EXHIBIT 2.3


                      AMENDMENT NO. 1 TO PURCHASE AGREEMENT

     This AMENDMENT NO. 1 dated as of February 13, 2004 (this "Amendment") to
the Purchase Agreement dated as of November 18, 2003 (the "Purchase Agreement")
among Ionics, Incorporated, a Massachusetts corporation (the "Purchaser"), and
the individuals and entities listed on Exhibit A thereto (the "Sellers").

     WHEREAS, the Purchaser and Sellers wish to amend certain sections of the
Purchase Agreement as provided below;

     NOW, THEREFORE, in consideration of the premises and the agreements herein
contained, and intending to be legally bound hereby, the parties hereby agree as
follows:

1.   AMENDMENT OF PURCHASE AGREEMENT.

     1.01 Section 1.04(a) of the Purchase Agreement is hereby amended by
deleting such section in its entirety and replacing it with the following:

          "(a) "Excess Cash" shall mean the amount equal to (i) the sum of (A)
          all cash, cash equivalents (including cash represented by undeposited
          checks) and marketable securities held by the Companies and their
          subsidiaries as of the close of business on January 31, 2004 (the
          "Allocation Date") plus (B) cash deposits made by the Companies and
          held by the Internal Revenue Service for Required Payment for Refund
          under Section 7519 of the Code (which, as of November 18, 2003, were
          in the approximate amount of $1,620,988) as described in SECTION
          1.04(a) OF THE SELLER DISCLOSURE SCHEDULE (collectively, the
          "Deposits"), plus (c) $900,000, which represents the agreed upon
          adjustment related to the Excess Cash that the Companies and their
          subsidiaries were expected to generate between the close of business
          on the Allocation Date and the close of business on the business day
          immediately prior to the Closing Date, minus (ii) the sum of (A) all
          amounts necessary for the Companies and their subsidiaries to satisfy
          and discharge in full all Borrowed Debt and all monetary liabilities
          and obligations arising under any Derivatives existing as of the
          Closing (including any Liens securing such Borrowed Debt and other
          items), (B) if, as of the close of business on the business day
          immediately prior to the Closing Date, the Companies and their
          subsidiaries shall not have made all Required Capital Calls (as
          defined below) in cash, the aggregate amount of all Required Capital
          Calls that have not been made by the Companies and their subsidiaries
          before the close of business on the business day immediately prior to
          the Closing Date, (C) the amount represented by checks issued by the
          Companies and their subsidiaries prior to the Allocation Date, but
          uncollected or unpaid as of the close of business on the Allocation
          Date and (D) $1,000,000, which represents the agreed upon adjustment
          related to UK deferred income taxes as disclosed in the Combined
          Balance Sheet. Between the date hereof and the close of business on
          the business day immediately prior to the Closing Date, the Companies
          and their subsidiaries shall make all investments in, and capital
          contributions to, the Nalco JV that the Companies and their
          subsidiaries are required to make through the Closing Date pursuant to
          any partnership, operating or other governing agreements of the Nalco






                 Amendment No. 1 to Purchase Agreement - Page 2


          JV (the "Required Capital Calls"); provided, however, that for
          purposes of determining Excess Cash, the investments in, and capital
          contributions to, the Nalco JV by the Companies and their subsidiaries
          relating to the Project that were not made prior to the close of
          business on the Allocation Date shall not constitute Required Capital
          Calls. Sellers hereby inform Purchaser that there are no unmade
          Required Capital Calls as of the date hereof, and that the Sellers
          currently expect that the investment in, or capital contribution to,
          the Nalco JV by the Companies and their subsidiaries relating to the
          Project will be approximately $450,000. For purposes of determining
          Excess Cash (and any related items), all assets and liabilities of the
          Nalco JV shall be excluded. The parties acknowledge that Sellers
          intend to cause to be distributed to Sellers before the Closing all
          Excess Cash and no more. Sellers Representatives shall prepare and
          deliver to Purchaser at least two business days before the Closing
          Date, a good faith estimate of the amount of Excess Cash as of the
          Closing (the "Estimated Closing Excess Cash Amount") (such estimate to
          separately set forth both the aggregate and detailed amounts
          supporting the Estimated Closing Excess Cash Amount and the amounts
          thereof allocated to each Seller under Section 1.01(c)). Since the
          Allocation Date neither the Companies nor their subsidiaries have
          made, and from and after the Allocation Date neither the Companies nor
          their subsidiaries shall make, any distribution of cash, cash
          equivalents, marketable securities or Deposits unless the making of
          such distribution and the amount thereof was specifically included in
          the Sellers' calculation of the Estimated Closing Excess Cash Amount.
          "Final Excess Cash Amount" shall mean the amounts of Excess Cash set
          forth on the Closing Excess Cash Statement that becomes final and
          binding on each Seller and Purchaser in accordance with this Section
          1.04."

