<PAGE>

                                                                Exhibit (10)(AK)

                                      LEASE

          THIS LEASE is made and entered into by and between Henry G. Luken,
III, a Tennessee resident, herein called "Owner", and Covista, Inc., a New
Jersey company, herein called "Tenant".

          For acknowledged consideration, Owner leases to Tenant and Tenant
rents from Owner the real property located at 4801 Highway 58 in the City of
Chattanooga, County of Hamilton, State of Tennessee, being the property more
fully described in Exhibit A, attached hereto, together with all improvements
and additions thereon, herein called the "premises"; and Owner and Tenant agree
as follows:

                                    SECTION 1
                         TERM AND OPTION TO EXTEND TERM

          1.1 The term of this lease shall be for five (5) years beginning on
the 1st day of September, 2001.

          1.2 Tenant shall have the option to extend the term of this lease for
an additional five (5) years, this option to be exercised by giving written
notice to Owner at least ninety (90) days prior to the expiration of the then
current term under this lease. During the extended term, the provisions of this
lease shall remain the same except that the amount of rent shall be increased if
and to the extent provided by this lease.

          1.3 Owner shall not be liable for failure to give possession of the
premises to Tenant upon the effective date of this lease if the failure occurs
because the premises are not ready for occupancy, or are being held over by a
prior tenant or are otherwise in the wrongful possession of another party, or
are not available for any other reason. In such event the rent shall not begin
until possession is given to or made available to Tenant, and the term of this
lease shall not be extended by such delay in delivering possession. If the delay
in possession exceeds thirty (30) days, either Owner or Tenant, by written
notice to the other, may terminate this lease and neither party shall have nor
incur any liability or obligation to the other party as a result of such
termination.

                                    SECTION 2
                                      RENT

          2.1 During the lease Tenant shall pay and Owner shall accept a rental
as follows:

           Rental Period                     Rent
September 1, 2001 - August 30, 2002   $ 7,200 per month
September 1, 2002 - August 30, 2003   $ 9,600 per month
September 1, 2003 - August 30, 2004   $12,000 per month

The rental for each month beginning on September 1, 2004 and the rental for any
extended term if the term of the of this lease is extended beyond the original
term, shall be Twelve Thousand Dollars ($12,000.00) per month or, if greater,
the amount determined by multiplying the rental for each month of the prior year
by a fraction, the numerator of which is the Consumers Price


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Index United States - All Items, for January of the fourth and fifth year or
each year of the extended term, and the denominator of which is such index
figure on the same base, for January of 2003, provided that such fraction shall
never be less than one (1).

          2.2 In addition to these rental payments, Tenant shall pay when due,
as additional rent, all other amounts to be paid by Tenant under this lease.

          2.3 It is the intention of Owner and Tenant that the rent paid under
this lease shall be net to Owner and that each year during the term of the lease
all costs, expenses and obligations of every kind relating to the premises
(except as otherwise specifically provided in this lease) which may arise or
become due during the term of this lease shall be paid by Tenant, and that Owner
shall be indemnified by Tenant against such costs, expenses and obligations.

          2.4 All payments of rent shall be made by Tenant to Owner without
notice or demand, at such place within the United States as Owner may from time
to time designate in writing. For the present Owner designates Owner's address
stated in or pursuant to the Notices provisions of this lease as the place for
making the payments of rent. All rents shall be payable in legal tender of the
United States as the same is then constituted.

          2.5 A late fee will accrue at the rate of twelve percent (12%) per
annum on all delinquent rent and other amounts due from Tenant. Such late fee
shall be immediately due and payable as additional rent under this lease.

                                    SECTION 3
                                    UTILITIES

          Tenant shall pay for all utilities, including but not limited to
water, gas, electricity, sewage disposal, and heat and other utilities used on
the premises during the term of this lease and shall pay all charges of any
party furnishing water pressure for any sprinkler system on the premises.

                                    SECTION 4
                                      TAXES

          4.1 Tenant shall pay all real property taxes, assessments and
governmental levies on the premises.

          4.2 Tenant shall pay any license tax or other tax on the business
activity of Tenant and on property belonging to Tenant and situated on the
premises, and any real property tax attributable to any additions or
improvements added to the premises by Tenant.

