<PAGE>

                                                                     EXHIBIT 4.1

                             SHAREHOLDER AGREEMENT
                                  DATED AS OF
                                JANUARY 31, 2002
                                     AMONG
                             MKS INSTRUMENTS, INC.
                                      AND
                              EMERSON ELECTRIC CO.





                                       1
<PAGE>

<Table>
<S>            <C>                                                           <C>
ARTICLE 1  DEFINITIONS
SECTION 1.01.  Definitions.................................................   3

ARTICLE 2  CORPORATE GOVERNANCE
SECTION 2.01.  Composition of the Board....................................   5
SECTION 2.02.  Replacement of Emerson Designee.............................   5

ARTICLE 3  STANDSTILL
SECTION 3.01.  Purchases of Shares.........................................   6
SECTION 3.02.  No Appraisal................................................   6

ARTICLE 4  RESTRICTIONS ON TRANSFER
SECTION 4.01.  Lock-Up Period..............................................   7
SECTION 4.02.  Lock-Up Expiration..........................................   7
SECTION 4.03.  Restrictions on Sale or Transfer of Shares..................   7
SECTION 4.04.  Resale Exceptions...........................................   7

ARTICLE 5  REGISTRATION RIGHTS
SECTION 5.01.  Demand Registration.........................................   7
SECTION 5.02.  Piggyback Registration......................................   8
SECTION 5.03.  Reduction of Offering.......................................   9
SECTION 5.04.  Filings; Information........................................   9
SECTION 5.05.  Registration Expenses.......................................  11
SECTION 5.06.  Indemnification by the Company..............................  11
SECTION 5.07.  Indemnification by Emerson..................................  12
SECTION 5.08.  Conduct of Indemnification Proceedings......................  12
SECTION 5.09.  Contribution................................................  13
SECTION 5.10.  Other Indemnification.......................................  13

ARTICLE 6  CERTAIN COVENANTS AND AGREEMENTS
SECTION 6.01.  Rule 144....................................................  14
SECTION 6.02.  Participation in Public Offering............................  14
SECTION 6.03.  Consolidation or Merger of the Company......................  14

ARTICLE 7  MISCELLANEOUS
SECTION 7.01.  Binding Effect; Assignability; Benefit......................  14
SECTION 7.02.  Notices.....................................................  15
SECTION 7.03.  Waiver; Amendment...........................................  15
SECTION 7.04.  Fees and Expenses...........................................  15
SECTION 7.05.  Governing Law...............................................  16
SECTION 7.06.  Jurisdiction................................................  16
SECTION 7.07.  Waiver of Jury Trial........................................  16
SECTION 7.08.  Specific Enforcement........................................  16
SECTION 7.09.  Counterparts; Effectiveness.................................  16
SECTION 7.10.  Entire Agreement............................................  16
SECTION 7.11.  Captions....................................................  16
SECTION 7.12.  Severability................................................  16
</Table>

                                       2
<PAGE>

                             SHAREHOLDER AGREEMENT

     AGREEMENT dated as of January 31, 2002 by and between MKS Instruments,
Inc., a Massachusetts corporation (the "COMPANY"), and Emerson Electric Co., a
Missouri corporation ("EMERSON").

                             W I T N E S S E T H :

     WHEREAS, the Company and Emerson have entered into an Agreement and Plan of
Merger with respect to the Acquisition of the ENI Business Agreement (the
"ACQUISITION AGREEMENT") dated as of October   , 2001, pursuant to which, among
other things, Emerson and its Subsidiaries shall acquire twelve million shares
of common stock of the Company;

     WHEREAS, simultaneously with the execution of the Acquisition Agreement,
Emerson and John R. Bertucci have entered into a Voting Agreement (the "VOTING
AGREEMENT"), pursuant to which, among other things, John R. Bertucci has agreed
to vote in favor of the transactions contemplated by the Acquisition Agreement
and the election of Emerson's designee as a director on the Board of the Company
in the circumstances specified in this Agreement;

     WHEREAS, effective from the Closing Date (as defined below), Emerson's
initial designee, James G. Berges, has been appointed to serve as Director on
the Board of the Company; and

     WHEREAS, pursuant to provisions of the Acquisition Agreement, Emerson and
the Company have agreed to execute and deliver this Agreement on the Closing
Date;

     NOW, THEREFORE, in consideration of the covenants and agreements contained
herein and in the Acquisition Agreement, the parties hereto agree as follows:

                                   ARTICLE 1

                                  DEFINITIONS

     SECTION 1.01.  Definitions.  (a) The following terms, as used herein, have
the following meanings:

     "ADJUSTMENT EVENT" means any stock dividend (including any distribution of
securities convertible into Shares), stock split, reverse split, rights
offering, reorganization, recapitalization, reclassification, combination or
other like change with respect to or affecting the Common Stock.

     "AFFILIATE" means, with respect to any Person, any other Person directly or
indirectly controlling, controlled by or under common control with such Person,
provided that neither the Company nor any of its Subsidiaries shall be deemed an
Affiliate of Emerson. For the purpose of this definition, the term "CONTROL"
(including, with correlative meanings, the terms "CONTROLLING", "CONTROLLED BY"
and "UNDER COMMON CONTROL WITH"), as used with respect to any Person, shall mean
the possession, directly or indirectly, of the power to direct or cause the
direction of the management and policies of such Person, whether through the
ownership of securities, by contract or otherwise.

     "BENEFICIAL OWNERSHIP" and "BENEFICIALLY OWN" shall be determined in
accordance with Rules 13d-3 and 13d-5 under the Exchange Act.

     "BOARD" means the board of directors of the Company.

     "BUSINESS DAY" means any day except a Saturday, Sunday or other day on
which commercial banks in New York City are authorized by law to close.

     "BUYER REQUISITE VOTE" shall have the meaning set forth in the Acquisition
Agreement.

     "BUYER VOTING PROPOSAL" shall have the meaning set forth in the Acquisition
Agreement.

     "CLOSING DATE" means [month]                , 200 .

                                       3
<PAGE>

     "COMMON STOCK" means the common stock, no par value, of the Company and any
stock of the Company into which such Common Stock may thereafter be converted or
changed.

     "CONFIDENTIALITY AGREEMENT" means the confidentiality agreement by and
between the Company and Emerson, dated as of September 6, 2001.

     "DILUTION TRANSACTION" means any transaction involving the issuance or sale
of Shares that would have the possible effect of reducing Emerson's Common Stock
Interest below 20%, where Emerson's Common Stock Interest before the earlier of
the date of announcement of any such transaction and the date that such
transaction was effected was equal to or greater than 20%.

