AMENDMENT NO. 1 TO THE RENEWED RIGHTS AGREEMENT
                 -----------------------------------------------


         AMENDMENT NO. 1, dated as of November 17, 2003 (this "Amendment"), to
the RENEWED RIGHTS AGREEMENT, dated as of August 19, 1997 between IONICS,
INCORPORATED, a Massachusetts corporation (the "Company"), and EQUISERVE TRUST
COMPANY, N.A. (as successor to BankBoston, N.A.), as Rights Agent (the "Rights
Agreement"). All terms not otherwise defined herein shall have the meanings
given such terms in the Rights Agreement. Unless otherwise specified herein, all
section references made herein are references to sections in the Rights
Agreement.

                              W I T N E S S E T H:

         WHEREAS, on December 22, 1987, the Board of Directors of the Company
(the "Board") adopted a stockholder rights plan (the "Existing Rights Plan") and
executed a Rights Agreement between the Company and the Rights Agent (the "1987
Agreement");

         WHEREAS, the Existing Rights Plan expired on December 31, 1997;

         WHEREAS, on August 19, 1997 the Board determined it desirable and in
the best interests of the Company and its stockholders for the Company to renew
the Existing Rights Plan upon its expiration and to implement such renewal by
executing the Rights Agreement;

         WHEREAS, pursuant to Section 26 of the Rights Agreement, the Company
may cause the Rights Agreement to be amended at any time prior to the
Distribution Date without the approval of any holders of certificates
representing shares of Common Stock of the Company;

         WHEREAS, on November 2, 2003, the Board authorized and approved the
acquisition by the Company of Ecolochem, Inc., Ecolochem S.A.R.L., Moson
Holdings, LLC and Ecolochem International, Inc. and their subsidiaries (the
"Ecolochem Acquisition") as provided under that certain Purchase Agreement (the
"Purchase Agreement") dated as of November 18, 2003 among the Company and the
individuals and entities listed on Exhibit A thereto (the "Sellers");

         WHEREAS, in connection with the Ecolochem Acquisition, the Company
intends to issue to Sellers shares of the Common Stock of the Company pursuant
to the Purchase Agreement (the "Shares Sale") (which will be deemed Beneficially
Owned by the Sellers under the Rights Agreement);
<PAGE>

         WHEREAS, in connection with the Ecolochem Acquisition, the Company and
Sellers intend to enter into that certain Stockholders Agreement contemplated by
the Purchase Agreement (the "Stockholders Agreement") granting certain rights
to, and imposing certain restrictions on, Sellers with respect to shares of
Common Stock of the Company; and

         WHEREAS, in anticipation of and in connection with the Ecolochem
Acquisition and Shares Sale, on November 2, 2003, the Board authorized and
approved an amendment of the Rights Agreement for the express purpose of
rendering the Rights Agreement inapplicable to the Transaction (as defined in
the Purchase Agreement), including without limitation, the Shares Sale and the
other transactions contemplated by the Purchase Agreement;

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

         1. Notwithstanding anything to the contrary in the Rights Agreement,
the Rights Agreement shall not apply to, and none of the Sellers will become an
Acquiring Person upon, and no Distribution Date, Section 11(a)(ii) Event, Stock
Acquisition Date or Triggering Event will occur as a result of, (i) the
approval, execution, delivery, consummation or performance of the Purchase
Agreement, (ii) the announcement of the Ecolochem Acquisition or Shares Sale,
(iii) the consummation of the Transaction, or (iv) following the consummation of
the Transaction, the sale, disposition, conveyance or other transfer by any
Sellers or their Permitted Transferees (as such term is defined in the
Stockholders Agreement) to any Permitted Transferees of shares of Common Stock
of the Company issued to Sellers pursuant to the Purchase Agreement.

         2. The definition of "Acquiring Person" set forth in Section 1(a) is
hereby amended and restated in its entirety as follows:

            "Acquiring Person" shall mean any Person (as hereinafter defined)
            who or which, together with all Affiliates and Associates (each as
            hereinafter defined) of such Person, shall be the Beneficial Owner
            (as hereinafter defined) of 15% or more of the shares of Common
            Stock of the Company then outstanding, but shall not include an
            Exempt Person or the 2003 Special Exempt Persons (each as
            hereinafter defined).

         3. A new definition is hereby added to Section 1 as Section 1(uu),
which such new definition shall read in its entirety as follows:

            "2003 Ecolochem Purchase Agreement" shall mean that certain Purchase
            Agreement dated as of November 4, 2003 among the Company and the
            Persons listed on Exhibit A thereto, as amended and supplemented
            from time to time in accordance with its terms.