                                    SECTION 5
                                TAX CERTIFICATION

          Owner hereby certifies that Owner is not a non-resident alien, or
foreign corporation, a foreign partnership, a foreign trust or a foreign estate
(as those terms are defined in


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the Internal Revenue Code and Income Tax Regulations); that Owner's Social
Security number or Federal Income Tax number and home or office address are as
shown in this Lease. Owner acknowledges that this certification may be disclosed
to the Internal Revenue Service pursuant to federal law.

                                    SECTION 6
                      REPAIRS, MAINTENANCE AND IMPROVEMENTS

          6.1 Tenant shall at its own expense keep the premises clean, neat and
free of all trash or rubbish.

          6.2 Tenant shall, at Tenant's expense, maintain and keep in good
repair the interior of the premises including but not limited to the ceiling,
light fixtures, interior walls and floors, all doors, windows, glass, and
plumbing, all water and gas pipes, and sprinkler system, if any.

          6.3 Owner shall, at Owner's expense, make all necessary exterior
structural repairs including but not limited to the roof, gutters and
downspouts, and the outside walls of the premises, and the exterior of all
improvements on the premises.

          6.4 The parking lot paving, parking areas, sidewalks, lawns and
landscaping shall be maintained by Tenant.

          6.5 Owner shall, at its own expense, make all structural repairs and
restorations, whether or not interior or exterior, ordinary or extraordinary,
recurring or nonrecurring in nature, and shall keep the premises in good repair,
ordinary wear and tear, and damage by reason of natural causes or fire excepted.

          6.6 Tenant may make reasonable alterations, additions and improvements
to the premises, including the erection of signs, at Tenant's expense but only
with the prior consent in writing of Owner. All such work shall be in compliance
with all applicable federal, state and local laws and regulations, including
those pertaining to access to public accommodations, and Owner's consent to make
such alterations will not relieve Tenant of such responsibility. All
alterations, additions or improvements made by either of the parties, except
movable office furniture and movable business fixtures and equipment put in at
the expense of Tenant, shall inure to the benefit of Owner and shall belong to
Owner absolutely as soon as made or installed. Tenant may, if Tenant is not in
default on any of the terms and conditions of this lease, remove at the
termination of the lease any movable office furniture or movable business
fixtures or equipment purchased or provided by Tenant that may be moved without
damage to the building, provided that Owner is notified before the termination
date that this right will be exercised, as to described fixtures or equipment.
If Tenant causes any damage to the premises in removing Tenant's property,
Tenant shall pay for all repairs.

          6.7 Upon termination of this lease Tenant shall return the premises to
Owner in the same condition as when received, ordinary wear and tear excepted.

                                    SECTION 7


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                        LIABILITY INSURANCE AND INDEMNITY

          7.1 In addition to any insurance which Tenant deems necessary to
protect Tenant's interests, Tenant shall, at Tenant's expense, secure and
maintain during the term and any extended term of this lease, liability
insurance with an insurance company satisfactory to Owner, with Tenant and Owner
as named insureds, in amounts not less than $1,000,000 per person, $1,000,000
per occurrence for all persons and $500,000 for property damage. Tenant may, in
lieu of delivering the original policies of insurance, deliver to Owner
insurance company certificates evidencing the coverage. The requirement of the
liability insurance notwithstanding, Owner shall not be liable for any injury or
damage to persons or property occurring in or about the premises, and Tenant
shall save Owner harmless from responsibility for any and all such injuries and
for all such damage arising from any cause whatsoever. Owner shall be under no
liability to Tenant arising from any discontinuance of heat or water, or both,
caused by accident, by breakage, by strike, or otherwise. Owner shall not be
liable for loss of or damage to the property of Tenant caused by rain, snow,
water or steam that may leak into or flow from any part of the premises as a
result of any defect in the roof or plumbing or any cause whatsoever, or for
loss or damage caused by the handling of electric wires or lights.

          7.2 If the Tenant shall fail, refuse or neglect to obtain such
insurance or to maintain the same, and furnish the Owner with proof of the same
upon demand, the Owner shall have the right, in addition to other remedies, to
procure such insurance and to add the cost thereof to any rental or other sums
payable under this lease, and the amount thereof shall be payable to the Owner
on demand with lawful interest thereon.

          7.3 Tenant shall cause any policy or certificate of insurance required
by this lease to be issued promptly upon any renewal or extension of such
coverage showing the Owner as insured.

