<PAGE>
                                SIPEX CORPORATION

                         INSTRUCTION SHEET FOR INVESTORS

            (to be read in conjunction with the entire Stock Purchase
                     Agreement and Investor Questionnaire)


A.       Complete the following items in the Stock Purchase Agreement and in
         the Investor Questionnaire:

         1.       Provide the information regarding the Investor requested on
                  the signature page to the Stock Purchase Agreement and in the
                  Investor Questionnaire. The Stock Purchase Agreement must be
                  executed by an individual authorized to bind the Investor.

         2.       Return the signed Stock Purchase Agreement and Investor
                  Questionnaire to:

                  Wilson Sonsini Goodrich & Rosati,
                  Professional Corporation
                  Attn:  Jack Helfand
                  650 Page Mill Road
                  Palo Alto, CA  94304
                  Telephone:  650-493-9300
                  Fax:  650-493-6811

                  And fax copies to:

                  Adams, Harkness & Hill, Inc.
                  Attn: Garin K. Arevian
                  Phone:  (617) 788-1543
                  Fax:  (617) 371-3798

                  An executed original Stock Purchase Agreement and Investor
                  Questionnaire or a fax thereof must be received by 5:00 p.m.
                  Boston time on a date to be determined and distributed to the
                  Investor at a later date.

B.       Instructions regarding the transfer of funds for the purchase of
         Shares will be faxed to the Investor at a later date.

C.       To resell the Shares after the Registration Statement covering the
         Shares is effective:

                  1. Provided that a suspension of the Registration Statement is
         not then in effect pursuant to the terms of the Stock Purchase
         Agreement, the Investor may sell Shares under the Registration
         Statement upon delivery of a current Prospectus to the transferee. The
         Company will provide an adequate number of current prospectuses to each
         investor and to supply copies to any other parties requiring such
         prospectuses upon request.

                  2. The Investor must also deliver to the Company's transfer
         agent, with a copy to the Company, a Certificate of Subsequent Sale in
         the form attached to the Stock Purchase Agreement, so that the Shares
         may be properly transferred.


<PAGE>

                            STOCK PURCHASE AGREEMENT

Sipex Corporation
22 Linnell Circle
Billerica, MA  01821

Ladies and Gentlemen:

         The undersigned, _________________________________ (the "INVESTOR"),
hereby confirms its agreement with you as follows:

1. This Stock Purchase Agreement (the "AGREEMENT") is made as of April __, 2002
between SIPEX Corporation, a Massachusetts corporation (the "COMPANY"), and the
Investor.

2. The Company has authorized the sale and issuance of up to 3,000,000 shares
(the "SHARES") of common stock of the Company, $0.01 par value per share (the
"COMMON STOCK"), subject to adjustment by the Company's Board of Directors, to
certain investors in a private placement (the "OFFERING").

3. The Company and the Investor agree that the Investor will purchase from the
Company and the Company will issue and sell to the Investor ___________ Shares,
for a purchase price of $_______ per share (the "SHARE Price"), or an aggregate
purchase price of $_______________, pursuant to the Terms and Conditions for
Purchase of Shares attached hereto as Annex I and incorporated herein by
reference as if fully set forth herein. Unless otherwise requested by the
Investor, certificates representing the Shares purchased by the Investor will be
registered in the Investor's name and address as set forth below.

4. The Investor represents that, except as set forth below, (a) neither it, nor
any group of which it is a member or to which it is related, beneficially owns
(including the right to acquire or vote) any securities of the Company and (b)
it has no direct or indirect affiliation or association with any member of the
National Association of Securities Dealers, Inc. ("NASD") as of the date hereof.
Exceptions:

_______________________________________________________________________________

_______________________________________________________________________________.

          (If no exceptions, write "none." If left blank, response will
                            be deemed to be "none.")

         Please confirm that the foregoing correctly sets forth the agreement
between us by signing in the space provided below for that purpose. By executing
this Agreement, you acknowledge that the Company may use the information in
paragraph 4 above and the name and address information below in preparation of
the Registration Statement (as defined in Annex I).

AGREED AND ACCEPTED:
-------------------

SIPEX CORPORATION                   INVESTOR


By:                                 By:
   --------------------------          -----------------------------------------
     Name:
     Title:                         Print Name:
                                                --------------------------------

                                    Title:
                                           -------------------------------------

                                    Address:
                                             -----------------------------------


                                    Tax ID No.:
                                                --------------------------------

                                    Contact name:
                                                  ------------------------------

                                    Telephone:
                                               ---------------------------------

                                    Name in which Shares
                                    should be registered
                                    (if different):
                                                    ----------------------------


<PAGE>


                                     ANNEX I

                   TERMS AND CONDITIONS FOR PURCHASE OF SHARES

         1.       AUTHORIZATION AND SALE OF THE SHARES. Subject to the terms
and conditions of this Agreement, the Company has authorized the sale of up to
3,000,000 Shares. The Company reserves the right to increase or decrease this
number.

         2.       AGREEMENT TO SELL AND PURCHASE THE SHARES; SUBSCRIPTION DATE.

                  2.1 At the Closing (as defined in Section 3), the Company will
sell to the Investor, and the Investor will purchase from the Company, upon the
terms and conditions hereinafter set forth, the number of Shares set forth in
Section 3 of the Stock Purchase Agreement to which these Terms and Conditions
are attached, at the Share Price set forth therein.

                  2.2 The Company may enter into the same form of Stock Purchase
Agreement including these Terms and Conditions, with certain other investors
(the "OTHER INVESTORS") and expects to complete sales of Shares to them. (The
Investor and the Other Investors are hereinafter sometimes collectively referred
to as the "INVESTORS," and the Stock Purchase Agreements to which these Terms
and Conditions are attached and the Stock Purchase Agreements executed by the
Other Investors are hereinafter sometimes collectively referred to as the
"AGREEMENTS.") The Company may accept executed Agreements from Investors for the
purchase of Shares commencing upon the date on which the Company provides the
Investors with the proposed Share Price and concluding upon the date (the
"SUBSCRIPTION DATE") on which the Company has notified Adams, Harkness & Hill,
Inc. and Deutsche Bank Securities Inc. (in their capacity as placement agents
for the Shares, the "PLACEMENT AGENTS") in writing that the Company is no longer
accepting Agreements from Investors for the purchase of Shares. The Company may
not enter into any Agreements after the Subscription Date.

                  2.3 Investor acknowledges that the Company intends to pay the
Placement Agents a fee in respect of the sale of Shares to the Investor.

         3. DELIVERY OF THE SHARES AT CLOSING. The completion of the purchase
and sale of the Shares (the "CLOSING") shall occur on April __, 2002 (the
"CLOSING DATE"), at the offices of Wilson Sonsini Goodrich & Rosati,
Professional Corporation, the Company's legal counsel, or such other date as is
mutually agreed to by the Company and the Investor. At the Closing, the Company
shall deliver to the Investor one or more stock certificates (such delivery to
be deemed effective upon placement by the Company of such certificate(s) with a
nationally reconized overnight courier service for delivery to Investor at the
address noted on the signature page of the Stock Purchase Agreement)
representing the number of Shares set forth in Section 3 of the Stock Purchase
Agreement, each such certificate to be registered in the name of the Investor
or, if so indicated on the signature page of the Stock Purchase Agreement, in
the name of a nominee designated by the Investor.

         The Company's obligation to issue the Shares to the Investor shall be
subject to the following conditions, any one or more of which may be waived by
the Company: (a) receipt by the Company of a certified or official bank check or
wire transfer of funds in the full amount of the purchase price for the Shares
being purchased hereunder as set forth in Section 3 of the Stock Purchase
Agreement; (b) completion of the purchases and sales under the Agreements with
the Other Investors; and (c) the accuracy of the representations and warranties
made by the Investors and the fulfillment of those undertakings of the Investors
to be fulfilled prior to the Closing.

