Exhibit 10.1

FIRST AMENDMENT TO CREDIT AGREEMENT

THIS FIRST AMENDMENT TO CREDIT AGREEMENT dated as of June 9, 2011 (this
“Agreement”) is entered into among Arch Chemicals, Inc., a Virginia Corporation
(the “Borrower”), the Lenders party hereto and Bank of America, N.A., as
Administrative Agent. All capitalized terms used herein and not otherwise
defined herein shall have the meanings given to such terms in the Credit
Agreement (as defined below).

RECITALS

WHEREAS, the Borrower, the Lenders and Bank of America, N.A., as Administrative
Agent, have entered into that certain Credit Agreement dated as of May 13, 2011
(as amended or modified from time to time, the “Credit Agreement”);

WHEREAS, the Borrower has requested that the Lenders amend the Credit Agreement
as set forth herein; and

WHEREAS, the Lenders have agreed to amend the Credit Agreement on the terms and
conditions set forth herein.

NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

1. Amendment. The Credit Agreement is hereby amended as follows:

(a) Clause (y) in Section 6.05 of the Credit Agreement is hereby amended to read
as follows:

“(y) 50% of the cumulative Consolidated Adjusted Net Income of the Borrower for
the period (taken as one accounting period) since March 31, 2011 through the
last day of the fiscal quarter for which financial statements have been
delivered pursuant to Section 5.01(a) or (b),”

2. Conditions Precedent. This Agreement shall be effective upon receipt by the
Administrative Agent of counterparts of this Agreement duly executed by the
Borrower, the Required Lenders and Bank of America, N.A., as Administrative
Agent.

3. Miscellaneous.

(a) The Credit Agreement and the obligations of the Borrower thereunder and
under the other Loan Documents, are hereby ratified and confirmed and shall
remain in full force and effect according to their terms.

(b) The Borrower (a) acknowledges and consents to all of the terms and
conditions of this Agreement, (b) affirms all of its obligations under the Loan
Documents and (c) agrees that this Agreement and all documents executed in
connection herewith do not operate to reduce or discharge its obligations under
the Credit Agreement or the Loan Documents.

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(c) The Borrower hereby represents and warrants as follows:

(i) The Borrower has taken all necessary action to authorize the execution,
delivery and performance of this Agreement.

(ii) This Agreement has been duly executed and delivered by the Borrower and
constitutes the Borrower’s legal, valid and binding obligation, enforceable in
accordance with its terms, subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other laws affecting creditor’s rights generally
and subject to general principles of equity, regardless of whether such
enforceability is considered in a proceeding in equity or at law.

(iii) No consent, approval, exemption, authorization or other action by, or
notice to, or filing with, any Governmental Authority or any other Person is
necessary or required in connection with the execution, delivery or performance
by the Borrower of this Agreement.

(d) The Borrower represents and warrants to the Lenders that after giving effect
to this Agreement (i) the representations and warranties of the Borrower set
forth in Article III of the Credit Agreement and in each other Loan Document are
true and correct in all material respects as of the date hereof with the same
effect as if made on and as of the date hereof, except to the extent such
representations and warranties expressly relate solely to an earlier date,
provided that, any representation and warranty that is qualified as to
“materiality,” “Material Adverse Effect” or similar language is true and correct
in all respects as of the date hereof and (ii) no event has occurred and is
continuing which constitutes a Default or an Event of Default.

(e) This Agreement may be executed in any number of counterparts, each of which
when so executed and delivered shall be an original, but all of which shall
constitute one and the same instrument. Delivery of an executed counterpart of
this Agreement by telecopy or electronic mail shall be effective as an original
and shall constitute a representation that an executed original shall be
delivered.

(f) THIS AGREEMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES HEREUNDER SHALL
BE GOVERNED BY AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF NEW YORK.

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Each of the parties hereto has caused a counterpart of this Agreement to be duly
executed and delivered as of the date first above written.

 

BORROWER:   ARCH CHEMICALS, INC.   By:  

/S/    W. Paul Bush

  Name:   W. Paul Bush   Title:   Treasurer ADMINISTRATIVE     AGENT:   BANK OF
AMERICA, N.A.,   as Administrative Agent   By:  

/S/    Irene Bertozzi Barenstein

  Name:   Irene Bertozzi Barenstein   Title:   Treasurer LENDERS:   BANK OF
AMERICA, N.A.,   as a Lender   By:  

/S/    Irene Bertozzi Barenstein

  Name:   Irene Bertozzi Barenstein   Title:   Treasurer   RBS CITIZENS, NA,  
as a Lender   By:  

/S/    Cindy Chen

  Name:   Cindy Chen   Title:   Senior Vice President   WELLS FARGO BANK, N.A.,
  as a Lender   By:  

/S/    John J. Mulvey

  Name:   John J. Mulvey   Title:   Senior Vice President   JPMORGAN CHASE BANK,
N.A.,   as a Lender   By:  

/S/    D. Scott Farquhar

  Name:   D. Scott Farquhar   Title:   Senior Vice President

 

ARCH CHEMICALS, INC.

FIRST AMENDMENT TO CREDIT AGREEMENT

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  HSBC BANK USA, N.A.,   as a Lender   By:  

/S/    Robert H. Rogers

  Name:   Robert H. Rogers   Title:   Senior Relationship Manager     as a
Lender  

BRANCH BANKING AND TRUST COMPANY,

as a Lender

  By:  

/S/    Roger Eric Searls

  Name:   Roger Eric Searls   Title:   Vice President  

COMERICA BANK,

as a Lender

  By:  

/S/    Daryl Krause

  Name:   Daryl Krause   Title:   Senior Vice President

 

ARCH CHEMICALS, INC.

FIRST AMENDMENT TO CREDIT AGREEMENT