                                    SECTION 8
                     CASUALTY INSURANCE AND CASUALTY DAMAGE

          8.1 Tenant shall secure and constantly maintain, at Tenant's expense,
insurance against loss or damage by fire and such other casualty risks and
hazards, including but not limited to lightning, flood and windstorm, as are
insurable under present and future standard forms of extended coverage insurance
policies, upon the buildings and other improvements erected on the premises.

Any such policy or policies of insurance shall name Owner as the insured, and
shall otherwise be in a form approved by Owner.

          8.2 Tenant shall furnish the original of such policy to Owner or
insurance company certificates evidencing the coverage.


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          8.3 If the premises are so used that casualty insurance cannot be
secured, Tenant will become the insurer, and Owner may cancel this lease by
giving written notice to Tenant.

          8.4 If the premises are rendered totally or substantially untenantable
by fire or other casualty, this lease, at the option of Owner or Tenant
exercised in writing within thirty (30) days of the date of the fire or
casualty, shall terminate; otherwise Owner shall restore the premises as rapidly
as sound business judgment permits.

          8.5 If the premises are rendered totally or substantially
untenantable, and are to be restored, rent will abate during restoration and the
term of this Lease shall be extended for a period of time equal to the period of
time of such restoration. If the premises are so damaged that Tenant can
continue to occupy the same or part of same, the rent shall abate pro rata only
and Owner shall repair the damage as rapidly as sound business judgment permits.

          8.6 The Owner shall have the sole and exclusive right to the proceeds
of any insurance covering the premises whether provided by Owner or Tenant. If
any restoration or repair work is to be done, the proceeds of any insurance
shall be provided to Owner for that purpose. Any insurance proceeds in excess of
the cost of such restoration or repairs, or all of the insurance proceeds if the
premises are not to be restored or repaired pursuant to the provisions of this
lease, shall be the sole property of and paid to Owner, and Tenant shall have no
interest therein. In the event of a mortgage or encumbrance on the premises
which requires that the insurance proceeds be used to retire or pay such
mortgage or encumbrance, then Owner shall have no obligation to rebuild or
repair and this lease may be terminated upon notice to Tenant following any fire
or casualty.

          8.7 Tenant shall carry and maintain at its own expense such insurance
as Tenant deems necessary or advisable to protect its interests under this lease
with regard to Tenant's fixtures, equipment and merchandise located at the
premises.

                                    SECTION 9
                               WARRANTIES OF OWNER

          9.1 Owner warrants and covenants that Owner is lawfully able to demise
the premises and that Tenant, on paying the rental herein provided and
performing the other covenants and conditions herein contained, shall have quiet
and peaceful possession of the premises during the lease term. No provisions of
this lease are intended to warrant or imply that Owner has any greater right or
interest than stated in this paragraph.

          9.2 Except as otherwise specifically provided in this lease, Tenant is
acquainted with the entire premises and accepts the same in their present
condition. Tenant assumes responsibility for the safety of the premises, for the
suitability of the premises for Tenant's use, and for the premises' compliance
with the requirements of Title III of the American with Disabilities Act of
1991.

          9.3 Owner makes no other warranties express or implied.


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                                   SECTION 10
                             SUBLEASE OR ASSIGNMENT

          Neither Tenant nor any court or officer thereof or receiver or trustee
in bankruptcy shall sublease, assign, or transfer the premises or any interest
in this lease without the consent in writing of Owner, which shall not be
unreasonably withheld. Landlord may withhold consent if the premises is not
currently a place of public accommodation and the subletting or assignment will
cause it to be used at such. In the event of a sublease or assignment, Tenant
shall always remain liable for any default of a subtenant or assignee. The
receipt by Owner of rents from any assignee, subtenant or occupant shall not be
deemed to be a waiver of these provisions.

                                   SECTION 11
                                 USE OF PREMISES

          The premises shall during the term of this lease be used only for
offices, and no part of the premises or improvements thereon shall be used in
any manner whatsoever for a purpose in violation of the laws of the United
States or the state in which the premises are located or any other applicable
ordinance, regulation or law. Tenant shall comply with all laws, ordinances,
regulations or orders enacted or passed during the term of this lease applicable
to the premises.

