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                                                                EXHIBIT 10.20




                               PURCHASE AGREEMENT
                       COMMERCIAL-INDUSTRIAL REAL ESTATE


1.       PARTIES: Great Lakes Chemical Corporation, a Delaware corporation
         ("Seller") agrees to sell and convey to Bioanalytical Systems, Inc.,
         an Indiana corporation ("Buyer") and Buyer agrees to buy from Seller
         the following property for the consideration and upon and subject to
         the terms, provisions, and conditions hereinafter set forth.

2.       PROPERTY: The property commonly known as The Great Lakes Annex
         Building, 2801 Kent Avenue, is a tract of land situated in the City of
         West Lafayette, Tippecanoe County, Indiana, together with all the
         buildings and permanent improvements and fixtures attached thereto
         (see Exhibit A); and all privileges, and appurtenances pertaining
         thereto including any right, title and interest of Seller in and to
         adjacent streets, alleys, or rights-of-way, Seller's interest in and
         to all leases or rents, and security deposits, Seller's interest in
         and to all licenses and permits with respect to the Property, Seller's
         interest in all service, maintenance, management or other contracts
         relating to the ownership or operation of the Property, and Seller's
         interest in all warranties or guaranties relating to the Property
         being sold; all of the above hereinafter collectively called
         "Property", and whose legal description will be provided upon
         completion  of the Survey.

3.       PRICE: The total purchase price shall be One Million Nine Hundred
         Thousand and 00/100 Dollars ($1,900,000.00) payable in accordance with
         the terms and conditions stated in this Agreement.

4.       EARNEST MONEY: Twenty Thousand and 00/100 Dollars ($20,000.00) is
         herewith tendered and is to be deposited as Earnest Money with The
         Shook Agency, Inc. as Escrow Agent, upon execution of the Agreement by
         both parties.  The Escrow Agent shall hold the Earnest Money in an
         interest-bearing account with interest to be disbursed with the
         Earnest Money in accordance with this Agreement.  If this Agreement is
         terminated by the Buyer, as provided herein and within the applicable
         time period, the Earnest Money shall be returned to the Buyer.

5.       CONTINGENCIES: In addition to those other conditions addressed herein,
         closing of this transaction shall be specifically contingent upon
         satisfaction of the following items:

         A.      Buyer's receipt of Preliminary Plat Approval from the
         Tippecanoe County Area Plan Commission for the purpose of joining
         Buyer's property with the Seller's property to form one lot.  Buyer
         shall bear all costs and expenses relating to and arising from the
         process of obtaining Preliminary Plat Approval.

         B.      Buyer's obtaining a Phase I environmental report, at Buyer's
         expense, satisfactory to Buyer at Buyer's sole discretion.



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         C.      Buyer shall have satisfied itself, in Buyer's sole discretion
         and without warranty or representation by Seller, with the nature and
         condition of the Property such that Buyer shall take the Property on
         the terms specified in Paragraph 8, below.

         D.      Buyer's receipt of a commitment for suitable financing for the
         acquisition of the Property and modification of the improvements.

         E.      Execution of a lease between Buyer and Seller, on mutually
         acceptable terms and conditions, for the lease of office space at the
         Property by Seller.

         F.      Buyer obtaining written approval and authorization of this
         transaction from its Board of Directors, Bank One, Primus Ventures and
         Middlewest Ventures, Inc.

         G.      Seller shall make available for one (1) year after the closing
         of this transaction, on an "as needed" basis, and at Buyer's expense,
         Seller's maintenance personnel for the purpose of consulting with
         Buyer on the management and maintenance of the Property's operating
         systems.

         H.      The Purdue Research Park restrictive covenants grant a right
         of first refusal to Purdue Research Foundation for all property sold
         or resold in Phase I of the Park.  Accordingly, Seller must obtain
         from the Purdue Research Foundation in advance of closing a waiver of
         any and all of their rights under the Park's restrictive covenants.

6.       CLOSING.  The closing of the sale (the "Closing Date") shall take
         place at the Title Company who insures this transaction or at the
         institution providing financing within thirty (30) days after all
         contingencies and conditions addressed herein are satisfied to the
         mutual satisfaction of the parties.  If the contingencies set forth in
         this Agreement have not been satisfied within one hundred eight (180)
         days of execution of this Agreement by both parties, either party may,
         by written notice to the other, terminate this Agreement in which
         event the Escrow Agent shall disburse the Earnest Money to the Buyer
         and the parties shall thereafter have no further obligations
         hereunder.

