Exhibt 4-b 
         

          UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED 
          REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW 
          YORK CORPORATION ("DTC"), TO ISSUER OR ITS AGENT FOR 
          REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY 
          CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. 
          OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED
          REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & 
          CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN 
          AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, 
          OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY 
          PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, 
          CEDE & CO., HAS AN INTEREST HEREIN.

NO. R-1                                                             $100,000,000

                                FMC CORPORATION

                        7 3/4% SENIOR DEBENTURE DUE 2011
                               CUSIP:  302491AL9

          FMC Corporation, a Delaware corporation (herein called the "Issuer,"
which term includes any successor corporation under the Indenture hereinafter
referred to), for value received, hereby promises to pay to CEDE & Co. or
registered assigns, the principal sum of $100,000,000 on July 1, 2011, and to
pay interest, semiannually on January 1 and July 1 of each year, commencing
January 1, 1997, on said principal sum, at the rate per annum specified in the
title of this Senior Debenture, on a semiannual bond equivalent basis using a
360-day year composed of twelve 30-day months from July 1, 1996 until payment of
said principal sum has been made or duly provided for.  Payments of such
principal and interest shall be made at the office or agency of the Issuer in
Chicago, Illinois, which, subject to the right of the Issuer to vary or
terminate the appointment of such agency, shall initially be at the principal
office of Harris Trust and Savings Bank.  If the Issuer shall default in the
payment of interest due on January 1 or July 1, then this Senior Debenture shall
bear interest from the next preceding January 1 or July 1, to which interest has
been paid or, if no interest has been paid on this Senior Debenture, from 
July 1, 1996.  The interest so payable on any January 1 or July 1, will, subject
to certain exceptions provided in the Indenture referred to on the reverse
hereof, be paid to the person in whose name this Senior Debenture is registered
at the close of business on the December 15 or June 15, as the case may be, next
preceding such January 1 or July 1.

          Reference is made to the further provisions of this Senior Debenture
set forth on the reverse hereof.  Such further provisions shall for all purposes
have the same effect as though fully set forth at this place.
      
 
          This Senior Debenture shall not be valid or become obligatory for any
purpose until the certificate of authentication hereon shall have been manually
signed by the Trustee under the Indenture referred to on the reverse hereof.

          IN WITNESS WHEREOF, FMC CORPORATION has caused this instrument to be
signed by its duly authorized officers and has caused its corporate seal to be
affixed hereunto or imprinted hereon.

                                       FMC CORPORATION


                                       By:_____________________________



                                       By:_____________________________
                                       
                                       

[CORPORATE SEAL]



                FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION

          This is one of the Securities of the Series designated herein referred
to in the within-mentioned Indenture.

Dated:                                 HARRIS TRUST AND SAVINGS BANK,
                                       as Trustee


                                       By:_____________________________
                                            Authorized Signatory


                                      -2-

 
                          REVERSE OF SENIOR DEBENTURE


                                FMC CORPORATION

                        7 3/4% SENIOR DEBENTURE DUE 2011

          This Senior Debenture is one of a duly authorized issue of debentures,
notes, bonds or other evidences of indebtedness of the Issuer (hereinafter
called the "Securities") of the Series hereinafter specified, all issued or to
be issued under and pursuant to an Indenture dated as of July 1, 1996 (herein
called the "Indenture"), duly executed and delivered by the Issuer to Harris
Trust and Savings Bank, as Trustee (herein called the "Trustee," which term
includes any successor trustee under the Indenture), to which Indenture and all
indentures supplemental thereto reference is hereby made for a description of
the rights, limitations of rights, obligations, duties and immunities thereunder
of the Trustee, the Issuer and the Holders of the Securities and of the terms
upon which the Securities are, and are to be, authenticated and delivered. The
Securities may be issued in one or more Series, which different Series may be
issued in various aggregate principal amounts, may bear interest at different
rates, which may be fixed or variable, may be subject to different redemption
provisions (if any), may be subject to different sinking, purchase or analogous
funds (if any) and may otherwise vary as provided in the Indenture. This Senior
Debenture is one of a Series designated as the 7 3/4% Senior Debentures Due 2011
of the Issuer, limited in aggregate principal amount to $100,000,000.

          The Senior Debentures are represented by a Global Debenture deposited
with, or on behalf of, The Depository Trust Company, New York, New York ("DTC"),
and registered in the name of a nominee of DTC. Except as set forth herein, the
Senior Debentures shall be available for purchase in book-entry form only. So
long as DTC or its nominee is the registered owner of the Global Debenture, DTC
or such nominee, as the case may be, will be considered the sole owner or Holder
of the Senior Debentures represented by the Global Debenture for all purposes
under the Indenture. Unless and until certificated Senior Debentures are issued
in exchange for the Global Debenture, no beneficial owner of a Senior Debenture
shall be entitled to receive a definitive certificate representing a Senior
Debenture. Upon such exchange, Senior Debentures in definitive form shall be
issued in registered form only, without coupons, in denominations of $1,000 and
integral multiples thereof.