                                      -2-
<PAGE>

         4. A new definition is hereby added to Section 1 as Section 1(vv),
which such new definition shall read in its entirety as follows:

            "2003 Ecolochem Stockholders Agreement" shall mean that certain
            Stockholders Agreement contemplated by the 2003 Ecolochem Purchase
            Agreement, as amended and supplemented from time to time in
            accordance with its terms.

         5. A new definition is hereby added to Section 1 as Section 1(ww),
which such new definition shall read in its entirety as follows:

            "2003 Special Exempt Persons" shall mean, collectively, (i) the
            Persons listed on Exhibit A to the 2003 Ecolochem Purchase Agreement
            (the "Sellers"), (ii) any Permitted Transferee (as such term is
            defined in the 2003 Ecolochem Stockholders Agreement) of any such
            Person who becomes a party to the 2003 Ecolochem Stockholders
            Agreement and (iii) any Persons to whom the shares of Common Stock
            of the Company issued in the Shares Sale are attributed due to their
            relationship with any Person described in the immediately preceding
            clauses (i) and (ii) (but only to the extent of such attribution);
            provided, however, that each such Person shall cease to be 2003
            Special Exempt Persons upon the earliest to occur, subsequent to the
            execution and delivery of the 2003 Ecolochem Purchase Agreement, of
            the following events: (A) all Persons described in the immediately
            preceding clauses (i) and (ii), together with their Affiliates,
            Associates and Permitted Transferees who become parties to the 2003
            Ecolochem Stockholders Agreement, cease to Beneficially Own in the
            aggregate 15% or more of the shares of Common Stock of the Company
            then outstanding, or (B) the percentage of outstanding shares of
            Common Stock of the Company Beneficially Owned by all Persons
            described in the immediately preceding clauses (i) and (ii),
            together with their Affiliates, Associates and Permitted Transferees
            who become parties to the 2003 Ecolochem Stockholders Agreement,
            exceeds the sum of (x) the lowest percentage of outstanding shares
            of Common Stock of the Company Beneficially Owned in the aggregate
            by all Persons described in the immediately preceding clauses (i)
            and (ii), together with their Affiliates, Associates and Permitted
            Transferees who become parties to the 2003 Ecolochem Stockholders
            Agreement, while any such Persons are 2003 Special Exempt Persons,
            plus (y) 1% (excluding any such changes to ownership resulting
            solely as a result of a reduction in the number of shares of Common
            Stock of the Company outstanding due to the repurchase of shares of
            Common Stock of the Company by the Company), or (C) the percentage
            of outstanding shares of Common Stock of the Company Beneficially
            Owned by the Sellers exceeds the sum of (x) that percentage of
            outstanding shares of Common Stock of the Company

                                      -3-
<PAGE>

            issued to the Sellers pursuant to the 2003 Ecolochem Purchase
            Agreement plus (y) 1% (excluding any such changes to ownership
            resulting solely as a result of a reduction in the number of shares
            of Common Stock of the Company outstanding due to the repurchase of
            shares of Common Stock of the Company by the Company), or (D) the
            2003 Ecolochem Purchase Agreement is terminated prior to the
            issuance of shares of Common Stock of the Company contemplated
            thereby.

         6. Section 3(a) is hereby amended and restated in its entirety as
follows:

            (a) Until the earliest of (i) the Close of Business on the tenth
            Business Day (or such specified or unspecified later date as may be
            determined by the Board before the occurrence of a Distribution
            Date) after the Stock Acquisition Date (or, if the tenth Business
            Day (or such later date) after the Stock Acquisition Date occurs
            before the Record Date, the Close of Business on the Record Date),
            (ii) the Close of Business on the tenth Business Day (or such
            specified or unspecified later date as may be determined by the
            Board before the occurrence of a Distribution Date) after the date
            that a tender or exchange offer by any Person (other than an Exempt
            Person or, solely with respect to the acquisition of shares of
            Common Stock of the Company pursuant to the 2003 Ecolochem Purchase
            Agreement, the 2003 Special Exempt Persons) is first published or
            sent or given within the meaning of Rule 14d-2(a) of the General
            Rules and Regulations under the Exchange Act if upon consummation
            thereof such Person would be the Beneficial Owner of 15% or more of
            the Common Stock of the Company then outstanding (the earlier of (i)
            and (ii) being herein referred to as the "Distribution Date"), (x)
            the Rights will be evidenced (subject to the provisions of
            paragraphs (b) and (c) of this Section 3) by the certificates for
            the Common Stock of the Company registered in the names of the
            holders thereof (which certificates shall be deemed also to be
            certificates for Rights) and not by separate certificates and (y)
            the Rights will be transferable only in connection with the transfer
            of the underlying shares of Common Stock of the Company (including a
            transfer to the Company). As soon as practicable after the
            Distribution Date, the Rights Agent will send by first-class,
            insured, postage prepaid mail, to each record holder of the Common
            Stock of the Company as of the Close of Business on the Distribution
            Date, at the address of such holder shown on the records of the
            Company, one or more rights certificates, substantially in the form
            attached hereto as Exhibit A (the "Rights Certificates"), evidencing
            one Right for each share of Common Stock of the Company so held,
            subject to adjustment as provided herein. In the event that an
            adjustment in the number of Rights per share of Common Stock of the
            Company has been made pursuant to Section 11(i) hereof, at the time
            of distribution of the Rights Certificates, the Company shall not be
            required to issue Rights Certificates evidencing fractional Rights,
            but

