EXHIBIT 4.10

                               FOURTH AMENDMENT TO
                                 CHEMFIRST INC.
           401(k) SAVINGS AND EMPLOYEE STOCK OWNERSHIP PLAN AND TRUST

      THIS AMENDMENT, effective as specifically stated herein, is made by
CHEMFIRST INC., a Business Corporation, having its principal office in Jackson,
Mississippi (hereinafter referred to as "Employer").

                                R E C I T A L S:

      A. WHEREAS, the Employer has previously established the ChemFirst Inc.
401(k) Savings and Employee Stock Ownership Plan and Trust ("Plan and Trust")
for the benefit of those employees who qualify thereunder and for their
beneficiaries; and

      B. WHEREAS, the accounts of certain Participants consist in part of shares
of stock in Placer Dome Corporation and/or Mississippi Chemical Corporation,
which were acquired at a time when such corporations and/or their affiliates
within merger, Getchell Gold Corporation and First Mississippi Corporation,
respectively, were members of the same Controlled Group (within the meaning of
Code Section 414(b) as the Employer; and

      C. WHEREAS, the Employer has appointed Fidelity Trust Company as successor
trustee to Charles Schwab Trust Company; and

      D. WHEREAS, shares of stock in Placer Dome Corporation and Mississippi
Chemical Corporation will no longer be permissible investments upon Fidelity
Trust Company succeeding as Trustee; and

      E. WHEREAS, the Employer desires to amend the Plan and Trust, prior to the
transfer of Plan assets to Fidelity Trust Company, to permit Participants who
meet the requirements set forth below, and who wish to retain ownership of
shares in Placer Dome Corporation and/or Mississippi Chemical Corporation, to
elect to withdraw such shares in a manner that is consistent with the
requirements under the Internal Revenue Code of 1986, as amended, and the
regulations and rulings promulgated thereunder;

      NOW, THEREFORE, pursuant to Section 10.01 of the Plan and Trust, the
following amendment is hereby made and shall be effective as specifically stated
herein:

      1. Effective as of the execution date specified below, Section 3.03(b) of
the Plan is amended by the addition of the following provision:

      For the period commencing with the date of execution of this amendment and
continuing until September 5, 2000, a Participant may elect, subject to the
limitations below, an in-service withdrawal of the shares of stock in Placer
Dome Corporation and/or Mississippi Chemical


                                       23
<PAGE>

Corporation held for the Participant's benefit in the Plan. Such election shall
be subject to the following:

            (1) The amount of shares which shall be withdrawn pursuant to such
      election shall be equal to the least of (i) such Participant's vested
      interest in his Company Matching Contributions Account, (ii) the amount
      attributable to Company Matching Contributions made prior to July 31,
      1998, or (iii) the number of shares in Placer Dome Corporation and/or
      Mississippi Chemical Corporation held for the benefit of such Participant;

            (2) The Participant must complete a written election to withdraw
      and/or elect a Direct Rollover (as herein defined) no later than September
      5, 2000. Any election for less than the entire amount described in (1)
      above shall be invalid.

            (3) A Participant shall be limited to electing either an in-kind
      lump sum distribution and/or a direct rollover of such shares subject,
      however, to the limitations otherwise applicable herein.

            (4) The Trustee shall effect the timely and valid election of a
      Participant as soon as administratively feasible following September 5,
      2000.

      2. Section 11.04 of the Plan and Trust shall be amended by the addition of
the following provision:

            (o) Effective September 5, 2000, shares of stock in Placer Dome
      Corporation and Mississippi Chemical Corporation will no longer be
      permissible investments. Notwithstanding any Participant investment
      direction, as soon as administratively feasible after September 5, 2000,
      any shares of stock in Placer Dome Corporation and Mississippi Chemical
      Corporation held in the Trust Fund which are not subject to an in-service
      withdrawal election under Section 3.03(b) above shall be sold by the
      Trustee. The Trustee shall reinvest the proceeds from the sale of such
      shares as directed by the Plan Administrator, pending investment direction
      of the Participant.

      IN WITNESS WHEREOF, this instrument has been executed by the duly
authorized and empowered officer of the Employer, this 5th day of September,
2000.

                                    EMPLOYER:

                                    CHEMFIRST INC.


                                    By: /s/ William B. Kemp, Jr.
                                        ------------------------


                                       24