Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACYGROUND
Many halogenate(l coml)ounds are employed for a varie-ty of practical uses,
e.~., as pesticides, soil fumigants, solvents, etc.. Many escape into the
environlnent, as -For examl)le in manufacturing or application wastes and spills.
Some, such dS pes-ticides, are applied in such a manner as to becorne part of
the enviromllerlt. It has been found tha-t a number of such compounds9 particularly
though not necessarily polyha'logenated compoun(ls, are toxic to plant and animal
iife. Although some o~ the compounds are bio~ and/or photo-degradable so that
they soon disappear from the environment9 a subs~ankial number are resis~an~ to
environmental degra~ation and re~ain in poisonous Form for periods as long as
many months or years. As a result, a good deal of research has been done to
find reliable and economiGal treatment methods to degrade such compounds into environmental'ly safe products.
Some ~ork has b'een done wi~h treatment of certain halogenated"compounds
variously with UV radiation or with UV'radiation and oxygen~ air or ozone? To
,
inventor's knowledge, there'have been no prior teachings of the use of a chemical
reduction treatmen~ employing UV and hydrogen free From any addecl oxidizer9 '' '
such as air or oxygPn per se, or the use of UV alone in which the compound is
in aqueous alkaline solutions. ~.S. patent'399779952 teaches the required use
of oxygen (or air) plus UV, preferably in'the presence of HCl catalyst. In
column 1, -the patent mentions the use of carbon dioxide, water vapor9 air or
.
hydrogen as carrier gases for gas phase reactionO The reference to hydrogen
appears to be inadvertent since no one skilled in the art would use hydrogen
within the context of an oxygen oxidation process. The hydrogen ~tould oxidize
to ~tater and present a serious hazard of explosion.
.
DRAI~II NGS
Figure l is a schematic drawing Qf apparatus used in the process.
Figure 2 shows comparative percent d'egradation of kepone in methanol
solution'with $rea~ment by UV plus H~ and in alkaline methanol solution with
~.
-2- . ~
:~2~
trea .,ent by U~/ alone~ UV i~lus 03 an(l UV plus H~. .
Figllre 3 sho~Js the comparative percent (legraclation of kepone in aqueous
alkalirle so'lution by UV alone, UV plus 03 and UV plus t~2
Fi~ure 4 shows the compara~ive percen~ o~ max;mum chloride ions released
froln kepone in aqueous alkaline solution by treatment with the three methods.
Figure 5 shows the comparative total percent degradation of Aroclor 125
in basic methanol by UV alone, UV plus 03, and UV plus H2.
Figures 6, 7 and 8 show the percent ~legradation of tlle individual com--
ponents of Aroclor 1254 by treatment wi~h UV alone9 UV plus 03 and UV plus H2
respectively..
Figure 9 shows the-percent degradation of TBPA in basic me~hano'l by
treatmen-t with UV alone~ UV plus 03', and UV plus H2.
Figure 10 shows the percent of maximum bromide ions relea.sed from TBPA
: using the three trea~ment`methodologies.
.' SUMMARY
. . .
The treatment of a halogenated organic compound having at least one
C~halogen group wi-th UV radiation and hydrogen in the absence of any substantial
amount of oxidizing agent reduces the compound by breaking the carbon~halogen
linkage and p~oducing halogen ions', thereby at.least partially dehalogenating
the compound ~in the cas.e of a polyhalogenated compound). The treatment may
also result in further.degradation of the at least partially dehalogenated
compound. The process may be employed with monohalogenated comp.ounds~ ~u-t will
more generally be used .~o treat'polyhalogenated compounds because of their
yenerally'greater toxicity and resistance to environmental degradation.
. The process can be used general.ly as a means for dehalogenation and is
.particularly.useful ih the treatment of contaminated efflllent wastes from manu' facturing processes or from contaminated water, soil9 sludges or other wastes already present in the environment.
; -3
2 V ~ 5 ,'
T~le dehalogenatloll m2chanisms ~hich occur in the process are generic
~ nature. -rhey at-e operatîYe regardless of ~he structure of the compound or ''
the preserlce of other substituents or molecu'lar conlponents7 such as oxygen,
sul-Fur, -nitrogen, metals or the like. The effect of these variable manifesta-tions is primarily in the enercgy of the C-halocJen bond and can be compensated
for by employing higher or lower energy UV radiation wlthin the stated range.