         The Investor's obligation to purchase the Shares shall be subject to
the following conditions, any one or more of which may be waived by the
Investor: (a) the representations and warranties of the Company set forth herein
shall be true and correct as of the Closing Date in all material respects; (b)
the Investor shall have received such documents as such Investor shall
reasonably have requested, including an opinion of Company counsel as to the
matters set forth in Section 4.2, and as to exemption from the registration
requirements of the Securities Act of 1933, as amended (the "SECURITIES ACT"),
of the sale of the Shares; (c) aggregate gross proceeds from the sale of Shares
in this Offering shall be at least $15,000,000 and not more than $27,000,000;
and (d) the Company shall have provided to the Investor a certificate as to the
satisfaction of the closing conditions.

<PAGE>


         4.       REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY.
The Company hereby represents and warrants to, and covenants with, the Investor,
as follows:

                  4.1 ORGANIZATION. The Company is duly organized and validly
existing in good standing under the laws of the jurisdiction of its
organization. Each of the Company and its subsidiaries listed on EXHIBIT 21.1 to
its Annual Report on Form 10-K for the year ended December 31, 2001 (the
"SUBSIDIARIES") has full power and authority to own, operate and occupy its
properties and to conduct its business as presently conducted and as described
in the Company's Annual Report on Form 10-K for the year ended December 31,
2001, including all exhibits, supplements and amendments thereto (the "SEC
FILINGS"), and is registered or qualified to do business and in good standing in
each jurisdiction in which the failure to be so qualified would have a material
adverse effect upon the business, financial condition, properties or operations
of the Company and its Subsidiaries, considered as one enterprise ("MATERIAL
ADVERSE EFFECT"), and to the Company's knowledge, no proceeding has been
instituted in any such jurisdiction, revoking, limiting or curtailing, or
seeking to revoke, limit or curtail, such power and authority or qualification.

                  4.2 DUE AUTHORIZATION AND VALID ISSUANCE. The Company has all
requisite power and authority to execute, deliver and perform its obligations
under the Agreements, and the Agreements have been duly authorized and validly
executed and delivered by the Company and constitute legal, valid and binding
agreements of the Company enforceable against the Company in accordance with
their terms, except as rights to indemnity and contribution may be limited by
state or federal securities laws or the public policy underlying such laws,
except as enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' and contracting
parties' rights generally and except as enforceability may be subject to general
principles of equity (regardless of whether such enforceability is considered in
a proceeding in equity or at law). The Shares being purchased by the Investor
hereunder will, upon issuance pursuant to the terms hereof, be duly authorized,
validly issued, fully paid and nonassessable.

                  4.3 NON-CONTRAVENTION. The execution and delivery of the
Agreements, the issuance and sale of the Shares to be sold by the Company under
the Agreements, the fulfillment of the terms of the Agreements and the
consummation of the transactions contemplated thereby will not (A) conflict with
or constitute a violation of, or default (with the passage of time or otherwise)
under (i) any bond, debenture, note or other evidence of indebtedness, lease,
contract, indenture, mortgage, deed of trust, loan agreement, joint venture or
other agreement or instrument to which the Company or any Subsidiary is a party
or by which it or any of its Subsidiaries or their respective properties are
bound when such violation, conflict or default would have a Material Adverse
Effect, (ii) the articles of organization, by-laws or other organizational
documents of the Company or any Subsidiary, or (iii) any law, administrative
regulation, ordinance or order of any court or governmental agency, arbitration
panel or authority applicable to the Company or any Subsidiary or their
respective properties when such violation, conflict or default would have a
Material Adverse Effect, or (B) result in the creation or imposition of any
lien, encumbrance, claim, security interest or restriction whatsoever upon any
of the properties or assets of the Company or any Subsidiary or an acceleration
of indebtedness pursuant to any obligation, agreement or condition contained in
any bond, debenture, note or any other evidence of indebtedness or any
indenture, mortgage, deed of trust or any other agreement or instrument to which
the Company or any Subsidiary is a party or by which any of them is bound or to
which any of the property or assets of the Company or any Subsidiary is subject
where such lien or other restriction would have a Material Adverse Effect. No
consent, approval, authorization or other order of, or registration,
qualification or filing with, any regulatory body, administrative agency, or
other governmental body in the United States or any other person is required for
the execution and delivery of the Agreements and the valid issuance and sale of
the Shares to be sold pursuant to the Agreements, other than such as have been
made or obtained, and except for any post-closing securities filings or
notifications required to be made under federal or state securities laws.

                  4.4 CAPITALIZATION. The Company's authorized capital stock as
of March 31, 2002 consisted of (i) 40,000,000 shares of Common Stock, $0.01 par
value per share, of which 24,908,934 shares are issued and outstanding and (ii)
1,000,000 shares of Preferred Stock, $0.01 par value per share, of which no
shares are issued and outstanding. The Company has not issued any capital stock
since that date other than pursuant to (i) employee benefit plans disclosed in
the SEC Filings, or (ii) outstanding warrants or options disclosed in the SEC
Filings. The

                                       3
<PAGE>

Shares to be sold by the Company pursuant to the Agreements have been duly
authorized, and when issued and paid for in accordance with the terms of the
Agreements, will be duly and validly issued, fully paid and nonassessable. The
outstanding shares of capital stock of the Company have been duly and validly
issued and are fully paid and nonassessable, have been issued in compliance with
all federal and state securities laws, and were not issued in violation of any
preemptive rights or similar rights to subscribe for or purchase securities.
Except as set forth in or contemplated by the SEC Filings, there are no
outstanding rights (including, without limitation, preemptive rights), warrants
or options to acquire, or instruments convertible into or exchangeable for, any
unissued shares of capital stock or other equity interest in the Company or any
Subsidiary, or any contract, commitment, agreement, understanding or arrangement
of any kind to which the Company is a party or of which the Company has
knowledge and relating to the issuance or sale of any capital stock of the
Company or any Subsidiary, any such convertible or exchangeable securities or
any such rights, warrants or options. Without limiting the foregoing, no
preemptive right, co-sale right, right of first refusal, registration right
(except as set forth herein), or other similar right exists with respect to the
Shares or the issuance and sale thereof. No further approval or authorization of
any stockholder, the Board of Directors of the Company or others is required for
the issuance and sale of the Shares. The Company owns the entire equity interest
in each of its Subsidiaries, free and clear of any pledge, lien, security
interest, encumbrance, claim or equitable interest, other than as described in
the SEC Filings. Except as disclosed in the SEC Filings, there are no
stockholders agreements, voting agreements or other similar agreements with
respect to the Common Stock to which the Company is a party or, to the knowledge
of the Company, between or among any of the Company's stockholders.

                  4.5 LEGAL PROCEEDINGS. There is no material legal or
governmental proceeding pending or, to the knowledge of the Company, threatened
to which the Company or any Subsidiary is or may be a party or of which the
business or property of the Company or any Subsidiary is subject that is not
disclosed in the SEC Filings.

                  4.6 NO VIOLATIONS. Neither the Company nor any Subsidiary (i)
is in violation of its charter, bylaws, or other organizational document, (ii)
is in violation of any law, administrative regulation, ordinance or order of any
court or governmental agency, arbitration panel or authority applicable to the
Company or any Subsidiary, which violation, individually or in the aggregate,
would be reasonably likely to have a Material Adverse Effect, or (iii) is in
default (and there exists no condition which, with the passage of time or
otherwise, would constitute a default) in any respect in the performance of any
bond, debenture, note or any other evidence of indebtedness in any indenture,
mortgage, deed of trust or any other agreement or instrument to which the
Company or any Subsidiary is a party or by which the Company or any Subsidiary
is bound or by which the properties of the Company or any Subsidiary are bound,
which would be reasonably likely to have a Material Adverse Effect.

