EXHIBIT 10.1



      THIS INSTRUMENT IS SECURED BY A DEED OF TRUST, ASSIGNMENT OF
      PERMITS, RENTS AND BENEFITS, SECURITY AGREEMENT AND FIXTURE FILING,
      DATED AS OF JUNE 18, 1991


                     EIGHTH AMENDMENT TO CREDIT AGREEMENT


            EIGHTH  AMENDMENT dated as of September 17, 1996 TO CREDIT AGREEMENT
dated as of March 20,  1991  among  RHEOX,  INC.,  a Delaware  corporation  (the
"Company");  RHEOX INTERNATIONAL,  INC., a Delaware corporation (the "Subsidiary
Guarantor");  each of the lenders that is a signatory  hereto  (individually,  a
"Bank" and,  collectively,  the "Banks"); THE CHASE MANHATTAN BANK (successor by
merger to The Chase  Manhattan  Bank (National  Association)),  a New York state
banking  corporation,  and THE NIPPON  CREDIT  BANK,  LTD.,  a Japanese  banking
corporation acting through its New York branch, as co-agents for the Banks (each
in such capacity,  a "Co-Agent" and,  collectively,  the  "Co-Agents");  and THE
CHASE MANHATTAN BANK, as  administrative  agent for the Banks (in such capacity,
together with its successors in such capacity, the "Administrative Agent").

            WHEREAS,  the parties hereto are parties to a Credit Agreement dated
as of March 20, 1991 among the Company, the Subsidiary Guarantor, the Banks, the
Co-Agents  and the  Administrative  Agent (as at any time  amended or  otherwise
modified, the "Credit Agreement";  terms defined therein having their respective
defined meanings when used herein unless otherwise defined herein);

            WHEREAS,  the Company has  requested  that the Credit  Agreement  be
amended  in  certain  respects,  and the Banks are  willing  to  consent to such
amendments upon the terms and conditions contained herein.

            NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency  of which are  hereby  acknowledged,  the  parties  hereto  agree as
follows:

            Section 1.  Amendments.  The  Credit  Documents  are hereby  amended
(effective as provided in Section 3 hereof) as follows:

            A. Each  reference  in the  Credit  Agreement  and the other  Credit
      Documents to the Credit Agreement shall be deemed to be a reference to the
      Credit Agreement as amended hereby.  Except as expressly  provided in this
      Section 1, the Credit  Agreement shall remain  unchanged and in full force
      and effect.

            B. Section 1.01 of the Credit  Agreement is hereby amended by adding
      the following new  definitions  and inserting the same in the  appropriate
      alphabetical locations:

                  "'Bankruptcy  Code' shall mean the Federal  Bankruptcy Code of
            1978, as amended from time to time."


                                      1

<PAGE>



                  "'Subordinated  Note' shall have the meaning  assigned to such
            term in Section 9.07(e) hereof."

                  "'Subordination   Agreement'   shall   mean  a   Subordination
            Agreement  substantially  in the  form of  Exhibit  A to the  Eighth
            Amendment dated as of September 17, 1996 to this Agreement."

            C. The  definition  of "Credit  Documents"  in  Section  1.01 of the
      Credit  Agreement  is hereby  amended by  inserting  ", the  Subordination
      Agreement" after "the NL Guaranty".

            D.  Clause (a) of the  definition  of  "Interest/Lease  Expense"  in
      Section 1.01 of the Credit Agreement is hereby amended to read as follows:

            "(a) all interest in respect of  Indebtedness of the Company and its
            Consolidated  Subsidiaries  (including  imputed  interest expense in
            respect of Capital Lease Obligations, if any, but excluding interest
            expense in respect of the  Subordinated  Note to the extent  accrued
            but not paid) paid, accrued or capitalized during such period;"

            E.  Clause (a) of the definition of "Leverage Ratio" in Section 1.01
      of the Credit Agreement is hereby amended to read as follows:

            "(a) the  aggregate  outstanding  principal  amount of  Indebtedness
            (other than Indebtedness  evidenced by the Subordinated Note) of the
            Company and its Consolidated Subsidiaries on such date by".

