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                                                                       Exhibit 4




                             AMENDMENT NO. 2, dated as of April 26, 2002, (this
                      "Amendment"), between ARCH CHEMICALS, INC., a Virginia
                      corporation (the "Company") and THE BANK OF NEW YORK, as
                      Rights Agent ("BNY"), to Rights Agreement dated as of
                      January 29, 1999, between the Company and Chase Mellon
                      Shareholder Services, L.L.C. ("ChaseMellon") as amended by
                      Amendment No. 1, dated July 23, 1999, between the Company
                      and EquiServe Trust Company, N.A., as successor to First
                      Chicago Trust Company of New York ("EquiServe") (such
                      Rights Agreement as so amended by Amendment No. 1 being
                      the "Rights Agreement").

                  WHEREAS EquiServe Trust Company, N.A. (as successor to First
Chicago Trust Company of New York) pursuant to Section 22 of the Rights
Agreement, has resigned as the Rights Agent effective at 5:00 p.m. on April 26,
2002;

                  WHEREAS effective with such resignation, the Company is
appointing BNY, which is the stock transfer agent of the Company's common stock,
as the Rights Agent pursuant to Section 22 of the Rights Agreement; and

                  WHEREAS the Company pursuant to Section 26 of the Rights
Agreement has determined to amend the Rights Agreement as provided herein.

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

                  SECTION 1. Appointment of New Rights Agent. Pursuant to and in
                             --------------------------------
accordance with Section 22 of the Rights Agreement, the Company hereby appoints
BNY as Rights Agent under the Rights Agreement effective at 5:00 p.m. on April
26, 2002, and BNY hereby accepts such appointment. Without any further action,
BNY shall be the Rights Agent under the Rights Agreement, and shall succeed to
all of the covenants, agreements, obligations, rights and benefits of EquiServe
in its former capacity as Rights Agent under the Rights Agreement (as amended
hereby).

                  SECTION 2. Section 3.  Section 3(d) of the Rights Agreement
                             ----------
is hereby amended as follows:

                  (a) By deleting the words "First Chicago Trust Company of New
York" in the first sentence of the legend set forth therein and replacing such
words with the words "The Bank of New York";


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                  SECTION 3. Section 25. Section 25 of the Rights Agreement is
                             -----------
hereby amended by deleting the name and address of First Chicago Trust Company
of New York and replacing it with the following:

                  "The Bank of New York
                  101 Barclay Street
                  New York, NY  10286

                  Attn:  Stock Transfer Administration".

                  SECTION 4. Exhibit B. Exhibit B of the Rights Agreement is
                             ----------
hereby amended by deleting the words, "First Chicago Trust Company of New York"
and "FIRST CHICAGO TRUST COMPANY OF NEW YORK", and replacing such words with the
words "The Bank of New York" and "THE BANK OF NEW YORK", respectively.

                  SECTION 5. Certain References.  (a)  All references in the
                             -------------------
Rights Agreement (and in any exhibits thereto) to the "Rights Agent" shall be
deemed to be references to BNY.

                  (b) All references in the Rights Agreement (and in any
exhibits thereto) to the term "Rights Agreement" or to the terms "herein",
"hereof" or words of similar import shall in each case be deemed to be
references to the Rights Agreement as amended hereby.

                  SECTION 6. Rights Agreement.  Except as expressly amended
                             -----------------
hereby, the Rights Agreement shall remain in full force and effect, and shall be
otherwise unaffected hereby.

                  SECTION 7. Governing Law. This Amendment shall be deemed to
                             --------------
be a contract made under the law of the Commonwealth of Virginia and for all
purposes shall be governed by and construed in accordance with the law of such
Commonwealth applicable to the contracts to be made and performed entirely
within such Commonwealth except that the duties and rights of the Rights Agent
shall be governed by the law of the State of New York without reference to the
choice of law doctrine of such State.

                  SECTION 8. Severability. If any term, provision, covenant or
                             -------------
restriction of this Amendment is held by a court of competent jurisdiction or
other authority to be invalid, void or unenforceable, the remainder of the
terms, provisions, covenants and restrictions of this Amendment shall remain in
full force and effect and shall in no way be affected, impaired or invalidated.

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                  SECTION 9. Counterparts; Effectiveness. This Amendment may be
                             ----------------------------
executed in any number of counterparts and each of such counterparts shall for
all purposes be deemed to be an original, and all such counterparts shall
together constitute one and the same instrument. This Amendment shall be
effective as of 5:00 p.m. New York City time on April 26, 2002.


                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be duly executed as of the day and year first above written.

                                          ARCH CHEMICALS, INC.,

                                          by
                                             /s/W. Paul Bush
                                             ---------------------------------
                                             Name: W. Paul Bush
                                             Title: Treasurer


                                          THE BANK OF NEW YORK
                                          as Rights Agent,

                                          by
                                             /s/Edward Timmons
                                             ---------------------------------
                                             Name: Edward Timmons
                                             Title: Vice President