1 EXHIBIT 4.6(b) [JPMORGAN LOGO] EXTENSION AGREEMENT Arch Chemicals, Inc. 501 Merritt 7 Norwalk, Connecticut 06856 Attention: Mr. W. Paul Bush The Chase Manhattan Bank, as Administrative Agent under the 364-Day Credit Agreement referred to below 270 Park Avenue New York, New York 10017 January 24, 2001 Gentlemen: Each undersigned Lender hereby agrees to extend, effective on January 24, 2001 (the "Extension Date"), the Maturity Date under the 364-Day Credit Agreement dated as of January 27, 1999 (as extended on January 26, 2000 and as the same may be amended, supplemented or otherwise modified from time to time, the "364-Day Credit Agreement") among Arch Chemicals, Inc., Olin Corporation, the Lenders and agents party thereto and The Chase Manhattan Bank, as administrative agent for the Lenders, to January 23, 2002. Terms defined in the 364-Day Credit Agreement are used herein as therein defined. This Agreement may be executed by one or more of the parties to this Agreement on any number of separate counterparts, and all of said counterparts taken together shall be deemed to constitute one and the same instrument. [Remainder of this page intentionally left blank] 2 This Extension Agreement shall be governed by and construed in accordance with the laws of the State of New York. THE CHASE MANHATTAN BANK, individually and as Administrative Agent, By: /s/ Lawrence Palumbo, Jr. ------------------------------- Name: Lawrence Palumbo, Jr. Title: Vice President BANK OF AMERICA, N.A., individually and as Syndication Agent, By: /s/ Donald J. Chin ------------------------------- Name: Donald J. Chin Title: Managing Director WACHOVIA BANK, N.A., individually and as Documentation Agent, By: /s/ Jane C. Deaver ------------------------------- Name: Jane C. Deaver Title: Senior Vice President 2 3 THE BANK OF NEW YORK By: /s/ Kenneth P. Sneider ------------------------------- Name: Kenneth P. Sneider Title: Vice President DAI ICHI KANGYO BANK LTD By: /s/ Robert Gallagher ------------------------------- Name: Robert Gallagher Title: Vice President FIRST UNION NATIONAL BANK By: /s/ Stephen T. Dorosh ------------------------------- Name: Stephen T. Dorosh Title: Vice President FLEET NATIONAL BANK By: /s/ Deanne M. Horn ------------------------------- Name: Deanne M. Horn Title: Director 3 4 SUNTRUST BANK By: /s/ W. David Wisdom ------------------------------- Name: Title: By: ------------------------------- Name: Title: ABN AMRO BANK N.V. By: /s/ George Dugan ------------------------------- Name: George Dugan Title: Group Vice President By: /s/ Patricia Christy ------------------------------- Name: Patricia Christy Title: Vice President PNC BANK, NATIONAL ASSOCIATION By: /s/ Donald V. Davis ------------------------------- Name: Donald V. Davis Title: Vice President THE NORTHERN TRUST COMPANY By: /s/ Nicole D. Boehm ------------------------------- Name: Nicole D. Boehm Title: Second Vice President 4 5 BBL INTERNATIONAL (U.K.) LIMITED By: /s/ C.R. Wright ------------------------------- Name: C.R. Wright Title: Authorized Signatory By: /s/ M-C Swinnen ------------------------------- Name: M-C Swinnen Title: Authorized Signatory 5 6 Agreed and accepted: ARCH CHEMICALS, INC. By: /s/ W. Paul Bush -------------------------- Name: W. Paul Bush Title: Treasurer 6