                  4.7 GOVERNMENTAL PERMITS, ETC. With the exception of the
matters which are dealt with separately in Sections 4.1, 4.12, 4.13, and 4.14,
each of the Company and its Subsidiaries has all necessary franchises, licenses,
certificates and other authorizations from any foreign, federal, state or local
government or governmental agency, department, or body that are currently
necessary for the operation of the business of the Company and its Subsidiaries
as currently conducted and as described in the SEC Filings except where the
failure to currently possess will not have a Material Adverse Effect.

                  4.8 INTELLECTUAL PROPERTY. Except as specifically disclosed in
the SEC Filings (i) each of the Company and its Subsidiaries owns or possesses
sufficient rights to use all patents, patent rights, trademarks, copyrights,
licenses, inventions, trade secrets, trade names and know-how (collectively,
"INTELLECTUAL PROPERTY") described or referred to in the SEC Filings as owned or
possessed by it or that are necessary for the conduct of its business as now
conducted or as described in the SEC Filings except where the failure to
currently own or possess would not have a Material Adverse Effect, and (ii) to
the Company's knowledge, neither the Company nor any of its Subsidiaries is
infringing, or has received any notice of or has any knowledge of any asserted
infringement by the Company or any of its Subsidiaries of, any rights of a third
party with respect to any Intellectual Property that, individually or in the
aggregate, would have a Material Adverse Effect.

                  4.9 FINANCIAL STATEMENTS. The financial statements of the
Company and the related notes contained in the SEC Filings present fairly, in
accordance with generally accepted accounting principles, the financial position
of the Company and its Subsidiaries as of the dates indicated, and the results
of its operations and cash flows for the periods therein specified. Such
financial statements (including the related notes) have been

                                       4
<PAGE>

prepared in accordance with generally accepted accounting principles
applied on a consistent basis throughout the periods therein specified, except
as disclosed in the SEC Filings. The other financial information contained in
the SEC Filings has been prepared on a basis consistent with the financial
statements of the Company.

                  4.10 NO MATERIAL ADVERSE CHANGE. Except as otherwise disclosed
in the SEC Filings and the Company's April 3, 2002 press release entitled "SIPEX
Puts 1st Quarter Revenue at $16 Million, Below Prior Forecasts," since December
31, 2001, the Company has not experienced or suffered an event or condition
which has caused a Material Adverse Effect.

                  4.11 DISCLOSURE. The information contained in the Company's
April 3, 2002 press release entitled "SIPEX Puts 1st Quarter Revenue at $16
Million, Below Prior Forecasts" and SEC Filings, excluding exhibits thereto,
including without limitation all information incorporated therein by reference,
as of the date hereof and as of the Closing Date, did not and shall not contain
an untrue statement of a material fact or omit to state a material fact required
to be stated therein or necessary to make the statements therein, in light of
the circumstances under which they were made, not misleading.

                  4.12 NASDAQ COMPLIANCE. The Company's Common Stock is
registered pursuant to Section 12(g) of the Exchange Act and is listed on The
Nasdaq Stock Market, Inc. National Market (the "NASDAQ NATIONAL MARKET"), and
the Company has taken no action designed to, or likely to have the effect of,
terminating the registration of the Common Stock under the Exchange Act or
de-listing the Common Stock from the Nasdaq National Market, nor has the Company
received any notification that the Securities and Exchange Commission (the
"SEC") or the NASD is contemplating terminating such registration or listing.

                  4.13 REPORTING STATUS. The Company has filed in a timely
manner (or pursuant to applicable extension periods) all documents that the
Company was required to file under the Securities Exchange Act of 1934, as
amended (the "EXCHANGE ACT") during the twelve (12) months preceding the date of
this Agreement (the "SEC DOCUMENTS"). The SEC Documents, as amended, and all
other materials filed with the SEC during such period complied in all material
respects with the SEC's requirements as of their respective filing dates or
amendment dates, and the information contained therein did not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein in light of the
circumstances under which they were made not misleading.

                  4.14 LISTING. The Company shall comply with all requirements
of the NASD with respect to the issuance of the Shares and the listing thereof
on the Nasdaq National Market.

                  4.15 NO MANIPULATION OF STOCK. The Company has not taken and
will not, in violation of applicable law, take, any action designed to or that
might reasonably be expected to cause or result in stabilization or manipulation
of the price of the Common Stock to facilitate the sale or resale of the Shares.

                  4.16 COMPANY NOT AN "INVESTMENT COMPANY". The Company has been
advised of the rules and requirements under the Investment Company Act of 1940,
as amended (the "INVESTMENT COMPANY ACT"). The Company is not, and immediately
after receipt of payment for the Shares will not be, an "investment company" or
an entity "controlled" by an "investment company" within the meaning of the
Investment Company Act and shall conduct its business in a manner so that it
will not become subject to the Investment Company Act.

         5.       REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE INVESTOR.

                  5.1 The Investor represents and warrants to, and covenants
with, the Company that: (i) the Investor is an "accredited investor" as defined
in Regulation D under the Securities Act and the Investor is also knowledgeable,
sophisticated and experienced in making, and is qualified to make decisions with
respect to investments in shares presenting an investment decision like that
involved in the purchase of the Shares, including investments in securities
issued by the Company and investments in comparable companies, and has
requested, received, reviewed and considered all information it deemed relevant
in making an informed decision to purchase the Shares; (ii) the Investor is
acquiring the number of Shares set forth on the signature page hereto in the
ordinary course of its business and for its own account for investment only and
with no present intention of distributing any of

                                       5
<PAGE>

such Shares or any arrangement or understanding with any other persons
regarding the distribution of such Shares; (iii) the Investor will not, directly
or indirectly, offer, sell, pledge, transfer or otherwise dispose of (or solicit
any offers to buy, purchase or otherwise acquire or take a pledge of) any of the
Shares except in compliance with the Securities Act, applicable state securities
laws and the respective rules and regulations promulgated thereunder; (iv) the
Investor has answered all questions on the signature page hereto for use in
preparation of the Registration Statement and the answers thereto are true and
correct as of the date hereof and will be true and correct as of the Closing
Date; (v) the Investor will notify the Company immediately of any change in any
of such information until such time as the Investor has sold all of its Shares
or until the Company is no longer required to keep the Registration Statement
effective; (vi) the Investor and Investor's representatives have been solely
responsible for the Investor's own "due diligence" investigation of the Company
and its management and business, for its own analysis of the merits and risks of
this investment, and for Investor's own analysis of the fairness and
desirability of the terms of the investment; and (vii) the Investor has, in
connection with its decision to purchase the number of Shares set forth on the
signature page hereto, relied only upon the SEC Filings and the representations
and warranties of the Company contained herein. Investor understands that its
acquisition of the Shares has not been registered under the Securities Act or
registered or qualified under any state securities law in reliance on specific
exemptions therefrom, which exemptions may depend upon, among other things, the
bona fide nature of the Investor's investment intent as expressed herein.
Investor has completed or caused to be completed and delivered to the Company
the Investor Questionnaire attached hereto as EXHIBIT A, which questionnaire is
true and correct in all material respects.

                  5.2 The Investor acknowledges and agrees that no action has
been or will be taken in any jurisdiction outside the United States by the
Company that would permit an offering of the Shares in any jurisdiction outside
the United States where legal action by the Company for that purpose is
required. Each Investor outside the United States will comply with all
applicable laws and regulations in each foreign jurisdiction in which it
purchases, offers, sells or delivers Shares or has in its possession or
distributes any offering material, in all cases at its own expense.

