Document:

Exhibit 10.13

             FIRST AMENDMENT TO STOCK PURCHASE AGREEMENTS AND WAIVER

     This First  Amendment  and Waiver  ("Amendment"),  effective as of March 5,
2002 to the Stock  Purchase  Agreements,  dated March 30,  1999 and  February 1,
2001,  respectively (the "Purchase  Agreements"),  between Hudson  Technologies,
Inc., a New York corporation (the "Company"), and Fleming US Discovery Fund III,
L.P. ("Discovery").

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

     WHEREAS, the Company and Discovery are parties to the Purchase Agreements;

     WHEREAS, pursuant to the Purchase Agreements,  Discovery purchased from the
Company an  aggregate of 81,874  shares of the  Company's  Series A  Convertible
Preferred Stock, par value $.01 per share;

     WHEREAS,  the Nasdaq  Stock  Market,  Inc.  has advised the Company that in
order to  maintain  the listing of its Common  Stock on Nasdaq the Company  must
amend  the  anti-dilution  provisions  relating  to  the  determination  of  the
conversion  price of the  Series A  Convertible  Preferred  Stock  contained  in
Section 5(d)(ii) of the Company's  Certificate of Incorporation (the "Conversion
Price") to provide that the Conversion Price shall not be less than $1.78;

     WHEREAS,  the Company and  Discovery  desire to maintain the listing of the
Company's Common Stock on Nasdaq;

     WHEREAS, certain provisions of the Purchase Agreements prohibit the Company
from amending  Section  5(d)(ii) of its  Certificate  of  Incorporation  without
obtaining the prior consent of Discovery;

     WHEREAS, pursuant to Section 15 of the Purchase Agreements, the Company and
Discovery  desire  to  waive  the  provisions  of  Sections  8.10 and 9.1 of the
Purchase  Agreements  to provide for the  amendment  to Section  5(d)(ii) of the
Company's  Certificate  of  Incorporation  to provide for the  adjustment in the
determination  of the Conversion Price as noted above, and to add a provision to
the Purchase  Agreements  providing that as long as the Fleming  Holders own any
shares of Series A  Convertible  Preferred  Stock the Company  will not sell any
additional  shares of its Common Stock for a per share  consideration  less than
the  Conversion  Price of the Series A Convertible  Preferred  Stock or issue or
sell any securities  convertible into or exchangeable for shares of Common Stock
at a per share  conversion or exercise price less that the  Conversion  Price of
the Series A Convertible  Preferred  Stock without the prior written  consent of
the Fleming Holders.

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

     1. Amendment to the Purchase Agreements. The Purchase Agreements are hereby
amended by adding new Section 9.A as follows:

          9A. Additional Negative Covenants

          "9A.1 Restrictions on Sales of Additional Securities.

     Without the prior written consent of the Fleming Holders,  the Company will
not issue or sell any additional  shares of its Common Stock or any evidences of
indebtedness,   shares  of  preferred  stock  or  other   securities  which  are
convertible  into  or  exchangeable,  with  or  without  payment  of  additional
consideration  in  cash  or  property,  into  shares  of  Common  Stock,  for  a
consideration  per share that is less than the conversion  price of the Series A
Convertible Preferred Stock in effect immediately prior to such issuance or sale
other than any options or other securities that may be

                                       47
<PAGE>

issued under any of the Company's  Stock Option or Stock  Incentive  Plans.  The
foregoing  restrictions  shall terminate and be of no further force or effect if
the Fleming  Holders no longer own any shares of Series A Convertible  Preferred
Stock."

     2. Consent to Amendment to Certificate of  Incorporation.  The  undersigned
hereby agrees to the amendment to Section 5(d)(ii) of the Company's  Certificate
of  Incorporation to provide that if the Company shall issue or sell "Additional
Shares of Stock" (as defined in the Company's Certificate of Incorporation) at a
price per share less than the Conversion  Price in effect  immediately  prior to
such  issuance or sale,  then the  Conversion  Price as to the Common Stock into
which the Series A Convertible  Preferred Stock is convertible shall be adjusted
to equal the higher of (a) the consideration paid per Additional Share of Stock,
or (b)$1.78.  The  undersigned  understands  that by virtue of the provisions of
Section 5(d)(iii) of the Company's  Certificate of Incorporation,  the foregoing
amendment  to the  determination  of the  Conversion  Price also  applies to any
warrants or other securities  convertible into Common Stock that the Company may
issue.