     "DIRECTOR" means a director of the Company.

     "EMERSON'S COMMON STOCK INTEREST" means, for any date, the percentage of
(i) outstanding Shares beneficially owned by Emerson and its Subsidiaries on
such date, to (ii) the total number of the then outstanding Shares based upon
the most recent Form 10-Q or Form 10-K filed by the Company or any more recent
notification from the Company to Emerson which specifically references Section
2.01 of this Agreement.

     "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended.

     "INSTITUTIONAL SHAREHOLDER" means a Person described in Rule 13d-1(b)(1)
promulgated under the Exchange Act (other than any such Person who acquires
Shares as part of such Person's market-making or broker-dealer activities).

     "NASD" means the National Association of Securities Dealers, Inc.

     "NASDAQ" means the National Association of Securities Dealers Automated
Quotation System.

     "PERSON" means an individual, corporation, limited liability company,
partnership, association, trust or other entity or organization, including a
government or political subdivision or an agency or instrumentality thereof.

     "PUBLIC OFFERING" means an underwritten public offering of Registrable
Securities of the Company pursuant to an effective registration statement under
the Securities Act, other than pursuant to a registration statement on Form S-4
or Form S-8 or any similar or successor form.

     "REASONABLE BEST EFFORTS" means best efforts, to the extent commercially
reasonable.

     "REGISTRABLE SECURITIES" means, at any time, all Shares held by Emerson or
its Subsidiaries, including any Shares and any securities of the Company issued
or issuable in respect of such Shares by way of conversion, exchange, stock
dividend, split or combination, recapitalization, merger, consolidation, other
reorganization or otherwise.

     "SEC" means the Securities and Exchange Commission.

     "SECURITIES ACT" means the Securities Act of 1933, as amended.

     "SHARES" means shares of Common Stock.

     "STANDSTILL PERIOD" means a period of three years commencing on the Closing
Date.

     "SUBSIDIARY" means, with respect to any Person, any entity of which
securities or other ownership interests having ordinary voting power to elect a
majority of the board of directors or other persons performing similar functions
are at the time directly or indirectly owned by such Person.

                                       4
<PAGE>

     (b) Each of the following terms is defined in the Section set forth
opposite such term:

<Table>
<Caption>
TERM                                                           SECTION
----                                                           --------
<S>                                                            <C>
Acquisition Agreement.......................................   Recitals
Announcement................................................       4.02
Company.....................................................   Preamble
Damages.....................................................       5.06
Demand Registration.........................................    5.01(a)
Emerson.....................................................   Preamble
Indemnified Party...........................................       5.08
Indemnifying Party..........................................       5.08
Lock-Up Period..............................................       4.01
New Registrable Securities..................................       6.03
Piggyback Registration......................................       5.02
Registration Statement......................................    5.01(a)
Successor Entity............................................       6.03
Transfer....................................................       4.01
Voting Agreement............................................   Recitals
</Table>

                                   ARTICLE 2

                              CORPORATE GOVERNANCE

     SECTION 2.01.  Composition of the Board.  (a) At all times from and after
the Closing Date, at the termination of the term of James G. Berges who was
appointed as a Director effective from the Closing Date, or at the termination
of the term of any subsequent designee of Emersion, or upon death, disability,
incapacity, retirement, resignation, disqualification, removal or otherwise of
James G. Berges or any subsequent designee of Emerson, Emerson will have the
right to designate one representative who is reasonably acceptable to the
Company, to serve as a Director, provided Emerson will no longer have such right
from after the first time that Emerson's Common Stock Interest has been less
than 12.5% for a period of thirty consecutive calendar days.

     (b) Subject to applicable law, if at any time after the Closing Date, the
Company notifies Emerson in writing that Emerson's Common Stock Interest has
been less than 12.5% for a period of thirty consecutive calendar days, after the
receipt of such notice, Emerson shall promptly direct the Director designated by
Emerson to resign from the Board.

     SECTION 2.02.  Replacement of Emerson Designee.  (a) If prior to the
expiration of the term of James G. Berges or any subsequent designee of Emerson,
James G. Berges or such subsequent designee of Emerson is no longer a Director
as a result of death, disability, incapacity, retirement, resignation,
disqualification, removal or otherwise, the Company will appoint a person
designated by Emerson in accordance with Section 2.01(a) as Director in the same
class of the Board as his or her predecessor (or if it is not permissible under
applicable law to appoint a Director to such class, then to another class, or if
more than one class is permissible, to the class of the Board with the longest
term outstanding), provided that if such appointment is not permissible under
applicable law (i) the Company shall take all actions in accordance with
applicable law and its Articles of Organization and by-laws to promptly and duly
call, give notice of, convene and hold as promptly as practicable, a meeting of
the Company's stockholders for the purposes of electing Emerson's designee on
the Board, (ii) the Board shall recommend such designee for election to the
Board and such recommendation shall be included in any proxy statement, and
(iii) the Company shall use Reasonable Best Efforts to solicit from the
stockholders of the Company eligible to vote for the election of Directors
proxies in favor of such designee.

                                       5
<PAGE>

     (b) Upon the expiration of the term of James G. Berges or any subsequent
designee of Emerson (i) the Company shall nominate the person designated by
Emerson in accordance with Section 2.01(a) for election to the Board, (ii) the
Board shall recommend such designee for election to the Board and such
recommendation shall be included in any proxy statement, and (iii) the Company
shall use Reasonable Best Efforts to solicit from the stockholders of the
Company eligible to vote for the election of Directors proxies in favor of the
representative designated by Emerson.

