<PAGE>   1
     As filed with the Securities and Exchange Commission on July 29, 1997.
                                                       Registration No. 333-____

================================================================================

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                      ------------------------------------
                                    FORM S-8
                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                      ------------------------------------
                                SIPEX CORPORATION
             (Exact name of registrant as specified in its charter)

<TABLE>
<CAPTION>

<S>                                                                                   <C>       
                    Massachusetts                                                     04-6135748
(State or other jurisdiction of incorporation or organization)            (I.R.S. Employer Identification No.)
</TABLE>


                                22 Linnell Circle
                         Billerica, Massachusetts 01821
                                 (508) 667- 8700
               (Address of Principal Executive Offices) (Zip Code)
                      ------------------------------------

                             1997 Stock Option Plan
                            (Full title of the plans)
                      ------------------------------------

                                James E. Donegan
                      President and Chief Executive Officer
                                SIPEX Corporation
                                22 Linnell Circle
                         Billerica, Massachusetts 01821
                                 (508) 667- 8700
           (Name and address including zip code and telephone number,
                   including area code, of agent for service)
                      ------------------------------------

                                    Copy to:
                            Timothy C. Maguire, Esq.
                         TESTA, HURWITZ & THIBEAULT, LLP
                       High Street Tower, 125 High Street
                           Boston, Massachusetts 02110
                                 (617) 248-7000

     Approximate date of commencement of proposed sale to the public: As soon as
practicable after this Registration Statement becomes effective.
                  --------------------------------------------



================================================================================
================================================================================

<PAGE>   2


<TABLE>
<CAPTION>
                                       CALCULATION OF REGISTRATION FEE

================================================================================================


                                               Proposed           Proposed
                                                Maximum            Maximum
          Title of              Amount         Offering           Aggregate         Amount of
        Securities to           to be          Price Per          Offering        Registration
        be Registered         Registered        Share               Price             Fee
------------------------------------------------------------------------------------------------
<S>                             <C>            <C>               <C>               <C>      
1997 STOCK OPTION PLAN

Common Stock (Par Value         600,000        $43.94 (1)        $26,362,500       $7,988.64
$.01)
------------------------------------------------------------------------------------------------
</TABLE>
(1)  The price of $43.94 per share, which is the average of the high and low
     prices of the common stock of the registrant reported on the Nasdaq
     National Market on July 23, 1997, is set forth solely for purposes of
     calculating the filing fee pursuant to Rule 457(c) and (h).


<PAGE>   3
                                     -3-



                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS


Item 1. Plan Information.
        ----------------
 
     The documents containing the information specified in this Item 1 will be
sent or given to employees, directors or others as specified by Rule 428(b)(1).
In accordance with the rules and regulations of the Securities and Exchange
Commission (the "Commission") and the instructions to Form S-8, such documents
are not being filed with the Commission either as part of this Registration
Statement or as prospectuses or prospectus supplements pursuant to Rule 424.

Item 2. Registrant Information and Employee Plan Annual Information.
        -----------------------------------------------------------

     The documents containing the information specified in this Item 2 will be
sent or given to employees as specified by Rule 428(b)(1). In accordance with
the rules and regulations of the Commission and the instructions to Form S-8,
such documents are not being filed with the Commission either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


Item 3. Incorporation of Documents by Reference.
        ---------------------------------------

     The following documents filed with the Commission are incorporated by
reference in this Registration Statement:

     (a)  The section entitled "Description of Registrant's Securities to be
          Registered," contained in the Registrant's Registration Statement on
          Form 8-A, filed on March 1, 1996 pursuant to Section 12(g) of the
          Securities Exchange Act of 1934, as amended (the "Exchange Act");

     (b)  Registrant's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1996, as filed with the Commission on March 28, 1997; and

     (c)  Registrants Form 10-Q for the fiscal quarter ended March 29, 1997, as
          filed with the Commission on May 6, 1997.

     All documents subsequently filed with the Commission by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to
the filing of a post-effective amendment which indicates that all securities
offered herein have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference in this Registration
Statement and to be a part hereof from the date of filing of such documents.


<PAGE>   4
                                     -4-



Item 4. Description of Securities.
        -------------------------

     Not applicable.

Item 5. Interest of Named Experts and Counsel.
        -------------------------------------   

     Not applicable.