     3.  Waiver.  Sections  8.10 and 9.1 of the Purchase  Agreements  are hereby
waived  solely for the purpose of the Company  effecting  the  amendment  to the
Company's  Certificate  of  Incorporation  described  in  paragraph  2  of  this
Agreement.

     4.  Severability.  If any provision of this  Agreement  shall be held to be
invalid or unenforceable,  such invalidity or unenforceability shall attach only
to such  provision and shall not affect or render invalid or  unenforceable  any
other provision of this  Agreement,  and this Agreement shall be construed as if
such provision had been drawn so as not to be invalid or unenforceable.

     5. Notices. Any notice or other communication required to, or which may, be
given  to any  party  hereunder  shall be in  writing  and  shall  be  delivered
personally or by overnight  courier to such party (or the  President  thereof in
the case of the Company or if mailed,  by registered or certified mail,  postage
prepaid, return receipt requested,  addressed to such other party at the address
first set forth above and shall be deemed given in all cases upon  receipt.  Any
party may change the address to which  notices are to be sent by giving  written
notice of any change in the manner provided herein.

     6. Entire  Agreement.  This  Agreement  represents and expresses the entire
understanding  and  agreement  between the parties  with  respect to the subject
matter  hereof and may not be modified or  terminated  except by an agreement in
writing signed by both of the parties hereto. Except specifically amended hereby
the Purchase Agreements shall remain in full force and effect in accordance with
their respective terms.

     7.  Definitions.  All capitalized  terms not otherwise defined herein shall
have the meanings ascribed to them in the Purchase Agreements.

     8. Benefit of Agreement.  The provisions of this Agreement shall be binding
upon and shall inure to the benefit of the successors  and permitted  assigns of
the parties hereto.

     9.  Governing  Law.  This  Agreement  shall be deemed to be a contract made
under the laws of the State of New York and for all purposes  shall be construed
in accordance with the laws of said state.

                                       48
<PAGE>

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

                                       HUDSON TECHNOLOGIES, INC.

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

                                       Name: Kevin J. Zugibe
                                       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
                                           ------------------
                                       Name: Robert L. Burr
                                       Title:Exhibit 10.14

             FIRST AMENDMENT TO STOCK PURCHASE AGREEMENTS AND WAIVER

     This First  Amendment  and Waiver  ("Amendment"),  effective as of March 5,
2002 to the Stock  Purchase  Agreements,  dated March 30,  1999 and  February 1,
2001,  respectively (the "Purchase  Agreements"),  between Hudson  Technologies,
Inc., a New York corporation (the "Company"),  and Fleming US Discovery Offshore
Fund III, L.P. ("Discovery").

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

     WHEREAS, the Company and Discovery are parties to the Purchase Agreements;

     WHEREAS, pursuant to the Purchase Agreements,  Discovery purchased from the
Company an  aggregate of 13,126  shares of the  Company's  Series A  Convertible
Preferred Stock, par value $.01 per share;

     WHEREAS,  the Nasdaq  Stock  Market,  Inc.  has advised the Company that in
order to  maintain  the listing of its Common  Stock on Nasdaq the Company  must
amend  the  anti-dilution  provisions  relating  to  the  determination  of  the
conversion  price of the  Series A  Convertible  Preferred  Stock  contained  in
Section 5(d)(ii) of the Company's  Certificate of Incorporation (the "Conversion
Price") to provide that the Conversion Price shall not be less than $1.78;

     WHEREAS,  the Company and  Discovery  desire to maintain the listing of the
Company's Common Stock on Nasdaq;

     WHEREAS, certain provisions of the Purchase Agreements prohibit the Company
from amending  Section  5(d)(ii) of its  Certificate  of  Incorporation  without
obtaining the prior consent of Discovery;

     WHEREAS, pursuant to Section 15 of the Purchase Agreements, the Company and
Discovery  desire  to  waive  the  provisions  of  Sections  8.10 and 9.1 of the
Purchase  Agreements  to provide for the  amendment  to Section  5(d)(ii) of the
Company's  Certificate  of  Incorporation  to provide for the  adjustment in the
determination  of the Conversion Price as noted above, and to add a provision to
the Purchase  Agreements  providing that as long as the Fleming  Holders own any
shares of Series A  Convertible  Preferred  Stock the Company  will not sell any
additional  shares of its Common Stock for a per share  consideration  less than
the  Conversion  Price of the Series A Convertible  Preferred  Stock or issue or
sell any securities  convertible into or exchangeable for shares of Common Stock
at a per share  conversion or exercise price less that the  Conversion  Price of
the Series A Convertible  Preferred  Stock without the prior written  consent of
the Fleming Holders.

