EXHIBIT 32.2

CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. §1350)

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. §1350), the undersigned, Dana M. Kelley, Vice President, Chief Financial Officer, and Treasurer of American Pacific Corporation, a Delaware corporation (the “Company”), does hereby certify, as of the date hereof, solely for purposes of Title 18, Chapter 63, Section 1350 of the United States Code, that, to her knowledge:

The Annual Report on Form 10-K for the year ended September 30, 2007 of the Company (the “Report”) fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Securities Exchange Act of 1934, and the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company at the dates and for the periods indicated.

     /s/ DANA M. KELLEY  

Dana M. Kelley 

Vice President, Chief Financial
Officer, and Treasurer
December 21, 2007