                  5.3 The Investor hereby covenants with the Company not to make
any sale of the Shares without complying with the provisions of this Agreement
and without causing the prospectus delivery requirement under the Securities Act
to be satisfied, and the Investor acknowledges that the certificates evidencing
the Shares will be imprinted with a legend that prohibits their transfer except
in accordance therewith. The Investor acknowledges that there may occasionally
be times when the Company determines that it must suspend the use of the
Prospectus forming a part of the Registration Statement, as set forth in Section
7.2(c).

                  5.4 The Investor further represents and warrants to, and
covenants with, the Company that (i) the Investor has full right, power,
authority and capacity to enter into this Agreement and to consummate the
transactions contemplated hereby and has taken all necessary action to authorize
the execution, delivery and performance of this Agreement, and (ii) this
Agreement constitutes a valid and binding obligation of the Investor enforceable
against the Investor in accordance with its terms, except as enforceability may
be limited by applicable bankruptcy, insolvency, reorganization, moratorium or
similar laws affecting creditors' and contracting parties' rights generally and
except as enforceability may be subject to general principles of equity
(regardless of whether such enforceability is considered in a proceeding in
equity or at law) and except as the indemnification and contribution agreements
of the Investors herein may be legally unenforceable.

                  5.5 The Investor will not, prior to the effectiveness of the
Registration Statement, if then prohibited by law or regulation: (i) sell, offer
to sell, solicit offers to buy, dispose of, loan, pledge or grant any right with
respect to the Shares (collectively, a "DISPOSITION"); or (ii) engage in any
hedging or other transaction that is designed to or could reasonably be expected
to lead to or result in a Disposition of the Shares by the Investor or any
person or entity.

                  5.6 The Investor understands that nothing in the SEC Filings,
this Agreement or any other materials presented to the Investor in connection
with the purchase and sale of the Shares constitutes legal, tax or investment
advice. The Investor has consulted such legal, tax and investment advisors as
it, in its sole discretion, has deemed necessary or appropriate in connection
with its purchase of Shares.

                                       6
<PAGE>

         6. SURVIVAL OF REPRESENTATIONS, WARRANTIES AND AGREEMENTS.
Notwithstanding any investigation made by any party to this Agreement, all
covenants, agreements, representations and warranties made by the Company and
the Investor herein shall survive the execution of this Agreement, the delivery
to the Investor of the Shares being purchased and the payment therefor.

         7.       REGISTRATION OF THE SHARES; COMPLIANCE WITH THE SECURITIES
ACT.

                  7.1       REGISTRATION PROCEDURES AND OTHER MATTERS. The
         Company shall:

                            (a)     subject to receipt of necessary information
from the Investors after prompt request from the Company to the Investors to
provide such information, prepare and file with the SEC, within twenty (20) days
after the Closing Date, a registration statement on Form S-3 (the "REGISTRATION
STATEMENT") to enable the resale of the Shares by the Investors from time to
time through the automated quotation system of the Nasdaq National Market or in
privately-negotiated transactions;

                            (b)     use its best efforts, subject to receipt of
necessary information from the Investors after prompt request from the Company
to the Investors to provide such information, to cause the Registration
Statement to become effective within sixty (60) days after the Registration
Statement is filed by the Company; PROVIDED, HOWEVER, that in the event that the
Registration Statement is not declared effective on or before the 90th day
following the Closing Date (the "PENALTY DATE"), the Company shall pay to each
Investor liquidated damages in an amount equal to 0.25% of the total purchase
price of the Shares purchased by such Investor pursuant to this Agreement for
each week after the Penalty Date that the Registration Statement is not declared
effective;

                            (c)     prepare and file with the SEC such
amendments and supplements to the Registration Statement and the Prospectus used
in connection therewith as may be necessary to keep the Registration Statement
current and effective for a period not to exceed the earlier of (i) the second
anniversary of the Closing Date, with respect to each Investor's Shares
purchased hereunder, (ii) the first date on which the Investor may sell all
Shares then held by the Investor within a ninety (90) day period pursuant to
Rule 144(k) under the Securities Act or any other rule of similar effect, or
(iii) such time as all Shares purchased by such Investor in this Offering have
been sold; (d) furnish to the Investor with respect to the Shares registered
under the Registration Statement such number of copies of the Registration
Statement, prospectuses and preliminary prospectuses in conformity with the
requirements of the Securities Act and such other documents as the Investor may
reasonably request, in order to facilitate the public sale or other disposition
of all or any of the Shares by the Investor; provided, however, that the
obligation of the Company to deliver copies of prospectuses or preliminary
prospectuses to the Investor shall be subject to the receipt by the Company of
reasonable assurances from the Investor that the Investor will comply with the
applicable provisions of the Securities Act and of such other securities or blue
sky laws as may be applicable in connection with any use of such prospectuses or
preliminary prospectuses;

                            (e)     file documents required of the Company for
normal blue sky clearance (x) in all U.S. jurisdictions in which any of the
Shares are originally sold and (y) in states where specified in writing by
Investor; PROVIDED, HOWEVER, that, as to clause (y), the Company shall not be
required to qualify to do business or consent to service of process in any
jurisdiction in which it is not now so qualified or has not so consented;

                            (f)     bear all expenses in connection with the
procedures in paragraph (a) through (e) of this Section 7.1 and the registration
of the Shares pursuant to the Registration Statement; other than fees and
expenses, if any, of counsel or other advisors to the Investor or underwriting
discounts, brokerage fees and commissions incurred by the Investor; and

                            (g)     advise the Investor promptly after it shall
receive notice or obtain knowledge of the issuance of any stop order by the SEC
delaying or suspending the effectiveness of the Registration Statement or of the
initiation or threat of any proceeding for that purpose; and it will promptly
use its reasonable best efforts to prevent the issuance of any stop order or to
obtain its withdrawal at the earliest possible moment if such stop order should
be issued.

                                       7
<PAGE>

         Notwithstanding anything to the contrary herein, the Registration
Statement shall cover only the Shares. In no event at any time before the
Registration Statement becomes effective with respect to the Shares shall the
Company publicly announce or file any other registration statement (other than a
Registration Statement on Form S-8) without the prior written consent of a
majority in interest of the Investors; provided, however, that the filing by the
Company of an amendment to a previously filed registration statement shall not
be subject to such requirement; provided, that such amendment does not increase
the number of shares of Common Stock or other securities subject to the
registration statement.

                  7.2       TRANSFER OF SHARES AFTER REGISTRATION; SUSPENSION.

                            (a)     The Investor agrees that it will not effect
any disposition of the Shares or its right to purchase the Shares that would
constitute a sale within the meaning of the Securities Act except as
contemplated in the Registration Statement referred to in Section 7.1 and as
described below or as otherwise permitted by law, and that it will promptly
notify the Company of any changes in the information set forth in the
Registration Statement regarding the Investor or its plan of distribution.

                            (b)     Except in the event that paragraph (c) below
applies, the Company shall (i) if deemed necessary by the Company, prepare and
file from time to time with the SEC a post-effective amendment to the
Registration Statement or a supplement to the related Prospectus or a supplement
or amendment to any document incorporated therein by reference or file any other
required document so that such Registration Statement will not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading, and
so that, as thereafter delivered to purchasers of the Shares being sold
thereunder, such Prospectus will not contain an untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
to make the statements therein, in light of the circumstances under which they
were made, not misleading; (ii) provide the Investor copies of any documents
filed pursuant to Section 7.2(b)(i); and (iii) inform each Investor that the
Company has complied with its obligations in Section 7.2(b)(i) (or that, if the
Company has filed a post-effective amendment to the Registration Statement which
has not yet been declared effective, the Company will notify the Investor to
that effect, will use its best efforts to secure the effectiveness of such
post-effective amendment as promptly as possible and will promptly notify the
Investor pursuant to Section 7.2(b)(i) hereof when the amendment has become
effective).

