Document:

<PAGE>

                                                                  EXHIBIT 10.58
                                                                 EXECUTION COPY

                       AMENDMENT NO. 8 TO CREDIT AGREEMENT

           AMENDMENT dated as of December 29, 2000 (the "AMENDMENT") to the
Revolving Credit and Guaranty Agreement dated as of May 4, 2000 and amended as
of May 15, 2000, June 1, 2000, August 31, 2000, October 6, 2000, October 30,
2000 and November 30, 2000 (as so amended, the "CREDIT AGREEMENT") among LAROCHE
INDUSTRIES INC. (the "BORROWER"), LAROCHE FORTIER INC. (the "GUARANTOR"), the
LENDERS party thereto (the "DIP LENDERS") and THE CHASE MANHATTAN BANK, as Agent
(the "AGENT").

                                   WITNESSETH:

           WHEREAS, the parties to the Credit Agreement have agreed to amend the
Credit Agreement as provided for herein to;

           NOW, THEREFORE, the parties hereto agree as follows:

           SECTION 1. DEFINITIONS; REFERENCES. Unless otherwise specifically
defined herein, each term used herein that is defined in the Credit Agreement
shall have the meaning assigned to such term in the Credit Agreement. Each
reference to "hereof", "hereunder", "herein" and "hereby" and each other similar
reference and each reference to "this Agreement" and each other similar
reference contained in the Credit Agreement shall, from and after the date of
effectiveness of this Amendment, refer to the Credit Agreement as amended
hereby.

           SECTION 2. MANDATORY PREPAYMENT, COMMITMENT REDUCTION AND
TERMINATION; CASH COLLATERAL. Section 2.13(a) of the Credit Agreement is hereby
amended by adding, immediately following the phrase "Net Proceeds" the first
time it appears therein, the following phrase: "(Net Proceeds as utilized solely
in this Section 2.13(a) shall be deemed to exclude the Insurance Payment
Amount)"

           SECTION 3. EFFECTIVENESS. This Amendment shall become effective if
and only if (a) the Agent shall have received duly executed counterparts hereof
signed by each of the Borrower, the Agent, the Guarantor and the Required DIP
Lenders (or, in the case of any party as to which an executed counterpart shall
not have been received, the Agent shall have received telegraphic, telex or
other written confirmation from such party of execution of a counterpart hereof
by such party) and (b) 100% of the Insurance Payment Amount shall have been paid
directly to the Agent by the Borrower's insurers and shall have been utilized,
in accordance with paragraph 13 of the Final Order, first, to prepay all Loans
outstanding under the Credit Agreement and second, to prepay Loans outstanding
under the Pre-Petition Credit Agreement.

           SECTION 4. GOVERNING LAW. This Amendment shall be governed by and
construed in accordance with the laws of the State of New York.

<PAGE>

           SECTION 5. COUNTERPARTS. This Amendment may be signed in any number
of counterparts, each of which shall be an original, with the same effect as if
the signatures thereto and hereto were upon the same instrument.

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

                          LAROCHE INDUSTRIES INC.

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

                          LAROCHE FORTIER INC.

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

                          THE CHASE MANHATTAN BANK, as Agent and as DIP Lender

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

                                       2

<PAGE>

                          HIBERNIA NATIONAL BANK

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

                          WACHOVIA BANK, N.A.

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

                          THE BANK OF NOVA SCOTIA

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

                          PERRY CAPITAL LLC

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

                                       3

<PAGE>

                          AMSOUTH BANK

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

                          BHF (USA) CAPITAL CORPORATION

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

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

                          COMERICA BANK

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

                          NATIONAL BANK OF CANADA

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

                                       4

<PAGE>

                          BNP PARIBAS

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

                                       5<PAGE>
                                                               Exhibit 10.59
                                                               EXECUTION COPY

                       AMENDMENT NO. 9 TO CREDIT AGREEMENT

           AMENDMENT dated as of January 10, 2001 (the "AMENDMENT") to the
Revolving Credit and Guaranty Agreement dated as of May 4, 2000 and amended as
of May 15, 2000, June 1, 2000, August 31, 2000, October 6, 2000, October 30,
2000, November 30, 2000 and December 29, 2000 (as so amended, the "CREDIT
AGREEMENT") among LAROCHE INDUSTRIES INC. (the "BORROWER"), LAROCHE FORTIER INC.
(the "GUARANTOR"), the LENDERS party thereto (the "DIP LENDERS") and THE CHASE
MANHATTAN BANK, as Agent (the "AGENT").

                                   WITNESSETH:

           WHEREAS, the parties to the Credit Agreement have agreed to amend the
Credit Agreement as provided for herein to;

           NOW, THEREFORE, the parties hereto agree as follows:

           SECTION 1. DEFINITIONS; REFERENCES. Unless otherwise specifically
defined herein, each term used herein that is defined in the Credit Agreement
shall have the meaning assigned to such term in the Credit Agreement. Each
reference to "hereof", "hereunder", "herein" and "hereby" and each other similar
reference and each reference to "this Agreement" and each other similar
reference contained in the Credit Agreement shall, from and after the date of
effectiveness of this Amendment, refer to the Credit Agreement as amended
hereby.

           SECTION 2. MANDATORY PREPAYMENT, COMMITMENT REDUCTION AND
TERMINATION. Subsection (i)(B) of the final sentence of Section 2.13(a) of the
Credit Agreement is hereby amended by replacing the phrase "seventy (70)"
therein with the phrase "one hundred seven (107)".

           SECTION 3. EFFECTIVENESS. This Amendment shall become effective if
and only if the Agent shall have received duly executed counterparts hereof
signed by each of the Borrower, the Agent, the Guarantor and the Required DIP
Lenders (or, in the case of any party as to which an executed counterpart shall
not have been received, the Agent shall have received telegraphic, telex or
other written confirmation from such party of execution of a counterpart hereof
by such party).

           SECTION 4.  GOVERNING LAW.  This Amendment shall be governed by and
construed in accordance with the laws of the State of New York.

<PAGE>

           SECTION 5. COUNTERPARTS. This Amendment may be signed in any number
of counterparts, each of which shall be an original, with the same effect as if
the signatures thereto and hereto were upon the same instrument.

                                        2
<PAGE>

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

                                             LAROCHE INDUSTRIES INC.

                                             By:____________________________
                                                Name:
                                                Title:

                                             LAROCHE FORTIER INC.

                                             By:____________________________
                                                Name:
                                                Title:

                                             THE CHASE MANHATTAN BANK,
                                             as Agent and as DIP Lender

                                             By:____________________________
                                                Name:
                                                Title:

                                        3

<PAGE>

                                             HIBERNIA NATIONAL BANK

                                             By:____________________________
                                                Name:
                                                Title:

                                             WACHOVIA BANK, N.A.

                                             By:____________________________
                                                Name:
                                                Title:

                                             THE BANK OF NOVA SCOTIA

                                             By:____________________________
                                                Name:
                                                Title:

                                             PERRY CAPITAL LLC

                                             By:____________________________
                                                Name:
                                                Title:

                                        4

<PAGE>

                                             AMSOUTH BANK

                                             By:____________________________
                                                Name:
                                                Title:

                                             BHF (USA) CAPITAL CORPORATION

                                             By:____________________________
                                                Name:
                                                Title:

                                             By:____________________________
                                                Name:
                                                Title:

                                             COMERICA BANK

                                             By:____________________________
                                                Name:
                                                Title:

                                             NATIONAL BANK OF CANADA

                                             By:____________________________
                                                Name:
                                                Title:

                                        5

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