                                      -4-
<PAGE>

            may, in lieu thereof, make the necessary and appropriate rounding
            adjustments (in accordance with Section 14(a) hereof) so that Rights
            Certificates representing only whole numbers of Rights are
            distributed and cash is paid in lieu of any fractional Rights. As of
            and after the Distribution Date, the Rights will be evidenced solely
            by such Rights Certificates.

         7. Section 11(a)(ii) is hereby amended and restated in its entirety as
follows:

            (ii) In the event (a "Section 11(a)(ii) Event") that any Person
            (other than an Exempt Person), alone or together with its Affiliates
            and Associates, shall, at any time after the Rights Dividend
            Declaration Date, become the Beneficial Owner of 15% or more of the
            shares of Common Stock of the Company then outstanding, unless the
            event causing the 15% threshold to be crossed (A) is a transaction
            set forth in Section 13(a) hereof, or (B) is an acquisition of
            shares of Common Stock of the Company pursuant to a tender offer or
            an exchange offer for all outstanding shares of Common Stock of the
            Company at a price and on terms determined by at least a majority of
            the Outside Directors, after receiving advice from one or more
            investment banking firms, to be (x) at a price that is fair to
            stockholders (taking into account all factors which such members of
            the Board deem relevant, including without limitation prices which
            could reasonably be achieved if the Company or its assets were sold
            on an orderly basis designed to realize maximum value) and (y)
            otherwise in the best interests of the Company and its stockholders,
            or (C) is the execution, delivery, consummation and performance of
            the 2003 Ecolochem Purchase Agreement, or (D) is the sale,
            disposition, conveyance or other transfer of shares of Common Stock
            of the Company from one or more Persons, each of whom was a 2003
            Special Exempt Person immediately prior to such transaction, to a
            Person who, immediately following such transaction, is a 2003
            Special Exempt Person, then promptly after the date of occurrence of
            a Section 11(a)(ii) Event, proper provision shall be made so that
            each holder of a Right (except as provided below and in Section 7(e)
            hereof) shall thereafter have the right to receive, upon exercise
            thereof at the then current Purchase Price in accordance with the
            terms of this Agreement, such number of shares of Common Stock of
            the Company as shall equal the result obtained by (1) multiplying
            the then current Purchase Price by the then number of shares of
            Common Stock of the Company for which a Right was exercisable
            immediately prior to the first occurrence of a Section 11(a)(ii)
            Event (whether or not such Right was then exercisable) and (2)
            dividing that product (which following such first occurrence, shall
            thereafter be referred to as the "Purchase Price" for each Right and
            for all purposes of this Agreement) by 50% of the Current Market
            Price per share of Common Stock of the Company on the date of such
            first occurrence (such number of shares being referred to as the
            "Adjustment Shares").

                                      -5-
<PAGE>

         8. Except as amended hereby, the Rights Agreement shall continue in
full force and effect.

         9. The laws of the Commonwealth of Massachusetts shall govern the
interpretation, validity and performance of the terms of this Amendment,
regardless of the law that might be applied under principles of conflicts of
laws.

         10. This Amendment may be executed in two or more counterparts, each of
which shall be deemed an original but all of which, when taken together, shall
constitute one and the same instrument.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]































                                      -6-
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1
to the Renewed Rights Agreement to be duly executed and their respective
corporate seals to be hereunto affixed and attested, all as of the day and year
first above written.

Attest:

                                          IONICS, INCORPORATED

By:  /s/ Martin G. Schaefer               By: /s/ Stephen Korn
   -------------------------------           -------------------------------
      Name: Martin G. Schaefer                 Name: Stephen Korn
      Title: Corporate Counsel and             Title: Vice President and General
             Assistant Clerk                          Counsel



Attest:

                                          EQUISERVE TRUST COMPANY, N.A.

By:  /s/ Kim Graziano                     By: /s/ Tyler Heynes
   -------------------------------           -------------------------------
      Name: Kim Graziano                       Name: Tyler Heynes
      Title: Account Manager                   Title: Managing Director
























                                      -7-