Item 6. Indemnification of Directors and Officers.
        -----------------------------------------

     Massachusetts General Laws Chapter 156B, Section 67 provides that a
corporation may indemnify its directors and officers to the extent specified in
or authorized by (i) the articles of organization, (ii) a by-law adopted by the
shareholders, or (iii) a vote adopted by the holders of a majority of the shares
of stock entitled to vote on the election of directors. In all instances, the
extent to which a corporation provides indemnification to its directors and
officers under Section 67 is optional. Massachusetts General Laws Chapter 156B,
Section 67 forbids the indemnification of any person with respect to any matter
to which he shall have been adjudicated in any proceeding not to have acted in
good faith in the reasonable belief that his action was in the best interest of
the corporation.

     The Company's Restated By-Laws indemnifies the directors and officers
against liabilities arising out of legal proceedings brought against them by
reason of their status as directors and officers or by reason of their agreeing
to serve, at the request of the Company, as a director or officer of another
organization. Under the Restated By-Laws, each director and officer shall be
indemnified by the Company for all costs and expenses (including attorneys'
fees), judgments, liabilities and amounts paid in settlement of such
proceedings, even if he is not successful on the merits, if he acted in good
faith in the reasonable belief that his action was in the best interest of the
Company. The Board of Directors may authorize advancing litigation expenses to a
director or officer at his request upon receipt of an undertaking by such
director or officer to repay such expenses if it is ultimately determined that
he is not entitled to indemnification for such expense. The Restated By-Laws
provide that the directors and officers of the Company shall be indemnified by
the Company to the fullest extent authorized by Massachusetts Law, as it now
exists or may in the future be amended. In addition, the Restated Articles
provide that the directors of the Company will not be personally liable for
monetary damages to the Company for breaches of their fiduciary duty as
directors, unless they violated their duty of loyalty to the Company or its
shareholders, acted in bad faith, knowingly or intentionally violated the law,
authorized illegal dividends or redemptions or derived an improper personal
benefit from their action as directors.

     The Company has entered into separate indemnification agreements with each
of its directors and executive officers, whereby the Company agreed, among other
things, (i) to indemnify them to the fullest extent permitted by the Business
Corporation Law of the Commonwealth of Massachusetts, subject to specified
limitations, against certain liabilities actually and reasonably incurred by
them in any proceedings in which they are a party that may arise by reason of
their status as directors, officers, employees or agents or may arise by reason
of their serving as such at the request of the Company for another entity and
(ii) to advance their expenses incurred as a result of any proceeding against
them as to which they could be indemnified. The Company intends to enter into
similar separate indemnification agreements with any directors or officers who
may join the Company in the future.


<PAGE>   5
                                     -5-


Item 7. Exemption From Registration Claimed.
        -----------------------------------
 
     Not applicable.

Item 8. Exhibits.
        --------

         Exhibit No.              Description of Exhibit
         ----------               ----------------------   

         Exhibit 4.1    Restated Articles of Organization of the Registrant
                        (filed as Exhibit 3.2 to the Registrant's Registration
                        Statement on Form S-1, File No. 333-1328, and
                        incorporated herein by reference).

         Exhibit 4.2    Restated By-Laws of the Registrant (filed as Exhibit
                        3.3 to the Registrant's Registration Statement on Form
                        S-1, File No. 333-1328, and incorporated herein by
                        reference).

         Exhibit 4.3    Specimen certificate representing the Common Stock of
                        the Registrant (filed as Exhibit 4.1 to the Registrant's
                        Registration Statement on Form S-1, File No. 333-1328,
                        and incorporated herein by reference).


         Exhibit 4.4    1997 Stock Option Plan (filed herewith).

         Exhibit 5.1    Opinion of Testa, Hurwitz & Thibeault, LLP (filed
                        herewith).

         Exhibit 23.1   Consent of Testa, Hurwitz & Thibeault, LLP (contained in
                        Exhibit 5.1).

         Exhibit 23.2   Consent of KPMG Peat Marwick LLP (filed herewith).

         Exhibit 23.2   Consent of Ernst & Young LLP (filed herewith).

         Exhibit 24.1   Power of Attorney (included as part of the signature
                        page to this Registration Statement).