7.       POSSESSION: Possession of the Property shall be delivered to Buyer at
         closing subject to tenant's rights, if applicable, in its present
         condition, ordinary wear and tear expected.  Seller agrees to maintain
         the property and related equipment in good condition until possession
         is delivered to Buyer.

8.       Seller has provided Buyer access to the Property and Buyer
         acknowledges having had opportunity to make such independent factual,
         physical and legal examinations and inquiries as Buyer deems necessary
         or desirable.  As a result, Buyer has had adequate opportunity to
         become fully acquainted with the nature and condition of the Property
         in all respects and, except as provided in Section 21 below, shall
         acquire the Property, if at all, AS IS, WHERE IS AND WITH ALL FAULTS.

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9.       TAXES: All taxes assessed for any prior calendar year and remaining
         unpaid, shall be paid by the Seller, and all taxes assessed for the
         current calendar year shall be prorated between Seller and Buyer on a
         calendar-year basis as of the day immediately prior to the Closing
         Date.  If the tax rate for taxes assessed in the current year has not
         been determined at the closing of the transaction, said rate shall be
         assumed to be the same as the prior year for the purpose of such
         proration and credit for due but unpaid taxes.

10.      INSURANCE: Insurance shall be canceled as of the date of closing and
         the Buyer shall provide its own insurance.

11.      SURVEY: A staked survey that complies with Minimum Standard Detail
         Requirements for Indiana Land Title Surveys, and which shall reflect
         whether the property is located in a designated flood zone area, shall
         be furnished at Seller's expense.

12.      TITLE AND SURVEY APPROVAL: Seller shall deliver to Buyer within
         fifteen (15) days after completion of the survey a Commitment for
         Title Insurance (the "Commitment") and, at Buyer's request, legible
         copies of all recorded instruments affecting the Property and recited
         as exceptions in the Commitment.  If Buyer has an objection to items
         disclosed in such Commitment or the survey provided for herein, Buyer
         shall promptly make written objections to Seller after receipt of each
         such instrument.  If Buyer or third party lender makes such objections
         or if the objections are disclosed in the Commitment, the survey or by
         the issuer of the Title Policy, Seller shall have thirty (30) days
         from the date such objections are disclosed to cure the same, and the
         Closing Date shall be extended, if necessary.  Seller agrees to
         utilize its best efforts and reasonable diligence to cure such
         objection, if any.  If the objections are not satisfied within such
         time period, Buyer may either terminate this Agreement or waive the
         unsatisfied objections and close the transaction.

13.      SALES EXPENSES: Seller and Buyer agree that all sales expenses are to
         be paid in cash prior to or at the closing.

         A.      Seller's Expenses: Seller agrees to pay all costs of releasing
         existing loans and recording the releases; Owner's Title Policy;
         survey;  1/2 of any closing fee, preparation of Deed and Vendor's
         Affidavit; and other expenses stipulated to be paid by Seller under
         other provisions of this Agreement.

         B.      Buyer's Expenses: Buyer agrees to pay all expenses incident to
         any loan (e.g., loan commitment fees, preparation of note, mortgage,
         and other loan documents, recording fees, Mortgagee's Title Policy,
         prepayable interest, credit reports);  1/2 of any closing fee; and
         expenses stipulated to be paid by Buyer under other provisions of this
         Agreement.


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14.      DEFAULT: If Buyer breaches this Agreement and is in default,
         Seller may seek specific performance or any other remedy
         provided by law or equity; or Seller may treat this Agreement
         as being terminated and receive the Earnest Money as
         liquidated damages.

         If Seller breaches this Agreement and is in default, then the Earnest
         Money shall be returned to Buyer.  In addition, if Seller is in
         default, the Buyer may seek specific performance or any other remedy
         provided by law or equity against the Seller.

15.      ESCROW: The Earnest Money is deposited with Escrow Agent with the
         understanding that Escrow Agent is not a party to this Agreement and
         does not assume or have any liability for performance or
         non-performance of any party.  Before the Escrow Agent has any
         obligation to disburse the Earnest Money in the event of dispute, he
         has the right to require from all signatories a written release of
         liability of the Escrow Agent, written notification of Agreement
         termination and written authorization to disburse the Earnest Money.
         At closing, Earnest Money shall be applied to the Purchase Price.