     1.02 Section 1.04(h) of the Purchase Agreement is hereby amended by
deleting such section in its entirety and replacing it with the following:

          "(h) "Working Capital" shall mean Current Assets minus Current
          Liabilities. "Current Assets" shall mean total current assets of the
          Companies and their subsidiaries, excluding any items included in the
          calculation of Excess Cash. Current Assets shall be calculated in a
          consistent manner, using the same GAAP accounting principles,
          practices, methodologies and policies as applied to current assets in
          the Combined Balance Sheet. "Current Liabilities" shall mean total
          current liabilities of the Companies and their subsidiaries, excluding
          any items included in the calculation of Excess Cash. Current
          Liabilities shall be calculated in a consistent manner, using the same
          GAAP accounting principles, practices, methodologies and policies as
          applied to current liabilities in the Combined Balance Sheet. Working
          Capital shall include Current Assets or Current Liabilities relating
          to Taxes properly accruable by the Companies or their subsidiaries
          calculated in a consistent manner, using the same GAAP accounting
          principles, practices, methodologies and policies as applied to Taxes
          in the




               Amendment No. 1 to the Purchase Agreement - Page 3

          Combined Balance Sheet (for the avoidance of doubt, deferred taxes
          related to the UK, as recorded in the Combined Balance Sheet, are not
          includable in Current Assets or Current Liabilities). Working Capital
          shall not include any Borrowed Debt or any Derivatives, which are
          included in the calculation of Excess Cash. Working Capital shall not
          include any accruals for (i) unused vacation or (ii) advances to
          Sellers that are reclassified as distributions to such Sellers before
          the Closing Date. For purposes of determining Working Capital (and any
          related items), all assets and liabilities of the Nalco JV shall be
          excluded. All bonuses payable to employees of the Companies and their
          subsidiaries that are currently scheduled to be paid in November 2003
          for sales bonuses and January 2004 for other employees, although
          discretionary, were paid before the close of business on the
          Allocation Date. "Closing Working Capital" shall mean Working Capital
          as of the close of business on the Allocation Date. "Closing WC
          Amount" shall mean Closing Working Capital minus $17,000,000. Sellers
          Representatives shall prepare and deliver to Purchaser at least two
          business days before the Closing Date, a good faith estimate of the
          amount of Closing Working Capital (the "Estimated Closing Working
          Capital") and Closing WC Amount (the "Estimated Closing WC Amount")
          (such estimates to separately set forth both the aggregate and
          detailed amounts supporting the Estimated Closing Working Capital and
          Estimated Closing WC Amount and the amounts thereof allocated to each
          Seller under Section 1.01(c)). "Final Closing Working Capital" shall
          mean the amounts of Closing Working Capital set forth on the Closing
          Working Capital Statement that becomes final and binding on each
          Seller and Purchaser in accordance with this Section 1.04. "Final
          Closing WC Amount" shall mean Final Closing Working Capital minus
          $17,000,000."

     1.03 Section 1.04(i) of the Purchase Agreement is hereby amended by
deleting such section in its entirety and replacing it with the following:

          "(i) Until final resolution of any issues regarding the Post-Closing
          Statements, Purchaser shall not take any actions with respect to the
          historical accounting books and records of the Companies on which the
          Post-Closing Statement are based not consistent with the past
          practices of the Companies. Without limiting the generality of the
          foregoing, no changes shall be made until such determination in any
          reserve or other account existing as of the date of the Combined
          Balance Sheet or the Allocation Date except as a result of events
          occurring after the date of the Combined Balance Sheet through the
          Allocation Date and, in such event, only in a manner consistent with
          the methodology used in the Combined Balance Sheet. During the period
          required for the preparation and review of, and resolution of disputes
          relating to, the Post-Closing Statements or any amounts set forth
          therein or based thereon, Sellers and Purchaser shall each afford the
          other's accountants and other designated representatives reasonable
          access during regular business hours to the books and records of the
          Companies and their respective subsidiaries as they may reasonably
          require in order to review and verify the items in the Post-Closing
          Statements."






