Document:

Exhibit 10.25

                FIRST AMENDMENT TO REGISTRATION RIGHTS AGREEMENT
                        effective as of February 16, 2001

     This First Amendment (this "Amendment"), effective as of February 16, 2001,
to  the  REGISTRATION  RIGHTS  AGREEMENT,  dated  as  of  March  30,  1999  (the
"Registration Rights Agreement"),  among Hudson  Technologies,  Inc., a New York
corporation (the "Company"),  Fleming US Discovery Fund III, L.P. and Fleming US
Discovery Offshore Fund III, L.P. (collectively, the "Fleming Funds").

                              W I T N E S S E T H:
                               - - - - - - - - - -

     WHEREAS,  the Company and the Fleming Funds are parties to the Registration
Rights Agreement;

     WHEREAS,  pursuant to the Stock Purchase Agreements,  dated as of March 30,
1999,  between the Company  and each of the Fleming  Funds (the "Stock  Purchase
Agreements"),  the Fleming Funds purchased 65,000 shares of the Company's Series
A Convertible Preferred Stock, par value $.01 per share (the "Series A Preferred
Stock");

     WHEREAS,  the Company and the Fleming  Funds  entered  into Stock  Purchase
Agreements,   dated  as  of  February   16,  2001  (the  "2001  Stock   Purchase
Agreements"), whereby the Fleming Funds purchased 30,000 shares of the Company's
Series A Convertible Preferred Stock, par value $.01 per share; and

     WHEREAS, pursuant to Section 11.4 of the Registration Rights Agreement, the
Company and the Fleming  Funds desire to (a) amend the first  WHEREAS  clause in
the Registration  Rights  Agreement to include the shares purchased  pursuant to
the 2001 Stock Purchase  Agreements,  (b) amend the second WHEREAS clause in the
Registration  Rights  Agreement  to  reflect  the  inclusion  of the 2001  Stock
Purchase Agreements and (c) amend the definition of "Stock Purchase  Agreements"
in the  Registration  Rights  Agreement  to  include  the  2001  Stock  Purchase
Agreements;

     NOW, THEREFORE,  in consideration of the foregoing and of the covenants and
agreements contained herein and for other good and valuable  consideration,  the
receipt of which is hereby  acknowledged,  the parties  hereto  hereby  agree as
follows:

     1. Capitalized  terms used but not otherwise  defined herein shall have the
respective meanings set forth in the Registration Rights Agreement.  Capitalized
terms  defined  in  this  Amendment  shall  be  deemed  to  be  defined  in  the
Registration  Rights  Agreement  with the meaning

<PAGE>

given to them herein. In the event of any inconsistency between the definitions,
terms or provisions of this Amendment and of the Registration  Rights Agreement,
this Amendment shall control.

     2. The first WHEREAS clause of the Registration  Rights Agreement is hereby
deleted and replaced in its entirety with the following:

     "WHEREAS,  pursuant to the terms of Stock Purchase Agreements,  dated as of
     March 30, 1999, and the Stock Purchase  Agreements,  dated as of February [
     ], 2001 (the "2001 Stock  Purchase  Agreements"),  the  Fleming  Funds have
     purchased 65,000 shares and 30,000 shares,  respectively,  of the Company's
     Series A Preferred Stock, par value $.01 per shares."

     3. The second WHEREAS clause of the Registration Rights Agreement is hereby
deleted and replaced in its entirety with the following:

     "WHEREAS,  (a) it was a condition of the  transactions  contemplated by the
     Stock  Purchase  Agreements  and (b) it is a condition to the  transactions
     contemplated  by the 2001 Stock Purchase  Agreements,  that the Company and
     Fleming enter into this Agreement  whereby the Company shall grant, and the
     Investors  shall obtain,  the rights  relating to the  registration  of the
     Registrable  Securities  under  the  Securities  Act,  as set forth in this
     Agreement;"

     4. The  definition of "Stock  Purchase  Agreements"  is hereby  deleted and
replaced in its entirety with the following:

     ""Stock  Purchase  Agreements"  means,  collectively,  the  separate  Stock
     Purchase  Agreements,  dated as of March 30, 1999,  between the Company and
     each of the Fleming Funds, and the 2001 Stock Purchase Agreements."