                            (c)     Subject to paragraph (d) below, in the event
(i) of any request by the SEC or any other federal or state governmental
authority during the period of effectiveness of the Registration Statement for
amendments or supplements to a Registration Statement or related Prospectus or
for additional information; (ii) of the issuance by the SEC or any other federal
or state governmental authority of any stop order suspending the effectiveness
of a Registration Statement or the initiation of any proceedings for that
purpose; (iii) of the receipt by the Company of any notification with respect to
the suspension of the qualification or exemption from qualification of any of
the Shares for sale in any jurisdiction or the initiation or threatening of any
proceeding for such purpose; or (iv) of any event or circumstance which, upon
the advice of its counsel, would necessitate the making of any changes in the
Registration Statement or Prospectus, or any document incorporated or deemed to
be incorporated therein by reference, so that, in the case of the Registration
Statement, it will not contain any untrue statement of a material fact or any
omission to state a material fact required to be stated therein or necessary to
make the statements therein not misleading, and that in the case of the
Prospectus, it will not contain any untrue statement of a material fact or any
omission to state a material fact required to be stated therein or necessary to
make the statements therein, in the light of the circumstances under which they
were made, not misleading; then the Company shall, deliver a certificate in
writing to the Investor (the "SUSPENSION NOTICE") to the effect of the foregoing
and, upon receipt of such Suspension Notice, the Investor will refrain from
selling any Shares pursuant to the Registration Statement (a "SUSPENSION") until
the Investor's receipt of copies of a supplemented or amended Prospectus
prepared and filed by the Company, or until it is advised in writing by the
Company that the current Prospectus may be used, and has received copies of any
additional or supplemental filings that are incorporated or deemed incorporated
by reference in any such Prospectus. In the event of any Suspension, the Company
will use its reasonable best efforts to cause the use of the Prospectus so
suspended to be resumed as expeditiously as practicable after the delivery of a
Suspension Notice to the Investor. In addition to, and without limiting any
other remedies (including, without limitation, at law or at

                                       8
<PAGE>

equity) available to Investor, the Investor shall be entitled to specific
performance in the event that the Company fails to comply with the provisions of
this Section 7.2(c).

                            (d)     Notwithstanding the foregoing paragraphs of
this Section 7.2, the Investor shall not be prohibited from selling Shares under
the Registration Statement as a result of Suspensions on more than one occasion
of not more than thirty (30) days in any twelve (12) month period, unless, in
the good faith judgment of the Company's Board of Directors, upon advice of
counsel, the sale of Shares under the Registration Statement in reliance on this
paragraph 7.2(d) would be reasonably likely to cause a violation of the
Securities Act or the Exchange Act and result in liability to the Company. If a
Suspension is in effect for more than thirty (30) days (consecutive or
non-consecutive) in any twelve (12) month period, the Company shall, on the
thirty-first (31st) day of the Suspension and each thirtieth (30th) day
thereafter, pay to each Investor liquidated damages in an amount in cash equal
to the product of (x) 0.01 multiplied by (y) the Share Price for each Common
Share then held by such Investor (the "SUSPENSION PENALTY"), until the earlier
of (x) the date upon which the Suspension is lifted and (y) the date upon which
the aggregate Suspension Penalty paid to such Investor is equal to the product
of (x) 0.09 multiplied by (y) the Share Price for each Common Share then held by
such Investor.

                            (e)     Provided that a Suspension is not then in
effect, the Investor may sell Shares under the Registration Statement, provided
that it arranges for delivery of a current Prospectus to the transferee of such
Shares.

                  7.3       INDEMNIFICATION.  For the purpose of this
Section 7.3:

                  (i)       the term "SELLING STOCKHOLDER" shall include the
Investor and any officer, director, trustee or affiliate of such Investor; and

                  (ii) the term "REGISTRATION STATEMENT" shall include any final
Prospectus, exhibit, supplement or amendment included in or relating to the
Registration Statement referred to in Section 7.1.

                            (a)     The Company agrees to indemnify and hold
harmless each Selling Stockholder from and against any losses, claims, damages
or liabilities to which such Selling Stockholder may become subject (under the
Securities Act or otherwise) insofar as such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) arise out of, or are
based upon (i) any untrue statement, or alleged untrue statement, or any
omission or alleged omission to state a material fact required to be stated in a
Registration Statement, or necessary to make the statements therein, in light of
the circumstances under which they were made not misleading, at the time of
effectiveness of the Registration Statement, (ii) violations of federal or state
securities laws, or (iii) any failure by the Company to fulfill any undertaking
included in the Registration Statement, and the Company will reimburse such
Selling Stockholder on demand for any reasonable legal or other expenses
reasonably incurred in investigating, defending or preparing to defend any such
action, proceeding or claim, PROVIDED, HOWEVER, that the Company shall not be
liable in any such case to the extent that such loss, claim, damage or liability
arises out of, or is based upon, (x) an untrue statement made or alleged untrue
statement or omission or alleged omission in such Registration Statement in
reliance upon and in conformity with written information furnished to the
Company by or on behalf of such Selling Stockholder specifically for use in
preparation of the Registration Statement, (y) the failure of such Selling
Stockholder to comply with its covenants and agreements contained in Section 7.2
hereof respecting sale of the Shares, or (z) any statement or omission in any
Prospectus that is corrected in any subsequent Prospectus that was delivered to
the Investor prior to the pertinent sale or sales by the Investor. The Company
shall reimburse each Selling Stockholder for the amounts provided for herein on
demand as such expenses are incurred.

                            (b)     The Investor agrees to indemnify and hold
harmless the Company (and each person, if any, who controls the Company within
the meaning of Section 15 of the Securities Act, each officer of the Company who
signs the Registration Statement and each director of the Company) from and
against any losses, claims, damages or liabilities to which the Company (or any
such officer, director or controlling person) may become subject (under the
Securities Act or otherwise), insofar as such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) arise out of, or are
based upon, (i) any failure by such Investor to comply with the covenants and
agreements contained in Section 7.2 hereof respecting sale of the Shares, or
(ii) any untrue statement, or alleged untrue statement, or any omission or
alleged omission to state a material fact contained required to be

                                       9
<PAGE>

stated in a Registration Statement, or necessary to make the statements therein,
in light of the circumstances under which they were made not misleading, if such
untrue statement or omission or alleged untrue statement or omission was made in
reliance upon and in conformity with written information furnished by or on
behalf of the Investor specifically for use in preparation of the Registration
Statement, and the Investor will reimburse the Company (or such officer,
director or controlling person) on demand, as the case may be, for any
reasonable legal or other expenses reasonably incurred in investigating,
defending or preparing to defend any such action, proceeding or claim; PROVIDED
that the Investor's obligation to indemnify the Company shall be limited to the
net amount received by the Investor from the sale of the Shares.