                                   SECTION 12
                                  CONDEMNATION

          If at any time a substantial part or all of the premises be taken for
any public or quasi-public use under any statute or by right of eminent domain
or by private purchase in lieu thereof by a body vested with the power of
eminent domain, this lease shall continue until the date of the taking, at which
time this lease shall terminate and Tenant shall have no rights in any award or
purchase price paid by reason of the taking. In the event a condemnation or
purchase takes place and the premises continue to be tenantable for Tenant's
purposes, the rent shall be abated pro rata, Tenant shall have no rights in any
award or purchase price paid by reason of the taking, and the lease shall
continue otherwise in full force and effect. The termination of this lease or
the abatement of rent by reason of the condemnation or purchase shall be without
prejudice to the rights of either Owner or Tenant (to the extent Tenant has an
independent claim) to recover compensation and damage caused by the condemnation
or taking from the condemner or taker. Neither Owner nor Tenant shall have any
rights in any award made to the other by reason of such condemnation or taking.

                                   SECTION 13
                            ENVIRONMENTAL COMPLIANCE

          13.1 Tenant, at Tenant's Expense, shall comply with all Environmental
Laws (as defined below) pertaining to Tenant's business use and occupancy of the
Premises and shall promptly advise Owner of any Notice, as defined herein.
Tenant hereby agrees to and does


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indemnify and holds Owner harmless from and against any and all liability,
obligations, losses, damages, penalties, claims, clean-up costs, fines, civil
penalties and actions, suits, including legal fees imposed on, incurred by, or
reserved against Owner arising out of the existence or presence of any
"Regulated Substance", as defined herein, on, under or from the Premises from
and after the commencement of the initial term of this lease ("Commencement
Date") arising out of Tenant's occupancy and use of the Premises; and any
liability, claims, or damages in any way related to or arising out of the
removal, treatment, storage, disposal, disposition, mitigation, clean-up or
remedying of by Tenant of Regulated Substances on the Premises. Notwithstanding
anything herein to the contrary, Owner agrees that Tenant has no obligation to
and does not indemnify Owner for any claims or damages due to any Regulated
Substances existing or present on the Demised Premises prior to the Commencement
Date or arising out of the acts of third parties not under Tenant's control.

          13.2 For the purposes of this Section 14, the following terms shall
have the meanings set forth herein:

               (a) "Environmental Laws" means any applicable federal, state,
regional, county or local laws, statutes, rules, regulations or ordinances,
including, but not limited to, the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, as amended by the Superfund Amendments
and Reauthorization Act of 1986, 42 U.S.C. Section 9601 et seq. ("CERCLA"), the
Resource Conservation and Recovery Act of 1976, as amended by the Hazardous and
Solid Waste Amendments of 1984, 42 U.S.C. Section 6901 et seq. ("RCRA"), the
Federal Water Pollution Control Act, as amended by the Clean Water Act of 1977,
33 U.S.C. Section 1251 et seq ("CWA"), the Toxic Substances Control Act of 1976,
15 U.S.C. Section 2601 et seq. ("TSCA"), the Emergency Planning and Community
Right-To-Know Act of 1986, as amended, 42 U.S.C. Section 11001 et seq. ("Sara
Title III"), the Clean Air Act of 1986, as amended, 42 U.S.C. Section 7401 et
seq. ("CAA"), the National Environmental Policy Act and Harbors Act of 1899, 33
U.S.C. Section 401 et seq. ("RHA"), the Occupational Safety and Health Act of
1970, 29 U.S.C. Section 651 et seq. ("OSHA"), and the Safe Drinking Water Act of
1974, as amended, 42 U.S.C. Section 300(f) et seq. ("SDWA"), and any and all
rules, regulations and guidance documents promulgated or published thereunder,
and any other federal, state, county or local statute, law, rule, regulation or
ordinance relating to public health, safety or the discharge, emission, or
disposal to air, water, land or groundwater, to the withdrawal or use of
groundwater, to the use, handling or disposal of polychlorinated biphenyls
(PCB's), asbestos or urea formaldehyde, to the treatment, storage, disposal or
management of regulated substances (including without limitation, petroleum, its
derivatives, by-products or other hydrocarbons), to exposure to toxic,
hazardous, or other controlled, prohibited or other regulated substances, to the
transportation, storage, disposal, management or release of gaseous or liquid
substances, and any regulation, order, injunction, judgment, declaration, notice
or demand issued thereunder.