The halogen substi-tuents can include chlorine, bromine9 fluorine, and iodine.
The different C-halogen groups generally differ in bond energy. C-F ~roups,
for example, generally have particularly high bond energies as compared with
the other ~-halogen grouljs ànd require more energetic UV wavelengths in the
dehalogenation process.
.
Examples of compounds which are particularly suitable for treatment by
the'UV plu's H2 process of the inven~ion because of their demonstrated or poten
tial toxicity include but are no~ limited ~o kepone (and its gemdiol)
decach'loropentacyclo(5.3 0 02'6 o3~9 o4,8 )decan-5-onei halogenated biphenyls;
halo~enated cyclodienes, such as aldrin, dieldrin, ancl hexach'lorocyclopenta-
'dienes; dibromochloropropane; halogenated phthatlic anhydridesg such as poly~
bromophthalic anhydride; tetrachloroethyleneg polychlorodioxins such as tetra- -chlorodlben~odioxin; halogenated organic phosphatesg such as 2,2-dichlorovinyl~
~0 dimethyl phosphate (Dichlorvos).
The process can be employed in gaseous phase where the halogenated
organic compound is gaseous or in the form of a finely divided liquid or solidt
' In such case, the hydrogen acts as diluent9 carrier, and reactant. ~Ihere the
compound is in liquid or solid formg it is generally deslrable to dissolve it
in a suitable solvent which preferably is substan~ially transparent -to the
particular UV wavelengths. Use of a solvent is particularly advantageous
where the compound is d contaminant which must be separated from other
materials, such as sludye or mud.
The particular solvent used is determined by the solubility character-
3D istics of the particular-h~logenated ompound. It can be, for exanple, water,
.
1~2~
, . . .
met lol, cthanol, 1- and 2-propanol, hexane, cyclohex2ne, acetonitrile, and
preferably their alkaline solutions.
An a~,ueous alkaline solu~ion, where alkalinity is preferably produced
by the presellce o-f alkali metal ions and preferably by means of an alkali metal
oxide or llydroxide ~to minilnize potentially obstruc-tive anions), such as sodium
or potassium oxides and hydroxides, is particu~arly useful in the case of
ilalogenatetl organic compounds which have substituents'that react to produce
soluble- alkali metal salts. Examples include but are not limited to kepone
(which normally hydrolyzes to the gem-diol in the presence oF ~ater or atmos-
pheric moisture); ary', compounds having aryl-0~ substituents~ e.g.? phénol-typecompollnds; diol-type compounds; carboxy'lic acids; anhydrides~ such as phthalicanhydride-type compounds, sulfonic ac'ids; anc', the like.
' Compounds ~Ihich are not soluble in aqueous alkaline solutlons can
generally be adequately solubilized by means of a sui~able organic solvent.
Preferably, thoùgh not essentially, the organic so'lvent is renc,ered alkaline,
e.~g.~ by add;tion of an alkali metal oxide or hydroxide~ ~ince it has been
found tha~ an alkaline pH can result in more rapid and greater degradation. --
Methanol is a preferrec, solvent because of its good solubilizing capability9
its good UV transmlssion properties, and its rela-tively low cost which is oF
particlllar importance in the case of large scale application.
The UV radiation~ as aforementioned 9 should be in the range of about
- 1800 to 4000 A. Pre-ferably, it is'in the shorter wavelength portion of this
O O O
range, ramely up to about 2537 A. ~lavelengths of about 2537A and 1850A are
particular'ly prtferred because of the generally high absorptivity of halogen-
ated organic compounds at these wavelengths. '
The hydrogen input., quantitatively, should be sufficient~ during thetime of the treating procedure, to be in stoichiometric equivalency to the
number of halogen atoms to be removed, or in excess theretoO In the case of
llquid phase solvent treatment~ the effective limiting value is the saturation
concentration of the hydrogen in solution. Continued input of hydrogen to
'maintain saturation provides the optimum amount.
.