                            (c)     Promptly after receipt by any indemnified
person of a notice of a claim or the beginning of any action in respect of which
indemnity is to be sought against an indemnifying person pursuant to this
Section 7.3, such indemnified person shall notify the indemnifying person in
writing of such claim or of the commencement of such action, but the omission to
so notify the indemnifying party will not relieve it from any liability which it
may have to any indemnified party under this Section 7.3 (except to the extent
that such omission materially and adversely affects the indemnifying party's
ability to defend such action) or from any liability otherwise than under this
Section 7.3. Subject to the provisions hereinafter stated, in case any such
action shall be brought against an indemnified person, the indemnifying person
shall be entitled to participate therein, and, to the extent that it shall elect
by written notice delivered to the indemnified party promptly after receiving
the aforesaid notice from such indemnified party, shall be entitled to assume
the defense thereof, with counsel reasonably satisfactory to such indemnified
person. After notice from the indemnifying person to such indemnified person of
its election to assume the defense thereof, such indemnifying person shall not
be liable to such indemnified person for any legal expenses subsequently
incurred by such indemnified person in connection with the defense thereof,
PROVIDED, HOWEVER, that if there exists or shall exist a conflict of interest
that would make it inappropriate, in the opinion of counsel to the indemnified
person, for the same counsel to represent both the indemnified person and such
indemnifying person or any affiliate or associate thereof, the indemnified
person shall be entitled to retain its own counsel at the expense of such
indemnifying person; provided, however, that no indemnifying person shall be
responsible for the fees and expenses of more than one separate counsel
(together with appropriate local counsel) for all indemnified parties. In no
event shall any indemnifying person be liable in respect of any amounts paid in
settlement of any action unless the indemnifying person shall have approved the
terms of such settlement; PROVIDED that such consent shall not be unreasonably
withheld. No indemnifying person shall, without the prior written consent of the
indemnified person, effect any settlement of any pending or threatened
proceeding in respect of which any indemnified person is or could have been a
party and indemnification could have been sought hereunder by such indemnified
person, unless such settlement includes an unconditional release of such
indemnified person from all liability on claims that are the subject matter of
such proceeding.

                            (d)     If the indemnification provided for in this
Section 7.3 is unavailable to or insufficient to hold harmless an indemnified
party under subsection (a) or (b) above in respect of any losses, claims,
damages or liabilities (or actions or proceedings in respect thereof) referred
to therein, then each indemnifying party shall contribute to the amount paid or
payable by such indemnified party as a result of such losses, claims, damages or
liabilities (or actions in respect thereof) in such proportion as is appropriate
to reflect the relative fault of the Company on the one hand and the Investor,
as well as any other Selling Stockholders under such Registration Statement on
the other in connection with the statements or omissions or other matters which
resulted in such losses, claims, damages or liabilities (or actions in respect
thereof), as well as any other relevant equitable considerations. The relative
fault shall be determined by reference to, among other things, in the case of an
untrue statement or omission, whether the untrue statement or omission relates
to information supplied by the Company on the one hand or an Investor or other
Selling Shareholder on the other and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such untrue
statement or omission. The Company and the Investor agree that it would not be
just and equitable if contribution pursuant to this subsection (d) were
determined by pro rata allocation (even if the Investor and other Selling
Stockholders were treated as one entity for such purpose) or by any other method
of allocation which does not take into account the equitable considerations
referred to above in this subsection (d). The amount paid or payable by an
indemnified party as a result of the losses, claims, damages or liabilities (or
actions in respect thereof) referred to above in this subsection (d) shall be
deemed to include any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. Notwithstanding the provisions of this subsection (d), the Investor
shall not be required to contribute any amount in excess of the amount by which
the net amount received by the Investor from the sale of the

                                       10
<PAGE>

Shares to which such loss relates exceeds the amount of any damages which such
Investor has otherwise been required to pay by reason of such untrue statement
or omission. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The Investor's obligations in this subsection to contribute
shall be in proportion to its sale of Shares to which such loss relates and
shall not be joint with any other Selling Shareholders.

                            (e)     The parties to this Agreement hereby
acknowledge that they are sophisticated business persons who were represented by
counsel during the negotiations regarding the provisions hereof including,
without limitation, the provisions of this Section 7.3, and are fully informed
regarding said provisions. They further acknowledge that the provisions of this
Section 7.3 fairly allocate the risks in light of the ability of the parties to
investigate the Company and its business in order to assure that adequate
disclosure is made in the Registration Statement as required by the Act and the
Exchange Act.

                  7.4 TERMINATION OF CONDITIONS AND OBLIGATIONS. The conditions
precedent imposed by Section 5 or this Section 7 upon the transferability of the
Shares shall cease and terminate as to any particular number of the Shares when
such Shares shall have been effectively registered under the Securities Act and
sold or otherwise disposed of in accordance with the intended method of
disposition set forth in the Registration Statement covering such Shares or at
such time as an opinion of counsel satisfactory to the Company shall have been
rendered to the effect that such conditions are not necessary in order to comply
with the Securities Act.

                  7.5 INFORMATION AVAILABLE.  So long as the Registration
Statement is effective covering the resale of Shares owned by the Investor, the
Company will furnish to the Investor upon the Investor's request:

                            (a)     as soon as practicable after it is
available, one copy of (i) its Annual Report to Stockholders (which Annual
Report shall contain financial statements audited in accordance with generally
accepted accounting principles by a national firm of certified public
accountants), (ii) its Annual Report on Form 10-K and (iii) its Quarterly
Reports on Form 10-Q (the foregoing, in each case, excluding exhibits);

                            (b)     all exhibits excluded by the parenthetical
to subparagraph (a) of this Section 7.5 as filed with the SEC and all other
information that is made available to shareholders;

                            (c)     a full copy of the Registration Statement;
and

                            (d)     an adequate number of copies of the
prospectuses to supply to any other party requiring such prospectuses; and upon
the reasonable request of the Investor, the Company will meet with the Investor
or a representative thereof at the Company's headquarters to discuss all
information relevant for disclosure in the Registration Statement covering the
Shares and will otherwise cooperate with any Investor conducting an
investigation for the purpose of reducing or eliminating such Investor's
exposure to liability under the Securities Act, including the reasonable
production of information at the Company's headquarters; provided, that the
Company shall not be required to disclose any confidential information to or
meet at its headquarters with any Investor until and unless the Investor shall
have entered into a confidentiality agreement in form and substance reasonably
satisfactory to the Company with the Company with respect thereto.

         8.    NOTICES. All notices, requests, consents and other communications
hereunder shall be in writing, shall be mailed (A) if within domestic United
States by first-class registered or certified airmail, or nationally recognized
overnight express courier, postage prepaid, or by facsimile, or (B) if delivered
from outside the United States, by International Federal Express or facsimile,
and shall be deemed given (i) if delivered by first-class registered or
certified mail domestic, three business days after so mailed, (ii) if delivered
by nationally recognized overnight carrier, one business day after so mailed,
(iii) if delivered by International Federal Express, two business days after so
mailed, (iv) if delivered by facsimile, upon electronic confirmation of receipt
and shall be delivered as addressed as follows:

                  (a)       if to the Company, to:

                           SIPEX Corporation

                                       11

<PAGE>

                           22 Linnell Circle
                           Billerica, MA  01821
                           Attention: Chief Financial Officer
                           Fax:  978-670-9088

                  (b)      with a copy to:

                           Wilson Sonsini Goodrich & Rosati, PC
                           650 Page Mill Road
                           Palo Alto, CA  94304-000
                           Attention:  Jeffrey D. Saper
                           Phone:  650-493-9300
                           Fax:  650-493-6811

                  (c)      if to the Investor, at its address on the signature
                           page hereto, or at such other address or addresses as
                           may have been furnished to the Company in writing.

         9.       CHANGES.  This Agreement may not be modified or amended
except pursuant to an instrument in writing signed by the Company and the
Investor.

         10.      HEADINGS.  The headings of the various sections of this
Agreement have been inserted for convenience of reference only and shall not be
deemed to be part of this Agreement.