     5. Section  11.6(d)(ii) is hereby deleted and replaced in its entirety with
the following:

        "If to the Company, to:

        Hudson Technologies, Inc.
        275 North Middletown Road
        Pearl River, NY  10965
        Facsimile No.:  (914) 368-2540
        Attn:  Stephen P. Mandracchia

<PAGE>

        with a copy to:

        Blank Rome Tenzer Greenblatt LLP
        405 Lexington Avenue
        New York, NY  10174
        Facsimile No.:  (212) 885-5001
        Attn:  Ethan Seer, Esq.

     6. The Registration  Rights Agreement shall remain in full force and effect
in accordance with its terms, except as expressly amended hereby.

     7.  This  Amendment  may be  executed  in one or more  counterparts,  which
together will constitute a single agreement.

     8. This Amendment shall be governed by and construed in accordance with the
laws of the State of New York.

     9. This Amendment,  together with the Registration Rights Agreement and all
agreements or documents  herein or therein referred or incorporated by reference
contains  the entire  agreement  between the parties with respect to the subject
matter hereof and  supersedes any and all prior  agreements and  understandings,
oral or written, with respect to such subject matter.

                  [remainder of page intentionally left blank]

<PAGE>

     IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the
date first written above.

                                   HUDSON TECHNOLOGIES, INC.

                                   By: /s/ Kevin J. Zugibe
                                       ------------------------------
                                       Name:
                                       Title:

                                   FLEMING US DISCOVERY FUND III, L.P.

                                   By: FLEMING US DISCOVERY
                                        PARTNERS, L.P.,
                                       its general partner

                                       By: FLEMING US DISCOVERY, LLC, its
                                           general partner

                                           By: /s/ Robert L. Burr
                                              ---------------------------------
                                                    Robert L. Burr, member

                                   FLEMING US DISCOVERY OFFSHORE
                                      FUND III, L.P.

                                   By:   FLEMING US DISCOVERY
                                            PARTNERS, L.P.,
                                         its general partner

                                         By: FLEMING US DISCOVERY, LLC,
                                             its general partner

                                                By: /s/ Robert L. Burr
                                                   ----------------------------
                                                     Robert L. Burr, memberExhibit 10.26

                   FIRST AMENDMENT TO STOCKHOLDERS' AGREEMENT
                        effective as of February 16, 2001

     This First Amendment (this "Amendment"),  effective as of February 16, 2001
to the STOCKHOLDERS'  AGREEMENT,  dated as of March 30, 1999 (the "Stockholders'
Agreement"),  among  Hudson  Technologies,  Inc.,  a New York  corporation  (the
"Company"),  Kevin J. Zugibe  ("KJZ"),  Thomas P. Zugibe  ("TPZ") and Stephen P.
Mandracchia  ("Mandracchia" and,  collectively with KJZ and TPZ,  "Management"),
and Fleming US Discovery  Fund III, L.P. and Fleming US Discovery  Offshore Fund
III, L.P. (collectively, the "Fleming Funds").

                              W I T N E S S E T H:
                               - - - - - - - - - -

     WHEREAS,  the Company,  Management and the Fleming Funds are parties to the
Stockholders' Agreement;

     WHEREAS,  pursuant to the Stock Purchase Agreements,  dated as of March 30,
1999,  between the Company  and each of the Fleming  Funds (the "Stock  Purchase
Agreements"),  the Fleming Funds purchased 65,000 shares of the Company's Series
A Convertible Preferred Stock, par value $.01 per share (the "Series A Preferred
Stock");

     WHEREAS,  the Company and the Fleming  Funds  entered  into Stock  Purchase
Agreements,   dated  as  of  February   16,  2001  (the  "2001  Stock   Purchase
Agreements"), whereby the Fleming Funds purchased 30,000 shares of the Company's
Series A Convertible Preferred Stock, par value $.01 per share; and

     WHEREAS,  pursuant  to Section  6(a) of the  Stockholders'  Agreement,  the
Company,  Management  and the Fleming  Funds desire to amend the  definition  of
"Series A  Preferred  Stock" in the first  WHEREAS  clause of the  Stockholders'
Agreement to include the shares  purchased  pursuant to the 2001 Stock  Purchase
Agreements;

     NOW, THEREFORE,  in consideration of the foregoing and of the covenants and
agreements contained herein and for other good and valuable  consideration,  the
receipt of which is hereby  acknowledged,  the parties  hereto  hereby  agree as
follows:

     1. Capitalized  terms used but not otherwise  defined herein shall have the
respective meanings set forth in the Stockholders' Agreement.  Capitalized terms
defined in this  Amendment  shall be deemed to be  defined in the  Stockholders'
Agreement  with  the  meaning  given  to  them  herein.