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p,'~ r~r ~ r~ ~r 7~ ?p>~ nrr~ yiV~ rr~ r S~ .*r~X~ r ~ r.~ Q~
~ ~ 2~2~i
The process can be carried out at ambient temperature in relatively
simple apparatus. T~e halogenated organic compound should receive maximum
exposure to the UV radiation. This can be accolnl)lished by such state-of-the-
art expedients as minimiziny the distance that the radiation needs to travel
to or through the ~reatment volume; recirculation of the treatment mediumi
turbulence-creating means such as baffles or ro~ors and the like. The process
can be designed for batch or continuous treatment.
ft has also been found that substantial de~radation can be obtained by
treatn!ent of the halogenated compound in a~ueous alkaline solution by treat-
ment with UV radia~ion within ~lie stated broad and preferred ranges of wave-
length. Such treatment is limited to compounds~ as aforedescribedg which are
soluble in aqueous alkallne solution without requiring additional use of an
organic solvent. In all other respec~s the aforediscussion of various aspects
oF the process ancl generio applica~ion regardless of compoLInd structure and
substituents are appl1cable to such process using UV radiation alone.
. DETAILED DESCRIPTION . - -
Figure 1 shows a schematic drawing of a reactor as employed ln experi
mental evaluation. U shaped UV ~ube 2 is positioned longitudinally in reactor
chamber 3~ and is held in air-tight position by Teflo ~plug 49 and is connected-by wires 5 to a transFormer (not shown). Hydroyen gas is pumped in via inlet
tube 6. Reac~ion solu~ion is pulnped in via inlet tube 7 and is continuously
recirculated by a pump (not shown) via outlet ~ube 8. Vent 9 provides for the
exit of volatiles.
As used in the experiments below the reactor diameter ~as 4 inches.
Capacity was 1.5 1. The lamp size was 15-1/4 tnches in overall length with an
arc length of 24-1/2 inches and tube diameter of 11/16 inch Lamp input was
30~l and output intensity was 10.4~l. UV wavelength was 2537A.
. ' ~ . . .
, :' . - . ,
Exa~ )le 1 ,,``',`
~epone Treatnlent: . .
Kepone wllicll has been used as an insecticide has posec~ Formidable ':
problems because of i-ts great toxicity and resistance to bio- and photo~
de~radatiorl in the environl1lent. It is hiyhly toxic -to normal'ly^occurrin.g
de~rading microorganisms. Alt~lougll it can undergo some photodeconlposition when . '
exposed to sunlight to the di~lydro compound ('leaving a compound having 8 Cl
substituents) this degradation produc~. does not signiFicant'ly reduce toxicity.
Kepone was made up into ~hree dif~erent stock solutions:
a. 212ppm in methanol; solution pH6.
b. 237ppm in.methanol alkalized to pH10 with NaOH.
' c. 23Qppm in water containing 5~ NaOHO
1.5 1 quantities of the kepone stock solutions ~"ere variously treated
' in the apparatus aforedescribed (UV ~ = 2537A~ wi th UV alonea UV pius 03 at an
ozone Flow rate o-f 0.~1- l/min. and UV plus Hz at a hydrogen flow rate of 0.75
l/min. ''
' Samples were prepared For quantitative gas chromatographic analysis in
the following manner.
1. Measured volumes of the samples were neutralized with.ULTRE)~
20 (Cl-free~ ni tric acid9 if basic. ' -'
2. The samples were evaporated to dryness.
3. . The dried sample was diluted to 100 ml with 6~ nlethanol in benzene.
The resulting solutions ~"ere analyzed on a Hewlett-Packar~Z'5750 with electron
capture detector. The Following conditions were used:
- injection port temperature - 3û0C .
- .'detector temperature 300C
- oYen temperature - 250C
- gas flow - 50 ml/min Ar/CH4 r(~
column - 10% [~C 200 on Chromoso HP 'IOO/200
The aqueous NaOII solutions wcre analyzcd on a llewlett-Pack~rd 3880 using the
following oonditions:
- injection port temperature - 200C
- oven temperature - 180C
- gas flo~ - 45ml/min AE?/C~
- column -- 5~ OV-210 on 100/120 GC~
Chloride ion concentration was also determined on all of the samples. An
Orion~solid state chloride ion electrode was u_ed for this purpose. Salllples in
methanol were prepared by neutralizincf 5 ml of the sample with ULT~X nitric acid
10 Following evaporation to d~yness, the samples were dissolve~d in 8 ml of distilled
water. In the case of the aqueous sodium hydroxide solutions, 10 Tnl samples were
neutralized with ULTE~nitric acid before the analyses. Chloride ion concentrations
were determined by ccmparison to standard curves generated frcm sodium chloride
standards containing equal am.ounts of sodium nitra-te as the samples.
