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                                                                      EXHIBIT 15

                               AMENDMENT NO. 2 TO
                          SHAREHOLDER RIGHTS AGREEMENT

     Amendment No. 2, dated as of November 23, 1999 ("Amendment No. 2") to the
Shareholder Rights Agreement, dated as of August 3, 1994, by and between
Ferrofluidics Corporation, a Massachusetts corporation (the "Company"), and
American Stock Transfer and Trust Company, a New York corporation (the "Rights
Agent"), as amended by the Amendment, dated as of October 20, 1999, by and
between the Company and the Rights Agent (the "Rights Agreement").

                                   WITNESSETH

     WHEREAS, Section 27 of the Rights Agreement provides that prior to the
Distribution Date (as defined therein), the Company and the Rights Agent shall,
if the Company so directs, supplement or amend any provision of the Rights
Agreement as the Company may deem necessary or desirable without the approval of
any holders of certificates representing shares of the Company's common stock,
par value $.004 per share (the "Common Stock");

     WHEREAS, the Company has entered into an Agreement and Plan of Merger (the
"Merger Agreement") with Ferrotec Corporation, a Delaware corporation
("Parent"), and Ferrotec Acquisition, Inc., a wholly-owned subsidiary of Parent
("Sub"), pursuant to which Sub will be merged with and into the Company upon the
terms and subject to the conditions set forth in the Merger Agreement (the
"Merger"); and

     WHEREAS, in connection with the Merger, the Company desires to amend
certain provisions of the Rights Agreement.

     NOW, THEREFORE, in consideration of the premises and the mutual agreements
herein set forth, the parties hereby agree as follows:

     1.   Section 7(a) of the Rights Agreement is amended by deleting such
Section 7(a) in its entirety and substituting therefor the following:

     "(a) Subject to Section 7(e) hereof, the registered holder of any Right
Certificate may exercise the Rights evidenced thereby (except as otherwise
provided herein) in whole or in part at any time after the Distribution Date
upon surrender of the Right Certificate, with the form of election to purchase
and the certificate on the reverse side thereof duly executed, to the Rights
Agent at the office or offices of the Rights Agent designated for such purpose,
together with payment of the aggregate Exercise Price for the total number of
one one-thousandths of a share of Preferred Stock (or other securities, cash or
other assets, as the case may be) as to which such surrendered Rights are then
exercised, at or prior to the earlier of (i) the close of business on August 3,
2004 (the "Final Expiration Date"), (ii) the time at which the Rights are
redeemed as provided in Section 23 hereof, (iii) the time at which such Rights
are exchanged


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as provided in Section 24 hereof, or (iv) the Acceptance Date (as defined in the
Merger Agreement) (the earlier of (i), (ii), (iii) or (iv) being herein referred
to as the "Expiration Date"). Except as set forth in Section 7(e) hereof and
notwithstanding any other provision of this Agreement, any Person who prior to
the Distribution Date becomes a record holder of shares of Common Stock may
exercise all of the rights of a registered holder of a Right Certificate with
respect to the Rights associated with such shares of Common Stock of the Company
in accordance with the provisions of this Agreement, as of the date such Person
becomes a record holder of shares of Common Stock."

     2.   Any term used herein and not defined shall have the meaning ascribed
to such term in the Rights Agreement.


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     IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 2 to
be duly executed as of the day and year first above written. This Amendment No.
2 may be executed in one or more counterparts all of which shall be considered
one and the same amendment and each of which shall be deemed to be an original.


ATTEST:                                     FERROFLUIDICS CORPORATION



By: /s/ Joan Deichler                       By: /s/ William B. Ford
   -----------------------------               ---------------------------------
                                                Name:  William B. Ford
                                                Title: Vice President



ATTEST:                                     AMERICAN TRANSFER AND TRUST COMPANY,
                                            as Rights Agent



By: /s/ Susan Silber                        By: /s/ Herbert Lemmer
   -----------------------------               ---------------------------------
    Name: Susan Silber                          Name:  Herbert J. Lemmer
          Assistant Secretary                   Title: Vice President