<PAGE>

In the event of any inconsistency  between the definitions,  terms or provisions
of this  Amendment and of the  Stockholders'  Agreement,  this  Amendment  shall
control.

     2. The  first  WHEREAS  clause  of the  Stockholders'  Agreement  is hereby
deleted and replaced in its entirety with the following:

     "WHEREAS,  pursuant to the terms of Stock Purchase Agreements,  dated as of
     March 30,  1999  (the  "1999  Stock  Purchase  Agreements"),  and the Stock
     Purchase  Agreements,  dated as of  February  16,  2001  (the  "2001  Stock
     Purchase Agreements" and, together with the 1999 Stock Purchase Agreements,
     the "Stock Purchase  Agreements"),  the Fleming Funds have purchased 65,000
     shares and 30,000 shares, respectively, of the Company's Series A Preferred
     Stock, par value $.01 per shares (the "Series A Preferred Stock")."

     3. The  third  WHEREAS  clause  of the  Stockholders'  Agreement  is hereby
deleted and replaced in its entirety with the following:

     "WHEREAS,  it was a condition  precedent to the  Company's  and the Fleming
     Fund's respective  obligations to consummate the transactions  contemplated
     by the Stock Purchase Agreements that the parties hereto shall have entered
     into this Agreement; and"

     4. Section  6(d)(ii) of the  Stockholders  Agreement is hereby  deleted and
replaced in its entirety with the following:

             "If to the Company, to:

             Hudson Technologies, Inc.
             275 North Middletown Road
             Pearl River, NY  10965
             Facsimile No.:  (914) 368-2540
             Attn:  Stephen P. Mandracchia

             with a copy to:

             Blank Rome Tenzer Greenblatt LLP
             405 Lexington Avenue
             New York, NY  10174
             Facsimile No.:  (212) 885-5001
             Attn:  Ethan Seer, Esq."

<PAGE>

     5. The  Stockholders'  Agreement  shall  remain in full force and effect in
accordance with its terms, except as expressly amended hereby.

     6.  This  Amendment  may be  executed  in one or more  counterparts,  which
together will constitute a single agreement.

     7. This Amendment shall be governed by and construed in accordance with the
laws of the State of New York.

     8.  This  Amendment,  together  with the  Stockholders'  Agreement  and all
agreements or documents herein or therein referred or incorporated by reference,
contains  the entire  agreement  between the parties with respect to the subject
matter hereof and  supersedes any and all prior  agreements and  understandings,
oral or written, with respect to such subject matter.

                  [remainder of page intentionally left blank]

<PAGE>

     IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the
date first written above.

                                 HUDSON TECHNOLOGIES, INC.

                                 By: /s/ Kevin J. Zugibe
                                    ---------------------------
                                    Name:  Kevin J. Zugibe
                                    Title: Chairman and Chief Executive Officer

                                   /s/ Kevin J. Zugibe
                                   -----------------------------
                                     Kevin J. Zugibe

                                   /s/ Thomas P. Zugibe
                                   -----------------------------
                                     Thomas P. Zugibe

                                   /s/ Stephen P. Mandracchia
                                   -----------------------------
                                     Stephen P. Mandracchia

<PAGE>

                            FLEMING US DISCOVERY FUND III, L.P.

                            By: FLEMING US DISCOVERY
                                   PARTNERS, L.P.,
                                its general partner

                                By: FLEMING US DISCOVERY, LLC, its
                                    general partner

                                    By: /s/ Robert L. Burr
                                       ----------------------------------
                                         Robert L. Burr, member

                            FLEMING US DISCOVERY OFFSHORE
                               FUND III, L.P.

                            By: FLEMING US DISCOVERY
                                   PARTNERS, L.P.,
                                its general partner

                                By: FLEMING US DISCOVERY, LLC,
                                    its general partner

                                    By: /s/ Robert L. Burr
                                       ----------------------------------
                                         Robert L. Burr, member

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