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                                                                   Exhibit 10.26

                             MKS INSTRUMENTS, INC.

                      CONSENT, WAIVER AND TENTH AMENDMENT

                              TO LOAN AGREEMENT

     This Consent, Waiver and Tenth Amendment (the "Amendment") dated as of
January 28, 2002 concerns the Loan Agreement dated as of October 31, 1995 (the
"Loan Agreement"), between MKS Instruments, Inc. (the "Borrower") and Fleet
National Bank (f/k/a BankBoston, N.A. and The First National Bank of Boston, the
"Lender"), as amended on February 23, 1996, February 4, 1997, February 3, 1998,
January 28, 1999, January 1, 2000, September 1, 2000, January 1, 2001, April 30,
2001 and July 31, 2001. Capitalized terms used herein but not otherwise defined
shall have the meanings assigned to them in the Loan Agreement.

     WHEREAS, the Borrower has requested that the Lender waive compliance with
certain covenants in the Loan Agreement and consent to its acquisition of ENI
Technology, Inc. and certain related transactions, as well as amend another
covenant in the Loan Agreement as a result of the effect of such acquisition;
and

     WHEREAS, the Lender is willing to agree to the Borrower's requests;

     NOW, THEREFORE, the Lender and the Borrower agree as follows:

     Section 1.  Consent and Waiver.  The Lender hereby consents to the
transactions contemplated by the Agreement and Plan of Merger with respect to
the Acquisition of the ENI Business, dated October 30, 2001, between the
Borrower and Emerson Electric Co. (the "Acquisition Agreement") including
without limitation the acquisition of ENI Technology, Inc. ("ENI") and waives
compliance with Sections 7.1(b) and 7.4 of the Loan Agreement with respect to
such transactions.

     Section 2.  Amendment of the Loan Agreement.  Section 7.9 of the Loan
Agreement is hereby amended by deleting "$292,000,000" therefrom and replacing
it with "$260,000,000".

     Section 3.  Representations and Warranties.  The Borrower hereby
represents and warrants as follows:

          (a)  The execution and delivery of this Amendment and the performance
of this Amendment, the Loan Agreement as amended hereby and each of the other
Loan Documents, and the transactions contemplated hereby and thereby, have been
authorized by all necessary corporate actions of the Borrower. This Amendment,
the Loan Agreement as amended hereby and each of the other Loan Documents
constitute the legal, valid and binding obligations of the Borrower,
enforceable against the Borrower in accordance with their respective terms.

          (b)  The Borrower has all requisite corporate power and authority to
execute, deliver and perform its obligations under this Amendment, the Loan
Agreement as amended hereby and each of the other Loan Documents. Neither the
authorization, execution, delivery or

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performance by the Borrower of this Amendment nor the performance of the Loan
Agreement as amended hereby or any other Loan Document nor the performance of
the transactions contemplated hereby or thereby violates or will violate any
provision of the corporate charter or by-laws of the Borrower, or does or will,
with the passage of time or the giving of notice or both, result in a breach of
or a default under, or require any consent under or result in the creation of
any lien, charge or encumbrance upon any property or assets of the Borrower
pursuant to, any material instrument, agreement or other document to which the
Borrower is a party or by which the Borrower or any of its properties may be
bound or affected.

     (c) The execution and delivery by the Borrower of this Amendment and the
performance by the Borrower of the Loan Agreement as amended hereby and the
Loan Documents do not and will not violate any provision of law or regulation
applicable to the Borrower, or any writ, order or decree of any court or
governmental or regulatory authority or agency applicable to the Borrower.

     (d) The representations and warranties contained in Article IV of the Loan
Agreement are true and correct, and the Borrower and its Subsidiaries are in
compliance with all covenants set forth in Article VII of the Loan Agreement,
provided that for this purpose that all references to the "Disclosure Schedule"
in such Articles IV and VII shall be deemed to mean the Disclosure Schedule
attached hereto, which is true and complete.

     Section 4. Loan Documents. This Amendment shall be a Loan Document for all
purposes.

     Section 5. Conditions to Effectiveness. The effectiveness of this
Amendment is conditioned on the following:

          (a) The Borrower and the Lender shall each have executed and
delivered a counterpart of this Amendment;

          (b) The representations and warranties contained in Article IV of the
Loan Agreement shall be true and correct in all material respects as of the
date hereof as though made on and as of the date hereof;

          (c) No Default or Event of Default under the Loan Agreement shall
have occurred and be continuing;

          (d) The conditions set forth in Sections 5.2-5.5 of the Loan
Agreement shall have been met as of the date hereof, provided that for purposes
thereof and Section 4.5 of the Loan Agreement, the "Balance Sheet Date" shall
mean September 30, 2001 and the financial statements referred to therein shall
mean the unaudited statements for the period ended September 30, 2001, that
have been furnished to the Lender.

          (e) Promptly following the closing under the Acquisition Agreement,
the Borrower shall cause to be delivered to the Lender a guaranty of the
Obligations by ENI in the form attached here to as well as a certificate of the
secretary of ENI as to the votes of ENI's directors authorizing the execution
and delivery of such guaranty and the incumbency of the officers authorized to
execute such guaranty on behalf of ENI.

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         (f)  The Lender shall have received a certificate of the clerk of the
Borrower as to the votes of Borrower's directors authorizing the execution and
delivery of this Amendment and the incumbency of the officers authorized to
execute this Amendment on behalf of the Borrower.

     Section 6.  Miscellaneous.

         (a)  On and after the date hereof, each reference in the Loan Agreement
to "this Agreement" or words of like import shall mean and be deemed to be a
reference to the Loan Agreement as amended hereby.

         (b)  Except as amended and modified hereby, the Loan Agreement is in
all respects ratified and confirmed as of the date hereof, and the terms,
covenants and agreements therein shall remain in full force and effect.

         (c)  This Amendment and the modifications to the Loan Agreement set
forth herein shall be deemed to be a document executed under seal and shall be
governed by and construed in accordance with the laws of The Commonwealth of
Massachusetts.

         (d)  This Amendment may be executed in counterparts, each of which
shall be deemed an original, but all of which shall constitute one and the same
document.

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     IN WITNESS WHEREOF, the parties have caused this Amendment to be duly
executed as of the date and the year first above written.


                                   MKS INSTRUMENTS, INC.



                                   By: /s/ Ronald C. Weigner
                                       ------------------------------------
                                   Title: Vice President and Chief
                                          Financial Officer
                                         ----------------------------------


                                   FLEET NATIONAL BANK



                                   By: /s/ Daniel G. Head
                                       ------------------------------------
                                   Title: Vice President
                                         ----------------------------------




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