            F.  The definition of "Revolving Credit Termination Date" in Section
      1.01 of the Credit Agreement is hereby amended to read as follows:

                  "'Revolving  Credit  Termination Date' shall mean December 31,
            1997."

            G. The last  sentence of the  definition  of "Tangible Net Worth" in
      Section 1.01 of the Credit Agreement is hereby amended to read as follows:

            "Notwithstanding  anything  in  this  definition  to  the  contrary,
            neither  (i)  cumulative  foreign  currency  translation  gains  (or
            losses) nor (ii) the  dividend  evidenced by the  Subordinated  Note
            shall be deemed to increase or decrease Tangible Net Worth."

            H.  Section 9.05 of the Credit  Agreement  is hereby  amended by (i)
      deleting "and" at the end of clause (h) thereof, (ii) replacing the period
      at the end of clause (i)  thereof  with "; and" and (iii)  inserting a new
      clause (j) therein reading as follows:

                  "(j) the  Company  may enter  into and issue the  Subordinated
            Note and make  payments and  otherwise  perform its  obligations  in
            respect thereof in accordance with the Subordination Agreement."


                                      2

<PAGE>



            I.  Section 9.07 of the Credit  Agreement  is hereby  amended by (i)
      relettering  clauses  (e),  (f) and (g) thereof to be clauses (f), (g) and
      (h)  respectively  and (ii) inserting a new clause (e) therein  reading as
      follows:

                  "(e)  Indebtedness  of  the  Company  to  NL  evidenced  by  a
            subordinated  note (the  "Subordinated  Note")  substantially in the
            form of Exhibit B to the Eighth  Amendment dated as of September 17,
            1996 to this  Agreement  and in an  original  principal  amount  not
            exceeding  $100,000,000,  provided  that  NL,  the  Company  and the
            Administrative   Agent  shall  have   executed  and   delivered  the
            Subordination Agreement;"

            J. The  proviso in Section  9.09 of the Credit  Agreement  is hereby
      amended to read as follows:

            "provided  that (a) the  Company may declare and pay the NL Dividend
            in cash on the date the Term  Loans are made  hereunder  and (b) the
            Company may declare the dividend to be evidenced by the Subordinated
            Note and may pay such dividend by issuing the Subordinated Note."

            K.  Section 9.18 of the Credit  Agreement  is hereby  amended by (i)
      replacing " and" at the end of clause  (iii)  thereof  with a comma,  (ii)
      replacing  the period at the end of clause  (iv)  thereof  with " and" and
      (iii) inserting a new clause (v) therein reading as follows:

            "(v) the Company may enter into and issue the Subordinated  Note and
      make payments and otherwise  perform its obligations in respect thereof in
      accordance with the Subordination Agreement."

            L.  Clause (b) of Section  9.23 of the  Credit  Agreement  is hereby
      amended by inserting "the  Subordinated  Note (other than a  modification,
      supplement  or  waiver  deferring  part  or all of the  Company's  payment
      obligations thereunder) or" before "the Tax Sharing Agreement," therein.

            M. The Credit  Agreement  is hereby  amended by adding a new Section
      9.29 thereto reading as follows:

                  "9.29  Subordinated  Note.  The Company will not, and will not
            permit  any of its  Subsidiaries  to,  purchase,  redeem,  retire or
            otherwise  acquire for value,  or set apart any money for a sinking,
            defeasance or other  analogous  fund for the  purchase,  redemption,
            retirement or other acquisition of, or make any voluntary payment or
            prepayment  of the  principal of or interest on, or any other amount
            owing in respect of, the Subordinated Note,  except,  subject to the
            Subordination   Agreement,   for  regularly  scheduled  payments  of
            interest thereon required pursuant thereto."