          If at any time DTC notifies the Issuer that it is unwilling or unable
to continue as depository for the Senior Debentures or if at any time DTC shall
no longer be registered or in good standing under the Securities Exchange Act of
1934, as amended, or other applicable statute or regulation and a successor

                                      -3-




 
depository is not appointed by the Issuer within 90 days after the Issuer
receives such notice or becomes aware of such condition, as the case may be, the
Issuer will execute, and the Trustee will authenticate and deliver, Senior
Debentures in definitive registered form in an aggregate principal amount equal
to the principal amount of the Global Debenture in exchange for the Global
Debenture.  In addition, the Issuer may at any time determine that some or all
of the Senior Debentures shall no longer be represented by a Global Debenture.
In such event, the Issuer will execute and the Trustee, upon receipt of an
Officers' Certificate evidencing such determination by the Issuer, will
authenticate and deliver Senior Debentures in definitive form, in authorized
denominations, (i) to the Person specified by DTC equal to and in exchange for
such Person's beneficial interest in the Global Debenture and (ii) to DTC a new
Global Debenture in a denomination equal to the difference, if any, between the
principal amount of the surrendered Global Debenture and the aggregate principal
amount of definitive Senior Debentures delivered to Holders thereof, or
interests in applicable portions thereof.  Upon the exchange of the Global
Debenture for all Senior Debentures in definitive form, in authorized
denominations, the surrendered Global Debenture shall be cancelled by the
Trustee.  Senior Debentures in definitive registered form issued in exchange for
the Global Debenture or portion thereof shall be issued in such authorized
denominations as DTC, pursuant to instructions from its direct or indirect
participants or otherwise, shall instruct the Trustee.  The Trustee shall
deliver such Senior Debentures to the Persons in whose name such Senior
Debentures are so registered.

          In case an Event of Default with respect to the 7 3/4% Senior
Debentures Due 2011 shall have occurred and be continuing, the principal hereof
may be declared, and upon such declaration shall become, due and payable, in the
manner, with the effect and subject to the conditions provided in the Indenture.

          The Indenture contains provisions permitting the Issuer and the
Trustee, with the consent of the Holders of a majority of the aggregate
principal amount of the Securities at the time Outstanding (as defined in the
Indenture) of all Series to be affected (treated as one class), evidenced as
provided in the Indenture, to execute supplemental indentures adding any
provisions to or changing in any manner or eliminating any of the provisions of
the Indenture or of any supplemental indenture or modifying in any manner the
rights of the Holders of the Securities of each such Series; provided, however,
that no such supplemental indenture shall (i) extend the final maturity of any
Security, or reduce the principal amount thereof or any premium thereon, or
reduce the rate or extend the time of payment of interest thereon, or reduce any
amount payable upon redemption thereof, or impair or affect the right of any
Holder to institute suit for the payment thereof or, if the Securities provide
therefor, any right of repayment at the option of the Securityholder, without
the consent of the Holder of

                                      -4-







each Security so affected, or (ii) reduce the aforesaid percentage of Securities
of any Series, the Holders of which are required to consent to any such
supplemental indenture, without the consent of the Holder of each Security
affected. It is also provided in the Indenture that, with respect to certain
defaults or Events of Default regarding the Securities of any Series, the
Holders of a majority in aggregate principal amount outstanding of the
Securities of such Series may on behalf of the Holders of all the Securities of
such Series waive any such past default or Event of Default and its
consequences. The preceding sentence shall not, however, apply to a default in
the payment of the principal of or interest on any of the Securities. Any such
consent or waiver by the Holder of this Senior Debenture (unless revoked as
provided in the Indenture) shall be conclusive and binding upon such Holder and
upon all future Holders and owners of this Senior Debenture and any Senior
Debenture which may be issued in exchange or substitution herefor, irrespective
of whether or not any notation thereof is made upon this Senior Debenture or
such other Senior Debenture.

          No reference herein to the Indenture, and no provision of this Senior
Debenture or of the Indenture, shall alter or impair the obligation of the
Issuer, which is absolute and unconditional, to pay the principal of and
interest on this Senior Debenture in the manner, at the respective times, at the
rate, and in the coin or currency herein prescribed.

          As provided in the Indenture, and subject to certain limitations set
forth therein, Senior Debentures in registered form are exchangeable for one or
more new Debentures of this Series and of like tenor, for the same aggregate
principal amount and of authorized denominations, as requested by the Holder
surrendering the same at the agency of the Issuer in Chicago, Illinois. No
service charge shall be made for any such exchange, but the Issuer may require
payment of a sum sufficient to cover any tax or other governmental charge
payable in connection therewith.

          The Senior Debentures will be redeemable in whole or in part, at the
option of the Issuer at any time, at a redemption price equal to the greater of
(i) 100% of their principal amount and (ii) the sum of the present values of the
remaining scheduled payments of principal and interest thereon discounted to the
date of redemption on a semiannual basis (assuming a 360-day year consisting of
twelve 30-day months) at the Treasury Yield plus in each case accrued interest
to the date of redemption (the "Redemption Date").

          "Treasury Yield" means, with respect to any Redemption Date, the rate
per annum equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
such Redemption Date.

