean ~olvent tank 38.
The fat was withdrawn from the drain 56 of the
evaporator and may be further processed or utilized~
The solid particles of the ~ample in the
extractor~desolventizer 44 were then washed with
additional solvent and subjected to heat to drive of f
solvent in vapor form from the particles. The ~olvent
vapors passed through the port 62 and were condensed in
the condenser 64 and returned to the clean solvent ~ank
38. The driPd solid particles were then removed
through the finished product opening 52. Analysis of
the particles indicated a yield of meal solids of 16.6%
of the batch by weight, a fat recovery of 30.9~ of the
batch by weight, residual moisture of 2.1~ and residual
fat of 0.48%.
The high purity distillation system 32 was
actuated on completion of the foragoing sample to
return the used solvent from tha used solvent tank 30
to the clean solvent tank 3~. The high purity system
could also be operated during the azeotrope process.
In addition to the foregoing example, beef
spleen, beef heart, and beef liver may be proce~sed
according to the foregoing example. The foregoing
process is also suitable for processing whole ground
fish or parts thereof, ground fowl, and all types of
animal tis~ue.
The present invention may be practiced when other
water miscible liquid solvents that form an azeotrope
with water. Low aliphatic alcohols such as isopropyl
alcohol, ethyl alcohol and tertiary butyl alcohol are
particularly suitable solvents.
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Those skilled in the art will devise many
mocli:Ei.cations of the Eoregoing processes and app~ratus
and many applications for the present invention beyond
that here disclosed. It is therefore intended khat the
scope of -the present invention be not limited by the
foregoing disclosure, but rather only by the appended
claims.