During the course of -the experimental runs, samples were taken at 15, 30, 60,
90 and 120 min. (+180 min for aqueous NaOH solution treated with W plus H2) to
determine rate of degradation with -time.
Table 1 gives the results ob-tained in tenns of the remaining c~ncentration of
kepone at the end of the indicated time period and the percent degradation.
TABLE 1
Initial Sample Treatment ConditionsFinal % Degra-
Conc. ppm Conditions Gas Time Conc. dation
212 Methanol 2537A120 min. 177 ppm 16.5P6
pl~l 5 Hydrogen
237 Methanol 2537A120 m~.155 ppm 34.69
pH 10
237 Methanol 2537A110 min. 190 ppm 19.8%
pH 10 OzonOe
237 Methanol Z537A120 min. 115 ppm 51.5~6
pH 10 Hydrogen
230 5~ Aq.NaOII Sol.2537A120 min. 140 ppm 39.1
pH ~ 14
230 5% Aq.NaOH Sol.2537A120 min. 181 ppm 21.3
pH > 14 Ozone
230 5% ~.NaOH Sol.2537A120 min37 ppm 83.9%
pH > 14 Hydrogen
230 5% ~q.NaOH Sol.2537A180 nun. 12 ppm 94.8
pH > 14 Hydrogen
-8
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Table 1 and I;igure 2 shaw the substantially higher ~ de~Jradation at
two hours by the basic n~thanol treabment with W plus ~12 as ccmpar.ecl with the
othe~r treatn~nt methodologies. They also indicate that, althouqh the W
plus H2 treatment with non-alkalized methanol(pll 6) yives appreciable
reduction, the alkaline m~tnanol gives very considerab.ly improved results.
Figure 2 also shows the considerably higher rate of reduction by the W
plus H2 treattnent.
Table 1 and Figure 3 shaw the very substantially higher rate and
percent degradation produced by the W plus ~l2 treatment in ac~ueous NaOI-I
as canpared with the UV alone and W plus 03 treatments. At the end of 3
hours, the W p3us H2 treatment almost completely removes the kepone. These
degradation results are substantially verified by Figure 4 which shcws
the percent of free Cl ions released as a function of time for the W
alone, W plus 03, and UV plus ~l2 treatments. After 3 hours only about 26.5%
of the chlorine appears to rernain in C-Cl group ccmhination in chlorine-
degraded products. At 120 minutes about 50.5% of the chlorine has been
transformed into free ions by W plus H2, about 23% (less than one-half)
by W, and only about 16.5% by W plus 03. These results indicate that as
many as 6 to 8 chlorine atoms are removed frorn the kepone molecules by
the W plus H2 treatment.
It should be noted that although the results obtained with W alone in
aq~leous aLkaline solution are not as good as those produced by the W plus H2
treatment, substantial degradation is obtained, so that this treatrnent can be
useful in the case of halogenated organic compounds which are subs-tantially
soluble in aqueous alkaline solution as aforedescribed~
Exar~ple 2
Treatment of Polychlorinated biphenyl (PCB):
Aroclor 1254 is a mixture of the higher chlorinated biphenyls contain-
ing 54% chlorine by weight (an average of 4.96 chlorine atcms per r~lecule).
