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                                                                    EXHIBIT 4-AD



                             AMENDMENT NO. 3 TO THE
                      AMENDED AND RESTATED TRUST AGREEMENT


         This AMENDMENT NO. 3 (the "AMENDMENT") is made as of January 24, 2000,
by Israel J. Floyd, Stuart C. Shears and Michael J. Scott (collectively, the
"ADMINISTRATIVE TRUSTEES"), The Chase Manhattan Bank, as Property Trustee
("CHASE"), Hercules Incorporated, a Delaware corporation (the "SPONSOR"), and by
the Holders, from time to time, of undivided beneficial interests in the assets
of Hercules Trust V (the "TRUST"), a business trust created pursuant to a Trust
Agreement dated as of October 14, 1998, as amended by the Amended and Restated
Trust Agreement dated as of November 12, 1998, the Amendment to the Amended and
Restated Trust Agreement dated as of July 6, 1999 and the Amendment No. 2 to the
Amended and Restated Trust Agreement dated as of October 25, 1999 (as amended,
the "TRUST AGREEMENT").

         WHEREAS, the Trustees and the Sponsor have established the Trust
pursuant to the Trust Agreement for the sole purpose of issuing and selling
certain securities representing undivided beneficial interests in the assets of
the Trust and investing the proceeds thereof in the Auction Rate Reset Junior
Subordinated Notes Series A of the Sponsor (the "SUBORDINATED NOTES") and
engaging in only those activities necessary, advisable or incidental thereto;

         WHEREAS, the Trust Agreement provides for the issuance of one class of
preferred securities representing undivided beneficial interests in the assets
of the Trust (the "PREFERRED SECURITIES") having such terms as are set forth in
Annex I thereto ("ANNEX I");

         WHEREAS, the Trust Agreement and Annex I provide for amendment of the
Trust Agreement and the Preferred Securities, subject to satisfaction of certain
requirements;

         WHEREAS, the parties hereto desire to extend the Mandatory Redemption
Date (as defined in the Trust Agreement) of the Preferred Securities;

         WHEREAS, this Amendment does not affect the rights, powers, duties,
obligations or immunities of the Property Trustee or of the Delaware Trustee;

         WHEREAS, all things necessary to make this Amendment a valid amendment
and agreement according to its terms have been done;

         NOW THEREFORE, in consideration of their mutual covenants contained
herein and in the Trust Agreement, the parties hereto, intending to be legally
bound, hereby mutually covenant and agree as follows:
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                                    Article 1

         Section 1.01.  Definitions.  The definition of "Mandatory Redemption
Date" contained in Section 1.01 of the Trust Agreement is hereby amended to read
in its entirety as follows:

             ""MANDATORY REDEMPTION DATE" means February 28, 2000."

                                    Article 2

         Section 2.01. Ratification of the Trust Agreement; this Amendment. The
Trust Agreement is in all respects ratified and confirmed, and this Amendment
shall be deemed part of the Trust Agreement in the manner and to the extent
herein and therein provided. The provisions of this Amendment shall supersede
the provisions of the Trust Agreement to extent the Trust Agreement is
inconsistent herewith.

         Section 2.02. Trustees Not Responsible for Recitals. The recitals
herein contained are made by the Sponsor and not by the Trustees, and the
Trustees assumes no responsibility for the correctness thereof. The Trustees
make no representation as to the validity or sufficiency of this Amendment.

         Section 2.03. Governing Law. This Amendment and the rights of the
parties hereunder shall be governed by and construed in accordance with the laws
of the State of Delaware, and all rights and remedies shall be governed by such
laws, without regard to its principles of conflicts of laws.

         Section 2.04. Severability. If any provision in the Trust Agreement or
this Amendment shall be invalid, illegal or unenforceable, the validity,
legality and enforceability of the remaining provisions shall not in any way be
affected or impaired thereby.

         Section 2.05. Counterparts. The parties may sign any number of copies
of this Amendment. Each signed copy shall be an original, but all of them
together represent the same agreement. Any signed copy shall be sufficient proof
of this Amendment.

         Section 2.06. Terms Defined. All terms defined elsewhere in the Trust
Agreement shall have the same meanings when used herein.

         Section 2.07. Waiver of Tax Opinion. The parties hereto (including the
Holder of the Preferred Securities by its separate consent to this Amendment)
waive the requirement set out in Section 8 of Annex I to the Trust Agreement for
a reasoned Opinion of Counsel of independent tax counsel.



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         IN WITNESS WHEREOF, the parties have signed this Amendment as of the
date and year first above written.




                             -------------------------------------------
                             Israel J. Floyd, not in his individual
                             capacity but solely as Administrative
                             Trustee of the Trust



                             -------------------------------------------
                             Michael J. Scott, not in his individual
                             capacity but solely as Administrative
                             Trustee of the Trust



                             -------------------------------------------
                             Stuart C. Shears, not in his individual
                             capacity but solely as Administrative
                             Trustee of the Trust


                             -------------------------------------------
                             HERCULES INCORPORATED,
                             as Sponsor and Holder of the
                             Common Securities


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


                             THE CHASE MANHATTAN BANK, not
                             in its individual capacity, but solely as
                             Property Trustee of the Trust


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