<PAGE>   6
                                     -6-



Item 9. Undertakings.
        ------------

     (a)  The undersigned registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
               made, a post-effective amendment to this Registration Statement:

               (i)   To include any prospectus required by Section 10(a)(3) of
                     the Securities Act of 1933;

               (ii)  To reflect in the prospectus any facts or events arising
                     after the effective date of the Registration Statement (or
                     the most recent post-effective amendment thereof) which,
                     individually or in the aggregate, represent a fundamental
                     change in the information set forth in the Registration
                     Statement;

               (iii) To include any material information with respect to the
                     plan of distribution not previously disclosed in the
                     Registration Statement or any material change to such
                     information in the Registration Statement;

                     PROVIDED, HOWEVER, that paragraphs (a)(1)(i) and (a)(1)(ii)
                     do not apply if the information required to be included in
                     a post-effective amendment by those paragraphs is
                     contained in periodic reports filed with or furnished to
                     the Commission by the Registrant pursuant to Section 13 or
                     Section 15(d) of the Securities Exchange Act of 1934 that
                     are incorporated by reference in the Registration
                     Statement.

          (2)  That, for the purpose of determining any liability under the
               Securities Act of 1933, each such post-effective amendment shall
               be deemed to be a new Registration Statement relating to the
               securities offered therein, and the offering of such securities
               at that time shall be deemed to be the initial bona fide offering
               thereof.

          (3)  To remove from registration by means of a post-effective
               amendment any of the securities being registered which remain
               unsold at the termination of the offering.

     (b)  The undersigned Registrant hereby undertakes that, for purposes of
          determining any liability under the Securities Act of 1933, each
          filing of the Registrant's annual report pursuant to Section 13(a) or
          Section 15(d) of the Securities Exchange Act of 1934 (and, where
          applicable, each filing of an employee benefit plan's annual report
          pursuant to Section 15(d) of the Securities Exchange Act of 1934) that
          is incorporated by reference in the Registration Statement shall be
          deemed to be a new registration statement relating to the securities
          offered therein, and the offering of such securities at that time
          shall be deemed to be the initial bona fide offering thereof.


<PAGE>   7
                                     -7-


     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Securities Act of 1933
          and is, therefore, unenforceable. In the event that a claim for
          indemnification against such liabilities (other than the payment by
          the Registrant of expenses incurred or paid by a director, officer or
          controlling person of the Registrant in the successful defense of any
          action, suit or proceeding) is asserted by such director, officer or
          controlling person in connection with the securities being registered,
          the Registrant will, unless in the opinion of its counsel the matter
          has been settled by controlling precedent, submit to a court of
          appropriate jurisdiction the question whether such indemnification by
          it is against public policy as expressed in the Act and will be
          governed by the final adjudication of such issue.


                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


<PAGE>   8
                                     -8-



                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant,
SIPEX Corporation, certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the Town of Billerica, Commonwealth of Massachusetts, on
this 29th day of July, 1997.

                                      SIPEX Corporation
                                 
                                 
                                      By:     /s/  James E. Donegan
                                              ----------------------------------
                                              James E. Donegan
                                              Chairman, Chief Executive Officer,
                                              President and Clerk
                                 
                                
                                POWER OF ATTORNEY

     We, the undersigned officers and directors of SIPEX Corporation hereby
severally constitute and appoint James E. Donegan and Frank R. DiPietro, and
each of them singly, our true and lawful attorneys, with full power to them and
each of them singly, to sign for us in our names in the capacities indicated
below, any amendments to this Registration Statement on Form S-8 (including
post-effective amendments), and to file the same, with all exhibits thereto and
other documents in connection therewith, with the Securities and Exchange
Commission, and generally to do all things in our names and on our behalf in our
capacities as officers and directors to enable SIPEX Corporation to comply with
the provisions of the Securities Act of 1933, as amended, hereby ratifying and
confirming our signatures as they may be signed by our said attorneys, or any of
them, to said Registration Statement and all amendments thereto.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

             SIGNATURE                      TITLE(S)                    DATE
             ---------                      --------                    ----


     /s/  James E. Donegan              President, Chief           July 29, 1997
---------------------------------          Executive Officer
        James E. Donegan                   (Principal Executive
                                           Officer) and Clerk