A typical analysis of Aroclor 1254 is presented in Table II (Versar Inc.,
1976).
wc/
~%~
q`~BIE II
EmpiricalMolf~eular ~o. of Chlorine No. of
FormulaWelghtper BiphenylWt ~ChlorineIs~merW~ht
C12H10 154 0 0 1 <0.1
C121l9C1 188 1 18.6 3 <0.1
Cl2H8Cl2 222 2 31.5 12 <0.5
C12~17C13256 3 41.0 24
C12H6C14 290 I 48.3 42 21
C12H5C15 324 5 54.0 46 48
C12~l4C16358 6 58.7 42 23
C12H3C17 392 7 62.5 24 6
C12H2C18 426 8 65.7 12~:0.01
Aroclor 1254 is slightly soluble in water, having an overall solubility
of 1.2X10 2mg/1. Solubility of the various components varies form U.0088 mg/l
for the hexachlorobiphenyls to 5.9 mg/l for the monochlorobiphenyls. rhe vapor
pressure for the 1254 mixture is 7.71X10 5mm Hg. q~heoretical half-life from a
l-meter water oolumn has been calculated as 1.2 minutes. qhus ~roclor 1254,
like many other slightly soluble chlorinated compounds, is readily vaporized
frc~n the surface of water. Sueh vaporized c~ound could, therefore, escape degrad-
ation treatment.
Aroclor 1254 was dissolved in methanol allcalized to pH 11 with NaOH to
make a 10.92 ppm sto k solution. 1.5 1 portions of this stock solution were
treated with W alone, W plus ozone at an ozone flcw rate of 0.41 l/mm.,
W plus hydrogen at a hydrogen flcw rate of 0.75 l/min. for 120 nunutes each in
the reactor aforedeseribed. Samples of ~, 8 ml each were talcen every 15 minutes.
Analyses were perfonred on the 15-, 30-, 60-, 90-, and 120-minute samples.
Quantitative analyses for the PCBs were performed on a Hewle-tt-Packard 3880 gasehrcmotograph with an EC-Ni63 electron capture detector. G.C. conditions were asfollc~ws:
- injection port temperature - 200C
r 30 - detector temperature - 300C
- oven temperature - 220C
.. ~ ,~
- gas flcw - 50 ml/min Ar/CH4
--10--
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- Column - 15% OV-17, 1.95~ QF-l on 100/120 GCQ
~he samples were prepared for analysis by neutraliæing a kncwn volume with
UL5`REX nitric acid, follcwed by evaporation of the solutlon to dryness at roc~l
temperature. trhe samples were brought up to 10 ml with pesticide grade he~ane.
- Stock solutions were treated in -the same manner to ensure that there was no loss
frcm evaporation.
Areas under the individual peaks were measured with an electronic in-te-
grator and ccmpared to standard curves to de-termine the concentration. Peaks
1-9 in the chromatogram were nonitored individually as well as the total area
; 10 under peaks 1-9. No attempt was made to identify the individual cc~ponents.
The results of the G.C. analysis of -the Aroclor 1254 degradation samples
are presented in Figures 5-8. ~igure 5 shc~s the total concentration of chlor-
inated biphenyls remaining as a Eunction of time for the -three treatment
methodologies. As indicated in -this figure, the W plus H2 treat~ent is more
effective than either W alone or W plus O . The initial rate for the W
plus H2 treatment is significantly faster than the other treatmen-t me-thodologies
even though the final amount degraded for the W alone and the UV plus H2 af-ter
2 hours is apprcIximately -the same.
Figures 6-8 show the concentration of the individual chlorinated
biphenyl cc~nponents as a f~mction of time for each treatment methodology.
Reten-tion time increases with the percentage of compound chlorine. Inspection
of these figures shcws the rapid degradation of the high chlorinated biphenyls
(peaks 5-9) with all treatment methodolcgies. m e lcwer chlorinated biphenyls
disappear at a slower rate and even increase in concentration in the W alone
and W plus O3 treatments. These curves are consistent with kncwn mechanisms
for photodegradation of PCBs.
--11--
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`` ~ ` 11~04ZS
Table III silows the total final concentrations of all of the PCB com-
ponents and their total % dc~radation at the end of t~lo hours. ~:.
TABLE III
., ' . ' .
ppm Final %
Treatment Concentration Degradation
UV 0.93 ~1.5
UV-~H2 0.5 95
~- UV-~03 3.49 68
,
- ' ' ' ' '
Tests of the stock solution treated with hydrogen gas only, showed tha-t
.
substantially none Or the PCB was los~ by vo1atilization. The degradation test
results, in ~act, show an increase in the more volatile components (low chlor
inated species) which is indicative of photochem;cal react;on.
:,. ~ ' . . ' . .
Example III
. . - ' ': ' '.