16.      DUTIES OF BUYER AND SELLER AT CLOSING:

         A.      At the closing, Seller shall deliver to Buyer, at Seller's
         sole cost and expense, the following:

                 (1)      duly executed and acknowledged Corporate Deed
                 conveying good and indefeasible title in fee simple to all of
                 the property, free and clear of any and all liens,
                 encumbrances, conditions, easements, assessments, reservations
                 and restrictions, except as permitted herein, and/or approved
                 by Buyer in writing and execute a Vendor's Affidavit;

                 (2)      A binder for an Owner's Policy of Title Insurance
                 issued by a reputable insurance company chosen by the Seller
                 in the full amount of the Sales Price dated as of closing,
                 insuring Buyer's fee simple title to the property to be good
                 and indefeasible subject only to those title exceptions
                 permitted herein, or as may be approved by Buyer in writing,
                 and the standard printed exceptions contained in the usual
                 form of the Title Policy.

                 (3)      Furnish evidence of its capacity and authority for 
                 the closing of this transaction.

                 (4)      Execute all other necessary documents to close this
                 transaction.

         B.      At the closing, Buyer shall perform the following:

                 (1)      Pay the cash portion of the Sales Price in the form 
                 of a certified or cashier's check;


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                 (2)      Execute the note(s) and mortgage(s) provided for
                 herein and cause the funds to be made available to the closing
                 officer for disbursement;

                 (3)      Furnish evidence of its capacity and authority for 
                 the closing of this transaction;

                 (4)      Furnish to Seller and/or Third Party Lender, at
                 Buyer's expense, a mortgagee's policy issued by Title Company
                 for the benefit of the holder(s) of the mortgage(s) provided
                 for herein;

                 (5)      Execute all other necessary documents to close this
                 transaction.

17.      CONDEMNATION: If prior to Closing Date condemnation proceedings are
         commenced against any portion of the property, Buyer may, at its
         option, terminate this Agreement by written notice to Seller within
         thirty (30) days after Buyer is advised of the commencement of
         condemnation proceedings, or Buyer shall have the right to appear and
         defend in such condemnation proceedings, and any award in condemnation
         shall, at the Buyer's election, become the property of Seller and
         reduce the purchase price by the same amount or shall become the
         property of Buyer and the purchase price not be reduced.

18.      CASUALTY LOSS: Risk of loss by damage or destruction to the Property
         prior to the closing shall be borne by Seller.  In the event any such
         damage or destruction is not fully repaired prior to closing, Buyer,
         at its option, may either terminate this Agreement or elect to close
         the transaction, in which event Seller's right to all insurance
         proceeds resulting from such damage or destruction shall be assigned
         in writing by Seller to Buyer.

19.      RESPONSIBLE PROPERTY TRANSFER LAW: The Seller believes it is not
         required to provide Purchaser with a Disclosure Statement pursuant to
         Indiana's Responsible Party Transfer Law (I.C. Section 13-7-22.5-1 et
         seq.) because (1) the Property does not contain any hazardous chemical
         or material; (2) the Property does not contain any underground storage
         tanks which are or have been utilized to hold petroleum or other
         regulated substances; (3) the Property is not listed on the
         Comprehensive Environmental Response, Compensation and Liability
         Information System; (4) and/or Property is exempt from the provisions
         of said law.  However, if after execution of this Agreement, Seller
         learns that the Property comes within the terms of the Responsible
         Property Transfer Law, then Seller agrees to provide Buyer with the
         required Disclosure Document and comply with all other parts of this
         Law.

20.      ENVIRONMENTAL ASSESSMENT:

         A.      Buyer, or its representative, may, at Buyer's sole cost and
         expense, conduct environmental assessments of the Property as the
         Buyer in its sole discretion may deem appropriate.  In the event such
         assessments are conducts, Buyer agrees to notify Seller


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         immediately of any findings of suspected environmental problems.
         Buyer shall provide Seller with duplicate originals of any reports
         date summaries or test results generated as a result of Buyer's
         investigations, but in no event shall Buyer, or its representatives,
         agents or contractors, provide any such materials to any governmental
         authority or other party or entity prior to closing, unless disclosure
         of such materials is required under Section 20 hereof or any other
         applicable State and/or Federal environmental law.