                                   ARTICLE 3

                                   STANDSTILL

     SECTION 3.01.  Purchases of Shares.  Except as contemplated by the
Acquisition Agreement, during the Standstill Period, Emerson shall not, and
shall not permit its Subsidiaries to;

          (a) directly or indirectly, acquire, announce an intention to acquire,
     make any proposal (or except in a confidential and non-public manner,
     request permission to make any proposal) to acquire, or agree or offer to
     acquire ownership of any Shares, or any other security convertible into, or
     any options, warrant or right to acquire any Shares or any property of the
     Company (other than property acquired in the ordinary course of business)
     from the Company or any other Person, except for:

             (i) Shares or other property of the Company acquired after the
        Closing Date pursuant to an Adjustment Event or any merger,
        consolidation or similar transaction involving the Company; or

               (ii) if prior approval of a majority of the members of the Board
     other than the designee of Emerson has been obtained for such acquisition
     proposal, agreement or offer;

          (b) "solicit", or propose to "solicit", or participate in any
     "solicitation" of, any "proxy" (as such terms are defined in Regulation 14A
     under the Exchange Act) from any holder of Shares, become a "participant"
     in a "solicitation" in opposition to any matter that has been recommended
     by a majority of the members of the Board, propose or otherwise solicit
     stockholders of the Company for approval of any stockholder proposals, or
     otherwise seek to influence or control the management or policies of the
     Company or any of its Affiliates;

          (c) take any action to form, join in or in any way participate in any
     partnership, limited partnership, syndicate or other Group (as such term is
     defined in Rule 13d-5 under the Exchange Act) with respect to Shares;

          (d) take any other action to seek control (as such term is defined in
     Rule 12b-2 of the Exchange Act) of the Company;

          (e) make any request or proposal to amend or waive any provision of
     Article 3, except on a confidential and nonpublic manner; or

          (f) assist or announce an intention to assist (including by knowingly
     providing or arranging financing for that purpose) any other person in
     doing any of the foregoing.

     SECTION 3.02.  No Appraisal.  If, pursuant to any transaction, the Shares
purchased by Emerson pursuant to the Acquisition Agreement are converted into
stock of any publicly traded company, Emerson and its Subsidiaries shall not
exercise any appraisal rights that they might otherwise have under Sections 86
through 98 of Chapter 156B of the Massachusetts General Laws. In any event, this
Section 3.02 shall no longer apply from the date upon which Emerson no longer
has the right to designate a Director in accordance with Article 2 of this
Agreement.

                                       6
<PAGE>

                                   ARTICLE 4

                            RESTRICTIONS ON TRANSFER

     SECTION 4.01.  Lock-Up Period.  Commencing on the Closing Date, for a
period of one year or such shorter period as determined pursuant to Section 4.02
below (the "LOCK-UP PERIOD"), except with prior approval of the Company or as
provided in Section 4.04, Emerson shall not, and shall not permit its
Subsidiaries to, directly or indirectly, sell, transfer, pledge, contract to
sell, sell any option or contract to purchase, purchase any option or contract
to sell, grant any option, right or warrant to purchase, transfer the economic
risk of ownership of or otherwise dispose of ("TRANSFER"), any Shares purchased
pursuant to the Acquisition Agreement (or Shares acquired as a result of an
Adjustment Event).

     SECTION 4.02.  Lock-Up Expiration.  If during the period of one year from
the Closing Date, the Company makes a public announcement (an "ANNOUNCEMENT") of
any Dilution Transaction or effects a Dilution Transaction (regardless of
whether publicly announced or not), the Lock-Up Period shall expire on the later
of (a) the date that is six months after the Closing Date, or (b) the earlier of
the date of such Announcement or the date such Dilution Transaction is effected.

     SECTION 4.03.  Restrictions on Sale or Transfer of Shares.  Subject to the
exceptions set forth in Section 4.04, Emerson shall not, and shall not permit
its Subsidiaries to, Transfer any Shares purchased pursuant to the Acquisition
Agreement:

          (a) to any Person that competes in any of same principal markets in
     which the Company competes; or

          (b) to any Person (other than an Institutional Purchaser) if, Emerson
     has knowledge that after giving effect to such sale, such Person and any
     Group of which such Person is a part would beneficially own (or, in the
     case of an underwritten Public Offering, if the lead underwriter has
     knowledge such Person and any Group of which such Person is a part would
     beneficially own) more than 5% of the then outstanding Shares,

provided that this Section 4.03 shall not preclude any bona fide transactions
conducted on NASDAQ or any national securities exchange on which the Shares are
then listed, and provided further that any block trade crossed through NASDAQ or
any national securities exchange on which the Shares are then listed will be
subject to Sections 4.03(a) and 4.03(b) to the extent the broker or market-maker
effecting such sale on behalf of Emerson has actual knowledge that such sale is
made to a Person referred to in Sections 4.03(a) and 4.03(b) above.

     SECTION 4.04.  Resale Exceptions.  Notwithstanding Sections 4.01 and 4.03,
Emerson and its Subsidiaries may Transfer any Shares purchased pursuant to the
Acquisition Agreement:

          (a) to Emerson or its Subsidiaries; or

          (b) pursuant to a tender or exchange offer made by the Company or any
     Affiliate or recommended by the Board to the Company's stockholders.

                                   ARTICLE 5

                              REGISTRATION RIGHTS

     SECTION 5.01.  Demand Registration.  (a) The Company agrees that, at any
time after the Closing Date, upon the request of Emerson (a "DEMAND
REGISTRATION"), it will file a registration statement (a "REGISTRATION
STATEMENT") under the Securities Act as to the number of shares of Registrable
Securities specified in such request subject to the limitations described in
Section 5.01(b); provided that (i) the Company shall not be required to file
more than three Registration Statements that become effective and remain
effective for the period referred to in Section 5.04(a), (ii) subject to the
second proviso in Section 5.01(b), Emerson shall not make more than one request
for a Demand Registration in any twelve month period, (iii) the Registrable
Securities for which a Demand Registration has been requested by

                                       7
<PAGE>

Emerson must be at least two million Shares (or, if less, all of the Shares then
held by Emerson and its Subsidiaries), (iv) the proposed offering of Shares of
Registrable Securities must be an underwritten offering, (v) the Company shall
not be required to file a shelf registration statement pursuant to Rule 415 of
the Securities Act under this Section 5.01(a), (vi) prior to the first
anniversary of the Closing Date, no request to register any Registrable
Securities may be made prior to such time as the Company is required to file a
Registration Statement for such Registrable Securities pursuant to Section
5.01(b), (vii) the Company shall not be required to effect a Demand Registration
if within 10 days after receipt of a request, therefor the Company provides
written notice of its bona fide intention to file within 60 days a registration
statement for an underwritten public offering of securities for its own account,
and (viii) the Company shall not be required to effect a Demand Registration
during the period from the date of filing of, and ending 90 days after the
effective date of, any registration statement for an underwritten public
offering of securities for the account of the Company. In no event shall the
Company's right to block or defer a Demand Registration pursuant to this Article
5 permit a block or deferral of longer than a cumulative period of six months,
and following any such deferrals, Emerson shall have the right to have a Demand
Registration effected at any time during the six month period following such
block or deferral without restriction hereunder.