            Section 2.  Representations and Warranties.  Each of the Company and
the Subsidiary Guarantor represents and warrants that:


                                      3

<PAGE>



            A.  The execution and delivery of this Amendment by it has been duly
      authorized by all necessary corporate action on its part.

            B. This  Amendment  has been duly  executed and delivered by it, and
      each of this  Amendment  and  the  Credit  Agreement  as  modified  hereby
      constitute  its  legal,  valid  and  binding  obligation   enforceable  in
      accordance with its respective terms subject,  however, to the application
      by a court of  general  principles  of  equity  and to the  effect  of any
      applicable bankruptcy, insolvency,  reorganization,  moratorium or similar
      laws affecting creditors' rights generally.

            Section  3.  Effectiveness.  The  amendments  set forth in Section 1
hereof shall become effective upon the receipt by the Administrative Agent on or
before October 15, 1996 of (a)  counterparts  hereof duly executed and delivered
by the Company,  the Banks and the  Administrative  Agent,  (b) a  Subordination
Agreement  substantially  in the form of  Exhibit  A hereto  duly  executed  and
delivered  by NL, the  Company  and the  Administrative  Agent and (c)  evidence
reasonably satisfactory to it as to the truth of the representation contained in
Section 2.A hereof. If the Revolving Credit  Commitments  terminate on September
23, 1996 by reason of failure of the  Administrative  Agent to have received the
documents and evidence  referred to in the preceding  sentence on or before such
date, then, upon the receipt by the  Administrative  Agent of such documents and
evidence on or before  October 15, 1996,  the  amendments set forth in Section 1
hereof  shall  become  effective  retroactive  to  September  23,  1996  and the
Revolving Credit Commitments shall be reinstated as of September 23, 1996.

            Section 4.  Counterparts.  This  Amendment  may be  executed  in any
number of counterparts, each of which may be deemed an original but all of which
together shall constitute one and the same instrument.

            Section 5.  Governing  Law.  This  Amendment  shall be governed  and
construed in accordance with the laws of the State of New York.

                                      4

<PAGE>





            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed by their  respective  officers duly  authorized as of the date first
above written.

                                    RHEOX, INC.


                                    By
                                      Name:
                                      Title:

                                    THE CHASE MANHATTAN BANK,
                                       as Co-Agent and
                                       Administrative Agent


                                    By_____________________________
                                      Name:
                                      Title:

                                    THE NIPPON CREDIT BANK, LTD.,
                                      as Co-Agent


                                    By_____________________________
                                      Name:
                                      Title:

                                    THE CHASE MANHATTAN BANK


                                    By_____________________________
                                      Name:
                                      Title:



                                      5

<PAGE>



                                    THE NIPPON CREDIT BANK, LTD.


                                    By_____________________________
                                      Name:
                                      Title:

                                    VAN KAMPEN AMERICAN CAPITAL PRIME
                                      RATE INCOME TRUST


                                    By_____________________________
                                      Name:
                                      Title:

                                    RESTRUCTURED OBLIGATIONS BACKED
                                      BY SENIOR ASSETS B.V.

                                    BY CHANCELLOR SENIOR SECURED
                                      MANAGEMENT, INC., its Portfolio Advisor:


                                    By_____________________________
                                      Name:
                                      Title:

                                    STICHTING RESTRUCTURED OBLIGATIONS
                                    BACKED BY SENIOR ASSETS 2 (ROSA2)

                                    BY CHANCELLOR SENIOR SECURED
                                      MANAGEMENT, INC., its Portfolio Advisor:


                                    By_____________________________
                                      Name:
                                      Title:



                                      6

<PAGE>


                                    GIROCREDIT BANK,
                                      NEW YORK
                                    K BRANCH


                                    By_____________________________
                                      Name:
                                      Title:

                                    BANQUE PARIBAS


                                    By_____________________________
                                      Name:


                                    By_____________________________
                                      Name:
                                      Title:


                                      7

<PAGE>