         11.      SEVERABILITY.  In case any provision contained in this
Agreement should be invalid, illegal or unenforceable in any respect, the
validity, legality and enforceability of the remaining provisions contained
herein shall not in any way be affected or impaired thereby.

         12.      GOVERNING LAW.  This Agreement shall be governed by, and
construed in accordance with, the internal laws of the State of California,
without giving effect to the principles of conflicts of law.

         13.      COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall constitute an original, but all of which, when
taken together, shall constitute but one instrument, and shall become effective
when one or more counterparts have been signed by each party hereto and
delivered to the other parties.

         14.      RULE 144. The Company covenants that it will file the reports
required to be filed by it under the Securities Act and the Exchange Act and the
rules and regulations adopted by the SEC thereunder (or, if the Company is not
required to file such reports, it will, upon the request of any Investor holding
Shares purchased hereunder made after the first anniversary of the Closing Date,
make publicly available such information as necessary to permit sales pursuant
to Rule 144 under the Securities Act), and it will take such further action as
any such Investor may reasonably request, all to the extent required from time
to time to enable such Investor to sell Shares purchased hereunder without
registration under the Securities Act within the limitation of the exemptions
provided by (a) Rule 144 under the Securities Act, as such rule may be amended
from time to time, or (b) any similar rule or regulation hereafter adopted by
the SEC. Upon the request of the Investor, the Company will deliver to such
holder a written statement as to whether it has complied with such information
and requirements.

         15.      CONFIDENTIAL INFORMATION. The Company represents that neither
it nor its agents have, to date, provided the Investor with any material
non-public information. The Investor represents that, if it receives material
non-public information after the Offering, the Investor will maintain in
confidence all such material non-public information regarding the Company
received by the Investor and it will not trade in the Company's securities on
the basis of any such non-public information and will continue to maintain in
confidence such information until such information becomes generally publicly
available other than through a violation of this provision by the Investor or
its agents.

                                       12
<PAGE>

                                    EXHIBIT A
                    SIPEX CORPORATION INVESTOR QUESTIONNAIRE
                (ALL INFORMATION WILL BE TREATED CONFIDENTIALLY)

To:      SIPEX Corporation

         This Investor Questionnaire ("QUESTIONNAIRE") must be completed by each
potential investor in connection with the offer and sale of the shares of the
common stock, par value $.01 per share, of SIPEX Corporation (the "SECURITIES").
The Securities are being offered and sold by SIPEX Corporation (the
"CORPORATION") without registration under the Securities Act of 1933, as amended
(the "ACT"), and the securities laws of certain states, in reliance on the
exemptions contained in Section 4(2) of the Act and on Regulation D promulgated
thereunder and in reliance on similar exemptions under applicable state laws.
The Corporation must determine that a potential investor meets certain
suitability requirements before offering or selling Securities to such investor.
The purpose of this Questionnaire is to assure the Corporation that each
investor will meet the applicable suitability requirements. The information
supplied by you will be used in determining whether you meet such criteria, and
reliance upon the private offering exemption from registration is based in part
on the information herein supplied.

         This Questionnaire does not constitute an offer to sell or a
solicitation of an offer to buy any security. Except as permitted in this
Agreement, your answers will be kept strictly confidential. However, by signing
this Questionnaire you will be authorizing the Corporation to provide a
completed copy of this Questionnaire to such parties as the Corporation deems
appropriate in order to ensure that the offer and sale of the Securities will
not result in a violation of the Act or the securities laws of any state and
that you otherwise satisfy the suitability standards applicable to purchasers of
the Securities. All potential investors must answer all applicable questions and
complete, date and sign this Questionnaire. Please print or type your responses
and attach additional sheets of paper if necessary to complete your answers to
any item.

A.       BACKGROUND INFORMATION

Name: __________________________________________________________________________


Business Address: ______________________________________________________________
                              (Number and Street)

________________________________________________________________________________
(City)                            (State)                         (Zip Code)

Telephone Number: (___) ________________________________________________________


Residence Address: _____________________________________________________________
                                  (Number and Street)

________________________________________________________________________________
(City)                             (State)                        (Zip Code)

Telephone Number: (___) ________________________________________________________


If an individual:

      Age: ____ Citizenship: __________ Where registered to vote: ______________

If a corporation, partnership, limited liability company, trust or other entity:

         Type of entity: _______________________________________________________

         State of formation: _______________ Date of formation: ________________

Social Security or Taxpayer Identification No. _________________________________

Send all correspondence to (check one): __ Residence Address __ Business Address


<PAGE>


B.       STATUS AS ACCREDITED INVESTOR

         The undersigned is an "accredited investor" as such term is defined in
Regulation D under the Act, as at the time of the sale of the Securities the
undersigned falls within one or more of the following categories (PLEASE INITIAL
ONE OR MORE, AS APPLICABLE):(1)

____ (1)       a bank as defined in Section 3(a)(2) of the Act, or a savings and
               loan association or other institution as defined in Section
               3(a)(5)(A) of the Act whether acting in its individual or
               fiduciary capacity; a broker or dealer registered pursuant to
               Section 15 of the Securities Exchange Act of 1934; an insurance
               company as defined in Section 2(13) of the Act; an investment
               company registered under the Investment Corporation Act of 1940
               or a business development company as defined in Section 2(a)(48)
               of that Act; a Small Business Investment Corporation licensed by
               the U.S. Small Business Administration under Section 301(c) or
               (d) of the Small Business Investment Act of 1958; a plan
               established and maintained by a state, its political
               subdivisions, or any agency or instrumentality of a state or its
               political subdivisions for the benefit of its employees, if such
               plan has total assets in excess of $5,000,000; an employee
               benefit plan within the meaning of the Employee Retirement Income
               Security Act of 1974 if the investment decision is made by a plan
               fiduciary, as defined in Section 3(21) of such Act, which is
               either a bank, savings and loan association, insurance company,
               or registered investment adviser, or if the employee benefit plan
               has total assets in excess of $5,000,000 or, if a self-directed
               plan, with the investment decisions made solely by persons that
               are accredited investors;

____ (2)       a private business development company as defined in Section
               202(a)(22) of the Investment Adviser Act of 1940;

____ (3)       an organization described in Section 501(c)(3) of the Internal
               Revenue Code of 1986, as amended, corporation, Massachusetts or
               similar business trust, or partnership, not formed for the
               specific purpose of acquiring the Securities offered, with total
               assets in excess of $5,000,000;

____ (4)       a natural person whose individual net worth, or joint net worth
               with that person's spouse, at the time of such person's purchase
               of the Securities exceeds $1,000,000;

____ (5)       a natural person who had an individual income in excess of
               $200,000 in each of the two most recent years or joint income
               with that person's spouse in excess of $300,000 in each of those
               years and has a reasonable expectation of reaching the same
               income level in the current year;

____ (6)       a trust, with total assets in excess of $5,000,000, not formed
               for the specific purpose of acquiring the Securities offered,
               whose purchase is directed by a sophisticated person as described
               in Rule 506(b)(2)(ii) of Regulation D; and

____ (7)       an entity in which all of the equity owners are accredited
               investors (as defined above).

C.       REPRESENTATIONS

         The undersigned hereby represents and warrants to the Corporation as
follows:

1.       Any purchase of the Securities would be solely for the account of the
         undersigned and not for the account of any other person or with a view
         to any resale, fractionalization, division, or distribution thereof.

----------

       (1) As used in this Questionnaire, the term "net worth" means the excess
of total assets over total liabilities. In computing net worth for the purpose
of subsection (4), the principal residence of the investor must be valued at
cost, including cost of improvements, or at recently appraised value by an
institutional lender making a secured loan, net of encumbrances. In determining
income, the investor should add to the investor's adjusted gross income any
amounts attributable to tax exempt income received, losses claimed as a limited
partner in any limited partnership, deductions claimed for depiction,
contributions to an IRA or KEOGH retirement plan, alimony payments, and any
amount by which income from long-term capital gains has been reduced in arriving
at adjusted gross income.