     (b) Pursuant to Demand Registrations the Company will not be required to
register more than (i) four million Shares prior to the date that is one year
after the expiration of the Lock-Up Period, (ii) eight million Shares (less any
Shares registered under clause (i)) prior to the date that is two years after
the expiration of the Lock-Up Period or (iii) twelve million Shares (less any
Shares registered under clause (i) and (ii)) prior to the date that is three
years after the expiration of the Lock-Up Period; provided that any of the
numbers shall be adjusted (x) based on the number of Shares in excess of twelve
million Shares delivered by the Company to Emerson and its Subsidiaries at the
Closing Date, (y) based on any Adjustment Event that occurs after the Closing
Date but before the effective date of the relevant Demand Registration, and (z)
if Emerson requests, and the Company consents, to increase the numbers in the
foregoing limitations (such consent not to be unreasonably withheld, where it
will be reasonable for the Company to refuse such consent if it would be
reasonably expected to have an adverse effect on the trading price of the
Shares), the numbers in clause (b)(i) and (b)(ii) above shall be increased by no
more than four million Shares multiplied by the proportion of the year that has
passed (as of the date of the request) from the date that is one year and two
years respectively after the expiration of the Lock-Up Period provided further
that the limitations described in Sections 5.01(a)(ii), (vii) and (viii), this
Section 5.01(b) and the proviso in Section 5.04(a) shall not apply if Emerson's
Common Stock Interest is equal to or greater than 12.5% and notwithstanding that
the Company has fully performed its obligations under Article 2: (A) Emerson
designates a representative to serve on the Board in accordance with Section
2.01 of this Agreement and such designee is not elected or appointed to the
Board for any reason, or (B) Emerson's representative on the Board is removed
and not replaced by a representative designated by Emerson in accordance with
Section 2.01 of this Agreement.

     (c) Emerson shall select the lead underwriter, any additional underwriters,
and any additional investment bankers and managers to be used, in connection
with the offering resulting from a request for a Demand Registration made
pursuant to Section 5.01(a), subject to the Company's reasonable approval (such
approval not to be unreasonably withheld).

     SECTION 5.02.  Piggyback Registration.  If the Company proposes to register
any Shares, whether for sale for its own account or for the account of any of
its holders of Shares, the Company shall each such time give prompt notice to
Emerson at least 15 Business Days prior to the anticipated filing date of the
registration statement relating to such registration, which notice shall set
forth Emerson's rights under this Section 5.02 and shall offer Emerson and its
Subsidiaries the opportunity to register such number of shares of Registrable
Securities as Emerson may request on the same terms and conditions as the
Company or such holder of Shares (a "PIGGYBACK REGISTRATION"); provided, that
Emerson shall not request the registration of a greater number of Shares than
that for which it could then demand a registration under Section 5.01(b). No
registration effected under this Section 5.02 shall relieve the Company of its
obligations to effect a Demand Registration to the extent required by Section
5.01,

                                       8
<PAGE>

provided, however, that any Shares sold pursuant to this Section 5.02 shall be
applied against the limitation set forth in Section 5.01(b).

     Notwithstanding anything to the contrary herein, Emerson shall have no
Piggyback Registration rights under this Section 5.02 with respect to a
Registration Statement filed to sell Shares solely for the account of Mr. or
Mrs. John R. Bertucci (or trusts established by either of them) at any time
within 12 months after the death of Mr. and Mrs. Bertucci.

     SECTION 5.03.  Reduction of Offering.  Notwithstanding anything contained
herein, if the managing underwriter of an offering described in Section 5.01 or
Section 5.02 advises the Company in writing that (i) the size of the offering
that Emerson, the Company and any other Persons intend to make or (ii) the
combination of securities that Emerson, the Company and such other Persons
intend to include in such offering would jeopardize the success of the offering,
then (A) if the size of the offering is the basis of such underwriter's advice,
the amount of Registrable Securities to be offered for the account of Emerson
shall be reduced to the extent necessary to reduce the total amount of
securities to be included in such offering to the amount recommended by such
managing underwriter; provided that (x) in the case of a Demand Registration,
the amount of Registrable Securities to be offered for the account of Emerson
shall be reduced only after the amount of securities to be offered for the
account of the Company and such other Persons has been reduced to zero, and (y)
in the case of a Piggyback Registration, if securities are being offered for the
account of Persons other than the Company, then the proportion by which the
amount of such Registrable Securities intended to be offered for the account of
Emerson is reduced shall not exceed the proportion by which the amount of such
securities intended to be offered for the account of such other Persons is
reduced, provided that in the case of a Piggyback Registration filed pursuant to
the exercise of demand registration rights by a Person other than Emerson,
Registrable Securities shall be included only if there is no reduction in the
amount of securities registered for the account of the Persons demanding such
registration; and (B) if the combination of securities to be offered is the
basis of such underwriter's advice, (x) the Registrable Securities to be
included in such offering shall be reduced as described in clause (A) above
(subject to the proviso in clause (A)), and (y) in the case of a Piggyback
Registration, if the actions described in sub-clause (x) of this clause (B)
would, in the judgment of the managing underwriter, be insufficient
substantially to eliminate the adverse effect that inclusion of the Registrable
Securities requested to be included would have on such offering, such
Registrable Securities will be excluded from such offering.

     SECTION 5.04.  Filings; Information.  Whenever Emerson requests that any
Registrable Securities be registered pursuant to Section 5.01 hereof, the
Company will use Reasonable Best Efforts to effect the registration of such
Registrable Securities as soon as is practicable, and in connection with any
such request:

          (a) The Company will use its Reasonable Best Efforts to prepare and
     file with the SEC as soon as practicable a Registration Statement on any
     form for which the Company then qualifies and which counsel for the Company
     shall deem appropriate and available for the sale of the Registrable
     Securities to be registered thereunder in accordance with the intended
     method of distribution thereof, and use Reasonable Best Efforts to cause
     such filed Registration Statement to become and remain effective for a
     period as is reasonably required to effect the proposed distribution of the
     Registrable Securities (but in any event, not less than 90 days); provided
     that, subject to the second proviso in Section 5.01(b), the Company's
     obligations to use Reasonable Best Efforts to file the Registration
     Statement shall be suspended for up to 90 days if the Company shall furnish
     to Emerson a certificate signed by the Company's Chief Executive Officer
     stating that in his reasonable good faith judgment the fulfillment of the
     foregoing obligations would (i) require the Company to make a disclosure
     that would be detrimental to the Company and premature, or (ii) occur at a
     time when the price or exchange ratio at which the Company is obligated to
     issue securities (other than Company employee or officer and director stock
     options or restricted stock grants) is being determined, except that the
     foregoing obligations of the Company shall be reinstated upon the making of
     such disclosure by the Company or expiration or termination of the
     circumstances referred to in clause (ii) above (or, if

                                       9
<PAGE>

     earlier, when such disclosure would no longer be necessary for the
     fulfillment of the foregoing obligations or no longer be detrimental).