               (b) "Regulated Substances" means any substances, materials,
wastes or pollutants that are from time to time defined by or pursuant to or are
regulated as such under any statute, law, ordinance, rule or regulation of any
federal, state, regional, county or local authority having jurisdiction over the
Premises or its use, including without limitation, petroleum, petroleum
derivatives or by-products, or other hydrocarbons or any material, substance,
pollutant or waste that is (a) defined as a hazardous substance under Section
311 of CWA, (b) defined as a


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hazardous waste under Section 1004 of RCRA, (c) defined as a hazardous substance
under Section 101 of CERCLA, or (d) otherwise regulated in its transportation,
storage, disposal, management or release by any federal, state, county or local
statute, law, rule, regulation or ordinance.

               (c) "Release" means releasing, spilling, leaking, pumping,
pouring, emitting, emptying, discharging, injecting, escaping, burying,
leaching, migrating, disposing or dumping (in the appropriate tense for the
context used).

               (d) "Notice" shall mean any summons, citation, directive, order,
claim, litigation, investigation, proceeding, judgment, letter or other
communication, written or oral, actual or threatened, from the Tennessee
Department of Environment and Conservation ("TDEC"), the United States
Environmental Protection Agency ("EPA") or other federal, state or local agency
or authority, or any other entity or any individual, concerning any intentional
or unintentional act or omission that has resulted or that may result in the
release of regulated substances into the waters (including groundwaters) or onto
the lands of the State of Tennessee or adjacent jurisdiction, or into the
"environment" as such term is defined in CERCLA from or on the Premises, and may
include, without limitation (i) the imposition of any lien on the Premises,
pursuant to any Environmental Laws (as defined above) (ii) any violation of
federal, state, regional, county or local environmental laws, statutes, rules,
regulations, ordinances, governmental actions, orders or permits, or (iii) any
knowledge, after due inquiry and investigation, of any facts that could give
rise to any of the above.

                                   SECTION 14
                       MECHANICS' AND MATERIALMEN'S LIENS

          Tenant shall not do or suffer anything to be done whereby the premises
shall be encumbered by a lien, and shall, whenever and as often as any lien is
filed against the premises purporting to be for labor or material furnished or
to be furnished to the Tenant, discharge the same of record within twenty (20)
days after the date of filing. Tenant shall indemnify Owner from all actions and
costs of suit by any person to enforce a lien, together with any costs and
attorney fees incurred by Owner. Tenant may contest the validity of any lien or
claim if Tenant shall have posted a bond with adequate surety to insure that
immediately upon final determination of validity of the lien or claim Owner
shall be paid for any judgment rendered, with all proper costs and charges, and
Tenant shall at such time have the lien released without cost to Owner. Notice
is hereby given that Owner shall not be liable for any labor or materials
furnished or to be furnished to the Tenant on credit, and that no mechanics',
materialmen's or other lien for any such labor or material shall attach to or
affect the reversionary or other estate or interest of Owner in and to the real
estate and improvements which are a part of the premises.

                                   SECTION 15
                                 ENTRY BY OWNER

          Tenant shall permit Owner, or Owner's agents or employees, at all
reasonable hours, to enter and examine the premises, or to show the premises to
persons wishing to rent or purchase the same, or to make proper repairs or
alterations, taking any space needed; and during


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the two (2) months preceding the termination of any term of this lease, Tenant
will permit customary "For Sale" or "For Rent" notices, or both, to be exhibited
on the premises.

                                   SECTION 16
                                     DEFAULT

          16.1 Should Tenant be in default in the payment of rent and remain in
default for a period of ten (10) days, such default shall, at Owner's option,
constitute a forfeiture of the lease.

          16.2 Should Tenant violate any other term, condition, or covenant of
this lease and not cease or otherwise cure the violation within thirty (30) days
after receiving written notice from Owner, or if Tenant should abandon or vacate
the premises prior to the expiration of the original or any extended term of
this lease, or if Tenant should be adjudicated a bankrupt or insolvent according
to law, or should make an assignment for the benefit of creditors, or if a
receiver, trustee or liquidator of Tenant's property shall be appointed and not
discharged within sixty (60) days, then the occurrence of such act or omission
shall, at Owner's option, constitute a forfeiture of the lease.