<PAGE>


2.       The information contained herein is complete and accurate and may be
         relied upon by the Corporation, and the undersigned will notify the
         Corporation immediately of any material change in any of such
         information occurring prior to the closing, if any, with respect to the
         purchase of Securities by the undersigned or any co-purchaser.

3.       There are no suits, pending litigation, or claims against the
         undersigned that could materially affect the net worth of the
         undersigned as reported in this Questionnaire.

4.       The undersigned acknowledges that there may occasionally be times when
         the Corporation determines that it must suspend the use of the
         Prospectus forming a part of the Registration Statement (as such terms
         are defined in the Stock Purchase Agreement to which this
         Questionnaire is attached), as set forth in Section 7.2(c) of the
         Stock Purchase Agreement. The undersigned is aware that, in such
         event, the Securities will not be subject to ready liquidation, and
         that any Securities purchased by the undersigned would have to be held
         during such suspension. The overall commitment of the undersigned to
         investments that are not readily marketable is not excessive in view
         of the undersigned's net worth and financial circumstances, and any
         purchase of the Securities will not cause such commitment to become
         excessive. The undersigned is able to bear the economic risk of an
         investment in the Securities.

5.       In addition to reviewing the Corporation's SEC Filings, the undersigned
         has carefully considered the potential risks relating to the
         Corporation and a purchase of the Securities, and fully understands
         that the Securities are speculative investments that involve a high
         degree of risk of loss of the undersigned's entire investment.

                  IN WITNESS WHEREOF, the undersigned has executed this
         Questionnaire this _____ day of _______ ___, 2002, and declares under
         oath that it is truthful and correct.



                                ------------------------------------------------
                                Print Name


                                By:
                                    --------------------------------------------
                                         Signature

                                Title:
                                       -----------------------------------------
                                        (required for any purchaser that is a
                                        corporation, partnership, trust or other
                                        entity)



<PAGE>



                                    ANNEX II

                       LETTER REGARDING RESALE PROCEDURES

                              [COMPANY LETTERHEAD]


                                 _________, 2002



         Re:      SIPEX CORPORATION; REGISTRATION STATEMENT ON FORM S-3
                  -----------------------------------------------------

Dear Selling Shareholder:

         Enclosed please find five (5) copies of a prospectus dated
______________, 2002 (the "PROSPECTUS") for your use in reselling your shares of
common stock, $.01 par value (the "SHARES"), of SIPEX Corporation (the
"COMPANY"), under the Company's Registration Statement on Form S-3 (Registration
No. 333-     ) (the "REGISTRATION STATEMENT"), which has been declared effective
by the Securities and Exchange Commission. AS A SELLING SHAREHOLDER UNDER THE
REGISTRATION STATEMENT, YOU HAVE AN OBLIGATION TO DELIVER A COPY OF THE
PROSPECTUS TO EACH PURCHASER OF YOUR SHARES, EITHER DIRECTLY OR THROUGH THE
BROKER-DEALER WHO EXECUTES THE SALE OF YOUR SHARES.

         The Company is obligated to notify you in the event that it suspends
trading under the Registration Statement in accordance with the terms of the
Stock Purchase Agreement between the Company and you. During the period that the
Registration Statement remains effective and trading thereunder has not been
suspended, you will be permitted to sell your Shares that are included in the
Prospectus under the Registration Statement. Upon a sale of any Shares under the
Registration Statement, you or your broker will be required to deliver to the
Transfer Agent, EquiServe, (1) your restricted stock certificate(s) representing
the Shares, (2) instructions for transfer of the Shares sold and (3) a
representation letter from your broker, or from you if you are selling in a
privately negotiated transaction, or from such other appropriate party, in the
form of EXHIBIT A attached hereto (the "REPRESENTATION LETTER"). The
Representation Letter confirms that the Shares have been sold pursuant to the
Registration Statement and in a manner described under the caption "Plan of
Distribution" in the Prospectus and that such sale was made in accordance with
all applicable securities laws, including the prospectus delivery requirements.

         Please note that you are under no obligation to sell your Shares during
the registration period. However, if you do decide to sell, you must comply with
the requirements described in this letter or otherwise applicable to such sale.
Your failure to do so may result in liability under the Securities Act of 1933,
as amended, and the Securities Exchange Act of 1934, as amended. Please remember
that all sales of your Shares must be carried out in the manner set forth under
the caption "Plan of Distribution" in the Prospectus if you sell under the
Registration Statement. The Company may require an opinion of counsel reasonably
satisfactory to the Company if you choose another method of sale. YOU SHOULD
CONSULT WITH YOUR OWN LEGAL ADVISOR(S) ON AN ONGOING BASIS TO ENSURE YOUR
COMPLIANCE WITH THE RELEVANT SECURITIES LAWS AND REGULATIONS.

         YOU MUST NOTIFY THE UNDERSIGNED IF YOU ENTER INTO ANY ARRANGEMENT WITH
A BROKER-DEALER FOR THE SALE OF SHARES THROUGH A BLOCK TRADE, SPECIAL OFFERING,
EXCHANGE DISTRIBUTION OR SECONDARY DISTRIBUTION OR A PURCHASE BY A
BROKER-DEALER. DEPENDING ON THE CIRCUMSTANCES, SUCH TRANSACTIONS MAY REQUIRE THE
FILING OF A SUPPLEMENT TO THE PROSPECTUS IN ORDER TO UPDATE THE INFORMATION SET
FORTH UNDER THE CAPTION "PLAN OF DISTRIBUTION" IN THE PROSPECTUS.

         Should you need any additional copies of the Prospectus, or if you have
any questions concerning the foregoing, please write to me at SIPEX Corporation,
22 Linnell Circle, Billerica, MA 01821. Thank you.

                                                   Sincerely,


                                                   Chief Financial Officer



<PAGE>


                                                                       EXHIBIT A

                         CERTIFICATE OF SUBSEQUENT SALE

[Name and address of transfer agent]


    RE:  Sale of Shares of Common Stock of _______________ (the "COMPANY")
         pursuant to the Company's Prospectus dated _____________, ____
         (the "PROSPECTUS")

Dear Sir/Madam:

         The undersigned hereby certifies, in connection with the sale of shares
of Common Stock of the Company included in the table of Selling Shareholders in
the Prospectus, that the undersigned has sold the shares pursuant to the
Prospectus and in a manner described under the caption "Plan of Distribution" in
the Prospectus and that such sale complies with all securities laws applicable
to the undersigned, including, without limitation, the Prospectus delivery
requirements of the Securities Act of 1933, as amended.

Selling Shareholder (the beneficial owner): ____________________________________

Record Holder (e.g., if held in name of nominee): ______________________________

Restricted Stock Certificate No.(s): ___________________________________________

Number of Shares Sold: _________________________________________________________

Date of Sale: __________________________________________________________________

         In the event that you receive a stock certificate(s) representing more
shares of Common Stock than have been sold by the undersigned, then you should
return to the undersigned a newly issued certificate for such excess shares in
the name of the Record Holder and BEARING A RESTRICTIVE LEGEND. Further, you
should place a stop transfer on your records with regard to such certificate.

                                        Very truly yours,

Dated: ____________________________     By: ____________________________________

                                        Print Name: ____________________________

                                        Title: _________________________________



cc:      SIPEX Corporation
         22 Linnell Circle
         Billerica, MA  01821
         Attn:  Chief Financial Officer