          (b) The Company will, if requested, prior to filing such Registration
     Statement or any amendment or supplement thereto, furnish to Emerson and
     each applicable managing underwriter, if any, copies thereof, and
     thereafter furnish to Emerson and each such underwriter, if any, such
     number of copies of such Registration Statement, amendment and supplement
     thereto (in each case including all exhibits thereto and documents
     incorporated by reference therein) and the prospectus included in such
     Registration Statement (including each preliminary prospectus) as Emerson
     or each such underwriter may reasonably request in order to facilitate the
     sale of the Registrable Securities.

          (c) After the filing of the Registration Statement, the Company will
     promptly notify Emerson of any stop order issued or, to the Company's
     knowledge, threatened to be issued by the SEC and take all reasonable
     actions required to prevent the entry of such stop order or to remove it if
     entered.

          (d) The Company will use Reasonable Best Efforts to qualify the
     Registrable Securities for offer and sale under such other securities or
     blue sky laws of such jurisdiction in the United States as Emerson
     reasonably requests; provided that the Company will not be required to (i)
     qualify generally to do business in any jurisdiction where it would not
     otherwise be required to qualify but for this Section 5.04(d), (ii) subject
     itself to taxation in any such jurisdiction or (iii) consent to general
     service of process in any such jurisdiction.

          (e) The Company will as promptly as is practicable notify Emerson, at
     any time when a prospectus relating to the sale of the Registrable
     Securities is required by law to be delivered in connection with sales by
     an underwriter or dealer, of the occurrence of any event requiring the
     preparation of a supplement or amendment to such prospectus so that, as
     thereafter delivered to the purchasers of such Registrable Securities, such
     prospectus will not contain an untrue statement of a material fact or omit
     to state any material fact required to be stated therein or necessary to
     make the statements therein, in the light of the circumstances under which
     they were made, not misleading and promptly make available to Emerson and
     to the underwriters any such supplement amendment. Emerson agrees that,
     upon receipt of any notice from the Company of the occurrence of any event
     of the kind described in the preceding sentence, Emerson will forthwith
     discontinue the offer and sale of Registrable Securities pursuant to the
     Registration Statement covering such Registrable Securities until receipt
     by Emerson and the underwriters of the copies of such supplemented or
     amended prospectus and, if so directed by the Company, Emerson will deliver
     to the Company all copies, other than permanent file copies then in
     Emerson's possession, of the most recent prospectus covering such
     Registrable Securities at the time of receipt of such notice. In the event
     the Company shall give such notice, the Company shall extend the period
     during which such Registration Statement shall be maintained effective as
     provided in Section 5.04(a) hereof by the number of days during the period
     from and including the date of the giving of such notice to the date when
     the Company shall make available to Emerson such supplemented or amended
     prospectus.

          (f) The Company will enter into customary agreements (including an
     underwriting agreement in customary form) and take such other actions as
     are reasonably required in order to expedite or facilitate the sale of such
     Registrable Securities, including but not limited to attendance by the
     Company's Chief Executive Officer and any other Company officers as may be
     reasonably requested by Emerson, at any analyst or investor presentation or
     any "road shows" undertaken in connection with the marketing or selling of
     the Registrable Securities provided that the Company's Chief Executive
     Officer and such Company officers (if any) shall not be required to
     participate in any such presentations or "road show" for more than three
     Business Days in connection with each Demand Registration.

          (g) The Company will furnish to each underwriter (i) an opinion or
     opinions of counsel to the Company and (ii) a comfort letter or comfort
     letters from the Company's independent public accountants, each in
     customary form and covering such matters of the type customarily covered by
     opinions or comfort letters, as the case may be, as the managing
     underwriter reasonably requests.
                                       10
<PAGE>
`
          (h) The Company will make generally available to its security holders,
     as soon as reasonably practicable, an earnings statement covering a period
     of 12 months, beginning within three months after the effective date of the
     Registration Statement, which earnings statement shall satisfy the
     provisions of Section 11(a) of the Securities Act and the rules and
     regulations of the SEC thereunder.

          (i) The Company will use Reasonable Best Efforts to (i) to secure the
     designation of all such Registrable Securities covered by such Registration
     Statement as a NASDAQ "national market system security" within the meaning
     of Rule 11Aa2-1 of the SEC or, failing that, to secure NASDAQ authorization
     for such Registrable Securities, in each case if the Registrable Securities
     so qualify, and, without limiting the generality of the foregoing, to
     arrange for at least two market makers to register as such with respect to
     such Registrable Securities with the NASD, or (ii) to cause all Registrable
     Securities covered by such Registration Statement to be listed on any
     national securities exchange (if such Registrable Securities are not
     already listed), and on each other securities exchange on which similar
     securities issued by the Company are then listed, if the listing of such
     Registrable Securities is then permitted under the rules of such exchange.

     The Company may require Emerson promptly to furnish in writing to the
Company such information regarding Emerson, the plan of distribution of the
Registrable Securities and such other information as the Company may from time
to time reasonably request or as may be legally required in connection with such
registration.