          16.3 If a forfeiture is declared by Owner for any reason, then in
addition to and not in substitution for any responsibilities or liabilities of
Tenant, or any options available to Owner, under this instrument or applicable
law:

               (a) Tenant shall be liable for all future rentals, any rents in
arrears and all other amounts necessary to compensate Owner for Tenant's
breaches of covenant, all such amounts to become immediately due and payable;
and

               (b) Owner may, at Owner's option: (i) lease the premises to
another tenant for part or all of the remainder of the term, in which event
there shall be set off against the amounts otherwise owed by Tenant the amount
of rents actually received from the new tenant less the costs related to
entering into the new lease and preparing the premises for the use of the new
tenant; or (ii) refrain from leasing the premises to another tenant, in which
event there shall be set off against the amounts owed by Tenant any portion of
the loss of net rental income available to Owner as to which Tenant may
establish, in a court of competent jurisdiction or to the satisfaction of Owner,
that Owner could have realized by leasing the premises to another tenant known
to Owner, or to another tenant with which Owner may have been able to contract
if Owner had expended reasonable efforts to locate such a tenant.

          16.4 If, upon any forfeiture, Owner shall elect to recover possession
of the premises, no demand shall be necessary before such recovery of
possession; and Owner may enter the premises, or any part, and take possession
and expel Tenant or other occupants and their effects, without being guilty of
any trespass.

          16.5 Should Owner or Tenant fail to pay taxes or make repairs or fail
to perform any other duty under this lease the other party may, after giving
thirty (30) days' notice in writing, perform such duty and the cost of
performance shall be offset against or added to the rental amount and in the
latter case shall become immediately due and owing.


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<PAGE>

          16.6 The failure of Owner to declare a breach or forfeiture of this
lease for the violation of any term, condition or covenant shall not be
construed as a waiver of the rights to declare a breach or forfeiture of this
lease upon the occurrence of any subsequent act or omission, the right to
declare a breach or forfeiture being a continuing one in Owner. Acceptance of
rentals subsequent to any forfeiture shall not be considered a confirmation or
renewal of this lease.

          16.7 Should Tenant vacate the premises prior to the expiration of the
original or any extended term of this lease, no act or actions taken by the
Owner or its agents shall be deemed an acceptance of a surrender of the
premises. No agreement to accept the surrender of the premises shall be valid
unless the same be in writing and signed by the Owner.

                                   SECTION 17
                                  SUBORDINATION

          This lease and all rights of Tenant hereunder are and shall be subject
and subordinate to the lien or liens of any and all mortgages, deeds of trust,
deeds to secure debt or other instruments in the nature thereof ("Owner's
mortgage"), and to all modifications, renewals or extensions thereof, which may
now or hereafter effect or encumber Owner's title to the premises. Tenant shall,
upon demand, at any time or times, execute, acknowledge, and deliver to Owner or
to a holder of Owner's mortgage, without expense, any instruments that may be
necessary to make this lease subordinate to the lien of Owner's mortgage.


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<PAGE>

                                   SECTION 18
                          OCCUPATION AFTER TERMINATION

          Should Tenant continue in possession, with or without the consent of
Owner, after expiration of the term or after a forfeiture incurred, Tenant shall
continue paying the amount of rent specified in this lease and shall continue to
be subject to all of the terms and conditions of this lease, except that Tenant
shall be the tenant at will of Owner, and in no event a tenant from year to year
or from month to month, and Tenant may be required to vacate the premises
without notice and may be removed by legal process as upon a forcible and
unlawful detainer.

                                   SECTION 19
                                 ATTORNEY'S FEE

          If it shall become necessary for Owner or Tenant to employ an attorney
to assert any right or enforce any obligation under this lease, after default,
such party, if he prevails, shall be entitled to recover, in addition to all
other costs and expenses, the reasonable costs and charges of such attorney.

                                   SECTION 20
                                     NOTICES

          All notices or communications which this instrument requires or
permits to be given shall be in writing and shall be mailed or delivered to the
respective addresses set forth below, or to such other address as may be
designated in writing by either party.

          To Owner as follows:

          Henry Luken
          900 Fairway Lane
          Soddy Daisy, TN 37379-4520

          To Tenant as follows:

          Covista, Inc.
          4801 Highway 58
          Chattanooga, TN 37416

                                   SECTION 21
                                 ENTIRE CONTRACT

          This lease contains the entire contract between the parties relating
to the demise of the premises and may not be altered, amended or changed except
by instrument in writing signed by both parties hereto.

                                   SECTION 22
                                BENEFIT OF LEASE


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<PAGE>

          This lease shall inure to the benefit of and shall be binding upon the
heirs, legatees, legal representatives, and successors and assigns of the
parties, subject to all the terms, conditions and contingencies set forth.