                 Amendment No. 1 to Purchase Agreement - Page 4


     1.04 The Purchase Agreement shall be amended by adding new Section 1.04(k),
which shall read in its entirety as follows:

          "(k) The Seller hereby represent and warrant to Purchaser that
          Ecolochem JV Holdings, Inc. is responsible for making a final capital
          contribution to the Nalco JV in the amount of $450,000 (the "Final
          Capital Call Amount") in respect of the last remaining project to be
          completed by the Nalco JV (the "Project"), that Ecolochem has
          previously provided equipment to the Nalco JV in respect of the
          Project with an aggregate value of $1,264,000 (the "Equipment Amount")
          and that Ecolochem will issue one or more invoices to the Nalco JV in
          respect of the Equipment Amount (the "Ecolochem Invoice") within 60
          days of the Closing Date. Within 10 business days after receipt of
          payment by Ecolochem from the Nalco JV with respect to the Ecolochem
          Invoice, Purchaser will pay to the Ecolochem Sellers an amount equal
          to the amount actually paid by the Nalco JV with respect to the
          Ecolochem Invoice less the Final Capital Call Amount. Such amount to
          be paid by Purchaser shall be allocated among the Ecolochem Sellers in
          the same proportion as the Initial Cash Consideration is to be
          apportioned as of the Closing Date.

     1.05 Section 8.02(m) of the Purchase Agreement shall be amended by deleting
such section in its entirety.





               Amendment No. 1 to the Purchase Agreement - Page 5

2.   MISCELLANEOUS.

     2.01. Effect. Except as previously amended and as amended hereby, the
Purchase Agreement shall remain in full force and effect.

     2.03. No Waiver. This Amendment is effective only in the specific instance
and for the specific purpose for which it is executed and, except as
specifically set forth herein, shall not be considered a waiver or agreement to
amend as to any provision of the Purchase Agreement (as amended) in the future.

     2.04. Defined Terms. All capitalized terms used but not specifically
defined herein shall have the same meanings given such terms in the Purchase
Agreement unless the context clearly indicates or dictates a contrary meaning.

     2.05. Notices. All notices, requests, demands and other communications
provided for in this Amendment shall be delivered in compliance with Section
11.04 of the Purchase Agreement.

     2.06. Governing Law. THIS AMENDMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF NEW YORK APPLICABLE TO
AGREEMENTS MADE AND TO BE PERFORMED ENTIRELY WITHIN THE STATE OF NEW YORK,
WITHOUT REGARD TO THE CONFLICTS OF LAW PRINCIPLES OF THE STATE OF NEW YORK.

     2.07. Counterparts. This Amendment may be executed in one or more
counterparts, all of which shall be considered one and the same agreement. This
Amendment shall become effective when each party hereto shall have received a
counterpart, or facsimile of a counterpart, of this Amendment, each signed by
the other party or parties hereto or thereto.


                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK.]






               Amendment No. 1 to the Purchase Agreement - Page 6


     IN WITNESS WHEREOF, the parties hereto have executed this Amendment No. 1
or have caused it to be executed by their respective officers thereunto duly
authorized, as of the date first above written.

PURCHASER:

                                        IONICS, INCORPORATED


                                        By: /s/ Stephen Korn
                                           ------------------------------------
                                            Stephen Korn
                                            Vice President and General Counsel







             [Amendment No. 1 to Purchase Agreement Signature Page]

SELLERS:

ECOLOCHEM, INC. SHAREHOLDERS

                                   THE LYMAN B. DICKERSON REVOCABLE TRUST DATED
                                   SEPTEMBER 9, 1996, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:   /s/ Lyman B. Dickerson
                                      -----------------------------------------
                                         LYMAN B. DICKERSON, Trustee


                                   THE RICHARD DICKERSON REVOCABLE TRUST DATED
                                   MARCH 5, 1993, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Trustee


                                   By:   /s/ Marguerite W. Dickerson
                                      -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Trustee







             [Amendment No. 1 to Purchase Agreement Signature Page]

                                   THE DOUGLAS G. DICKERSON REVOCABLE TRUST
                                   DATED JUNE 22, 1988,  OR ANY SUCCESSOR
                                   TRUSTEE, AS AMENDED


                                   By:  /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Trustee


ECOLOCHEM INTERNATIONAL, INC. SHAREHOLDERS

                                   THE LYMAN B. DICKERSON REVOCABLE TRUST DATED
                                   SEPTEMBER 9, 1996, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:  /s/ Lyman B. Dickerson
                                      -----------------------------------------
                                        LYMAN B. DICKERSON, Trustee