     SECTION 5.05.  Registration Expenses.  In connection with any Demand
Registration and in connection with any Piggyback Registration, the Company
shall pay the following expenses incurred in connection with such registration:
(i) registration and filing fees with the SEC, (ii) fees and expenses of
compliance with securities or blue sky laws (including reasonable fees and
disbursements of counsel in connection with blue sky qualifications of the
Registrable Securities), (iii) expenses in connection with the preparation,
printing, mailing and delivery of any registration statements, prospectuses and
other documents in connection therewith and any amendments or supplements
thereto, (iv) fees and expenses incurred in connection with the listing of the
Registrable Securities, (v) fees and expenses of counsel and independent
certified public accountants for the Company, (vi) the reasonable fees and
expenses of any additional experts retained by the Company in connection with
such registration, (vii) internal expenses of the Company (including, without
limitation, all salaries and expenses of its officers and employees performing
legal or accounting duties), (viii) for any Piggyback Registration fees and
expenses in connection with any review by the NASD of the underwriting
arrangements or other terms of the offering, and all fees and expenses of any
"qualified independent underwriter," including the fees and expenses of any
counsel thereto, (ix) costs of printing and producing any agreements among
underwriters, underwriting agreements, any "blue sky" or legal investment
memoranda and any selling agreements and other documents in connection with the
offering, sale or delivery of the Registrable Securities, (x) transfer agents'
and registrars' fees and expenses and the fees and expenses of any other agent
or trustee appointed in connection with such offering, (xi) expenses incurred by
the Company in connection with any analyst or investor presentations or any
"road shows" attended by the Company in connection with the registration,
marketing or selling of the Registrable Securities, and (xii) fees and expenses
payable in connection with any ratings of the Registrable Securities, including
expenses relating to any presentations to rating agencies; provided, however,
that the Company shall not be required to pay, and Emerson shall reimburse the
Company for, any such expenses for any Demand Registration that is withdrawn at
the request of Emerson unless such withdrawn Registration Statement is counted
toward the maximum number of Demand Registrations to which Emerson is entitled
under Section 5.01. Emerson shall pay any underwriting fees, discounts or
commissions attributable to the sale of Registrable Securities and any out-
of-pocket expenses of Emerson.

     SECTION 5.06.  Indemnification by the Company.  The Company agrees to
indemnify and hold harmless Emerson, its officers, directors, employees, and
agents, and each Person, if any, who controls Emerson within the meaning of
Section 15 of the Securities Act or Section 20 of the Exchange Act from and
against any and all losses, claims, damages, liabilities and expenses (including
reasonable expenses of
                                       11
<PAGE>

investigation and reasonable attorneys' fees and expenses) ("DAMAGES") caused by
or relating to any untrue statement or alleged untrue statement of a material
fact contained in any registration statement or prospectus relating to the
Registrable Securities (as amended or supplemented if the Company shall have
furnished any amendments or supplements thereto) or any preliminary prospectus
(including documents incorporated by reference therein), or caused by or
relating to any omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, except insofar as such Damages are caused by or related to any such
untrue statement or omission or alleged untrue statement or omission so made
based upon information furnished in writing to the Company by Emerson or on
Emerson's behalf expressly for use therein, provided that, with respect to any
untrue statement or omission or alleged untrue statement or omission made in any
preliminary prospectus, or in any prospectus, as the case may be, the indemnity
agreement contained in this paragraph shall not apply to the extent that any
Damages result from the fact that a current copy of the prospectus (or such
amended or supplemented prospectus, as the case may be) was not sent or given to
the Person asserting any such Damages at or prior to the written confirmation of
the sale of the Registrable Securities concerned to such Person if it is
determined that the Company has provided such prospectus to Emerson and it was
the responsibility of Emerson to provide such Person with a current copy of the
prospectus (or such amended or supplemented prospectus, as the case may be) and
such current copy of the prospectus (or such amended or supplemented prospectus,
as the case may be) would have cured the defect giving rise to such Damages. The
Company also agrees to indemnify any underwriters of the Registrable Securities,
their officers and directors and each Person who controls such underwriters
within the meaning of Section 15 of the Securities Act or Section 20 of the
Exchange Act on substantially the same basis as that of the indemnification of
Emerson provided in this Section 5.06.

     SECTION 5.07.  Indemnification by Emerson.  Emerson agrees to indemnify and
hold harmless the Company, its officers, directors and agents and each Person,
if any, who controls the Company within the meaning of either Section 15 of the
Securities Act or Section 20 of the Exchange Act to the same extent as the
foregoing indemnity from the Company to Emerson, but only (i) with respect to
information furnished in writing by Emerson or on Emerson's behalf expressly for
use in any registration statement or prospectus relating to the Registrable
Securities, or any amendment or supplement thereto, or any preliminary
prospectus or (ii) to the extent that any Damages result from the fact that a
current copy of the prospectus (or such amended or supplemented prospectus, as
the case may be) was not sent or given to the Person asserting any such Damages
at or prior to the written confirmation of the sale of the Registrable
Securities concerned to such Person if it is determined that it was the
responsibility of Emerson to provide such Person with a current copy of the
prospectus (or such amended or supplemented prospectus, as the case may be) and
such current copy of the prospectus (or such amended or supplemented prospectus,
as the case may be) would have cured the defect giving rise to such loss, claim,
damage, liability or expense. Emerson also agrees to indemnify and hold harmless
underwriters of the Registrable Securities, their officers and directors and
each Person who controls such underwriters within the meaning of either Section
15 of the Securities Act or Section 20 of the Exchange Act on substantially the
same basis as that of the indemnification of the Company provided in this
Section 5.07. As a condition to including Registrable Securities in any
registration statement filed in accordance with Article 5, the Company may
require that it shall have received an undertaking reasonably satisfactory to it
from any underwriter to indemnify and hold it harmless to the extent customarily
provided by underwriters with respect to similar securities. Emerson shall not
be liable under this Section 5.07 for any Damages in excess of the net proceeds
realized by Emerson in the sale of Registrable Securities of Emerson to which
such Damages relate.

     SECTION 5.08.  Conduct of Indemnification Proceedings.  If any proceeding
(including any governmental investigation) shall be instituted involving any
Person in respect of which indemnity may be sought pursuant to this Article 5,
such Person (an "INDEMNIFIED PARTY") shall promptly notify the Person against
whom such indemnity may be sought (the "INDEMNIFYING PARTY") in writing and the
Indemnifying Party shall assume the defense thereof, including the employment of
counsel reasonably satisfactory to such Indemnified Party, and shall assume the
payment of all fees and expenses, provided that the failure of any Indemnified
Party so to notify the Indemnifying Party shall not relieve the Indemnifying
Party of its
                                       12
<PAGE>

obligations hereunder except to the extent that the Indemnifying Party is
materially prejudiced by such failure to notify. In any such proceeding, any
Indemnified Party shall have the right to retain its own counsel, but the fees
and expenses of such counsel shall be at the expense of such Indemnified Party
unless (i) the Indemnifying Party and the Indemnified Party shall have mutually
agreed to the retention of such counsel or (ii) in the reasonable judgment of
such Indemnified Party representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between them. It
is understood that, in connection with any proceeding or related proceedings in
the same jurisdiction, the Indemnifying Party shall not be liable for the
reasonable fees and expenses of more than one separate firm of attorneys (in
addition to any local counsel) at any time for all such Indemnified Parties, and
that all such fees and expenses shall be reimbursed as they are incurred. In the
case of any such separate firm for the Indemnified Parties, such firm shall be
designated in writing by the Indemnified Parties. The Indemnifying Party shall
not be liable for any settlement of any proceeding effected without its written
consent, but if settled with such consent, or if there be a final judgment for
the plaintiff, the Indemnifying Party shall indemnify and hold harmless such
Indemnified Parties from and against any loss or liability (to the extent stated
above) by reason of such settlement or judgment. Without the prior written
consent of the Indemnified Party, no Indemnifying Party shall effect any
settlement of any pending or threatened proceeding in respect of which any
Indemnified Party is or could have been a party and indemnity could have been
sought hereunder by such Indemnified Party, unless such settlement includes an
unconditional release of such Indemnified Party from all liability arising out
of such proceeding.