<PAGE>   9
                                     -9-




             SIGNATURE                      TITLE(S)                    DATE
             ---------                      --------                    ----

     /s/  Frank R. DiPietro             Executive Vice             July 29, 1997
---------------------------------          President, Chief      
         Frank R. DiPietro                 Financial Officer and
                                           Treasurer (Principal 
                                           Financial Officer and
                                           Principal Accounting 
                                           Officer)             
                                        


     /s/   Daniel Deroux                Director                   July 29, 1997
---------------------------------                         
          Daniel Deroux                                   
                                                          
                                                          
     /s/  Manfred Loeb                  Director                   July 29, 1997
---------------------------------                         
         Manfred Loeb                                     
                                                          
                                                          
     /s/  Lionel H. Olmer               Director                   July 29, 1997
---------------------------------                         
         Lionel H. Olmer                                  
                                                          
                                                          
      /s/  Steward S. Flaschen          Director                   July 29, 1997
---------------------------------                         
          Steward S. Flaschen                             
                                                          

     /s/  John L. Sprague               Director                   July 29, 1997
---------------------------------                         
         John L. Sprague                               


<PAGE>   10

                                  Exhibit Index
                                  -------------



  Exhibit No.             Description of Exhibit
  -----------             ----------------------

      4.1*      Restated Articles of Organization of the
                Registrant

      4.2*      Restated By-Laws of the Registrant

      4.3*      Specimen certificate representing the
                Common Stock of the Registrant

      4.4       1997 Stock Option Plan

      5.1       Opinion of Testa, Hurwitz & Thibeault,
                LLP

     23.1       Consent of Testa, Hurwitz & Thibeault,
                LLP (contained in Exhibit 5.1)

     23.2       Consent of KPMG Peat Marwick LLP

     23.3       Consent of Ernst & Young LLP

     24.1       Power of Attorney (included as part of the
                signature page to this Registration
                Statement)

--------------------------

*    Incorporated by reference to Exhibits to the Registrant's Registration
     Statement on Form S-1, No. 333-1328
[{"type": "S-8", "sequence": "1", "description": "SIPEX CORPORATION", "secsgml_size_bytes": 22671}]
{"company-data": {"conformed-name": "SIPEX CORP", "cik": "0001007800", "assigned-sic": "3674", "irs-number": "046135748", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-32329", "film-number": "97647312"}, "business-address": {"street1": "22 LINNELL CIRCLE", "city": "BILLERICA", "state": "MA", "zip": "01821", "phone": "5086678700"}, "mail-address": {"street1": "22 LINNELL CIRCLE", "city": "BILLERICA", "state": "MA", "zip": "01821"}}
1
     As filed with the Securities and Exchange Commission on July 29, 1997.
                                                       Registration No. 333-____

================================================================================

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                      ------------------------------------
                                    FORM S-8
                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                      ------------------------------------
                                SIPEX CORPORATION
             (Exact name of registrant as specified in its charter)
Massachusetts                                                     04-6135748
(State or other jurisdiction of incorporation or organization)            (I.R.S. Employer Identification No.)
22 Linnell Circle
                         Billerica, Massachusetts 01821
                                 (508) 667- 8700
               (Address of Principal Executive Offices) (Zip Code)
                      ------------------------------------

                             1997 Stock Option Plan
                            (Full title of the plans)
                      ------------------------------------

                                James E. Donegan
                      President and Chief Executive Officer
                                SIPEX Corporation
                                22 Linnell Circle
                         Billerica, Massachusetts 01821
                                 (508) 667- 8700
           (Name and address including zip code and telephone number,
                   including area code, of agent for service)
                      ------------------------------------

                                    Copy to:
                            Timothy C. Maguire, Esq.
                         TESTA, HURWITZ & THIBEAULT, LLP
                       High Street Tower, 125 High Street
                           Boston, Massachusetts 02110
                                 (617) 248-7000

     Approximate date of commencement of proposed sale to the public: As soon as
practicable after this Registration Statement becomes effective.
                  --------------------------------------------

================================================================================
================================================================================
2
CALCULATION OF REGISTRATION FEE

================================================================================================