                                      -5-

 
          "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker (as defined herein) as having a
maturity comparable to the remaining term of the Senior Debentures that would be
utilized, at the time of selection and in accordance with customary financial
practice, in pricing new issues of corporate debt securities of comparable
maturity to the remaining term of the Senior Debentures. "Independent Investment
Banker" means Morgan Stanley & Co. Incorporated or, if such firm is unwilling or
unable to select the Comparable Treasury Issue, an independent investment
banking institution of national standing appointed by the Trustee.

          "Comparable Treasury Price" means with respect to any Redemption Date,
(i) the average of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) on the third
Business Day preceding such Redemption Date, as set forth in the daily
statistical release (or any successor release) published by the Federal Reserve
Bank of New York and designated "Composite 3:30 p.m. Quotations for U.S.
Government Securities" or (ii) if such release (or any successor release) is not
published or does not contain such prices on such Business Day, (A) the average
of the Reference Treasury Dealer Quotations for such Redemption Date, after
excluding the highest and lowest such Reference Treasury Dealer Quotations, or
(B) if the Trustee obtains fewer than four Reference Treasury Dealer Quotations,
the average of all such Quotations. "Reference Treasury Dealer Quotations"
means, with respect to each Reference Treasury Dealer and any Redemption Date,
the average, as determined by the Trustee, of the bid and asked prices for the
Comparable Treasury Issue (expressed in each case as a percentage of its
principal amount) quoted in writing to the Trustee by such Reference Treasury
Dealer at 5:00 p.m. on the third Business Day preceding such Redemption Date.

          "Reference Treasury Dealer" means each of Morgan Stanley & Co.
Incorporated, Salomon Brothers Inc and two other Primary Treasury Dealers (as
defined herein) selected by the Issuer, provided, however, that if any of the
foregoing shall cease to be a primary U.S. Government securities dealer in New
York City (a "Primary Treasury Dealer"), the Issuer shall substitute therefor
another Primary Treasury Dealer.

          Holders of Senior Debentures to be redeemed will receive notice
thereof by first-class mail at least 30 and not more than 60 days prior to the
date fixed for redemption.

          Upon due presentment for registration of transfer of this Senior
Debenture at the office or agency of the Issuer in Chicago, Illinois, a new
Senior Debenture or Senior Debenture of this Series of authorized denominations
for an equal aggregate principal amount will be issued to the transferee in
exchange therefor, subject to the limitations provided in the Indenture, without
charge except

                                      -6-


 
for any tax or other governmental charge imposed in connection therewith.

          The Issuer, the Trustee and any agent of the Issuer or the Trustee may
deem and treat the registered Holder hereof as the absolute owner of this Senior
Debenture (whether or not this Senior Debenture shall be overdue and
notwithstanding any notation of ownership or other writing hereon), for the
purpose of receiving payment of, or on account of, the principal hereof and
interest hereon, and for all other purposes, and neither the Issuer nor the
Trustee nor any authorized agent of the Issuer or the Trustee shall be affected
by any notice to the contrary.

          No recourse under or upon any obligation, covenant or agreement of the
Issuer in the Indenture or any indenture supplemental thereto or in this Senior
Debenture, or because of the creation of any indebtedness represented thereby,
shall be had against any incorporator, stockholder, officer or director, as
such, of the Issuer or of any successor corporation, either directly or through
the Issuer or any successor corporation, under any rule of law, statute or
constitutional provision or by the enforcement of any assessment or by any legal
or equitable proceeding or otherwise, all such liability being expressly waived
and released by the acceptance hereof and as part of the consideration for the
issue hereof.

          The Indenture with respect to any Series will be discharged and
cancelled except for certain Sections thereof, subject to the terms of the
Indenture, upon the payment of all the Securities of such Series or upon the
irrevocable deposit with the Trustee of cash or Government Obligations (or a
combination thereof) sufficient for such payment in accordance with Article Ten
of the Indenture.

          The Indenture and this Senior Debenture shall be deemed to be
contracts made under the internal laws of the State of Illinois (without regard
to conflicts of laws provisions hereof), and for all purposes shall be governed
by and construed in accordance with the laws of such State.

          Terms used herein which are defined in the Indenture shall have the
respective meanings assigned thereto in the Indenture.

                                      -7-


 
               _________________________________________________

                  FOR VALUE RECEIVED, the undersigned hereby
                       sells, assigns and transfers unto

Please Insert Social Security or
Other Identifying Number of Assignee


______________________________________________________________________
           [Please Print or Typewrite Name and Address of Assignee]

______________________________________________________________________
the within Senior Debenture and hereby does irrevocably constitute and appoint
_______________________________________________ Attorney to transfer said Senior
Debenture on the books of the within-mentioned Issuer, with full power of
substitution in premises.


Dated:_______________________    _______________________________*


                                 ________________________________
                                 NOTICE: The signature to this assignment must
                                 correspond with the name as written upon the
                                 face of the Senior Debenture in every
                                 particular, without alteration or enlargement
                                 or any change whatever.
                                 
____________________________________
          *  Your signature must be guaranteed by a commercial bank or trust
company or by a member or members' organization of the New York Stock Exchange
or American Stock Exchange.

                                      -8-