     SECTION 5.09.   Contribution.  If the indemnification provided for in this
Article 5 is unavailable to the Indemnified Parties in respect of any Damages,
then each such Indemnifying Party, in lieu of indemnifying such Indemnified
Party, shall contribute to the amount paid or payable by such Indemnified Party
as a result of such Damages in such proportion as is appropriate to reflect the
relative fault of the Company, Emerson and the underwriters in connection with
the statements or omissions that resulted in such Damages, as well as any other
relevant equitable considerations. The relative fault of the Company, Emerson
and the underwriters shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission or alleged omission to state a material fact relates to information
supplied by such party and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.

     The Company and Emerson agree that it would not be just and equitable if
contribution pursuant to this Section 5.09 were determined by pro rata
allocation (even if the underwriters were treated as one entity for such
purpose) or by any other method of allocation that does not take account of the
equitable considerations referred to in the immediately preceding paragraph.
Notwithstanding the provisions of this Article 5, no underwriter shall be
required to contribute any amount in excess of the amount by which the total
price at which the securities underwritten by it and distributed to the public
were offered to the public exceeds the amount of any Damages which such
underwriter has otherwise been required to pay by reason of such untrue or
alleged untrue statement or omission or alleged omission, and Emerson shall not
be required to contribute any amount in excess of the amount by which the net
proceeds of the offering (before deducting expenses) received by Emerson exceeds
the amount of any Damages which Emerson has otherwise been required to pay by
reason of such untrue or alleged untrue statement or omission or alleged
omission. No person guilty of fraudulent misrepresentation (within the meaning
of Section 11(f) of the Securities Act) shall be entitled to contribution from
any Person who was not guilty of such fraudulent misrepresentation.

     SECTION 5.10.   Other Indemnification.  Indemnification similar to that
specified herein (with appropriate modifications) shall be given by the Company
and Emerson with respect to any required registration or other qualification of
securities under any federal or state law or regulation or governmental
authority other than the Securities Act.

                                       13
<PAGE>

                                   ARTICLE 6

                        CERTAIN COVENANTS AND AGREEMENTS

     SECTION 6.01.   Rule 144.  The Company covenants that it will file any
reports required to be filed by it under the Securities Act and the Exchange Act
and that it will take such further action as Emerson may reasonably request to
the extent required from time to time to enable Emerson or its Subsidiaries to
sell Registrable Securities without registration under the Securities Act within
the limitation of the exemptions provided by Rule 144 under the Securities Act,
as such Rule may be amended from time to time, or any similar rule or regulation
hereafter adopted by the SEC. Upon the request of Emerson, the Company will
deliver to Emerson a written statement as to whether it has complied with such
reporting requirements.

     SECTION 6.02.   Participation in Public Offering.  Emerson may not
participate in any Public Offering hereunder unless Emerson (a) agrees to sell
its Registrable Securities on the basis provided in any underwriting
arrangements approved by the Persons entitled hereunder to approve such
arrangements and (b) completes and executes all questionnaires, powers of
attorney, indemnities, underwriting agreements and other documents reasonably
required under the terms of such underwriting arrangements and the provisions of
this Agreement in respect of registration rights.

     SECTION 6.03.   Consolidation or Merger of the Company.  If the Company
considers any transaction in which the Company consolidates or merges with or
into any Person, as a result of which the Shares are converted into or become,
in whole or in part, securities of any other Person ("SUCCESSOR ENTITY"), the
Company shall use its best efforts to cause the Successor Entity to agree with
Emerson to file a registration statement under the Securities Act covering the
resale of all of the securities issued by the Successor Entity with respect to
the Registrable Securities in such merger or consolidation (and any other
securities issued or issuable in respect of such securities by way of
conversion, exchange, stock dividend, split or combination, recapitalization,
merger, consolidation, other reorganization or otherwise) (collectively, the
"NEW REGISTRABLE SECURITIES") during the period commencing as soon as
practicable after the closing of such merger or consolidation and ending on the
first anniversary thereof, provided, however, that (a) the Successor Entity
shall not be required to register New Registrable Securities to the extent it
conflicts with other pre-existing contractual rights to which the Successor
Entity is a party, and (b) such registration obligation shall be subject to
reasonable customary deferral and suspension periods. Emerson agrees to
cooperate in executing and delivering any agreement reasonably necessary to
implement such registration rights. Notwithstanding the foregoing, the Company
shall not be required to use its best efforts to cause the Successor Entity to
grant any such registration rights if (i) Emerson would be able to sell all of
the New Registrable Securities within the 12-month period following the closing
of such merger or consolidation pursuant to the provisions of Rule 144 (based on
the combined (at the applicable exchange ratio) outstanding shares and combined
(at the applicable exchange ratio) average weekly trading volumes of the Company
and the Successor Entity during the three months prior to the Closing), or (ii)
Emerson, in the opinion of its counsel, would not be considered an affiliate of
the Company for purposes of Rule 145 under the Securities Act if its designee
were to resign as a Director prior to mailing of proxy materials to the
Company's stockholders with respect to such transaction and Emerson is given
sufficient notice to be able to consider and take such action.

                                   ARTICLE 7

                                 MISCELLANEOUS

     SECTION 7.01.  Binding Effect; Assignability; Benefit.  (a) This Agreement
shall inure to the benefit of and be binding upon the parties hereto and their
respective heirs, successors, legal representatives and permitted assigns,
provided that no party may assign, delegate or otherwise transfer any of its
rights or obligations under this Agreement without the prior consent of the
other party hereto. Without limiting the foregoing, (i) Emerson and its
subsidiaries shall not sell or otherwise transfer any of the Shares to any
Subsidiary or Affiliate unless the transferee agrees in writing to be bound by
the provisions of Article 3

                                       14
<PAGE>

and Article 4 hereof to the same extent as Emerson, and (ii) the provisions of
Articles 2 and 5 are not assignable under any circumstances except to any
Affiliate or Subsidiary of Emerson.