                                               Proposed           Proposed
                                                Maximum            Maximum
          Title of              Amount         Offering           Aggregate         Amount of
        Securities to           to be          Price Per          Offering        Registration
        be Registered         Registered        Share               Price             Fee
------------------------------------------------------------------------------------------------
1997 STOCK OPTION PLAN

Common Stock (Par Value         600,000        $43.94 (1)        $26,362,500       $7,988.64
$.01)
------------------------------------------------------------------------------------------------
(1)  The price of $43.94 per share, which is the average of the high and low
     prices of the common stock of the registrant reported on the Nasdaq
     National Market on July 23, 1997, is set forth solely for purposes of
     calculating the filing fee pursuant to Rule 457(c) and (h).
3
                                     -3-

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

Item 1. Plan Information.
        ----------------
 
     The documents containing the information specified in this Item 1 will be
sent or given to employees, directors or others as specified by Rule 428(b)(1).
In accordance with the rules and regulations of the Securities and Exchange
Commission (the "Commission") and the instructions to Form S-8, such documents
are not being filed with the Commission either as part of this Registration
Statement or as prospectuses or prospectus supplements pursuant to Rule 424.

Item 2. Registrant Information and Employee Plan Annual Information.
        -----------------------------------------------------------

     The documents containing the information specified in this Item 2 will be
sent or given to employees as specified by Rule 428(b)(1). In accordance with
the rules and regulations of the Commission and the instructions to Form S-8,
such documents are not being filed with the Commission either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference.
        ---------------------------------------

     The following documents filed with the Commission are incorporated by
reference in this Registration Statement:

     (a)  The section entitled "Description of Registrant's Securities to be
          Registered," contained in the Registrant's Registration Statement on
          Form 8-A, filed on March 1, 1996 pursuant to Section 12(g) of the
          Securities Exchange Act of 1934, as amended (the "Exchange Act");

     (b)  Registrant's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1996, as filed with the Commission on March 28, 1997; and

     (c)  Registrants Form 10-Q for the fiscal quarter ended March 29, 1997, as
          filed with the Commission on May 6, 1997.

     All documents subsequently filed with the Commission by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to
the filing of a post-effective amendment which indicates that all securities
offered herein have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference in this Registration
Statement and to be a part hereof from the date of filing of such documents.
4
                                     -4-

Item 4. Description of Securities.
        -------------------------

     Not applicable.

Item 5. Interest of Named Experts and Counsel.
        -------------------------------------   

     Not applicable.

Item 6. Indemnification of Directors and Officers.
        -----------------------------------------

     Massachusetts General Laws Chapter 156B, Section 67 provides that a
corporation may indemnify its directors and officers to the extent specified in
or authorized by (i) the articles of organization, (ii) a by-law adopted by the
shareholders, or (iii) a vote adopted by the holders of a majority of the shares
of stock entitled to vote on the election of directors. In all instances, the
extent to which a corporation provides indemnification to its directors and
officers under Section 67 is optional. Massachusetts General Laws Chapter 156B,
Section 67 forbids the indemnification of any person with respect to any matter
to which he shall have been adjudicated in any proceeding not to have acted in
good faith in the reasonable belief that his action was in the best interest of
the corporation.

     The Company's Restated By-Laws indemnifies the directors and officers
against liabilities arising out of legal proceedings brought against them by
reason of their status as directors and officers or by reason of their agreeing
to serve, at the request of the Company, as a director or officer of another
organization. Under the Restated By-Laws, each director and officer shall be
indemnified by the Company for all costs and expenses (including attorneys'
fees), judgments, liabilities and amounts paid in settlement of such
proceedings, even if he is not successful on the merits, if he acted in good
faith in the reasonable belief that his action was in the best interest of the
Company. The Board of Directors may authorize advancing litigation expenses to a
director or officer at his request upon receipt of an undertaking by such
director or officer to repay such expenses if it is ultimately determined that
he is not entitled to indemnification for such expense. The Restated By-Laws
provide that the directors and officers of the Company shall be indemnified by
the Company to the fullest extent authorized by Massachusetts Law, as it now
exists or may in the future be amended. In addition, the Restated Articles
provide that the directors of the Company will not be personally liable for
monetary damages to the Company for breaches of their fiduciary duty as
directors, unless they violated their duty of loyalty to the Company or its
shareholders, acted in bad faith, knowingly or intentionally violated the law,
authorized illegal dividends or redemptions or derived an improper personal
benefit from their action as directors.