                                   THE RICHARD DICKERSON REVOCABLE TRUST DATED
                                   MARCH 5, 1993, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:  /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Trustee


                                   By:   /s/ Marguerite W. Dickerson
                                      -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Trustee


                                   THE DOUGLAS G. DICKERSON REVOCABLE TRUST
                                   DATED JUNE 22, 1988, OR ANY SUCCESSOR
                                   TRUSTEE, AS AMENDED


                                   By:  /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Trustee







             [Amendment No. 1 to Purchase Agreement Signature Page]


                                   THE LYMAN DICKERSON IRREVOCABLE TRUST, DATED
                                   JULY 1, 1991


                                   By:   /s/ Lyman B. Dickerson
                                      -----------------------------------------
                                        LYMAN B. DICKERSON, Trustee


                                   By:   /s/ Charles C. Kline
                                      -----------------------------------------
                                        CHARLES C. KLINE, Independent Trustee


                                   THE RICHARD DICKERSON IRREVOCABLE TRUST
                                   NO. 3, DATED JULY 1, 1991

                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Trustee


                                   By:   /s/ Marguerite W. Dickerson
                                       -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Trustee


                                   By:   /s/ Frederick T. Stant
                                       -----------------------------------------
                                        FREDERICK T. STANT, III,
                                        Independent Trustee


                                   THE DOUGLAS DICKERSON IRREVOCABLE TRUST
                                   NO. 3, DATED JULY 1, 1991


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Trustee


                                   By:   /s/ Frederick T. Stant
                                      -----------------------------------------
                                        FREDERICK T. STANT, III,
                                        Independent Trustee





             [Amendment No. 1 to Purchase Agreement Signature Page]



MOSON HOLDINGS, L.L.C., MEMBERS


                                   THE LYMAN B. DICKERSON REVOCABLE TRUST DATED
                                   SEPTEMBER 9, 1996, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:   /s/ Lyman B. Dickerson
                                      -----------------------------------------
                                        LYMAN B. DICKERSON, Trustee


                                   THE RICHARD DICKERSON REVOCABLE TRUST DATED
                                   MARCH 5, 1993, OR ANY SUCCESSOR TRUSTEE,
                                   AS AMENDED


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Trustee


                                   By:   /s/ Marguerite W. Dickerson
                                      -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Trustee


                                   THE DOUGLAS G. DICKERSON REVOCABLE TRUST
                                   DATED JUNE 22, 1988, OR ANY SUCCESSOR
                                   TRUSTEE, AS AMENDED


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Trustee


                                   THE LYMAN DICKERSON IRREVOCABLE TRUST, DATED
                                   JULY 1, 1991


                                   By:   /s/ Lyman B. Dickerson
                                      -----------------------------------------
                                        LYMAN B. DICKERSON, Trustee


                                   By:   /s/ Charles C. Kline
                                      -----------------------------------------
                                        CHARLES C. KLINE, Independent Trustee







             [Amendment No. 1 to Purchase Agreement Signature Page]


                                   THE RICHARD DICKERSON IRREVOCABLE TRUST
                                   NO. 3, DATED JULY 1, 1991


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Trustee


                                   By:   /s/ Marguerite W. Dickerson
                                      -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Trustee


                                   By:   /s/ Frederick T. Stant
                                      -----------------------------------------
                                        FREDERICK T. STANT, III,
                                        Independent Trustee


                                   THE DOUGLAS DICKERSON IRREVOCABLE TRUST
                                   NO. 3, DATED JULY 1, 1991


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Trustee


                                   By:   /s/ Frederick T. Stant
                                      -----------------------------------------
                                        FREDERICK T. STANT, III,
                                        Independent Trustee






             [Amendment No. 1 to Purchase Agreement Signature Page]

ECOLOCHEM, S.A.R.L. SHAREHOLDERS

                                   /s/ Lyman B. Dickerson
                                   --------------------------------------------
                                   LYMAN B. DICKERSON


                                   /s/ Douglas G. Dickerson
                                   --------------------------------------------
                                   DOUGLAS G. DICKERSON


                                   THE ESTATE OF RICHARD C. DICKERSON


                                   By:   /s/ Douglas G. Dickerson
                                      -----------------------------------------
                                        DOUGLAS G. DICKERSON, Co-Executor


                                   By:   /s/ Marguerite W. Dickerson
                                      -----------------------------------------
                                        MARGUERITE W. DICKERSON, Co-Executor