     (b) Nothing in this Agreement, expressed or implied, is intended to confer
on any Person other than the parties hereto, and their respective heirs,
successors, legal representatives and permitted assigns, any rights, remedies,
obligations or liabilities under or by reason of this Agreement.

     SECTION 7.02.  Notices.  All notices, requests and other communications to
any party shall be in writing and shall be delivered in person, mailed by
certified or registered mail, return receipt requested, or sent by facsimile
transmission,

     if to the Company to:

     MKS Instruments, Inc.
     Six Shattuck Road
     Andover, MA 01810-2449
     Fax: (978) 975-3756
     Attention: John R. Bertucci, Chairman and CEO

     with a copy to:

     Hale and Dorr LLP
     60 State Street
     Boston, MA 02109
     Fax: (617) 526-5000
     Attention: Mark G. Borden, Esq.

     if to Emerson:

     Emerson Electric Co.
     8000 West Florissant Avenue
     P.O. Box 4100
     St. Louis, MO 63136-8506
     Fax: (314) 553-2958
     Attention: Senior Vice President, Secretary and General Counsel

     with a copy to:

     Davis Polk & Wardwell
     450 Lexington Avenue
     New York, NY 10017
     Fax: (212) 450-4800
     Attention: Phillip R. Mills, Esq.

     All notices, requests and other communications shall be deemed received on
the date of receipt by the recipient thereof if received prior to 5:00 p.m. in
the place of receipt and such day is a Business Day in the place of receipt.
Otherwise, any such notice, request or communication shall be deemed not to have
been received until the next succeeding Business Day in the place of receipt.
Any notice, request or other written communication sent by facsimile
transmission shall be confirmed by certified or registered mail, return receipt
requested, posted within one Business Day, or by personal delivery, whether
courier or otherwise, made within two Business Days after the date of such
facsimile transmissions.

     SECTION 7.03.  Waiver; Amendment.  No provision of this Agreement may be
waived except by an instrument in writing executed and delivered by duly
authorized officers of the respective parties.

     SECTION 7.04.  Fees and Expenses.  Except as otherwise provided in the
Acquisition Agreement, each party shall bear its own costs and expenses incurred
in connection with the preparation of this Agreement, or any amendment or waiver
hereof.

                                       15
<PAGE>

     SECTION 7.05.  Governing Law.  This Agreement shall be governed by, and
construed in accordance with, the laws of the Commonwealth of Massachusetts,
without regard to the conflicts of laws rules of such state.

     SECTION 7.06.  Jurisdiction.  The parties hereby agree that any suit,
action or proceeding seeking to enforce any provision of, or based on any matter
arising out of or in connection with, this Agreement or the transactions
contemplated hereby may be brought in the United States District Court for the
District of Boston or any Massachusetts court sitting in Boston, so long as one
of such courts shall have subject matter jurisdiction over such suit, action or
proceeding, and that any cause of action arising out of this Agreement shall be
deemed to have arisen from a transaction of business in the Commonwealth of
Massachusetts, and each of the parties hereby irrevocably consents to the
jurisdiction of such courts (and of the appropriate appellate courts therefrom)
in any such suit, action or proceeding and irrevocably waives, to the fullest
extent permitted by law, any objection that it may now or hereafter have to the
laying of the venue of any such suit, action or proceeding in any such court or
that any such suit, action or proceeding which is brought in any such court has
been brought in an inconvenient form. Process in any such suit, action or
proceeding may be served on any party anywhere in the world, whether within or
without the jurisdiction of any such court. Without limiting the foregoing, each
party agrees that service of process on such party as provided in Section 7.02
shall be deemed effective service of process on such party.

     SECTION 7.07.  Waiver of Jury Trial.  EACH OF THE PARTIES HERETO HEREBY
IRREVOCABLY WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING
ARISING OUT OF OR RELATED TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED
HEREBY.

     SECTION 7.08.  Specific Enforcement.  Each party hereto acknowledges that
the remedies at law of the other party for a breach or threatened breach of this
Agreement would be inadequate and, in recognition of this fact, any party to
this Agreement, without posting any bond, and in addition to all other remedies
that may be available, shall be entitled to obtain equitable relief in the form
of specific performance, a temporary restraining order, a temporary or permanent
injunction or any other equitable remedy that may then be available.

     SECTION 7.09.  Counterparts; Effectiveness.  This Agreement may be executed
in any number of counterparts, each of which shall be deemed to be an original,
with the same effect as if the signatures thereto and hereto were upon the same
instrument. This Agreement shall become effective when each party hereto shall
have received counterparts hereof signed by the other party hereto.

     SECTION 7.10.  Entire Agreement.  This Agreement, the Acquisition Agreement
and the Voting Agreement constitute the entire agreement among the parties
hereto and supersede all prior and contemporaneous agreements and
understandings, both oral and written, among the parties hereto with respect to
the subject matter hereof and thereof, provided that the Confidentiality
Agreement shall survive, except that the provisions of Article 3 of this
Agreement shall be deemed to supersede the standstill provisions contained in
paragraph 3 of the Confidentiality Agreement.

     SECTION 7.11.  Captions.  The captions herein are included for convenience
of reference only and shall be ignored in the construction or interpretation
hereof.

     SECTION 7.12.  Severability.  If any term, provision, covenant or
restriction of this Agreement is held by a court of competent jurisdiction or
other authority to be invalid, void or unenforceable, the remainder of the
terms, provisions, covenants and restrictions of this Agreement shall remain in
full force and effect and shall in no way be affected, impaired or invalidated
so long as the economic or legal substance of the transactions contemplated
hereby is not affected in any manner materially adverse to any party. Upon such
a determination, the parties shall negotiate in good faith to modify this
Agreement so as to effect the original intent of the parties as closely as
possible in an acceptable manner so that the transactions contemplated hereby be
consummated as originally contemplated to the fullest extent possible.

                                       16
<PAGE>

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

                                          MKS INSTRUMENTS, INC.

                                          By: /s/ John R. Bertucci
                                            ------------------------------------
                                              Name: John R. Bertucci
                                              Title:  Chairman and Chief
                                              Executive Officer

                                          EMERSON ELECTRIC CO.

                                          By: /s/ James D. Switzer
                                            ------------------------------------
                                              Name: James D. Switzer
                                              Title:  Senior Vice
                                              President -- Development

                                       17