     The Company has entered into separate indemnification agreements with each
of its directors and executive officers, whereby the Company agreed, among other
things, (i) to indemnify them to the fullest extent permitted by the Business
Corporation Law of the Commonwealth of Massachusetts, subject to specified
limitations, against certain liabilities actually and reasonably incurred by
them in any proceedings in which they are a party that may arise by reason of
their status as directors, officers, employees or agents or may arise by reason
of their serving as such at the request of the Company for another entity and
(ii) to advance their expenses incurred as a result of any proceeding against
them as to which they could be indemnified. The Company intends to enter into
similar separate indemnification agreements with any directors or officers who
may join the Company in the future.
5
                                     -5-

Item 7. Exemption From Registration Claimed.
        -----------------------------------
 
     Not applicable.

Item 8. Exhibits.
        --------

         Exhibit No.              Description of Exhibit
         ----------               ----------------------   

         Exhibit 4.1    Restated Articles of Organization of the Registrant
                        (filed as Exhibit 3.2 to the Registrant's Registration
                        Statement on Form S-1, File No. 333-1328, and
                        incorporated herein by reference).

         Exhibit 4.2    Restated By-Laws of the Registrant (filed as Exhibit
                        3.3 to the Registrant's Registration Statement on Form
                        S-1, File No. 333-1328, and incorporated herein by
                        reference).

         Exhibit 4.3    Specimen certificate representing the Common Stock of
                        the Registrant (filed as Exhibit 4.1 to the Registrant's
                        Registration Statement on Form S-1, File No. 333-1328,
                        and incorporated herein by reference).

         Exhibit 4.4    1997 Stock Option Plan (filed herewith).

         Exhibit 5.1    Opinion of Testa, Hurwitz & Thibeault, LLP (filed
                        herewith).

         Exhibit 23.1   Consent of Testa, Hurwitz & Thibeault, LLP (contained in
                        Exhibit 5.1).

         Exhibit 23.2   Consent of KPMG Peat Marwick LLP (filed herewith).

         Exhibit 23.2   Consent of Ernst & Young LLP (filed herewith).

         Exhibit 24.1   Power of Attorney (included as part of the signature
                        page to this Registration Statement).
6
                                     -6-

Item 9. Undertakings.
        ------------

     (a)  The undersigned registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
               made, a post-effective amendment to this Registration Statement:

               (i)   To include any prospectus required by Section 10(a)(3) of
                     the Securities Act of 1933;

               (ii)  To reflect in the prospectus any facts or events arising
                     after the effective date of the Registration Statement (or
                     the most recent post-effective amendment thereof) which,
                     individually or in the aggregate, represent a fundamental
                     change in the information set forth in the Registration
                     Statement;

               (iii) To include any material information with respect to the
                     plan of distribution not previously disclosed in the
                     Registration Statement or any material change to such
                     information in the Registration Statement;

                     PROVIDED, HOWEVER, that paragraphs (a)(1)(i) and (a)(1)(ii)
                     do not apply if the information required to be included in
                     a post-effective amendment by those paragraphs is
                     contained in periodic reports filed with or furnished to
                     the Commission by the Registrant pursuant to Section 13 or
                     Section 15(d) of the Securities Exchange Act of 1934 that
                     are incorporated by reference in the Registration
                     Statement.

          (2)  That, for the purpose of determining any liability under the
               Securities Act of 1933, each such post-effective amendment shall
               be deemed to be a new Registration Statement relating to the
               securities offered therein, and the offering of such securities
               at that time shall be deemed to be the initial bona fide offering
               thereof.

          (3)  To remove from registration by means of a post-effective
               amendment any of the securities being registered which remain
               unsold at the termination of the offering.