'
Treatment of tetrabromophthalic anhydride (TBP~):
TBPA ;s a high melting white crystalline material wh;ch is ;nsoluble ;n
.
- water and sparingly soluhle in methanol. In basic methano1~ e.g., methanol
rendered alkaline with NaOH, the anhydride functional group is reactive, form-
ing the sodium salts and the methyl esters.
A weighed amount of TBPA WdS dissolved in methanol alkalized.to pHll
to make a 100 ppm stock solution. 1;5 1 portions were treated with W alone,
UV and o~one at an ozone flo~ rate of 0.41 l/min., and UV and hydrogen at a
hydrogen flow rate o-F 0.75 l/min. in the reaotor aforedescribed. Sanlples of
each treatrnent methodology were taken at 15, 30a 60, 90 and 120 ~inutes for
analysis.
u~` The analyses were made using a ~ater ~high pressure liquid chromato-
graph with-a 2537A detector. The carrier solvent was methanol and the flow
- . .
-12-
~ 2 ~ '
rat as 1 m~ in. Salllples were inj~cle~l into the LC ~lithout any pretreatment.
The TBP~ concentration o~ the treated samples was obtained by co~parison to a
stan~drd curve.
Brolllide ion concel7trations were measLIred with an Orior(~ romide elec-
trode. Samp'les were prepared by neutralizing 5 ml o~ each solution with Ultrex `~
nitric aci~'. The resulting methanolic solution was evaporated to dryness and
-then diluted to ~ ml wit~ clistilled water. Bromide ion concentrations were
calculated by comparison'with a standard curve constructed from NaBr standarcls
' of known compositionO
'~ The results obtained from the l.C analysis o~ the.TBPA concentration of
the samples are presented in Figure 9. The UV alone and UV plus 03 da~a appear
to be very erra-t1c. This erratic appearance is due to ~he forma~ion of decom-
position produc-t~ probably the tri- or di-brominated product which is not
separated from the original TBPA peal~. Figure 10 shows tlle comparative forma
tion af Br ion as a functioll of time for ~lle three methodoloyies and îs a moreaccurate indication of debromination than in Figure 9.
The brolnide analysis correlates well wi~h the LC analysis.of TBPA when
,; .
. treated wi~h UV p'lus H~. Upon treatment wit~l UV plus H2~ the TBPA is decomposed
extremely rapidly during the first 15 minutesa after which T~PA degradation and
~0 bron~ide fornlation slo~ down. The lowest TBPA concentration (~ 16~ of the
original) coupled ~ith the highest bromide concentration obtained (~ 50 ppm)
in~icate that the molecules were completely debrominated. An equilibr'ium is
then established between the TBPA and the resultant phthalic anhydride. 'To
debrominate the remaining TBPA, this equilibrium mus~ be shifted.
Both the UU.alone and the UV plus 03 approach the three bromine removal
level but a~ much slower rates. Wi~h these treatment methodologies~ several
other compounds also appear in significant quantities on the LC chromatogramsO
These subs-tances did not appear in substantia'l quantities when the TBPA was
treated with UV plus H2.
.
.
2~
Thus, the UV plus li2 t1eatment in basic methanol not only results in
significant'1y 1nore rapid degrddatio1) oF TBPA than UV alone or UV plus 03 but in
different ~ecomposit;on pro~iucts.
It is clearly apparent from all of khe foregoin~ data that degradation
of haloyena'ted organic compounds by treatment with UV plus i12~ preferably in
alkaline solution, provides an effectiYe and economical means For removing such
co!npol1nds' from mAnufacturi1lg effluent and/or the environ1llent~ It has'also been
`shown that the treatmen~ of such compouncls with UV alone in aqueous alkaline
solutions also providès significant degradation. By "UV alone"9 as used ;n
ti!e speci.fica-tion ancl claims, is meant treatment with u'1traviolet radiation~ithou-t additional chemicai treatment other than the use o~ a solvent for the
halogenated compound. The term "aqueous alkaline'solukion" means a solvent
free from additional or.~anic solvent.
' Although t'his invention has beendescribed w;th reFerence to illustra-
tive embod1ments thereo~, it will be apparent to those skilled in the ar.t that
' the princ;ples o~ ~h;s invention can be embodied in other forms but wlthin the
scope o~ t'he claims.
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