         B.      Seller shall cooperate fully with Buyer or its representatives
         during any investigation or other activities conducted pursuant to
         this Section 21.

         C.      Seller, at its cost, may correct any and all such deficiencies
         disclosed by said assessment.

         D.      If Seller fails or refuses to correct such deficiencies on or
         before the Closing Date, Buyer may, at its sole option, terminate this
         Agreement.

21.      MISCELLANEOUS

         A.      Any notice required or permitted to be delivered hereunder,
         shall be deemed received when personally delivered or sent by United
         States mail, postage prepaid, certified and return receipt requested,
         addressed to Seller or Buyer, as the case may be, at the address set
         forth below the signature of such party hereto.

         B.      This Agreement shall be construed under and in accordance with
         the laws of the State of Indiana.

         C.      This Agreement shall be binding upon and inure to the benefit
         of the parties hereto and their respective heirs, executors,
         administrators, legal representatives, successors, and permitted
         assigns.  This Agreement may not be assigned by Buyer without written
         consent of the Seller.

         D.      In case any one or more of the provisions contained in this
         Agreement shall for any reason be held to be invalid, illegal, or
         unenforceable in any respect, such invalidity, illegality, or
         unenforceability shall not affect any other provision hereof, and this
         Agreement shall be construed as if such invalid, illegal, or
         unenforceable provision had never been contained herein.

         E.      This Agreement constitutes the sole and only agreement of the
         Parties hereto and supersedes any prior understandings or written or
         oral agreements between the parties respecting the transaction and
         cannot be changed except by their written consent.

         F.      Time is of the essence of this Agreement.


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         G.       Words of any gender used in this Agreement shall be
         held and construed to include any other gender, and words in
         the singular number shall be held to include the plural, and
         vice versa, unless the context requires otherwise.

         H.      All rights, duties and obligations of the signatories hereto
         shall survive the passing of title to, or an interest in, the
         property.

         I.      Buyer shall not record or attempt to record this Agreement.

         J.      Wavier.  Each party hereto may waive any breach by the other
         party of any of the provisions contained in this Agreement or any
         default by such other party in the observance or performance of any
         covenant or condition required to be observed or performed by it
         contained herein; provided, however, that such waiver or waivers shall
         be in writing, shall not be construed as a continuing waiver, and
         shall not extend to or be taken in any manner whatsoever to affect any
         subsequent breach, act or omission or default or affect each party's
         rights resulting therefrom.  No waiver will be implied from any delay
         or failure by either party to take action on account of any default by
         the other party.  No extension of time for performance of any
         obligations or acts shall be deemed an extension of the time for
         performance of any other obligations or acts.

         K.      Further Assurances.  Each party hereto shall do such further
         acts and execute and deliver such further agreements and assurances as
         the other party may reasonably require to give full effect and meaning
         to this Agreement.

         L.      Brokerage Commissions.  Buyer hereby represents and warrants
         to Seller that Buyer has not incurred, and shall not have incurred as
         of the Closing Date, any liability for the payment of any brokerage
         fee or commission in connection with the transaction contemplated in
         this Agreement.  Seller hereby represents and warrants to Buyer that
         Seller has not incurred, and shall not have incurred as of the Closing
         Date, any liability for the payment of any brokerage fee or commission
         in connection with the transaction contemplated in this Agreement,
         except for the commission due to the Shook Agency (for which Seller
         shall be solely responsible).  Seller and Buyer hereby agree to
         defend, indemnify and hold harmless the other from and against any and
         all claims of any other person claiming a brokerage fee or commission
         through such party.

22.      Expiration of Agreement.  This Agreement shall expire unless accepted
         and executed by Buyer and delivered to Seller by 5:00 PM, EST, January
         12, 1996.  If this Agreement is not timely accepted by Seller, it
         shall be null and void and all parties hereto shall stand relieved and
         released of any and all liability or obligations hereunder.

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EXECUTED by Seller this _______ day of ___________________, 1997.

By:__________________________________    By:_______________________________________

   __________________________________       _______________________________________
              (Printed)                                    (Printed)                   

Seller's Address for Notice Purposes:

                        ACCEPTANCE OF PURCHASE AGREEMENT

EXECUTED by Buyer this _______ day of ___________________, 1997.

By:__________________________________    By:_______________________________________

   __________________________________       _______________________________________
              (Printed)                                    (Printed)


Buyer's Address for Notice Purposes:_______________________________________________


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