     (b)  The undersigned Registrant hereby undertakes that, for purposes of
          determining any liability under the Securities Act of 1933, each
          filing of the Registrant's annual report pursuant to Section 13(a) or
          Section 15(d) of the Securities Exchange Act of 1934 (and, where
          applicable, each filing of an employee benefit plan's annual report
          pursuant to Section 15(d) of the Securities Exchange Act of 1934) that
          is incorporated by reference in the Registration Statement shall be
          deemed to be a new registration statement relating to the securities
          offered therein, and the offering of such securities at that time
          shall be deemed to be the initial bona fide offering thereof.
7
                                     -7-

     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Securities Act of 1933
          and is, therefore, unenforceable. In the event that a claim for
          indemnification against such liabilities (other than the payment by
          the Registrant of expenses incurred or paid by a director, officer or
          controlling person of the Registrant in the successful defense of any
          action, suit or proceeding) is asserted by such director, officer or
          controlling person in connection with the securities being registered,
          the Registrant will, unless in the opinion of its counsel the matter
          has been settled by controlling precedent, submit to a court of
          appropriate jurisdiction the question whether such indemnification by
          it is against public policy as expressed in the Act and will be
          governed by the final adjudication of such issue.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
8
                                     -8-

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant,
SIPEX Corporation, certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the Town of Billerica, Commonwealth of Massachusetts, on
this 29th day of July, 1997.

                                      SIPEX Corporation
                                 
                                 
                                      By:     /s/  James E. Donegan
                                              ----------------------------------
                                              James E. Donegan
                                              Chairman, Chief Executive Officer,
                                              President and Clerk
                                 
                                
                                POWER OF ATTORNEY

     We, the undersigned officers and directors of SIPEX Corporation hereby
severally constitute and appoint James E. Donegan and Frank R. DiPietro, and
each of them singly, our true and lawful attorneys, with full power to them and
each of them singly, to sign for us in our names in the capacities indicated
below, any amendments to this Registration Statement on Form S-8 (including
post-effective amendments), and to file the same, with all exhibits thereto and
other documents in connection therewith, with the Securities and Exchange
Commission, and generally to do all things in our names and on our behalf in our
capacities as officers and directors to enable SIPEX Corporation to comply with
the provisions of the Securities Act of 1933, as amended, hereby ratifying and
confirming our signatures as they may be signed by our said attorneys, or any of
them, to said Registration Statement and all amendments thereto.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

             SIGNATURE                      TITLE(S)                    DATE
             ---------                      --------                    ----

     /s/  James E. Donegan              President, Chief           July 29, 1997
---------------------------------          Executive Officer
        James E. Donegan                   (Principal Executive
                                           Officer) and Clerk
9
                                     -9-

             SIGNATURE                      TITLE(S)                    DATE
             ---------                      --------                    ----

     /s/  Frank R. DiPietro             Executive Vice             July 29, 1997
---------------------------------          President, Chief      
         Frank R. DiPietro                 Financial Officer and
                                           Treasurer (Principal 
                                           Financial Officer and
                                           Principal Accounting 
                                           Officer)             
                                        

     /s/   Daniel Deroux                Director                   July 29, 1997
---------------------------------                         
          Daniel Deroux                                   
                                                          
                                                          
     /s/  Manfred Loeb                  Director                   July 29, 1997
---------------------------------                         
         Manfred Loeb                                     
                                                          
                                                          
     /s/  Lionel H. Olmer               Director                   July 29, 1997
---------------------------------                         
         Lionel H. Olmer                                  
                                                          
                                                          
      /s/  Steward S. Flaschen          Director                   July 29, 1997
---------------------------------                         
          Steward S. Flaschen                             
                                                          

     /s/  John L. Sprague               Director                   July 29, 1997
---------------------------------                         
         John L. Sprague
10

                                  Exhibit Index
                                  -------------

  Exhibit No.             Description of Exhibit
  -----------             ----------------------

      4.1*      Restated Articles of Organization of the
                Registrant

      4.2*      Restated By-Laws of the Registrant

      4.3*      Specimen certificate representing the
                Common Stock of the Registrant

      4.4       1997 Stock Option Plan

      5.1       Opinion of Testa, Hurwitz & Thibeault,
                LLP

     23.1       Consent of Testa, Hurwitz & Thibeault,
                LLP (contained in Exhibit 5.1)

     23.2       Consent of KPMG Peat Marwick LLP

     23.3       Consent of Ernst & Young LLP

     24.1       Power of Attorney (included as part of the
                signature page to this Registration
                Statement)

--------------------------

*    Incorporated by reference to Exhibits to the Registrant's Registration
     Statement on Form S-1, No. 333-1328