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

     1. Amendment to the Purchase Agreements. The Purchase Agreements are hereby
amended by adding new Section 9.A as follows:

          9A. Additional Negative Covenants

          "9A.1 Restrictions on Sales of Additional Securities.

     Without the prior written consent of the Fleming Holders,  the Company will
not issue or sell any additional  shares of its Common Stock or any evidences of
indebtedness,   shares  of  preferred  stock  or  other   securities  which  are
convertible  into  or  exchangeable,  with  or  without  payment  of  additional
consideration  in  cash  or  property,  into  shares  of  Common  Stock,  for  a
consideration  per share that is less than the conversion  price of the Series A
Convertible Preferred Stock in effect immediately prior to such issuance or sale
other than any options or other  securities  that may be issued under any of the
Company's  Stock Option or Stock  Incentive  Plans.  The foregoing  restrictions
shall  terminate and

                                       50
<PAGE>

be of no further force or effect if the Fleming Holders no longer own any shares
of Series A Convertible Preferred Stock."

     2. Consent to Amendment to Certificate of  Incorporation.  The  undersigned
hereby agrees to the amendment to Section 5(d)(ii) of the Company's  Certificate
of  Incorporation to provide that if the Company shall issue or sell "Additional
Shares of Stock" (as defined in the Company's Certificate of Incorporation) at a
price per share less than the Conversion  Price in effect  immediately  prior to
such  issuance or sale,  then the  Conversion  Price as to the Common Stock into
which the Series A Convertible  Preferred Stock is convertible shall be adjusted
to equal the higher of (a) the consideration paid per Additional Share of Stock,
or (b)$1.78.  The  undersigned  understands  that by virtue of the provisions of
Section 5(d)(iii) of the Company's  Certificate of Incorporation,  the foregoing
amendment  to the  determination  of the  Conversion  Price also  applies to any
warrants or other securities  convertible into Common Stock that the Company may
issue.

     3.  Waiver.  Sections  8.10 and 9.1 of the Purchase  Agreements  are hereby
waived  solely for the purpose of the Company  effecting  the  amendment  to the
Company's  Certificate  of  Incorporation  described  in  paragraph  2  of  this
Agreement.

     4.  Severability.  If any provision of this  Agreement  shall be held to be
invalid or unenforceable,  such invalidity or unenforceability shall attach only
to such  provision and shall not affect or render invalid or  unenforceable  any
other provision of this  Agreement,  and this Agreement shall be construed as if
such provision had been drawn so as not to be invalid or unenforceable.

     5. Notices. Any notice or other communication required to, or which may, be
given  to any  party  hereunder  shall be in  writing  and  shall  be  delivered
personally or by overnight  courier to such party (or the  President  thereof in
the case of the Company or if mailed,  by registered or certified mail,  postage
prepaid, return receipt requested,  addressed to such other party at the address
first set forth above and shall be deemed given in all cases upon  receipt.  Any
party may change the address to which  notices are to be sent by giving  written
notice of any change in the manner provided herein.

     6. Entire  Agreement.  This  Agreement  represents and expresses the entire
understanding  and  agreement  between the parties  with  respect to the subject
matter  hereof and may not be modified or  terminated  except by an agreement in
writing signed by both of the parties hereto. Except specifically amended hereby
the Purchase Agreements shall remain in full force and effect in accordance with
their respective terms.

     7.  Definitions.  All capitalized  terms not otherwise defined herein shall
have the meanings ascribed to them in the Purchase Agreements.

     8. Benefit of Agreement.  The provisions of this Agreement shall be binding
upon and shall inure to the benefit of the successors  and permitted  assigns of
the parties hereto.

     9.  Governing  Law.  This  Agreement  shall be deemed to be a contract made
under the laws of the State of New York and for all purposes  shall be construed
in accordance with the laws of said state.

                                       51

<PAGE>

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

                                       HUDSON TECHNOLOGIES, INC.

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

                                       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
                                           ------------------
                                       Name: Robert L. Burr
                                       Title:

                                       52

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