                                   SECTION 23
                                 LAW APPLICABLE

          This is a lease under the laws of the state in which the premises are
located, and the validity and applicability of its provisions shall be governed
by the laws of that state.

                                   SECTION 24
                          AMERICANS WITH DISABILITY ACT

          Tenant represents and covenants that it shall conduct its occupancy
and use of the Premises in accordance with the Americans with Disabilities Act
("ADA"), or any other federal, state or local law or regulation pertaining to
public accommodation access (including, but not limited to, modifying its
policies, practices and procedures, and providing auxiliary aids and services to
disabled persons at Tenant's expense). Tenant agrees to indemnify and hold Owner
harmless from all liability, damages, penalties, costs and attorney fees arising
from any claims brought or made against Owner resulting from Tenant's use,
operation or occupancy of the premises brought pursuant to the ADA or any other
federal, state or local law or regulation pertaining to public accommodation
access. If the Tenant is allowed to make alterations and improvements to the
Premises in conjunction with the Tenant taking occupancy of the Premises, Tenant
agrees that all such work shall comply with the ADA. Furthermore, Tenant
covenants and agrees that any and all future alterations or improvements made by
Tenant to the Premises shall comply with the ADA. Any improvements in the
premises necessary for Tenant's reasonable accommodation of its employees will
be made at Tenant's expense.

                                   SECTION 25
                              ESTOPPEL CERTIFICATE

          At any time and from time to time, Tenant, on or before the date
specified in a request theretofore made by Owner, shall execute, acknowledge and
deliver to Owner a certificate prepared by Owner at Owner's expense, evidencing
whether or not (a) this lease is in full force and effect, (b) this lease has
been amended in any way, (c) there are any existing defaults on the part of
Owner hereunder to the knowledge of Tenant and specifying the nature of such
default, if any, and (d) the date to which rent, and other amounts due
hereunder, if any, have been paid. Each certificate delivered pursuant to this
Section 27 may be relied on by any prospective purchaser or transferee of
Owner's interest hereunder or of any part of Owner's property or by any holder
or prospective holder of Owner's mortgage, or a mortgage or prospective mortgage
of any part of Owner's other property.

                                   SECTION 26
                            TERMINOLOGY AND CAPTIONS


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<PAGE>

          The terms "Owner" and "Tenant" as used in this lease shall be
construed to apply to the parties in the appropriate gender and number; and the
term "Owner" shall in no way indicate that a tenancy greater than that described
in this lease is either demised or warranted. The captions in this lease are
inserted only as a matter of convenience and for reference and in no way define,
limit, amplify or describe the scope of this lease or the intent of any
provision thereof.

          IN WITNESS WHEREOF, the Owner and Tenant have executed duplicate
copies of this lease this ______ day of ______________, 2001.

Copy No. ___


                                      ---------------------------------
                                      (Henry G. Luken, III)

                                                                          OWNER


                                      COVISTA, INC.


                                      By:
                                         ------------------------------
                                                  President

                                                                          TENANT


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<PAGE>

STATE OF TENNESSEE                  )
                                    )
COUNTY OF HAMILTON                  )

          Before me, a Notary Public, duly appointed, commissioned and qualified
in and for the State and County aforesaid, personally appeared Henry G. Luken,
III, the within named bargainor, with whom I am personally acquainted, and who
signed, sealed and delivered the foregoing instrument in my presence, and who,
upon oath, acknowledged that he executed the foregoing instrument for the
purposes therein contained as his free act and deed.

          IN WITNESS WHEREOF, I have hereunto set my hand and affixed my seal at
my office in said State and County, on this the _______ day of
_____________________, 2001.


                                      ------------------------------------------
                                                  Notary Public

                                      My commission expires: __________

STATE OF TENNESSEE                  )
                                    )
COUNTY OF HAMILTON                  )

          Before me, a Notary Public, duly appointed, commissioned and qualified
in and for the State and County aforesaid, personally appeared
________________________, with whom I am personally acquainted, and who, upon
oath, acknowledged himself to be the President of Covista, Inc., the within
named bargainor, a corporation, and that he, as such officer of said
corporation, being authorized so to do, executed the foregoing instrument for
the purposes therein contained, by signing the name of the corporation by
himself as President.

          IN WITNESS WHEREOF, I have hereunto set my hand and affixed my seal at
my office in said State and County, on this the _______ day of
_____________________, 2001.


                                      ------------------------------------------
                                                  Notary Public

                                        My commission expires:_________